Alt a 1 allergen homologs from Alternaria and related taxa: analysis of phylogenetic content and secondary structure

Revision of Alternaria sections Pseudoulocladium and Ulocladioides: Assessment of species boundaries, determination of mating-type loci, and identification of Russian strains

Alternaria is a large genus within Pleosporaceae and consists of fungi that have up to recently been considered to be 15 separate genera, including Ulocladium. The majority of Ulocladium species after incorporation into Alternaria were placed in three sections: Ulocladioides, Pseudoulocladium, and Ulocladium. In this study, phylogeny of 26 reference strains of 22 species and 20 Russian Ulocladium-like isolates was recovered. The partial actin gene (act), Alternaria major allergen (alta1), calmodulin (cal), glyceraldehyde-3-phosphate dehydrogenase (gapdh), RNA polymerase II second largest subunit (rpb2), and translation elongation factor 1-α (tef1) were sequenced for Russian isolates. All these fungi were examined using multilocus phylogenetic analysis according to the genealogical concordance phylogenetic species recognition (GCPSR) principle and the coalescent-based model Poisson tree processes (PTP, mPTP) and evaluated for the presence of recombination. All strains were combined into two clades that corresponded to the Pseudoulocladium and Ulocladioides sections. The Pseudoulocladium clade included four reference strains and nine local isolates and considered to be a single species, whereas the Ulocladioides section comprises 11 species, instead of 17 names previously adopted. Nine species were abolished by joining four other species. Species A. atra and A. multiformis were combined into the single species A. atra. Five species, A. brassicae-pekinensis, A. consortialis, A. cucurbitae, A. obovoidea, and A. terricola, were united in the species A. consortialis. Alternaria heterospora and A. subcucurbitae were combined into one species, A. subcucurbitae. Alternaria aspera, A. chartarum, A. concatenata, and A. septospora were combined into a single species, A. chartarum. Also, amplification with two different primer sets was performed to define mating-type locus 1 (MAT1) idiomorph. All studied isolates were heterothallic, contradicting some prior studies. Twenty Russian Ulocladium-like isolates were assigned to five species of two sections, A. atra, A. cantlous, A. chartarum, A. consortialis, and A. subcucurbitae. Species A. cantlous and A. subcucurbitae were found in Russia for the first time.

Alternaria solani core effector Aex59 is a new member of the Alt a 1 protein family and is recognized as a PAMP

Early blight caused by Alternaria solani is a destructive disease in potato production. Here, through systematically screening of an effector protein pool consisting of 115 small cysteine-containing candidate Aex (Alternariaextracellular proteins) in A. solani, we identified a core effector protein named Aex59, a pathogen-associated molecular pattern (PAMP) molecule. Aex59 is uniquely present in the Ascomycota of fungi and can activate defense responses in multiple plants. Targeted gene disruption showed that Aex59 is a virulence factor and participates in spore development. Perception of Aex59 in Nicotiana benthamiana does not depend on the receptor-like kinases Brassinosteroid-associated kinase1 (BAK1) and Suppressor of BIR1-1 (SOBIR1), which are required for multiple pattern recognition receptors (PRR) pathways. Sequence analysis revealed that Aex59 is a new member of the Alt a 1 protein family and is a potential molecular marker capable of aiding in the classification of the fungi Alternaria spp.

Three Alternaria Species, Including a New Species, Causing Leaf Spot Disease of Loquat (Eriobotrya japonica) in China

Loquat (Eriobotrya japonica) is an economically important subtropical fruit crop in China. Field surveys conducted in different loquat orchards located in Chongqing, Sichuan, and Fujian provinces between 2017 and 2020 resulted in a collection of 56 Alternaria-like isolates from trees exhibiting symptoms of loquat leaf spot. Multigene phylogenetic analyses using seven gene regions, namely, ITS, gapdh, RPB2, tef1, Alt a 1, endoPG, and OPA10-2, showed that all the isolates belonged to the genus Alternaria, and supporting morphological analysis identified them as members of species A. alternata, A. gaisen, and A. chongqingensis sp. nov. In vitro and in vivo pathogenicity tests showed all the identified species to be pathogenic and able to cause leaf spot disease on loquat. Moreover, comprehensive phylogenetic analyses employing all combinations of the above seven gene sequences revealed the capability of Alt a 1-tef1-endoPG to provide a well-resolved gene tree for Alternaria spp. at the species level. This study adds to the current knowledge on an unknown species (A. chongqingensis sp. nov.) and is the first report of A. gaisen in loquat worldwide.

Morphological and phylogenetic analyses reveal two new Alternaria species (Pleosporales, Pleosporaceae) in Alternaria section from Cucurbitaceae plants in China

Alternaria species are commonly found as saprophytes, endophytes and plant pathogens. During a survey of small-spored Alternaria in China, two new species were discovered from Cucurbitaceae plants collected in Hubei and Sichuan provinces. This study identified two new species of Alternaria using seven genes (ITS, GAPDH, TEF1, RPB2, Alt a 1, EndoPG, and OPA10-2) for phylogenetic analyses and morphological characteristics. The two new species A.jingzhouensis and A.momordicae were described and illustrated. Alternariajingzhouensis sp. nov., associated with Citrulluslanatus, is characterized by producing muriform, ellipsoidal, flask-shaped, rostrate, and beaked conidia. It differs from A.koreana, A.ovoidea, and A.baoshanensis by bearing conidia in a simple conidiogenous locus with occasionally longer beaks in a chain, and from A.momordicae sp. nov. by having shorter beaks. Alternariamomordicae sp. nov. from Momordicacharantia was distinct from A.koreana, A.ovoidea, and A.baoshanensis by producing muriform, long ellipsoid or ovoid to obclavate, sometimes inverted club-shaped conidia on a single conidiogenous locus with a wider body and longer beak in a chain, and distinct from A.jingzhouensis sp. nov. by a longer beak conidia. These two species were clearly distinguished from other species in the section Alternaria based on DNA based phylogeny and morphological characteristics. The morphological features were discussed and compared to relevant species in the present paper.

Aggressive Alternaria brassicicola with Reduced Fungicide Sensitivity Can Be Associated with Naturally Infested Broccoli Seeds

Alternaria brassicicola is a part of the Alternaria complex that causes leaf blight and head rot (ABHR) in brassica crops. Infested broccoli seeds can play an important role in introducing A. brassicicola in transplant houses and production fields. However, characterization of natural seed infestation and seed-to-seedling transmission of A. brassicicola in broccoli is yet to be demonstrated. In this research, we characterized Alternaria spp. isolates from commercial broccoli seedlots for their species identity, pathogenicity, and aggressiveness on broccoli and their sensitivity to a quinone-outside inhibitor (QoI) fungicide (azoxystrobin). Two hundred commercial seedlots from two broccoli cultivars, Cultivar 1 (EC; n = 100 seedlots) and Cultivar 2 (ED; n = 100 seedlots) were, evaluated for the presence of A. brassicicola under in vitro conditions using a seedling grow-out assay. Alternaria spp. was detected in 31 and 28% of the commercial seedlots of Cultivar 1 and Cultivar 2, respectively. The seed-to-seedling transmission (%) varied considerably within each positive-infested seedlot, which ranged from 1.3 to 17.3%. Subsequent molecular identification of single-spore cultures (n = 138) was made by sequencing four housekeeping genes: actin, the major allergen (Alta1), plasma membrane ATPase, and glyceraldehyde-3-phosphate dehydrogenase (GPD), and the sequences were concatenated and compared for the phylogenetic distance with diverse Alternaria species. Ninety-six percent (n = 133) of the isolates formed a cluster with a known A. brassicicola based on a multigene phylogeny, which were later confirmed as A. brassicicola using a species-specific PCR assay. One hundred percent of the A. brassicicola seed isolates (n = 133) were either highly or moderately aggressive on broccoli (cultivar Emerald Crown) based on a detached leaf assay. Sensitivity of representative A. brassicicola isolates (n = 58) to azoxystrobin was evaluated using a spore germination assay, and the EC50 values (effective fungicide concentration [ppm] at which germination of conidia of isolates were reduced by 50% compared to control) for each isolate was determined. A. brassicicola isolates from naturally infested commercial broccoli seeds were sensitive to azoxystrobin with considerably low EC50 values in the range of <0.0001 to 0.33 ppm; however, there were a few isolates (14%) that showed 100-fold reduced sensitivity from the most sensitive isolate (EC50 = 0.0001 ppm). Our results confirm that commercial broccoli seedlots can be naturally contaminated with pathogenic and aggressive A. brassicicola. We also provide evidence for the potential presence of A. brassicicola isolates with reduced azoxystrobin-sensitivity in naturally infested commercial broccoli seedlots, which has never been reported before. Together, these findings may have implications in considerations for seed-health testing, seed treatments, and greenhouse scouting to limit introduction of infested seedlots in commercial broccoli fields.

Two novel species and a new host record of Alternaria (Pleosporales, Pleosporaceae) from sunflower (Compositae) in Myanmar

Sunflower (Helianthusannuus L.) is a widely cultivated, fast-growing crop known for its seeds and oil, with substantial ecological and economic importance globally. However, it faces challenges from leaf diseases caused by Alternaria species, which threaten its yield. Three small-spored Alternaria species were isolated from leaf spot and blight symptoms on sunflower in Myanmar. All the species were determined based on morphological characterization and a multi-locus phylogenetic assessment of seven genes, including the internal transcribed spacer of rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), RNA polymerase second largest subunit (RPB2), translation elongation factor 1-α (TEF1), Alternaria major allergen gene (Alt a 1), endopolygalacturonase gene (EndoPG), and an anonymous gene region (OPA10-2). The results introduced two new Alternaria species, A.myanmarensis sp. nov. and A.yamethinensis sp. nov., and a known species of A.burnsii, firstly reported from sunflower.

Identification the Pathogen Cause a New Apple Leaf Blight in China and Determination the Controlling Efficacy for Five Botanical Fungicides

Alternaria leaf blight has recently been described as an emerging fungal disease of apple trees which is causing the significant damage in the apple-growing areas of Tianshui and Jingning, Gansu, China. In the present study, the pathogen species involved in apple leaf blight and its biological characteristics were identified, and the inhibitory activity of different botanical fungicides against the pathogen was evaluated in vitro. Four strains were isolated from the symptomatic areas of necrotic apple leaves, and initially healthy leaves showed similar symptoms to those observed in orchards after inoculation with the ABL2 isolate. The ABL2 isolate was identified as Alternaria tenuissima based on the morphological characteristics of its colonies, conidiophores, and conidia, and this was also confirmed by multi-gene sequence (ITS, OPA10-2, Alta-1, and endoPG) analysis and phylogenic analysis. The optimum temperature, pH, carbon source, and nitrogen source for the growth of A. tenuissima mycelia were 28 °C, 6-7, soluble starch, and soy flour, respectively. In addition, the botanical fungicide eugenol exhibited the highest inhibitory effect on the mycelial growth and conidia germination of A. tenuissima, and the median effective concentration (EC50) values were 0.826 and 0.755 μg/mL, respectively. The protective and curative efficacy of eugenol were 86.85% and 76.94% after inoculation in detached apple leaves at a concentration of 4 μg/mL. Our research provides new insights into the control of apple leaf blight disease by applying botanical fungicides.

Alternaria diseases on potato and tomato

Alternaria spp. cause different diseases in potato and tomato crops. Early blight caused by Alternaria solani and brown spot caused by Alternaria alternata are most common, but the disease complex is far more diverse. We first provide an overview of the Alternaria species infecting the two host plants to alleviate some of the confusion that arises from the taxonomic rearrangements in this fungal genus. Highlighting the diversity of Alternaria fungi on both solanaceous hosts, we review studies investigating the genetic diversity and genomes, before we present recent advances from studies elucidating host-pathogen interactions and fungicide resistances.

TAXONOMY

Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Pleosporales, Family Pleosporaceae, Genus Alternaria.

BIOLOGY AND HOST RANGE

Alternaria spp. adopt diverse lifestyles. We specifically review Alternaria spp. that cause disease in the two solanaceous crops potato (Solanum tuberosum) and tomato (Solanum lycopersicum). They are necrotrophic pathogens with no known sexual stage, despite some signatures of recombination.

DISEASE SYMPTOMS

Symptoms of the early blight/brown spot disease complex include foliar lesions that first present as brown spots, depending on the species with characteristic concentric rings, which eventually lead to severe defoliation and considerable yield loss.

CONTROL

Good field hygiene can keep the disease pressure low. Some potato and tomato cultivars show differences in susceptibility, but there are no fully resistant varieties known. Therefore, the main control mechanism is treatment with fungicides.

Characterization and toxicological potential of Alternaria alternata associated with post-harvest fruit rot of Prunus avium in China

Post-harvest fruit rot caused by Alternaria species is one of the most important threats to the fruit industry. Post-harvest rot on sweet cherry (Prunus avium) fruit was observed in the fruit markets of the Haidian district of Beijing, China. The fungal isolates obtained from the infected sweet cherry fruits matched the descriptions of Alternaria alternata based on the morphology and multi-gene (ITS, endo-PG, and Alta1) sequence analysis. Pathogenicity tests indicated that ACT-3 was the most virulent isolate, exhibiting typical post-harvest fruit rot symptoms. Physiological studies revealed that the optimal conditions for the growth of ACT-3 were temperature of 28°C, water activity of 0.999, and pH of 8 with 87, 85, and 86 mm radial growth of ACT-3 on a potato dextrose agar (PDA) medium, respectively, at 12 days post-inoculation (dpi). Moreover, the fungus showed the highest growth on a Martin agar medium (MAM) modified (85 mm) and a PDA medium (84 mm) at 12 dpi. The proliferation of the fungus was visualized inside the fruit tissues by confocal and scanning electron microscope (SEM), revealing the invasion and destruction of fruit tissues. Alternaria mycotoxins, tenuazonic acid (TeA), and alternariol (AOH) were detected in five representative isolates by HPLC analysis. The highest concentrations of TeA (313 μg/mL) and AOH (8.9 μg/mL) were observed in ACT-6 and ACT-3 isolates, respectively. This study is the first to present a detailed report on the characteristics and proliferation of A. alternata associated with sweet cherry fruit rot and the detection of toxic metabolites.

Assessing the contributions of phylogenetic and environmental determinants of allergic cosensitization to fungi in humans

BACKGROUND

Understanding how allergies to 1 environmental fungus can lead to cosensitization to related fungi is important for the clinical management of allergies. Cosensitization can be caused by monosensitization combined with antibody cross-reactivity, or by coexposures driving independent sensitizations. A pioneering study showed that patterns of IgE cosensitization among 17 fungal species mirror fungal phylogeny. This could reflect either epitope or habitat similarity. Thanks to an improved understanding of fungal phylogeny, larger serologic testing datasets, and environmental data on household fungi, we can now characterize the relationship between cosensitization, species similarity, and likely coexposure with greater precision.

OBJECTIVE

To assess the degree to which IgE cosensitization in a group of 17 fungi can be attributed to species similarity or environmental coexposure.

METHODS

Cosensitization patterns among 17 fungal species were estimated from a dataset of approximately 8 million serologic tests on 1.6 million patients. Linear regression of cosensitization on phylogenetic distance and imputed coexposure was performed. In addition, branch lengths for the phylogenetic tree were re-estimated on the basis of cosensitization and compared with corresponding phylogenetic branch lengths.

RESULTS

Phylogenetic distance explains much of the observed cosensitization (adjusted r2 = .68, p < .001). Imputed environmental coexposures and test co-ordering patterns do not significantly predict cosensitization. Branch length comparisons between the cosensitization and phylogenetic trees identified several species as less cosensitizing than phylogenetic distance predicts.

CONCLUSION

Combined evidence from clinical IgE testing data on fungi, along with phylogenetic and environmental exposure data, supports the hypothesis that cosensitization is caused primarily by monosensitization plus cross-reactivity, rather than multisensitization. A serologic test result should be interpreted as pointing to a group of related species that include the sensitizing agent rather than as uniquely identifying the agent. The identified patterns of cross-reactivity may help optimize test panel design.

Assessment of Resistance Induction in Mungbean against Alternaria alternata through RNA Interference

A comprehensive survey of mungbean-growing areas was conducted to observe leaf spot disease caused by Alternaria alternata. Alternaria leaf spot symptoms were observed on the leaves. Diversity of 50 genotypes of mungbean was assessed against A. alternata and data on pathological traits was subjected to cluster analysis. The results showed that genotypes of mungbean were grouped into four clusters based on resistance parameters under the influence of disease. The principal component biplot demonstrated that all the disease-related parameters (% disease incidence, % disease intensity, lesion area, and % of infection) were strongly correlated with each other. Alt a 1 gene that is precisely found in Alternaria species and is responsible for virulence and pathogenicity. Alt a 1 gene was amplified using gene specific primers. The isolated pathogen produced similar symptoms when inoculated on mungbean and tobacco. The sequence analysis of the internal transcribed spacer (ITS) region, a 600 bp fragment amplified using specific primers, ITS1 and ITS2 showed 100% identity with A. alternata. Potato virus X (PVX) -based silencing vector expressing Alt a 1 gene was constructed to control this pathogen through RNA interference in tobacco. Out of 50 inoculated plants, 9 showed delayed onset of disease. Furthermore, to confirm our findings at molecular level semi-quantitative reverse transcriptase polymerase chain reaction was used. Both phenotypic and molecular investigation indicated that RNAi induced through the VIGS vector was efficacious in resisting the pathogen in the model host, Tobacco (Nicotiana tabacum). To the best of our knowledge, this study has been reported for the first time.

Isolation and Identification of Alternaria alternata from Potato Plants Affected by Leaf Spot Disease in Korea: Selection of Effective Fungicides

Brown leaf spot disease caused by Alternaria spp. is among the most common diseases of potato crops. Typical brown spot symptoms were observed in commercial potato-cultivation areas of northern Korea from June to August 2020-2021. In total, 68 isolates were collected, and based on sequence analysis of the internal transcribed spacer (ITS) region, the collected isolates were identified as Alternaria spp. (80.9%). Phylogenetic analysis revealed that a majority of these isolates clustered within a clade that included A. alternata. Additionally, the ITS region and rpb2 yielded the most informative sequences for the identification of A. alternata. Pathogenicity tests confirmed that the collected pathogens elicited symptoms identical to those observed in the field. In pathogenicity tests performed on seven commercial cultivars, the pathogens exhibited strong virulence in both wound and non-wound inoculations. Among the cultivars tested, Arirang-1ho, Arirang-2ho, and Golden Ball were resistant to the pathogens. Furthermore, among the fungicides tested in vitro, mancozeb and difenoconazole were found to be effective for inhibiting mycelial growth. In summary, our findings suggest that A. alternata plays a critical role in leaf disease in potato-growing regions and emphasise the necessity of continuous monitoring and management to protect against this disease in Korea.

Seven new species of Alternaria (Pleosporales, Pleosporaceae) associated with Chinese fir, based on morphological and molecular evidence

Chinese fir (Cunninghamialanceolata) is a special fast-growing commercial tree species in China and has significant ecological and economic value. However, it experienced damage from leaf blight caused by pathogenic fungi of the genus Alternaria. To determine the diversity of Alternaria species associated with leaf blight of Chinese fir in China, infected leaves were collected from five major cultivation provinces (Fujian, Henan, Hunan, Jiangsu and Shandong provinces). A total of 48 fungal strains of Alternaria were obtained. Comparison of morphology and phylogenetic analyses, based on nine loci (ITS, SSU, LSU, GAPDH, RPB2, TEF1, Alt a1, endoPG and OPA10-2) of the representative isolates as well as the pairwise homoplasy index tests, revealed that the fungal strains belonged to seven undescribed taxa of Alternaria, which are described here and named as Alternariacunninghamiicolasp. nov., A.dongshanqiaoensissp. nov., A.hunanensissp. nov., A.kunyuensissp. nov., А. longqiaoensissp. nov., A.shandongensissp. nov. and A.xinyangensissp. nov. In order to prove Koch's postulates, pathogenicity tests on detached Chinese fir leaves revealed significant pathogenicity amongst these species, of which A.hunanensis is the most pathogenic to Chinese fir. This study represents the first report of A.cunninghamiicola, A.dongshanqiaoensis, A.hunanensis, A.kunyuensis, A.longqiaoensis, A.shandongensis and A.xinyangensis causing leaf blight on Chinese fir. Knowledge obtained in this study enhanced our understanding of Alternaria species causing leaf blight on Chinese fir and was crucial for the disease management and the further studies in the future.

Lytic and Molecular Evidence of the Widespread Coriander Leaf Spot Disease Caused by Alternaria dauci

Coriandrum sativum L. is a globally significant economic herb with medicinal and aromatic properties. While coriander leaf blight disease was previously confined to India and the USA, this study presents new evidence of its outbreak in Africa and the Middle East caused by Alternaria dauci. Infected leaves display irregular chlorotic to dark brown necrotic lesions along their edges, resulting in leaf discoloration, collapse, and eventual death. The disease also impacts inflorescences and seeds, significantly reducing seed quality. Koch's postulates confirmed the pathogenicity of the fungus through the re-isolation of A. dauci from artificially infected leaves, and its morphology aligns with typical A. dauci features. Notably, this study identified strong lytic activity (cellulase: 23.76 U, xylanase: 12.83 U, pectinase: 51.84 U, amylase: 9.12 U, and proteinase: 5.73 U), suggesting a correlation with pathogenicity. Molecular characterization using ITS (ON171224) and the specific Alt-a-1 gene (OR236142) supports the fungal morphology. This research provides the first comprehensive documentation of the pathological, lytic, and molecular evidence of A. dauci leaf blight disease on coriander. Future investigations should prioritize the development of resistant coriander varieties and sustainable disease management strategies, including the use of advanced molecular techniques for swift and accurate disease diagnosis to protect coriander from the devastating impact of A. dauci.

Untargeted metabolomic analyses support the main phylogenetic groups of the common plant-associated Alternaria fungi isolated from grapevine (Vitis vinifera)

Alternaria, a cosmopolitan fungal genus is a dominant member of the grapevine (Vitis vinifera) microbiome. Several Alternaria species are known to produce a variety of secondary metabolites, which are particularly relevant to plant protection and food safety in field crops. According to previous findings, the majority of Alternaria species inhabiting grapevine belong to Alternaria sect. Alternaria. However, the phylogenetic diversity and secondary metabolite production of the distinct Alternaria species has remained unclear. In this study, our aim was to examine the genetic and metabolic diversity of endophytic Alternaria isolates associated with the above-ground tissues of the grapevine. Altogether, 270 Alternaria isolates were collected from asymptomatic leaves and grape clusters of different grapevine varieties in the Eger wine region of Hungary. After analyses of the nuclear ribosomal DNA internal transcribed spacer (ITS) and RNA polymerase second largest subunit (rpb2) sequences, 170 isolates were chosen for further analyses. Sequences of the Alternaria major allergen gene (Alt a 1), endopolygalacturonase (endoPG), OPA10-2, and KOG1058 were also included in the phylogenetic analyses. Identification of secondary metabolites and metabolite profiling of the isolates were performed using high-performance liquid chromatography (HPLC)-high-resolution tandem mass spectrometry (HR-MS/MS). The multilocus phylogeny results revealed two distinct groups in grapevine, namely A. alternata and the A. arborescens species complex (AASC). Eight main metabolites were identified in all collected Alternaria isolates, regardless of their affiliation to the species and lineages. Multivariate analyses of untargeted metabolites found no clear separations; however, a partial least squares-discriminant analysis model was able to successfully discriminate between the metabolic datasets from isolates belonging to the AASC and A. alternata. By conducting univariate analysis based on the discriminant ability of the metabolites, we also identified several features exhibiting large and significant variation between A. alternata and the AASC. The separation of these groups may suggest functional differences, which may also play a role in the functioning of the plant microbiome.

Mechanisms of Alternaria pathogenesis in animals and plants

Alternaria species are cosmopolitan fungi darkly pigmented by melanin that infect numerous plant species causing economically important agricultural spoilage of various food crops. Alternaria spp. also infect animals, being described as entomopathogenic fungi but also infecting warm-blooded animals, including humans. Their clinical importance in human health, as infection agents, lay in the growing number of immunocompromised patients. Moreover, Alternaria spp. are considered some of the most abundant and potent sources of airborne sensitizer allergens causing allergic respiratory diseases, as severe asthma. Among the numerous strategies deployed by Alternaria spp. to attack their hosts, the production of toxins, carrying critical concerns to public health as food contaminant, and the production of hydrolytic enzymes such as proteases, can be highlighted. Alternaria proteases also trigger allergic symptoms in individuals with fungal sensitization, acting as allergens and facilitating antigen access to the host subepithelium. Here, we review the current knowledge about the mechanisms of Alternaria pathogenesis in plants and animals, the strategies used by Alternaria to cope with the host defenses, and the involvement Alternaria allergens and mechanisms of sensitization.

Luobuma Leaf Spot Disease Caused by Alternaria tenuissima in China

Luobuma (Apocynum venetum and Poacynum hendersonni) is widely cultivated for environmental conservation, medicinal purposes and the textile industry. In 2018, a severe leaf spot disease that attacked the leaves of Luobuma was observed in plants cultivated in Yuzhong County, Gansu Province, China. Symptoms of the disease appeared as white or off-white spots surrounded by brown margins on the leaves of A. venetum. The spots expanded and covered a large area of the leaf, presenting as "cankers" with progression of the disease, leading to leaf death. The initial symptoms of the disease on P. hendersonni were similar to the symptoms of A. venetum, with a larger disease spot than A. venetum, and the spot was black and thicker. The aim of this study was to identify the fungal species and evaluate the effectiveness of fungicides (hymexazol and zhongshengmycin) against the pathogen in vitro. The fungi species that caused the new disease was identified as Alternaria tenuissima based on the morphological characteristics, pathogenicity tests, and phylogenetic analysis of the internal transcribed spacer (ITS) region, glyceraldehyde 3-phosphate dehydrogenase (gpd), translation elongation factor 1-alpha (TEF) and the histone 3 (H3) gene sequences. The findings showed that hymexazol fungicide can be used to control leaf spot disease. This is the first report on Luobuma leaf spot disease caused by A. tenuissima in China.

Molecular Characterization and Pathogenicity of Alternaria spp. Associated with Black Rot of Sweet Cherries in Italy

Black rot is limiting the production of sweet cherries in Italy. Dark brown to black patches and sunken lesions on fruits are the most common symptoms of Alternaria black rot on sweet cherry fruits. We isolated 180 Alternaria spp. from symptomatic cherry fruits 'Kordia', 'Ferrovia', and 'Regina' harvested in Northern Italy, over three years, from 2020 to 2022. The aim was to identify and characterize a selection of forty isolates of Alternaria spp. based on morphology, pathogenicity, and combined analysis of rpb2, Alt-a1, endoPG and OPA10-2. The colonies were dark greyish in the center with white margins. Ellipsoidal or ovoid shaped conidia ranging from 19.8 to 21.7 μm in length were observed under a microscope. Based on the concatenated session of four gene regions, thirty-three out of forty isolates were identified as A. arborescens species complex (AASC), and seven as A. alternata. Pathogenicity was evaluated on healthy 'Regina' sweet cherry fruits. All the tested strains were pathogenic on their host. This study represents the first characterization of Alternaria spp. associated with black rot of cherries in Italy and, to the best of our knowledge, it is also the first report of AASC as an agent of black rot of sweet cherries in Italy.

Identification and Fungicide Control of Bipolaris sorokiniana Causing Leaf Spot and Blight on Common Hop (Humulus lupulus) in Korea

Hop (Humulus lupulus) is a perennial herbaceous vine belonging to the family Cannabaceae. This crop is commercially grown for the brewing industry for its bitter and aromatic flavor, as well as its antiseptic properties. In June 2021, leaf spot and blight was observed on common hop plants in Buan-gun, Jeollabuk-do, South Korea. The typical symptoms were small to large, dark-brown, necrotic lesions with yellow halos on the leaves. This study aimed to clarify the causal agent of this disease. Two fungal species, Alternaria alternata and Bipolaris sorokiniana, were isolated from the diseased leaf samples and identified by combining morphological observations and phylogenetic analysis using sequence datasets of internal transcribed spacer (ITS), Alt a1, rpb2, endoPG, and OPA10-2; and ITS, gpd, and tef1, respectively. Pathogenicity of the fungal isolates on detached leaves and living plants revealed that B. sorokiniana is the causal pathogen of this disease, while A. alternata is potentially a saprophyte. Fungicide sensitivity of the pathogen B. sorokiniana was further estimated in vitro using three classes of fungicides represented by fluxapyroxad, pyraclostrobin, and hexaconazole. The effective concentrations that inhibited 50% of spore germination (EC50) were 0.72, 1.90, and 0.68 μg ml-1, respectively. Moreover, all of these fungicides were able to control B. sorokiniana on detached common hop leaves at their recommended concentrations. In conclusion, this study reports leaf spot and blight of common hop caused by B. sorokiniana for the first time and proposes potential fungicides for this disease.

Alternaria arborescens and A. italica Causing Leaf Blotch on Celtis julianae in China

Celtis julianae Schneid. is widely planted as a versatile tree species with ecological and economic significance. In September 2022, a leaf blotch disease of C. julianae was observed in Nanjing, Jiangsu, China, with an infection incidence of 63%. The disease led to severe early defoliation, significantly affecting the ornamental and ecological value of the host tree. The accurate identification of pathogens is imperative to conducting further research and advancing disease control. Koch's postulates confirmed that the fungal isolates (B1-B9) were pathogenic to C. julianae. The morphology of the characteristics of the pathogen matched those of Alternaria spp. The internal transcribed spacer region (ITS), large subunit (LSU) and small subunit (SSU) regions of rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen gene (Alt a 1), RNA polymerase second largest subunit (RPB2), and portions of translation elongation factor 1-alpha (TEF1-α) genes were sequenced. Based on multi-locus phylogenetic analyses and morphology, the pathogenic fungi were identified as Alternaria arborescens and A. italica. The findings provided useful information for disease management and enhanced the understanding of Alternaria species diversity in China. This is the first report of A. arborescens and A. italica causing leaf blotch of C. julianae in China and worldwide.

Four New Species of Small-Spored Alternaria Isolated from Solanum tuberosum and S. lycopersicum in China

Small-spored Alternaria species have been frequently isolated from diseased leaves of Solanum plants. To clarify the diversity of small-spored Alternaria species, a total of 118 strains were obtained from leaf samples of S. tuberosum and S. lycopersicum in six provinces of China during 2022-2023. Based on morphological characterization and multi-locus phylogenetic analysis of the internal transcribed spacer of the rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), endopolygalacturonase gene (EndoPG) and an anonymous gene region (OPA10-2), seven species were determined, including four novel species and three known species (A. alternata, A. gossypina and A. arborescens). The novel species were described and illustrated as A. longxiensis sp. nov., A. lijiangensis sp. nov., A. lycopersici sp. nov. and A. solanicola sp. nov.. In addition, the pathogenicity of the seven species was evaluated on potato leaves. The species exhibited various aggressiveness, which could help in disease management.

Diversity of Mycotoxins and Other Secondary Metabolites Recovered from Blood Oranges Infected by Colletotrichum, Alternaria, and Penicillium Species

This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides, and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of A. alternata, C. gloeosporioides, and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.

Potential Biocontrol Agents of Corn Tar Spot Disease Isolated from Overwintered Phyllachora maydis Stromata

Tar spot disease in corn, caused by Phyllachora maydis, can reduce grain yield by limiting the total photosynthetic area in leaves. Stromata of P. maydis are long-term survival structures that can germinate and release spores in a gelatinous matrix in the spring, which are thought to serve as inoculum in newly planted fields. In this study, overwintered stromata in corn leaves were collected in Central Illinois, surface sterilized, and caged on water agar medium. Fungi and bacteria were collected from the surface of stromata that did not germinate and showed microbial growth. Twenty-two Alternaria isolates and three Cladosporium isolates were collected. Eighteen bacteria, most frequently Pseudomonas and Pantoea species, were also isolated. Spores of Alternaria, Cladosporium, and Gliocladium catenulatum (formulated as a commercial biofungicide) reduced the number of stromata that germinated compared to control untreated stromata. These data suggest that fungi collected from overwintered tar spot stromata can serve as biological control organisms against tar spot disease.

Differential Detection of Alternaria alternata Haplotypes Isolated from Carya illinoinensis Using PCR-RFLP Analysis of Alt a1 Gene Region

Alternaria black spot disease on pecan is caused by the opportunistic pathogen Alternaria alternata and poses a serious threat to the local South African and global pecan industry. Several diagnostic molecular marker applications have been established and used in the screening of various fungal diseases worldwide. The present study investigated the potential for polymorphism within samples of A. alternata isolates obtained from eight different geographical locations in South Africa. Pecan (Carya illinoinensis) leaves, shoots, and nuts-in-shuck with Alternaria black spot disease were sampled, and 222 A. alternata isolates were retrieved. For rapid screening to identify Alternaria black spot pathogens, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the Alternaria major allergen (Alt a1) gene region was used, followed by the digestion of the amplicons with HaeIII and HinfI endonucleases. The assay resulted in five (HaeIII) and two (HinfI) band patterns. Unique banding patterns from the two endonucleases showed the best profile and isolates were grouped into six clusters using a UPGMA (unweighted pair group method with arithmetic averages) distance matrix (Euclidean) dendrogram method on R-Studio. The analysis confirmed that the genetic diversity of A. alternata does not depend on host tissues or the pecan cultivation region. The grouping of selected isolates was confirmed by DNA sequence analysis. The Alt a1 phylogeny corroborated no speciation within the dendrogram groups and showed 98-100% bootstrap similarity. This study reports the first documented rapid and reliable technique for routine screening identification of pathogens causing Alternaria black spot in South Africa.

Using qPCR and microscopy to assess the impact of harvesting and weather conditions on the relationship between Alternaria alternata and Alternaria spp. spores in rural and urban atmospheres

Alternaria is a plant pathogen and human allergen. Alternaria alternata is one of the most abundant fungal spores in the air. The purpose of this study was to examine whether Alternaria spp. spore concentrations can be used to predict the abundance and spatio-temporal pattern of A. alternata spores in the air. This was investigated by testing the hypothesis that A. alternata dominates airborne Alternaria spp. spores and varies spatio-temporally. Secondarily, we aimed at investigating the relationship between airborne Alternaria spp. spores and the DNA profile of A. alternata spores between two proximate (~ 7 km apart) sites. These were examined by sampling Alternaria spp. spores using Burkard 7-day and cyclone samplers for the period 2016-2018 at Worcester and Lakeside campuses of the University of Worcester, UK. Daily Alternaria spp. spores from the Burkard traps were identified using optical microscopy whilst A. alternata from the cyclone samples was detected and quantified using quantitative polymerase chain reaction (qPCR). The results showed that either A. alternata or other Alternaria species spores dominate the airborne Alternaria spore concentrations, generally depending on weather conditions. Furthermore, although Alternaria spp. spore concentrations were similar for the two proximate sites, A. alternata spore concentrations significantly varied for those sites and it is highly likely that the airborne samples contained large amounts of small fragments of A. alternata. Overall, the study shows that there is a higher abundance of airborne Alternaria allergen than reported by aerobiological networks and the majority is likely to be from spore and hyphal fragments.

Multigene Phylogeny and Pathogenicity Trials Revealed Alternaria alternata as the Causal Agent of Black Spot Disease and Seedling Wilt of Pecan (Carya illinoinensis) in South Africa

The pecan (Carya illinoinensis) industry in South Africa is growing rapidly, and it is becoming increasingly crucial to understand the risks posed to pecans by fungal pathogens. Black spots on leaves, shoots, and nuts in shucks caused by Alternaria species have been observed since 2014 in the Hartswater region of the Northern Cape Province of South Africa. Species of Alternaria include some of the most ubiquitous plant pathogens on earth. The aim of this study was to use molecular techniques to identify the causative agents of Alternaria black spot and seedling wilt isolated from major South African pecan-production areas. Symptomatic and non-symptomatic pecan plant organs (leaves, shoots, and nuts-in-shucks) were collected from pecan orchards, representing the six major production regions in South Africa. Thirty Alternaria isolates were retrieved from the sampled tissues using Potato Dextrose Agar (PDA) culture media and molecular identification was conducted. The phylogeny of multi-locus DNA sequences of Gapdh, Rpb2, Tef1, and Alt a 1 genes revealed that the isolates were all members of Alternaria alternata sensu stricto, forming part of the Alternaria alternata species complex. The virulence of six A. alternata isolates were tested on detached nuts of Wichita and Ukulinga cultivars, respectively, as well as detached leaves of Wichita. The A. alternata isolates were also evaluated for their ability to cause seedling wilt in Wichita. The results differed significantly between wounded and unwounded nuts of both cultivars, but not between the cultivars. Similarly, the disease lesions on the wounded detached leaves were significantly different in size from the unwounded leaves. The seedling tests confirmed that A. alternata is pathogenic and that A. alternata causes black spot disease and seedling wilt of pecans. This study is one of the first documentations of Alternaria black spot disease of pecan trees and its widespread occurrence in South Africa.

Interacting Abiotic Factors Affect Growth and Mycotoxin Production Profiles of Alternaria Section Alternaria Strains on Chickpea-Based Media

Chickpea is susceptible to fungal infection and mycotoxin contamination. Argentina exports most of its chickpea production; thus, its quality is of concern. The Alternaria fungal genus was found to be prevalent in chickpea samples from Argentina. The species within this genus are able to produce mycotoxins, such as alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA). In this context, we evaluated the effect of water activity (0.99, 0.98, 0.96, 0.95, 0.94, 0.92, and 0.90 a_W), temperature (4, 15, 25, and 30 °C), incubation time (7, 14, 21, and 28 days), and their interactions on mycelial growth and AOH, AME, and TA production on chickpea-based medium by two A. alternata strains and one A. arborescens strain isolated from chickpea in Argentina. Maximum growth rates were obtained at the highest a_W (0.99) and 25 °C, with growth decreasing as the a_W of the medium and the temperature were reduced. A. arborescens grew significantly faster than A. alternata. Mycotoxin production was affected by both variables (a_W and temperature), and the pattern obtained was dependent on the strains/species evaluated. In general, both A. alternata strains produced maximum amounts of AOH and AME at 30 °C and 0.99-0.98 a_W, while for TA production, both strains behaved completely differently (maximum levels at 25 °C and 0.96 a_W for one strain and 30 °C and 0.98 a_W for the other). A. arborescens produced maximum amounts of the three toxins at 25 °C and 0.98 a_W. Temperature and a_W conditions for mycotoxin production were slightly narrower than those for growth. Temperature and a_W conditions assayed are those found during chickpea grain development in the field, and also could be present during storage. This study provides useful data on the conditions representing a risk for contamination of chickpea by Alternaria toxins.

First Report of New Guinea Impatiens (Impatiens hawkeri) Leaf Spot Caused by Alternaria burnsii - A. tomato species complex in Taiwan

New Guinea impatiens (Impatiens hawkeri) is a common ornamental crop usually planted in pots and planters, flower beds, home gardens, or parks in Taiwan. In June 2021, leaf spots on 87.1% (27/31) of potted I. hawkeri plants on National Chung Hsing University (NCHU) campus were observed. Initially, tiny chlorotic leaf spots were found, which aged into brown to grayish white necrotic spots with reddish-purple margins. The necrotic spots enlarged, coalesced, and formed concentric rings. To isolate the pathogen, diseased leaves were surface-disinfected with 70% ethanol for 15 seconds and blotted dry with a paper towel. Small pieces (~2×6 mm2) of tissues were excised from the junction of the lesions and healthy areas, placed onto 2% water agar, and incubated at 25°C with 12-h photoperiod for three days. Individual hyphal tips growing out of diseased tissues were transferred onto potato dextrose agar (PDA). Three isolates, OM10, OM43, and OM45, were obtained and grown on half-strength PDA at 28°C in the dark for at least two weeks. Conidia of each isolate produced on the half-strength PDA were washed off in sterile water with 0.01% of Tween 20. Pathogenicity tests were performed by spraying leaves of 2- to 3-month-old potted healthy I. hawkeri plants with 5 ml of conidial suspension (1 × 105 conidia/ml) of the three isolates, respectively. Control plants were sprayed with sterile water. There were four plants per treatment and the experiments were conducted twice. Inoculated plants were covered with plastic bags for two days and incubated in a greenhouse with a temperature range of 19 to 31°C. Leaf spots similar to those observed in the field were observed at 7 to 14 days after inoculation in both trials. The same fungus was isolated from inoculated plants, whereas control plants showed no symptoms. Thereafter, the three isolates were subjected to morphological and molecular identification. Colonies were brown to gray in the center and white in the border with abundant aerial mycelia. Conidia were brown, obclavate to ovoid, produced in single or branched chains, one to seven transverse and zero to three longitudinal septa. Conidial size of the three isolates ranged between 11.2 to 43.1 × 6.0 to 12.7 μm (n = 50 for each isolate). Conidiophores of the three isolates were dark-brown, septate, branched or unbranched, and measured 27.0 to 147.65 × 2.71 to 4.54 μm (n = 50 for each isolate). Based on the morphological characteristics, the three isolates were identified as Alternaria spp. (Simmons 2007). For molecular identification, the internal transcribed spacer (ITS) region, RNA polymerase II second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and major allergen Alt-a-1 gene (Alt-a-1) were amplified using primer pairs ITS1/ITS4 (White et al. 1990), RPB2-5F2/RPB2-7cR (Sung et al. 2007), gpd1/gpd2 (Berbee et al. 1999), and Alt-for/Alt-rev (Hong et al. 2005), respectively. Sequence analyses of isolates OM10 (ITS: GenBank Accession no. OP358436; RPB2: OP377483; GAPDH: OP377468; Alt-a-1: OP377471), OM43 (ITS: OP358437; RPB2: OP377484; GAPDH: OP377469; Alt-a-1: OP377472), and OM45 (ITS: OP358438; RPB2: OP377485; GAPDH: OP377470; Alt-a-1: OP377473) showed 100%, 99.61 to 100%, 99.65%, and 100% identities with a reference strain CBS 107.38 of A. burnsii for ITS (KP124420), RPB2 (KP124889), GAPDH (JQ646305), and Alt-a-1 (KP123967), respectively. They also showed 100%, 99.61 to 100%, 99.65%, and 99.58% identities with an A. tomato strain CBS 103.30 for ITS (KP124445), RPB2 (KP124915), GAPDH (KP124294), and Alt-a-1 (KP123991), respectively. Based on the morphological and sequence characteristics, the pathogen causing New Guinea impatiens leaf spot was identified as a member of the Alternaria burnsii - A. tomato species complex. The diseased plants on NCHU campus were destroyed. There have been no reports of the disease in other landscape areas or nurseries. To our knowledge, this is the first report of A. burnsii - A. tomato species complex causing New Guinea impatiens leaf spot in Taiwan. Since the pathogens in the species complex have been documented causing diseases on several important economic crops and the New Guinea impatiens is widely planted in nurseries and landscapes, the host range and the significance of the pathogen in agro-ecosystem may warrant further investigations.

Alternaria alternata, the Causal Agent of a New Needle Blight Disease on Pinus bungeana

Pinus bungeana, an endangered and native coniferous tree species in China, has considerable timber and horticulture value. However, little is known about needle diseases in P. bungeana. A needle blight of P. bungeana has been observed in Hebei Province, China. P. bungeana inoculated with mycelial plugs of fungal isolates presented symptoms similar to those observed under field conditions. Ten virulent fungal isolates were identified as a small-spored Alternaria species based on morphological observations. Maximum likelihood and Bayesian phylogenetic analyses carried out with multilocus sequence typing of eight regions (SSU, LSU, ITS, gapdh, tef1, Alt a 1, endoPG, OPA10-2) assigned the pathogen to Alternaria alternata. This is the first report of A. alternata causing needle blight on P. bungeana in China.

First report of leaf blight caused by Alternaria alternata on Platanus acerifolia in China

Platanus acerifolia Willd. is widely planted in cities in China due to its strong adaptability to different environmental conditions. In August 2021, light brown, oval to circular, sunken spots were observed on leaves of P. acerifolia trees with 8-35% incidence, leading to severe necrosis and abscission of leaves on a street in Haidian district of Beijing (116°29'84''E, 39°95'93''N). Small pieces (5 mm×5 mm) were taken from the margin of diseased tissues, disinfected with 0.3% sodium hypochlorite for 2 min and 70% ethanol for 40 s, rinsed with sterile water, then plated on potato dextrose agar (PDA) and incubated at 28°C. After 4 days, representative isolates were transferred to new PDA plates. Four isolates with similar morphological characteristics were obtained and deposited in the culture collection (ID: DAA3, DAA5, DAA6 and DAA7) of our laboratory. Colonies on PDA were dense, fluffy, and light to dark gray, with a prominent white margin. Conidia formed in chains on the branched conidiophores, and were obpyriform to ellipsoid, 19.5-32.3×5.5-10.2 μm (average=26.4×7.1 µm, n=30) in size, with 3 to 5 transversal and 1 to 3 longitudinal septa. These morphological characteristics matched those of Alternaria spp. (Simmons 2007). Genomic DNA was extracted with modified CTAB method and the internal transcribed spacer (ITS) region, translation elongation factor 1-α (EF1-α), RNA polymerase II largest subunit (RPB2), glyceraldehyde 3 - dehydrogenase (GPD), endopolygalacturonase (EndoPG), as well as Alternaria major allergen (Alt a1) genes were amplified with primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), RPB2-5F/RPB2-7cR (Liu et al. 1999), gpd1/gpd2 (Berbee et al. 1999), PG3/PG2b (Andrew et al. 2009), and Alt-for/Alt-rev (Hong et al. 2005), respectively. The obtained sequences were deposited in GenBank (accession numbers: OM228653-OM228656, OM221523-OM221542). In a BLAST search, the sequences were 100% identical with corresponding sequences of A. alternata. Phylogenetic analysis based on combined sequences using maximum parsimony method showed that the four isolates clustered together with the type strain CBS 916.96 of A. alternata. For pathogenicity test, three healthy leaves of three one-year-old P. acerifolia plants were wounded with a sterile needle and inoculated with 20 µl of spore suspension (106 conidia/ml). Plants inoculated with sterile water were treated as control. The pathogenicity test was also conducted on the unwounded leaves. After 8 days of inoculation at 25°C and 90% RH with a 12-h photoperiod, the symptoms on spore suspension-inoculated leaves were similar to those observed on trees in the street, whereas the control leaves remained symptomless. Lesions on wounded leaves were larger than those on unwounded leaves. The assay was repeated twice with consistent results. The pathogen was re-isolated from symptomatic leaf tissues and identified based on morphological and rDNA-ITS sequencing, thus, fulfilling Koch's postulates. Examples of other tree species where Alternaria alternata has been reported to cause leaf blight were Ophiopogon japonicas in China (Wang et al. 2021) and Pistacia terebinthus in Spain (López-Moral et al. 2018). To our knowledge, this is the first report of A. alternata causing leaf blight on P. acerifolia in China. The identification could provide information for developing effective disease management strategies.

Phylogeny and mycotoxin profiles of pathogenic Alternaria and Curvularia species isolated from date palm in southern Tunisia

Date palm (Phoenix dactylifera L.), is a widely cultivated crop across North Africa, with about 300 thousand tons of fruits produced per year, in Tunisia. A wide range of fungal pathogens has been associated with leaf spots of date palm, Alternaria species being the most frequently reported. Symptomatic leaves of Deglet Nour variety were randomly collected in six localities in Tunisia. We used a polyphasic approach to identify 45 Alternaria and five Curvularia strains isolated from date palm, confirming their pathogenicity. Sequencing of allergen Alt-a1, glyceraldehyde-3-phosphate dehydrogenase (gpd) and calmodulin genes allowed us to group 35 strains in Alternaria Section, and 10 strains in Ulocladioides section. Based on sequencing analyses of Internal Transcribed Spacer, gpd and elongation factor genomic regions, all Curvularia strains were identified as Curvularia spicifera. All Alternaria and Curvularia species tested on date palm plantlets proved to be pathogenic, fulfilling Koch’s postulates. Although no significant differences were observed among the species, the highest mean disease severity index was observed in A. arborescens, while the lowest corresponded to C. spicifera. The capability of these strains to produce mycotoxins in vitro was evaluated. None of the A. consortialis strains produced any known Alternaria mycotoxin, whereas more than 80% of the strains included in Alternaria section Alternaria produced variable amounts of multiple mycotoxins such as alternariol, alternariol monomethyl ether, altenuene, tenuazonic acid and tentoxin. Curvularia spicifera strains produced detectable traces of fumonisins B. This work reports a first comprehensive multidisciplinary study of mycotoxigenic Alternaria species and C. spicifera associated with leaf spot disease on date palm.

Phylogenetic Analysis and Toxigenic Profile of Alternaria Species Isolated from Chickpeas (Cicer arietinum) in Argentina

Chickpeas are a very important legume due to their nutritional richness and high protein content and they are used as food for humans and as fodder for livestock. However, they are susceptible to fungal infections and mycotoxin contamination. The Alternaria genus was among the main fungi isolated from chickpea samples in Argentina. The species within this genus are able to produce several mycotoxins such as alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA). So, the objectives of this study were to identify the Alternaria spp. found in the chickpea samples and to determine their toxigenic potential in vitro. A phylogenetic analysis of 32 Alternaria strains was carried out based on the combined sequences of the tef1, gpd, and Alt a1 genes. All Alternaria strains clustered into the section Alternaria and were identified as A. alternata and A. arborescens. Further, the toxigenic profile of each strain was determined in a ground rice–corn steep liquor medium and analysed by HPLC. Most strains were able to co-produce AOH, AME, and TA. These results indicate a potential risk for human health when consuming chickpeas since this legume could be contaminated with Alternaria and its mycotoxins, which are not yet regulated in food.

Alternaria species in section Alternaria associated with Iris plants in China

Plants of the Iris genus have been widely cultivated because of their medicinal, ornamental, and economic values. It commonly suffers from Alternaria leaf spot or blight disease leading to considerable losses for their commercial values. During an investigation of 14 provinces or municipalities of China from 2014 to 2022, a total of 122 Alternaria strains in section Alternaria were obtained from diseased leaves of Iris spp.. Among them, 12 representative strains were selected and identified based on morphological characterization and multi-locus phylogenetic analysis, which encompassed the internal transcribed spacer of rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), an anonymous gene region (OPA10-2), and endopolygalacturonase gene (EndoPG). The strains comprised two known species of A. alternata and A. iridicola, and two new species of A. setosae and A. tectorum, which were described and illustrated here. Their pathogenicity evaluated on Iris setosa indicated that all the strains could induce typical Alternaria leaf spot or blight symptoms. The results showed that the virulence was variable among those four species, from which A. tectorum sp. nov. was the most virulent one, followed by A. setosae sp. nov., A. iridicola and A. alternata.

First Record of Alternaria pogostemonis: A Novel Species Causing Leaf Spots in Pogostemon cablin

Pogostemon cablin (Lamiaceae) is a component of traditional medicines in Southern China. The identification of P. cablin pathogens is essential for the production and development of this industry. During 2019–2020, a leaf spot on P. cablin was observed in Zhanjiang, Guangdong Province. The pathogen of the leaf spot was isolated and identified using morphological and phylogenetic methods. Phylogenetic analysis was performed using the internal transcribed spacer (ITS) region, glyceraldehyde-3-phosphate dehydrogenase (gapdh), RNA polymerase II (rpb2), translation extension factor 1-alpha (tef1), and Alternaria major allergen 1 (Alt-a1) genes. Based on phylogenetic and morphological studies, this was confirmed to be a novel species of Alternaria pogostemonis, with description and illustrations presented. The pathogenicity test of A. pogostemon was verified by Koch’s postulates as causing leaf spot disease. This is the first report of leaf spot disease in P. cablin caused by the Alternaria species. This study contributes to the knowledge of P. cablin leaf spot diseases.

First report of Alternaria alternata causing leaf spot of Cynanchum atratum Bunge in China

Cynanchum atratum Bunge belongs to Asclepiadaceae, and is distributed in North Korea, Japan and China. Its roots and rhizomes have antibacterial, antiviral, anti-inflammatory and anti-tumor effects. In July 2021, a leaf spot was observed in a 1.3 ha plantation of C. atratum in Harbin, Heilongjiang Province in China. The incidence was more than 85%. Initial symptoms were yellowing leaves with circular, or ellipsoid brown spots forming on leaf apexes or leaf margins. Small spots expanded and coalesced to form large circular or irregular, pale to light brown lesions, and leaves finally withered. Thirty, 5 × 5 mm, leaf pieces excised from the junction of symptomatic and healthy tissues were collected from different leaves with typical symptoms on ten plants, sterilized in 75% ethanol for 30s, then in 2% NaClO for 30s, rinsed in sterile water three times, placed on potato dextrose agar (PDA) plates, incubated for 5 days at 28°C in the dark, further purified by single spore method and transferred to new PDA and potato carrot agar (PCA) plates. Finally, 12 fungal isolates, most with similar morphology, were selected. After a 7-day incubation in the dark, colonies on PDA were 53 to 70 mm in diameter, circular and grayish brown. A total of 150 conidia were evaluated for morphology. Conidia were single or in chains, ovoid to inverted pear-shaped, with 2 to 6 transverse septa, 0 to 4 longitudinal or oblique septa, and measured 16.5 to 56.5μm × 9.0 to 16.5 μm. Beaks and supposititious beaks were mostly columnar, rarely conical, 0 to 22.5 μm × 2.5 to 4.0 μm. Conidiophores were solitary or clustered, pale brown, erect or bent, branched or unbranched, separated, 53.5 to 120.5 μm × 2.5 to 6.0 μm (Fig 1). Based on morphological characteristics, the fungus was identified as Alternaria alternata (Simmons 2007). Two representative isolates (BW and BW2) were used for molecular identification. Internal transcribed spacer rDNA regions (ITS), RNA polymerase II second largest subunit (RPB2), Alternaria major allergen (Alt a 1), translation elongation factor 1-alpha (TEF-1 α) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene were amplified and sequenced with the primers ITS1/ITS4 (White, et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou. 2013), Alt-F /Alt-R (Hong et al. 2005), TEF-F/TEF-R (Carbone and Kohn. 1999) and GDF/GDR (Templeton et al. 1992). The sequences obtained were deposited in GenBank (ITS: OM317915, ON534349; RPB2: OM296253, ON550475; Alt a 1: OM171248, O550474; TEF: OM238096, O550473; GAPDH: OM296217, ON550472). The phylogenetic analysis of maximum likelihood tree by MEGA 7 showed that the two isolates had 98% similarity with A. alternata CBS 916.96 (Fig 2). To test pathogenicity, 40-day-old plants were sprayed with spore suspensions (1×106 spores /mL) from 7-day-old cultures of BW and BW2. Each isolate was inoculated onto 3 leaves on 3 separate plants. Three other plants were sprayed with sterile distilled water as a control. The plants were incubated in the greenhouse (natural light, T: 25℃, H: 50%). After 15 days, the leaves turned yellow and irregular grayish spots appeared. The fungi reisolated from the inoculated leaves shared the same morphological and molecular features as A. alternata, fulfilling Koch's postulates. No fungi were isolated from the control group. This is the first time to report A. alternata causing leaf spot on C. atratum. Leaf spot can reduce the yields of C. atratum and this study provides a basis for the prevention and control of the disease.

Additions to the Inventory of the Genus Alternaria Section Alternaria (Pleosporaceae, Pleosporales) in Italy

The genus Alternaria is comprised of well-known plant pathogens causing various important diseases in plants, as well as being common allergens in animals and humans. Species of Alternaria can be found as saprobes associated with various dead plant materials. This research aims to enhance the taxonomy of saprobic species in the genus Alternaria found on grasses and herbaceous plants from Italy, based on multi-locus phylogenetic analyses of a concatenated ITS, LSU, SSU, tef1-α, rpb2, gapdh and Alt-a1 DNA sequence dataset combined with morphological characteristics. Multi-locus phylogenetic analyses demonstrated six novel species belonging to the genus Alternaria sect. Alternaria as: A. muriformispora sp. nov., A. obpyriconidia sp. nov., A. ovoidea sp. nov., A. pseudoinfectoria sp. nov., A. rostroconidia sp. nov. and A. torilis sp. nov. Detailed morphological descriptions, illustrations and an updated phylogenetic relationship of taxa in the genus Alternaria sect. Alternaria are provided herein.

New Species of Large-Spored Alternaria in Section Porri Associated with Compositae Plants in China

Alternaria is a ubiquitous fungal genus including saprobic, endophytic, and pathogenic species associated with a wide variety of substrates. It has been separated into 29 sections and seven monotypic lineages based on molecular and morphological data. Alternaria sect. Porri is the largest section, containing the majority of large-spored Alternaria species, most of which are important plant pathogens. Since 2015, of the investigations for large-spored Alternaria species in China, 13 species were found associated with Compositae plants based on morphological comparisons and phylogenetic analyses. There were eight known species and five new species (A. anhuiensis sp. nov., A. coreopsidis sp. nov., A. nanningensis sp. nov., A. neimengguensis sp. nov., and A. sulphureus sp. nov.) distributed in the four sections of Helianthiinficientes, Porri, Sonchi, and Teretispora, and one monotypic lineage (A. argyranthemi). The multi-locus sequence analyses encompassing the internal transcribed spacer region of rDNA (ITS), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen gene (Alt a 1), translation elongation factor 1-alpha (TEF1), and RNA polymerase second largest subunit (RPB2), revealed that the new species fell into sect. Porri. Morphologically, the new species were illustrated and compared with other relevant large-spored Alternaria species in the study. Furthermore, A. calendulae, A. leucanthemi, and A. tagetica were firstly detected in Brachyactis ciliate, Carthamus tinctorius, and Calendula officinalis in China, respectively.

First Report of Alternaria alternata Inciting Leaf Spot of Dangshen (Codonopsis pilosula) in China

As a commonly traditional Chinese medicine, the perennial herb Dangshen (Codonopsis pilosula) has superior curative effects including regulating immunity, strengthening the spleen, and tonifying lungs (Bai et al. 2020). To imitate natural ecological conditions, plants were grown on hillside fields with stems prostrate on the ground, tangle-up with each other. In August 2020, leaf spots were observed on C. pilosula in Wutai county, Shanxi province, China, and indicated a high disease incidence (70%-80%) in investigated fields (6.67 ha). Small brown necrotic spots, occasionally enclosed by chlorotic halos, were observed on leaves, stems, and sepals. For identification of the pathogen, 15 small pieces (5×5 mm) of symptomatic tissues from 5 randomly-collected diseased plants were surface sterilized, placed on potato dextrose agar plates, and incubated for 4 d in darkness at 25 °C to obtain the colonies. Cultures were purified by single spore isolation from these colonies. A total of 15 isolates named as Dcp-3, and Dcp-5~Dcp-18 were recovered. They produced ovoid or obclavate spores with 15.9-57.5×9.1-20.1 μm in size, 1-6 transverse septa, and 0-4 longitudinal septa. The conidial chains with 4 to 6 spores had numerous secondary and occasionally tertiary chains on potato carrot agar plates. Because all isolates had identical morphological traits, five genes from the representative isolate Dcp-3, actin (ACT), Alternaria major allergen (Alt a1), plasma membrane ATPase (ATP), histone 3 (H3), and rDNA ITS, were amplified with primer pairs ACTDF1/ACTDR1, Alt-for/Alt-rev, ATPDF1/ATPDR1, H3-1a/H3-1b, and ITS1/ITS4, respectively (Hong et al. 2005; Lawrence et al. 2013; Ma et al. 2020). BLASTn searches indicated species of Dcp-3 could not be accurately confirmed by rDNA ITS, ATP, ACT, and Alt a1 (GenBank accession nos. OM334894, OM362504, OM326344, OM362500). Phylogenetic analysis showed it was most closely related to Alternaria alternata, A. arborescens, and A. tenuissima based on concatenated sequences of above four genes. The H3 sequence (OM362508) shared 100% homology with that of A. alternata (MN481948). The phylogenetic tree using H3 also confirmed Dcp-3 as A. alternata. Heathly, two-year-old C. pilosula were transplanted to a greenhouse. A surface-sterilized leaf was sprayed with 50 μL spore suspension (106 conidia/mL) of Dcp-3. A leaf sprayed with isometric sterile water was used as controls. Each treatment used six plants (five leaves per plant). Plants were covered with sterilized plastic bags and incubated at 22 ℃. The test was repeated twice. A week later, control leaves were healthy, but brown necrotic spots similar to field symptoms emerged on treated leaves. The A. alternata isolates were re-isolated from the border of lesions, and confirmed by morphological and molecular characteristics mentioned above, fulfilling Koch's postulates. Leaf spot of C. pilosula caused by Septoria codonopsidis has been reported in China (Wang et al. 2011). However, to our knowledge, this is the first report of A. alternata inciting leaf spot of C. pilosula in China. Our report would promote growers to enhance the field management and consider associated strategies on controlling Alternaria leaf spot of C. pilosula.

First report of Alternaria alternata causing leaf blight on Actaea dahurica in China

In July 2019, leaf blight on Actaea dahurica, a plant with high value in Chinese traditional medicine, was discovered in a 2 ha planting area in Heilongjiang Province (129.6°E, 44.6°N), China. Disease incidence was 90% in the field. Symptoms consisted of irregular black spots with gray margins on both sides of the leaf, often at the leaf margin, mostly on the older leaves. To isolate the pathogen, ten diseased leaves were randomly collected, surface disinfested, and 5 x 5 mm segments were removed from the margin of the lesions. Leaf segments were placed onto potato dextrose agar (PDA) and incubated at 25 ℃ for 7 days. Ten pure cultures with the same morphological characteristics were obtained from three leaves showing typical symptoms. Cultures on PDA initially had a cottony mycelium, white-gray to gray. After two to three weeks of growth, mycelium color changed from gray to black. Conidiophores were clustered, dark at the base, tapering to the apex, born from simple sublates, unbranched, with 1 to 5 septa, and 70.4-530.3 × 5-7.5 μm in size. Conidia were 12.5-82.5 × 5.2-20.3 μm, usually in chains, had 2 to 8 transverse septa, 0 to 4 longitudinal or oblique septa, and a smooth brown surface. Simple, pale, vimineous or verrucous beaks developed from the apical cells with 0 to 4 septa. The morphological characteristics were consistent with Alternaria species (Simmons, 2007). To fulfill Koch's postulates, pathogenicity tests were carried out on three-month-old A. dahurica plants. A spore suspension was prepared from PDA cultures of isolates SM0101 and SM0102 and adjusted to 105 spores/mL using a hemocytometer. Each leaf was sprayed with 2 mL of the spore suspension, then incubated at 25 ℃ for 7 days. The same number of healthy A. dahurica plants were sprayed with sterile water as a control. After 7 days, small brown necrotic spots appeared on inoculated plants, but the control group showed no symptoms. A fungus with the same characteristics as that used for inoculation was re-isolated from the lesions. This experiment was replicated three times, and the results of each experiment were consistent. Genomic DNA was extracted from isolates SM0101 and SM0102 and used for PCR amplification of the rDNA internal transcribed spacer regions (ITS), RNA polymerase II gene (RPB2) and Alternaria allergen a 1 (Alt a 1) gene sequences using the primer pairs ITS1/ITS4 (White et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou, 2013) and Alt-for/Alt-rev (Hong et al. 2005), respectively. The ITS (OL703042, OL616086), RPB2 (OL703043, OL898416), and Alt a 1 sequences (OL616087, OL898415) were deposited in GenBank. The sequences obtained in this study had the highest match to corresponding sequences of Alternaria alternata CBS 916.96 (AF347031, KC584375, AY563301). For isolate SM0101 the matches were ITS (461/461 bp), RPB2 (897/985 bp), and Alt a 1 (488/488 bp). For isolate SM0202 the matches were ITS (457/457 bp), RPB2 (893/985 bp), and Alt a 1 (484/484 bp). A phylogenetic analysis was performed using MEGA7 software. The alignment included sequences from 16 ex-type Alternaria species and the two isolates causing leaf blight on A. dahurica. Branch supports were calculated with 1,000 bootstrap replicates, and phylogenetic inference was performed using the maximum likelihood estimation. The fungus isolated from A. dahurica clustered with A. alternata. This is the first report of A. alternata on A. dahurica in the world. This report will help to identify the disease symptoms in the field and provides a basis for research into the occurrence, distribution, and control of leaf blight on A. dahurica.

First report of leaf spot disease caused by Alternaria alternata on Lonicera caerulea L. in China

Relatively few studies investigating plant diseases in blue honeysuckle (Lonicera caerulea L.) have been conducted in China. In September 2021, a leaf spot disease was observed on approximately 10% of blue honeysuckle 'Lanjingling' leaves in a 0.02 ha field plantation in Tiekuang Street (124.36°E, 40.12°N) in Dandong City, Liaoning Province, China. The main symptom consisted of leaf spots with black mildew centers typically surrounded by yellow halos. Small pieces (3-4 mm) of the infected leaves were plated onto potato dextrose agar (PDA) medium as described by Wang et al. (2020) and six purified cultures were obtained through single spore culture on PDA. The observed conidia, consistent with the morphology of Alternaria alternata, were obpyriform and dark brown, measuring 5.8 to 15.3 μm × 7.9 to 42.5 μm, with 1-6 transverse septa and 0-3 longitudinal septa (n = 50) (Simmons 2007). For molecular verification, genomic DNA was extracted from a representative isolate LD-8. The ITS (GenBank OL454815), GPD (GenBank OL601993), TEF (GenBank OL538256), RPB2 (GenBank OL601966), and Alt (GenBank OL538257) genes were partially amplified with the respective primers ITS1/ITS4 (White et al. 1990), GPD1/GPD2 (Woudenberg et al. 2015), EFl-728F/EFI-986R (Carbone and Kohn 1999), RPB2-5F2/RPB2-7CR (Liu et al. 1999), and Alt-for/Alt-rev (Hong et al. 2005). BLAST analysis revealed that these genes shared 99%-100% identity with OK345332, MK451977, MN756011, KU933459, and MN655781, respectively. A greenhouse experiment was conducted using six, healthy two-year-old blue honeysuckle 'Lanjingling' plants to observe disease development (Mirzwa-Mróz et al. 2018). After 10 d, we noted typical leaf spot symptoms on inoculated leaves sprayed with a conidial suspension (106 spores/mL) while no symptoms were detected on uninoculated leaves. The same isolate, reisolated from infected leaves with the same morphological and molecular traits, was also identified as A. alternata, confirming Koch's postulates. The fungus was previously reported in cockscomb plants in Heilongjiang Province, China (Wang et al. 2020). To our knowledge, this is the first report of leaf spot disease caused by A. alternata in blue honeysuckle grown in China. This study will provide a basis for future development of effective protection strategies against blue honeysuckle leaf spot in China.

First Report of Alternaria alternata Causing Leaf Spot Disease on Daylily in China

Daylilies (Hemerocallis spp.; Xanthorrhoeaceae) originated from Eastern Asia and are widely cultivated as perennial ornamentals from the tropics to their native high latitudes. In June 2021, daylily cultivar 'Tao Hua Zhai' with leaf spot symptoms were found at the Shanghai Institute of Technology, Shanghai, China. The disease prevalence was about 14.5 % in a 33,000 m2 planting area indicated by survey statistics. Symptoms of the disease initially appeared as small, circular, brown spots on the leaves. As disease progressed, spots increased gradually until they were distributed uniformly over the lamina, the leaf tip became withered and the rest of the leaf became chlorotic. Symptomatic leaf tissue pieces (5 × 5 mm) from lesion margins were sterilized with 75 % ethanol for 1 min, rinsed three times with sterile distilled water, then incubated on potato dextrose agar (PDA) plates at 28 °C in the dark. A pure culture (ATHF-1) was obtained. Its upper surface on PDA was olive green with loose aerial hyphae, and its lower surface was brown.Conidiophores were brown, single or branched, producing numerous short chains conidia. Conidia were obclavate to obpyriform or ellipsoid, pale brown to dark brown, with a short cylindrical beak at the tip, contained 2-6 transverse septa and 0-4 longitudinal septa. The size of conidia were 15.9-47.3 µm × 7.6-16.6 µm (n=50), and length/width ratios were 1.51 to 4.92. Based on the morphological characteristics, the fungus was identified as Alternaria spp. (Simmons, 2007). For molecular characterization, three genes (the internal transcribed spacers [ITS], plasma membrane ATPase [ATPase] and major allergen Alt a 1) of ATHF-1 were amplified with primer pairs ITS1/ITS4 (White et al. 1990), ATPDF1/ATPDR1 (Lawrence et al. 2013) and Alt-for/Alt-rev (Hong et al. 2005), respectively. The sequences were deposited in GenBank (ITS, MZ983611; ATPase, MZ962978; Alt a 1, OK021654). Blastn searches showed the nucleotide sequences of ATHF-1 were highly similar to the reference sequences of Alternaria tenuissima (ITS, 99 % to KU982591; ATPase, 98 % to MT833928; Alt a 1, 100 % to MT109294). A phylogenetic tree based on the ITS, ATPase and Alt a 1 sequences was constructed by MEGA7.0, which showed that ATHF-1 was closely related to A. tenuissima and A. alternata. But according to Woudenberg et al. (2015), they were synonymized under the species name A. alternata. So, based on morphological and molecular characteristics, the fungus was identified as A. alternata. For pathogenicity tests, ten healthy two-month-old potted seedlings from tissue culture daylilies were sprayed with 20 ml of suspension (approximately 2×105 spores/ml), ten daylilies were used as controls and sprayed with sterile water. After covering with transparent plastic bags for 48 h to maintain humidity, the plants were placed in the greenhouse at 25 ℃ with 12 h photoperiod. The pathogenicity tests were repeated twice. Seven days after inoculation, lesions appeared on the plants inoculated with the pathogen, which were consistent with the symptoms observed in the field, while the controls remained symptomless. The morphological characteristics and gene sequences of the re-isolated strain from the diseased leaves were consistent with those of the inoculated strain. To our knowledge, this is the first report of A. alternata affecting leaf spot disease on daylily in China. Identification of the causal agent of the disease is important for developing effective disease management strategies. References: Hong, S.G., et al. 2005. Fungal Genet Biol. 42(2):119-129. https://doi.org/10.1016/j.fgb.2004.10.009 Lawrence, D.P., et al. 2013. Mycologia. 105(3):530-546. https://doi.org/10.3852/12-249 Simmons, E.G. 2007. Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, the Netherlands. White, T. J., et al. 1990. Amplification and Direct Sequencing of Fungal Ribosomal RNA Genes for Phylogenetics. PCR protocols: a guide to methods and applications, 18(1), 315-322. Woudenberg J.H.C., et al. 2015. Studies in Mycology. 82(82):1-21. https://doi.org/10.1016/j.simyco.2015.07.001.

First Record of Alternaria alternata causing necrosis of Thuja (Thuja occidentalis) in Kazakhstan

Thuja is one of the ornamental plants used for landscaping parks and health resorts. The plant is distinguished by a pyramidal and conical crown shape and the presence of many thin branches with scale-shaped needles, green all year round. In addition, this plant has a number of antimicrobial properties, which affects the popularity of the plant in landscaping the health resort territory (Bakht et al. 2020, Chindyaeva et al. 2020). In January 2020, symptomatic Thuja plants were observed in Southern Kazakhstan. Symptoms included distortion of the crown. External examination of the trees revelaed the presence of white fluffy mycelium on Thuja branches. The branches acquired a yellow color with a necrotic lesion developing below the affected area. Samples of infected branches from different Thuja trees (n = 13) were collected. The infected branches were cut into small pieces (5 × 5 mm), washed in 70% ethanol for 30 min, and then rinsed three times with sterile distilled water. Later, these pieces were placed on Sabouraud's medium (Laboratorios Conda S.A., Spain) and incubated at 28°C for 7 days. Yellow-green colonies grew from the pieces of wood. The colonies had a light gray-whitish aerial mycelium. Conidia (n = 35) were pale to dark brown in color, irregular and ellipsoid to ovoid conical in shape. The size of the conidia varied from 5 to 25 µm × 6 to 12 µm (n = 40) with longitudinal and transverse septations. These morphological characters were previously described and corresponded to the Alternaria alternata (Simmons et al. 2007). Genomic DNA was extracted from mycelium using the liquid nitrogen and phenol-chloroform extraction method (Butler 2012). A 568 bp product of the Alt a1 gene and 472 bp product of the calmodulin protein-coding gene was amplified using following primer pairs Alt-for/Alt-rev (Hong et al. 2005) and CALDF1/CALDR1, respectively (Lawrence et al. 2013) (Integrated DNA Technologies, Inc., Coralville, IA, USA). The PCR reaction was done in a SimpliAmp thermal cycler (Applied biosystems, Waltham, MA, USA) under the following conditions: initial denaturation at 94 °C for 1 min, 35 cycles at 94°C for 30 s to denature, 57°C for 1 min for annealing, and 72°C for 1 min for extension. A final extension step at 72°C for 10 min was also included. The sequencing was done using BigDye® Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems) and the sequence was deposited in GenBank with accession no. OL542696 calmodulin). These sequences were compared with other sequences in the GenBank by using the BLAST analysis (MZ222274.1 and MN473132.1). The phylogenetic analysis was carried out with MEGA 6 software (The Pennsylvania State University, University Park, PA, USA). To confirm the pathogenicity, 10 thuja branches from healthy trees from another area without visible pathologies were inoculated with a suspension of conidia (100 conidia/ml; obtained from 2-week-old cultures). Control samples were inoculated with sterile distilled water. The inoculated branches were placed in sterile plastic containers to maintain high humidity and incubated for 10 days at 28°C. After 7 days, irregular shaped lesions and fungal growth was observed at the site of inoculation. The affected area gradually increased in size with simioar symptomatology to that described above. Re-isolation of the pathogen and identification based on morphological features and sequencing confirmed the presence of the A. alternata pathogen. To our knowledge, this is the first report of A. alternata causing branches of thuja in Kazakhstan. Thuja is a rare plant species for this region; the cost and care are expensive. This case will allow timely diagnosis of the disease caused by Alternaria spp. in the future. It is necessary to develop preventive measures and a protocol for the treatment of thuja from a fungal infection. Bakht, J., 2020. Antibacterial activity of the crude extracts from medicinally important Thuja occidentalis. Pak J Pharm Sci. 33(2): 627-630. PMID: 32276908. Butler, J.M., 2012. Chapter 2 - DNA extraction methods. pp. 29-47 in Butler JM (Ed) Advanced topics in forensic DNA typing: Methodology. San Diego, Academic Press. doi: 10.1016/C2011-0-04189-3. Chindyaeva., L.N., et al. 2020. Comparative assessment of the phytoncidity of woody plants in the selection of species for landscaping: the possibility of use in sanatorium-and-spa practice. Vopr Kurortol Fizioter Lech Fiz Kult. 97(4): 44-51. Russian. doi: 10.17116/kurort20209704144. Hong, S.G. et al. 2005. Alt a1 allergen homologs from Alternaria and related taxa: analysis of phylogenetic content and secondary structure. Fungal Genet Biol 42:119-129. doi:10.1016/j.fgb.2004.10.009 Lawrence, D.P. et al. 2013. The sections of Alternaria: formalizing species-group concepts. Mycologia 105: 530-546. DOI: 10.3852/12-249. Simmons, E. G., 2007. Alternaria: An Identification Manual. CBS, Fungal Biodiversity Center, Utrecht, Netherlands.

New Insight in the Occurrence of Early Blight Disease on Potato Reveals High Distribution of Alternaria solani and Alternaria protenta in Serbia

Early blight is an economically important disease of potato worldwide. Understanding which fungal pathogens are the causal agents of early blight and their distribution on the same host is essential to finding the best strategy for the control of this disease. Previous studies have shown that Alternaria solani is the main early blight pathogen parasitizing potato. Here, we analyzed genetic and phenotypic diversity in isolates of Alternaria spp. covering all potato production areas in Serbia. We showed that the four species of Alternaria were found in areas with different distributions of the species. The occurrence of Alternaria spp. was studied by analyzing isolates from symptomatic potato leaves during multiyear sampling. In addition to Alternaria solani, we detected three more large-spored species identified as A. linariae (syn. A. tomatophila), A. protenta, and A. grandis that were involved in early blight disease on naturally infected potato leaves in Serbia. Differentiation of species was supported by phylogeny obtained from the DNA sequences of the GAPDH, calmodulin and Rpb2 genes. Our findings present a new perspective into the population structure of large-spored Alternaria species associated with early blight disease. Within the groups of large-spored Alternaria present in Serbia, evidence of A. protenta at high frequency reveals new insight into the contribution of Alternaria species in early blight disease. This work opens new perspectives for early blight management, while the distribution of different species on the same host suggests that the etiology of disease could depend on crop organization and the presence of other Alternaria hosts in close proximity to potato plants.

Fungal Allergen and Mold Allergy Diagnosis: Role and Relevance of Alternaria alternata Alt a 1 Protein Family

Alternaria is a genus of worldwide fungi found in different habitats such as soil, the atmosphere, plants or indoor environments. Alternaria species are saprobic-largely involved in the decomposition of organic material-but they can also act as animal pathogens, causing disease in humans and animals, developing infections, toxicosis and allergic diseases. A. alternata is considered one of the most important sources of fungal allergens worldwide and it is associated with severe asthma and respiratory status. Among the A. alternata allergens, Alt a 1 is the main sensitizing allergen and its usefulness in diagnosis and immunotherapy has been demonstrated. Alt a 1 seems to define a protein family that can be used to identify related pathogenic fungi in plants and fruits, and to establish taxonomic relationships between the different fungal divisions.

First Report of Postharvest Fruit Rot in Solanum muricatum Aiton Caused by Alternaria alternata in southwest China

Solanum muricatum is native to South America and well known for its sweet, attractive, nutritious fruits. S. muricatum has been cultivated in China since the 1980s and increasingly popular (Li et al. 2015). In November 2021, an unknown fruit rot was observed in Shilin County of Yunnan Province (24.77 °N, 103.28 °E). The incidence of this disease was about 16% of 500 postharvest S. muricatum fruits after 7 d in storage room (25°C, 90% relative humidity). The initial symptoms were small brown spots on the fruit surface, which gradually expanded into irregular brown or black lesions, and gray-white mold developed in the center of the lesions, eventually the fruit turned rot. To isolate the pathogen, ten fruits with typical symptoms were collected and surface-sterilized with 75% ethanol for 45 s. Small fragments (5 × 5 mm) from the margin of lesions on fruit were disinfected with 1% sodium hypochlorite for 60 s, washed three times with sterile water then transferred to potato dextrose agar (PDA), and incubated at 28 ± 1℃ for 3 days (Li et al. 2022). Two fungal isolates with the same morphology were obtained and purified by single-spore isolation method. The colony was covered with thick fluffy aerial mycelia and the center was dark brown or black with white margins. Conidia were brown, pyriform or ellipsoid, with 1 to 3 longitudinal and 2 to 6 transverse septa, 15.12 to 34.01 × 6.90 to 12.73 μm (21.22 × 9.69 μm on average, n=50) in size. These morphological characteristics were consistent with Alternaria alternata (Li et al. 2015; Xiang et al. 2021; Alberto. 1992). For molecular identification, genomic DNA was extracted from a representative isolate, and primers ITS1/ITS4 (Gardes et al. 1993), TEF-F/TEF-R (Lawrence et al. 2013), Alt-F/Alt-R (Hong et al. 2005), GPD-F/GPD-R (Berbee et al. 1999) and EPG-F/EPG-R (Peever et al. 2004) were used to amplify the internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF), Alternaria major allergen (Alt a1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and endo-polygalacturonase (endoPG), respectively. The obtained DNA sequences (ITS: OM049821; TEF: OM069656; Alt a1: OM069655; GAPDH: OM069654 and endoPG: OM069653) showed over 99% homology with that of A. alternata (GenBank Accession No. MN856355.1 (565/573 bp); MN258023.1 (267/267 bp); KY923227.1 (491/501 bp); LC131645.1 (608/609 bp) and MN698284.1 (452/454 bp)). A phylogenetic tree based on the combined ITS, TEF, Alt a1, GAPDH, and endoPG sequences using the maximum likelihood methods with Kimura 2-parameter model, bootstrap nodal support for 1000 replicates in MEGA7.0 (Li et al. 2019) revealed that the isolate was assigned to A. alternata. To confirm pathogenicity, 10 μL spore suspension (1.0 × 106 conidia/ml) obtained from 7-day-old PDA cultures of each isolate were inoculated on 15 needle-wounded and 15 non-wounded surface-disinfected fruits, respectively. Healthy fruits were inoculated with sterile water as controls and the experiment was repeated 3 times. All fruit were incubated at 25 ± 1℃, 90% relative humidity. After 7 days, all the wounded and non-wounded fruit inoculated with A. alternata showed similar symptoms to those observed on the previously fruits, while the control fruits remained healthy. The same pathogen was again isolated from the inoculated fruits, thus Koch's postulates were fulfilled. A. alternata causing fruit rot of Prunus avium and Mangifera indica in China were reported in previous studies (Ahmad et al. 2020; Liu et al. 2019). As far as we know, this is the first report of postharvest fruit rot on S. muricatum caused by A. alternata in southwest China. This work provides a basis for the development of control strategies of the disease in the future.

Alternaria spp. Associated with Leaf Blight of Maize in Heilongjiang Province, China

Maize (Zea mays L.) is a major economic crop worldwide. Maize can be infected by Alternaria species causing leaf blight that can result in significant economic losses. In this study, 168 Alternaria isolates recovered from symptomatic maize leaves were identified based on morphological characteristics, pathogenicity, and multilocus sequence analyses of the genes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the internal transcribed spacer of ribosomal DNA (rDNA ITS), the RNA polymerase II second largest subunit (RPB2), and histone3 (HIS3). Maize isolates grouped to four Alternaria species including Alternaria tenuissima, A. alternata, A. burnsii, and Alternaria sp. Notably, A. tenuissima (71.4%) was the most prevalent of the four isolated species, followed by A. alternata (21.5%), Alternaria sp. (4.1%), and A. burnsii (3.0%). Pathogenicity tests showed that all four Alternaria species could produce elliptic to nearly round, or strip, lesions on leaves of maize, gray-white to dry white in the lesion centers and reddish-brown at the edges. The average disease incidence (58.47%) and average disease index (63.55) of maize leaves inoculated with A. alternata were significantly higher than levels resulting from A. tenuissima (55.28% and 58.49), Alternaria sp. (55.34% and 58.75), and A. burnsii (56% and 55). Haplotype analyses indicated that there were 14 haplotypes of A. tenuissima and five haplotypes of A. alternata in Heilongjiang Province and suggested the occurrence of a population expansion. Results of the study showed that Alternaria species associated with maize leaf blight in Heilongjiang Province are more diverse than those that have been previously reported. This is the first report globally of A. tenuissima, A. burnsii, and an unclassified Alternaria species as causal agents of leaf blight on maize.