Molecular phylogeny of Cytospora species associated with canker diseases of fruit and nut crops in California, with the descriptions of ten new species and one new combination

Evolutionary divergence of CXE gene family in green plants unveils that PtoCXEs overexpression reduces fungal colonization in transgenic Populus

Plant enzymes significantly contribute to the rapidly diversified metabolic repertoire since the colonization of land by plants. Carboxylesterase is just one of the ubiquitous, multifunctional and ancient enzymes that has particularly diversified during plant evolution. This study provided a status on the carboxylesterase landscape within Viridiplantae. A total of 784 carboxylesterases were identified from the genome of 31 plant species representing nine major lineages of sequenced Viridiplantae and divided into five clades based on phylogenetic analysis. Clade I carboxylesterase genes may be of bacterial origin and then expanded and diversified during plant evolution. Clade II was first gained in the ancestor of bryophytes after colonization of land by plants, Clade III and Clade IV in ferns which were considered the most advanced seedless vascular plants, while Clade V was gained in seed plants. To date, the functions of carboxylesterase genes in woody plants remain unclear. In this study, 51 carboxylesterase genes were identified from the genome of Populus trichocarpa and further divided into eight classes. Tandem and segmental duplication events both contributed to the expansion of carboxylesterase genes in Populus. Although carboxylesterase genes were proven to enhance resistance to pathogens in many herbaceous species, relevant researches on forest trees are still needed. In this study, pathogen incubation assays showed that overexpressing of six Class VI carboxylesterases in Populus tomentosa, to a greater or lesser degree, reduced colonization of detached leaves by fungus Cytospora chrysosperma. A significant difference was also found in functional divergence patterns for genes derived from different gene duplication events. Functional differentiation of duplicated carboxylesterase genes in Populus was proved for the first time by in vivo physiological analysis. The identification of the potentially anti-fungal PtoCXE06 gene also laid a theoretical foundation for promoting the genetic improvement of disease-resistance traits in forest trees.

Fungal Trunk Diseases Causing Decline of Apricot and Plum Trees in the Czech Republic

Fungal trunk diseases (FTDs) have been a significant threat to the global stone fruit industry. FTDs are caused by a consortium of wood-decaying fungi. These fungi colonize woody tissues, causing cankers, dieback, and other decline-related symptoms in host plants. In this study, a detailed screening of the fungal microbiota associated with the decline of stone fruit trees in the Czech Republic was performed. The wood fragments of plum and apricot trees showing symptoms of FTDs were subjected to fungal isolation. The partial internal transcribed spacer region, partial beta-tubulin, and translation elongation factor 1-α genes were amplified from genomic DNA extracted from fungal cultures. All isolates were classified, and the taxonomic placement of pathogenic strains was illustrated in phylogenetic trees. The most abundant pathogenic genus was Dactylonectria (31%), followed by Biscogniauxia (13%), Thelonectria (10%), Eutypa (9%), Dothiorella (7%), Diplodia (6%), and Diaporthe (6%). The most frequent endophytic genus was Aposphaeria (17%). The pathogenicity of six fungal species (Cadophora daguensis, Collophorina africana, Cytospora sorbicola, Dothiorella sarmentorum, Eutypa lata, and E. petrakii var. petrakii) to four Prunus spp. was evaluated, and Koch's postulates were fulfilled. All tested isolates caused lesions on at least one Prunus sp. The most aggressive species was E. lata, which caused the largest lesions on all four tested Prunus spp., followed by E. petrakii var. petrakii and D. sarmentorum. Japanese plum (Prunus salicina) and almond (P. amygdalus) were the most susceptible hosts, while apricot (P. armeniaca) was the least susceptible host in the pathogenicity trial.

Determining the Main Infection Courts in Sweet Cherry Trees of the Canker Pathogens Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata

The major fungal canker pathogens causing branch dieback of sweet cherry trees in California include Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata. These pathogens have long been known to infect cherry trees mainly through pruning wounds. However, recent field observations revealed numerous shoots and fruiting spurs exhibiting dieback symptoms with no apparent pruning wounds or mechanical injuries. Accordingly, this study was conducted to assess the incidence of the three pathogens in symptomatic terminal shoots and dying fruiting spurs, in addition to the wood below pruning wounds in branches. Surveys were conducted in five sweet cherry orchards across three counties in California. We also investigated the possibility that leaf scars, bud scars, and wounds resulting from fruit picking could serve as infection courts for Cal. pulchella, Cyt. sorbicola, and E. lata by means of artificial inoculations in the field. Orchard surveys revealed that Cal. pulchella had the highest pathogen incidence below pruning wounds in branch samples, followed by Cyt. sorbicola and E. lata. Among terminal shoots with dieback symptoms and dying fruiting spurs, Cyt. sorbicola was the most prevalent, followed by Cal. pulchella. Results from field inoculations indicated that fruit-picking wounds could serve as important infection courts for Cal. pulchella, Cyt. sorbicola, and E. lata, with average pathogen recovery of 41.5, 63, and 36.2%, respectively. Results also indicated that leaf and bud scars could serve as an entry site for Cyt. sorbicola, although recovery was relatively low. The present study is the first to identify harvest-induced wounds on fruiting spurs of sweet cherry as an important infection court of Cal. pulchella, Cyt. sorbicola, and E. lata.

Taxonomy and pathogenicity of fungi associated with oak decline in northern and central Zagros forests of Iran with emphasis on coelomycetous species

Oak decline is a complex disorder that seriously threatens the survival of Zagros forests. In an extensive study on taxonomy and pathology of fungi associated with oak decline in the central and northern part of Zagros forests, 462 fungal isolates were obtained from oak trees showing canker, gummosis, dieback, defoliation, and partial or total death symptoms. Based on inter-simple sequence repeat (ISSR) fingerprinting patterns, morphological characteristics, and sequences of ribosomal DNA (28S rDNA and ITS) and protein coding loci (acl1, act1, caM, tef-1α, rpb1, rpb2, and tub2), 24 fungal species corresponding to 19 genera were characterized. Forty percent of the isolates were placed in eight coelomycetous species from seven genera, namely, Alloeutypa, Botryosphaeria, Cytospora, Didymella, Gnomoniopsis, Kalmusia, and Neoscytalidium. Of these, four species are new to science, which are introduced here as taxonomic novelties: Alloeutypa iranensis sp. nov., Cytospora hedjaroudei sp. nov., Cytospora zagrosensis sp. nov., and Gnomoniopsis quercicola sp. nov. According to pathogenicity trials on leaves and stems of 2-year-old Persian oak (Quercus brantii) seedlings, Alternaria spp. (A. alternata, A. atra, and A. contlous), Chaetomium globosum, and Parachaetomium perlucidum were recognized as nonpathogenic. All coelomycetous species were determined as pathogenic in both pathogenicity trials on leaves and seedling stems, of which Gnomoniopsis quercicola sp. nov., Botryosphaeria dothidea, and Neoscytalidium dimidiatum were recognized as the most virulent species followed by Biscogniauxia rosacearum.

Morphology and phylogeny of Cytospora (Cytosporaceae, Diaporthales) species associated with plant cankers in Tibet, China

During our biodiversity investigations in Tibet, China, typical Cytospora canker symptoms were observed on branches of hosts Myricariapaniculate, Prunuscerasifera and Sibiraeaangustata. Samples were studied, based on morphological features coupled with multigene phylogenetic analyses of ITS, act, rpb2, tef1 and tub2 sequence data, which revealed two new species (Cytosporamyricicolasp. nov. and C.sibiraeicolasp. nov.) and a known species (C.populina). In addition, Cytosporapopulina is newly discovered on the host Prunuscerasifera and in Tibet.

Apple crown and collar canker and necrosis caused by Cytospora balanejica sp. nov. in Iran

Apple is the most important fruit tree in West Azarbaijan province of Iran. In a survey of apple orchards, a disease with crown and collar canker and necrosis symptoms was observed in three young apple orchards in Urmia, affecting 15% and 1% of 'Red Delicious' and 'Golden Delicious' cultivars, respectively. A fungus with typical characteristics of the asexual morph of Cytospora was regularly isolated from the diseased tissues. Morphological characteristics and phylogenetic analyses inferred from the combined dataset of the ITS-rDNA, parts of LSU, tef1-α, rpb2, and act1 genes revealed that the isolates represent a new species of Cytospora, described herein as Cytospora balanejica sp. nov.. The pathogenicity of all isolates was confirmed on apple cv. 'Red Delicious' based on Koch's postulates. Also, the reaction of 12 other apple cultivars was assessed against five selected isolates with the highest virulence. The results showed that except for cv. 'Braeburn', which did not produce any symptoms of the disease, the other 11 cultivars showed characteristic disease symptoms including sunken and discolored bark and wood. The mean length of the discolored area was different among the 11 so-called susceptible cultivars, hence cvs. 'M4' and 'Golden Delicious' showed the highest and the lowest lesion length, respectively. Moreover, the aggressiveness of the five tested isolates was different, and the isolates BA 2-4 and BA 3-1 had the highest and lowest aggressiveness, respectively. Based on our observations on the potential ability of the fungus to cause disease on young and actively growing apple trees, it will be a serious threat to apple cultivation and industry.

Multigene phylogeny and morphology reveal three new species of Cytospora isolated from diseased plant branches in Fengtai District, Beijing, China

Members of Cytospora include saprobes, endophytes and important plant pathogens, which are widely distributed on various wood hosts and have a wide global distribution. In this study, the species definitions were conducted, based on multigene phylogeny (ITS, act, rpb2, tef1-α and tub2 genes) and comparisons of morphological characters. A total of 22 representative isolates obtained from 21 specimens in Fengtai District of Beijing City were identified as seven species of Cytospora, including four known species (C.albodisca, C.ailanthicola, C.euonymina, C.haidianensis) and three novel species (C.fengtaiensis, C.pinea, C.sorbariae). The results provide an understanding of the taxonomy of Cytospora species associated with canker and dieback diseases in Fengtai District, Beijing, China.

Effects of Temperature on Spore Germination and Mycelial Growth of Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata Isolates Associated with Sweet Cherry Canker Diseases

Although fungal canker diseases constitute a limiting factor to orchard productivity and longevity, little is known about the effects of temperature on spore germination and mycelial growth of the fungal causal agents. Accordingly, the germination of spores and colony growth of Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata were evaluated after incubation on 2% water agar and 4% potato dextrose agar, respectively, at 5, 10, 15, 20, 25, 30, 35, and 40°C. Temperature optima for spore germination and mycelial growth were derived from nonlinear models fitted to germination rates and colony diameter data. The optimal temperatures for spore germination of Cal. pulchella were 28.5°C for ascospores and 29.2°C for conidia. The optimal temperatures for Cyt. sorbicola conidia and E. lata ascospore germination were 25.8 and 23.1°C, respectively. The germination of ascospores and conidia of Cal. pulchella at temperatures below 15°C required an incubation time of at least 72 h. Ascospores of E. lata and conidia of Cyt. sorbicola germinated at 10°C after 36 h. The optimal temperature for colony growth of Cal. pulchella was 24.6°C, whereas it was 21.7°C for both Cyt. sorbicola and E. lata. Our study indicates that temperature requirements for basic biological functions are higher for Cal. pulchella than for Cyt. sorbicola and E. lata. The overall higher temperatures of California relative to other cherry-producing regions in the United States or worldwide could explain the prevalence of Calosphaeria canker in the state. Conversely, Cyt. sorbicola and E. lata appear better adapted to cooler temperatures.

Seasonal Susceptibility of Sweet Cherry Pruning Wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata

Fungal canker pathogens commonly infect trees at pruning wounds leading to branch dieback and loss of productivity in sweet cherry orchards. However, the seasonal susceptibility of sweet cherry pruning wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata is not well understood. This study compared the susceptibility of sweet cherry pruning wounds made during the dormant season (January) and the postharvest season (late May to June) to infection by main canker pathogens in California. Field trials were conducted in three cherry orchards and trees were pruned at the different periods over 2 years. Fresh pruning wounds were inoculated with spores of each pathogen, and pathogen recovery was assessed through microbiological isolations at 3 to 4 months after inoculations. Pruning wounds made in late May and June resulted in significantly higher infection by Cal. pulchella compared to pruning wounds made in January. Pruning wounds made during both seasons were generally equally susceptible to Cyt. sorbicola and E. lata infections. However, there was one orchard where dormant pruning wounds were more susceptible to infection by E. lata and there was one particularly cold winter where Cyt. sorbicola did not infect pruning wounds. Overall, our findings suggest that Cal. pulchella infections of cherry pruning wounds are more likely to occur during periods of warm temperatures such as late spring and early summer. However, infections by Cyt. sorbicola and E. lata can occur year-round if inoculum is present and if winter temperatures are not abnormally low for California. Finally, our results suggest that the emergence of Cal. pulchella as a major canker pathogen of sweet cherry in California may be the result of a shift from dormant to after-harvest pruning of sweet cherry trees.

Genetic Diversity and Fungicide Sensitivity of Cytospora plurivora on Peach

Cytospora plurivora D.P. Lawr., L.A. Holland & Trouillas has been associated with recent premature peach tree decline in South Carolina, but very little is known about the pathogen or chemical control options. Ninety-three C. plurivora isolates were collected in 2016 and 2017 from 1-year-old peach wood and symptomatic scaffold limbs, respectively, from orchards in six towns in South Carolina. Six unique genotypes were identified based on substantial ITS1-5.8S-ITS2 sequence variability and classified G1 to G6. Three of the genotypes (G2, G3, and G6) were isolated in high frequency in multiple locations of both years. In addition to the genotypic variation, multiple phenotypes were observed between and within genotype groups. Species identity was determined using additional gene loci: ACT, TUB, and EF, and isolates were found to belong to C. plurivora for all genotype groups. All tested genotypes were sensitive to thiophanate-methyl (FRAC 1) but exhibited slightly lower sensitivity to propiconazole and difenoconazole (both FRAC 3). Boscalid, fluopyram (both FRAC 7s), azoxystrobin, and pyraclostrobin (both FRAC 11s) were ineffective in vitro at inhibiting mycelial growth of C. plurivora genotypes. Field inoculation of peach and nectarine trees revealed that all genotypes developed twig cankers with differences in virulence. G1 was most virulent, and G6 was least virulent. This study provides a link between the C. plurivora genetic variability and virulence and provides fungicide sensitivity information that could be used to improve disease management practices.

First Report of Olive Branch Dieback in Croatia Caused by Cytospora pruinosa Défago

Olive (Olea europaea L.) is a very important crop grown in the Mediterranean part of Croatia. Olive branch and fruit dieback symptoms were observed in two olive orchards in Istria, Croatia. The samples from symptomatic trees were collected and brought to the laboratory for analysis. Based on their morphological characterization, isolated fungi were identified as Cytospora sp. Two representative isolates (one per orchard) were taken for molecular analysis, and based on DNA sequence data of the ITS and TUB gene regions, and phylogenetic analysis of the sequences, the isolates were identified as Cytospora pruinosa Défago. To determine pathogenicity, pathogenicity tests were conducted on detached olive branches and two-year-old olive trees in the greenhouse. This is the first report of C. pruinosa causing olive branch and fruit dieback in Croatia.

The Influence of Cone Age and Urbanisation on the Diversity and Community Composition of Culturable Seed Fungal Endophytes within Native Australian Banksia ericifolia L.f. subsp. ericifolia

Seed fungal endophytes play a crucial role in assisting the overall health and success of their host plant; however, little is known about the factors that influence the diversity and composition of these endophytes, particularly with respect to how they change over time and within urban environments. Using culturing techniques, morphological analyses, and Sanger sequencing, we identified the culturable seed fungal endophytes of Banksia ericifolia at two urban and two natural sites in Sydney, New South Wales, Australia. A total of 27 Operational Taxonomic Units were obtained from 1200 seeds. Older cones were found to contain, on average, more colonised endophytes than younger cones. Species richness was also significantly influenced by cone age, with older cones being more speciose. Between urban and natural sites, the overall community composition did not change, although species richness and diversity were greatest at urban sites. Understanding how these endophytes vary in time and space may help provide an insight into the transmission pathways used and the potential role they play within the development and survival of the seed. This knowledge may also be crucial for restoration purposes, especially regarding the need to consider endophyte viability in ex situ seed collection and storage in seed-banking practices.

Profiling Walnut Fungal Pathobiome Associated with Walnut Dieback Using Community-Targeted DNA Metabarcoding

Walnut dieback can be caused by several fungal pathogenic species, which are associated with symptoms ranging from branch dieback to fruit necrosis and blight, challenging the one pathogen-one disease concept. Therefore, an accurate and extensive description of the walnut fungal pathobiome is crucial. To this end, DNA metabarcoding represents a powerful approach provided that bioinformatic pipelines are evaluated to avoid misinterpretation. In this context, this study aimed to determine (i) the performance of five primer pairs targeting the ITS region in amplifying genera of interest and estimating their relative abundance based on mock communities and (ii) the degree of taxonomic resolution using phylogenetic trees. Furthermore, our pipelines were also applied to DNA sequences from symptomatic walnut husks and twigs. Overall, our results showed that the ITS2 region was a better barcode than ITS1 and ITS, resulting in significantly higher sensitivity and/or similarity of composition values. The ITS3/ITS4_KYO1 primer set allowed to cover a wider range of fungal diversity, compared to the other primer sets also targeting the ITS2 region, namely, GTAA and GTAAm. Adding an extraction step to the ITS2 sequence influenced both positively and negatively the taxonomic resolution at the genus and species level, depending on the primer pair considered. Taken together, these results suggested that Kyo set without ITS2 extraction was the best pipeline to assess the broadest fungal diversity, with a more accurate taxonomic assignment, in walnut organs with dieback symptoms.

Identification and pathogenicity of six fungal species causing canker and dieback disease on golden rain tree in Beijing, China

Golden rain trees (Koelreuteria paniculata) are largely cultivated because of their important ornamental, medicinal, and economic value. However, they are affected by canker and dieback disease to a large extent. To determine the fungi associated with canker and dieback disease of golden rain trees, isolations were obtained from diseased branches and twigs during 2019 and 2020 in greenbelts and nurseries in Beijing, China. Isolates were identified as six species (Allocryptovalsa castaneicola, Botryosphaeria dothidea, Cytospora koelreutericola sp. nov., Dothiorella acericola, Eutypella citricola, and Peroneutypa scoparia) based on morphological features and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2. The results of pathogenicity tests indicated that all fungi produced discoloration and Botryosphaeria dothidea was highly aggressive to golden rain tree. In conclusion, this study explored the taxonomy, phylogeny, and pathogenicity of different fungal species associated with canker and dieback disease on golden rain tree and provided fundamental knowledge to improve disease management.

Identification and Characterization of Neofusicoccum stellenboschiana in Branch and Twig Dieback-Affected Olive Trees in Italy and Comparative Pathogenicity with N. mediterraneum

For about a decade, olive groves in Apulia (Southern Italy) have been progressively destroyed by Olive Quick Decline Syndrome (OQDS), a disease caused by the bacterium Xylella fastidiosa subsp. pauca (Xfp). Recently, we described an additional wilting syndrome affecting olive trees in that area. The botryosphaeriaceous fungus Neofusicoccum mediterraneum was found associated with the diseased trees, and its high virulence toward olive trees was demonstrated. Given the common features with Branch and Twig Dieback (BTD) of olive tree, occurring in Spain and California, we suggested that the observed syndrome was BTD. During our first survey, we also found a botryosphaeriaceous species other than N. mediterraneum. In the present article, we report the morphological and molecular characterization of this fungal species which we identified as Neofusicoccum stellenboschiana. In the study, we also included for comparison additional N. stellenboschiana isolates obtained from olive trees in Latium and Tuscany region (Central Italy). The occurrence of N. stellenboschiana in olive trees is reported here for the first time in the northern hemisphere. The pathogenicity and virulence were tested in nine inoculation trials, where the Apulian N. stellenboschiana isolate was compared with the isolate from Latium and with the Apulian isolate of N. mediterraneum. Both isolates of N. stellenboschiana proved pathogenic to olive trees. They caused evident bark canker and wood discolouration when inoculated at the base of the stem of two/three-year-old trees and on one-year-old twigs. However, virulence of N. stellenboschiana was significantly lower, though still remarkable, compared with N. mediterraneum in term of necrosis progression in the bark and the wood and capacity of wilting the twigs. Virulence of N. stellenboschiana and N. mediterraneum did not substantially change when inoculations were performed in spring/summer and in autumn, suggesting that these fungal species have the potential to infect and damage olive trees in all seasons. The high thermotolerance of N. stellenboschiana was also revealed with in vitro growth and survival tests. The high virulence of these Botryosphaeriaceae species highlights their contribution in BTD aetiology and the necessity to investigate right away their diffusion and, possibly, the role of additional factors other than Xfp in the general decline of olive groves in Apulia. Hence the importance of assessing the degree of overlap of BTD/Botryosphariaceae with OQDS/Xfp is discussed.

Cytospora paraplurivora sp. nov. isolated from orchards with fruit tree decline syndrome in Ontario, Canada

A new species of Cytospora was isolated from cankered wood of Prunus spp. during a survey of orchards exhibiting symptoms of fruit tree decline syndrome in southern Ontario, Canada. We found isolates that are morphologically similar to species in the Cytosporaceae family, which is characterized by single or labyrinthine locules, filamentous conidiophores or clavate to elongate obovoid asci and allantoid, hyaline conidia. Multi-gene phylogenetic analysis of ITS, LSU, act and tef1- α showed that the isolates form a distinct clade, sister to Cytospora plurivora. Morphologically, our isolates showed differences in the length of conidia and culture characteristics compared to C. plurivora, suggesting the establishment of a new species. The species is described as Cytospora paraplurivora sp. nov. and placed in the family Cytosporaceae of Diaporthales. Additionally, we sequenced, assembled and characterized the genome of the representative isolate for this new species. The phylogenomic analysis confirms the species order and family level classification. C. paraplurivora sp. nov. has the potential to severely affect stone fruits production, causing cankers and dieback in stressed trees, and eventually leads to tree decline. Pathogenicity tests show that the species is pathogenic to Prunus persica var. persica.

Multigene phylogeny, morphology, and pathogenicity trials reveal novel Cytospora species involved in perennial canker disease of apple trees in Iran

In recent years, canker and die-back diseases have become a growing threat for the productivity and longevity of apple orchards in Iran. In this study, 131 Cytospora isolates were recovered from symptomatic tissues of apple trees in apple orchards of Iran. Multigene phylogenetic inference based on combined sequence data of ITS, act, rpb2, and tef1-α loci, supplemented with morphological characteristics and pathogenicity assay revealed four novel Cytospora species which were described as C. avicennae, C. azerbaijanica, C. ershadii, and C. iranica, and four known species, namely C. chrysosperma, C. parasitica, C. paratranslucens, and C. sorbicola. Also, C. sorbicola is newly reported on apple trees worldwide. Koch's postulates were fulfilled to confirm that all eight species in this study were pathogenic on apple trees in Iran, among which C. sorbicola was the most intensive species. The results of this study further highlight rich diversity among Cytospora species occurring on apple trees, revealing several novel Cytospora species on this host. The host range, geographical distribution, and economic significance of novel species on apple industry remains to be studied.

Fungal species associated with grapevine trunk diseases in Washington wine grapes and California table grapes, with novelties in the genera Cadophora, Cytospora, and Sporocadus

Grapevine trunk diseases cause serious economic losses to grape growers worldwide. The identification of the causal fungi is critical to implementing appropriate management strategies. Through a culture-based approach, we identified the fungal species composition associated with symptomatic grapevines from wine grapes in southeastern Washington and table grapes in the southern San Joaquin Valley of California, two regions with contrasting winter climates. Species were confirmed through molecular identification, sequencing two to six gene regions per isolate. Multilocus phylogenetic analyses were used to identify novel species. We identified 36 species from 112 isolates, with a combination of species that are new to science, are known causal fungi of grapevine trunk diseases, or are known causal fungi of diseases of other woody plants. The novel species Cadophora columbiana, Cytospora macropycnidia, Cytospora yakimana, and Sporocadus incarnatus are formally described and introduced, six species are newly reported from North America, and grape is reported as a new host for three species. Six species were shared between the two regions: Cytospora viticola, Diatrype stigma, Diplodia seriata, Kalmusia variispora, Phaeoacremonium minimum, and Phaeomoniella chlamydospora. Dominating the fungal community in Washington wine grape vineyards were species in the fungal families Diatrypaceae, Cytosporaceae and Sporocadaceae, whereas in California table grape vineyards, the dominant species were in the families Diatrypaceae, Togniniaceae, Phaeomoniellaceae and Hymenochaetaceae. Pathogenicity tests demonstrated that 10 isolates caused wood discoloration similar to symptomatic wood from which they were originally isolated. Growth rates at temperatures from 5 to 35°C of 10 isolates per region, suggest that adaptation to local climate might explain their distribution.

Effects of Temperature on Development of Canker-Causing Pathogens in Almond and Prune

Between 2000 and 2020, canker diseases of nut and stone fruit trees have become very widespread and severe in California. This study determined the effects of temperature on the development of canker-causing pathogens of almond and prune. Five pathogen taxa, Botryosphaeria dothidea, Cytospora leucostoma, Diaporthe (Phomopsis) neotheicola, Lasiodiplodia citricola, and Neofusicoccum mediterraneum, were used. Colony growth on medium and canker lesion development on detached shoots were measured at 10, 15, 20, 25, 30, and 35°C. The effects of temperature on colony growth differed among different pathogen taxa, although 25°C was the optimal temperature for most of the pathogens tested. The patterns of lesion growth as response to temperature were different among the different pathogens and tree crops. On almond, the highest growth rates appeared at 30°C for B. dothidea and L. citricola, but at 20°C for N. mediterraneum. The growth rates for C. leucostoma were lower than those of the other three pathogen taxa, with the highest rates recorded at 25°C. However, on prune, C. leucostoma showed greater lesion growth rates at different temperatures than the other pathogen taxa and maximum growth at 30 to 35°C. Similar trends were observed for L. citricola. The growth rates of B. dothidea and N. mediterraneum were comparatively lower than those of C. leucostoma and L. citricola.

Development of PCR-Based Assays for Rapid and Reliable Detection and Identification of Canker-Causing Pathogens from Symptomatic Almond Trees

Trunk and scaffold canker diseases (TSCDs) of almond cause significant yield and tree losses and reduce the lifespan of orchards. In California, several pathogens cause TSCDs, including Botryosphaeriaceae, Ceratocystis destructans, Eutypa lata, Collophorina hispanica, Pallidophorina paarla, Cytospora, Diaporthe, and Phytophthora spp. Field diagnosis of TSCDs is challenging because symptom delineation among the diseases is not clear. Accurate diagnosis of the causal species requires detailed examination of symptoms and subsequent isolation on medium and identification using morphological criteria and subsequent confirmation using molecular tools. The process is time-consuming and difficult, particularly as morphological characteristics are variable and overlap among species. To facilitate diagnosis of TSCD, we developed PCR assays using 23 species-specific primers designed by exploiting sequence differences in the translation elongation factor, β-tubulin, or internal transcribed spacer gene. Using genomic DNA from pure cultures of each fungal and oomycete species, each primer pair successfully amplified a single DNA fragment from the target pathogen but not from selected nontarget pathogens or common endophytes. Although 10-fold serial dilution of fungal DNA extracted from either pure cultures or infected wood samples detected as little as 0.1 pg of DNA sample, consistent detection required 10 ng of pathogen DNA from mycelial samples or from wood chips or drill shavings from artificially or naturally infected almond wood samples with visible symptoms. The new PCR assay represents an improved tool for diagnostic laboratories and will be critical to implement effective disease surveillance and control measures.

Comparative Profiling of Wood Canker Pathogens from Spore Traps and Symptomatic Plant Samples Within California Almond and Walnut Orchards

Fungi causing wood canker diseases are major factors limiting productivity and longevity of almond and walnut orchards. The goal of this study was to compare pathogen profiles from spore traps with those of plant samples collected from symptomatic almond and walnut trees and assess if profiles could be influenced by orchard type and age, rainfall amount and frequency, and/or neighboring trees. Three almond orchards and one walnut orchard with different characteristics were selected for this study. Fungal inoculum was captured weekly from nine trees per orchard using a passive spore-trapping device, during a 30-week period in the rainy season (October to April) and for two consecutive years. Fungal taxa identified from spore traps were compared with a collection of fungal isolates obtained from 61 symptomatic wood samples collected from the orchards. Using a culture-dependent approach coupled with molecular identification, we identified 18 known pathogenic species from 10 fungal genera (Ceratocystis destructans, Collophorina hispanica, Cytospora eucalypti, Diaporthe ampelina, Diaporthe chamaeropis/rhusicola, Diaporthe eres, Diaporthe novem, Diplodia corticola, Diplodia mutila, Diplodia seriata, Dothiorella iberica, Dothiorella sarmentorum, Dothiorella viticola, Eutypa lata, Neofusicoccum mediterraneum, Neofusicoccum parvum, Neoscytalidium dimidiatum, and Pleurostoma richardsiae), plus two unidentified Cytospora and Diaporthe species. However, only four species were identified with both methods (Diplodia mutila, Diplodia seriata, Dothiorella Iberica, and E. lata), albeit not consistently across orchards. Our results demonstrate a clear disparity between the two diagnostic methods and caution against using passive spore traps to predict disease risks. In particular, the spore trap approach failed to capture: insect-vectored pathogens such as Ceratocystis destructans that were often recovered from almond trunk and scaffold; Diaporthe chamaeropis/rhusicola commonly isolated from wood samples likely because Diaporthe species have a spatially restricted dispersal mechanism, as spores are exuded in a cirrus; and pathogenic species with low incidence in wood samples such as P. richardsiae and Collophorina hispanica. We propose that orchard inoculum is composed of both endemic taxa that are characterized by frequent and repeated trapping events from the same trees and isolated from plant samples, as well as immigrant taxa characterized by rare trapping events. We hypothesize that host type, orchard age, precipitation, and alternative hosts at the periphery of orchards are factors that could affect pathogen profile. We discuss the limitations and benefits of our methodology and experimental design to develop guidelines and prediction tools for fungal wood canker diseases in California orchards.

Fungal Richness of Cytospora Species Associated with Willow Canker Disease in China

Species of Cytospora are considered important plant pathogens of a wide range of plant hosts, especially Salicaceae plants. Salix (Salicaceae, Malpighiales) has been widely cultivated in China because of its strong ecological adaptability, fast growth, and easy reproduction. In this study, a total of eight species of Cytospora were discovered on Salix in China, including C. ailanthicola, C. alba, C. chrysosperma, C. gigaspora, C. nivea, C. paracinnamomea, C. rostrata, and C. sophoriopsis. Among them, C. alba and C. paracinnamomea were identified as novel species based on morphology and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2 gene sequences and were confirmed as pathogens of willow canker disease by pathogenicity tests. The mycelial growth rates of strains from these two novel species (C. alba and C. paracinnamomea) had optimum temperatures of 21 to 22 °C and an optimum pH value of 5 to 6. The effectiveness of six carbon sources on the mycelial growth showed that fructose and maltose had the highest influence. Cytospora species richness was significantly positively correlated with dry and wet areas. This study represents a significant evaluation of Cytospora associated with willow canker disease in China and provides a theoretical basis for predicting the potential risk of willow canker disease.

Genetic and Phenotypic Characterization of the Fungal Pathogen Cytospora plurivora from Western Colorado Peach Orchards and the Development of a ddPCR Assay for Detection and Quantification

Cytospora canker is one of the most important diseases affecting peach production in Colorado, yet previous efforts to characterize Cytospora species diversity in Colorado have relied exclusively on morphological traits. Recently, several new Cytospora species were described from peach orchards within the United States using molecular and morphological data, prompting the need to reexamine Cytospora spp. present on peach trees in Colorado. A total of 137 isolates of Cytospora spp. were collected from eight orchards in western Colorado. Isolates were sequenced at the internal transcribed spacer region and elongation factor 1-α and assessed with reference sequences in phylogenetic analyses. All isolates from western Colorado peach trees resolved with the newly described Cytospora plurivora. In addition to molecular characterization, temperature growth and virulence assays were conducted to assess phenotypic variation among the isolates from western Colorado. Variation across isolates was found both in growth at different temperatures and in virulence. Ancestral state reconstruction analyses resolved the most virulent (and most often collected) haplotypes together in a well-supported clade from which a single monophyletic origin of high virulence can be inferred. Finally, a droplet digital PCR assay was developed for use in ongoing and future studies to detect and quantify C. plurivora from field and laboratory samples.

Etiology of Botryosphaeria Panicle and Shoot Blight of Pistachio (Pistacia vera) Caused by Botryosphaeriaceae in Italy

Pistachio (Pistacia vera) is an important crop in Italy, traditionally cultivated in Sicily (southern Italy) for several decades now. In recent years, new orchards have been planted in new areas of the island. Field surveys conducted in 2019 revealed the presence of symptomatic trees showing shoot dieback, cankers, fruit spots, and leaf lesions. Isolations from symptomatic samples consistently yielded fungal species in the Botryosphaeriaceae family. Identification of collected isolates was conducted using morphological and molecular analyses. Morphological characterization was based on conidia measurements of representative isolates and also effects of temperatures on mycelial growth was evaluated. DNA data derived from sequencing the ITS, tef1-α, and tub2 gene regions were analyzed via phylogenetic analyses (maximum parsimony and maximum likelihood). Results of the analyses confirmed the identity of Botryosphaeria dothidea, Neofusicoccum hellenicum, and N. mediterraneum. Pathogenicity tests were conducted on detached twigs and in the fields both on shoots as well as on fruit clusters using the mycelial plug technique. The inoculation experiments revealed that among the Botryosphaeriaceae species identified in this study N. hellenicum (occasionally detected) and N. mediterraneum were the most aggressive based on lesion length on shoots and fruits. N. mediterraneum was the most widespread among the orchards while B. dothidea can be considered a minor pathogen involved in this complex disease of pistachio. Moreover, to our knowledge, this is the first report of N. hellenicum in Italy.

Pathogenicity Testing of Fungal Isolates Associated with Olive Trunk Diseases in South Africa

A recent olive trunk disease survey performed in the Western Cape Province, South Africa, identified several fungi associated with olive trunk disease symptoms, including species of Basidiomycota, Botryosphaeriaceae, Coniochaetaceae, Calosphaeriaceae, Diaporthaceae, Diatrypaceae, Phaeomoniellaceae, Phaeosphaeriaceae, Symbiotaphrinaceae, Togniniaceae, and Valsaceae. Many of the species recovered had not yet been reported from olive trees; therefore, the aim of this study was to determine their pathogenicity toward this host. Pathogenicity tests were first conducted on detached shoots to select virulent isolates, which were then used in field trials. During field trials, 2-year-old olive branches of 15-year-old trees were inoculated by inserting colonized agar plugs into artificially wounded tissue. Measurements were made of the internal lesions after 8 months. In total, 58 isolates were selected for the field trials. Species that formed lesions significantly larger than the control could be considered as olive trunk pathogens. These included Biscogniauxia rosacearum, Celerioriella umnquma, Coniochaeta velutina, Coniothyrium ferrarisianum, isolates of the Cytospora pruinosa complex, Didymocyrtis banksiae, Diaporthe foeniculina, Eutypa lata, Fomitiporella viticola, Neofusicoccum stellenboschiana, Neofusicoccum vitifusiforme, Neophaeomoniella niveniae, Phaeoacremonium africanum, Phaeoacremonium minimum, Phaeoacremonium oleae, Phaeoacremonium parasiticum, Phaeoacremonium prunicola, Phaeoacremonium scolyti, Phaeoacremonium spadicum, Pleurostoma richardsiae, Pseudophaeomoniella globosa, Punctularia atropurpurascens, Vredendaliella oleae, an undescribed Cytospora sp., Geosmithia sp., two undescribed Neofusicoccum spp., and four Xenocylindrosporium spp. Pseudophaeomoniella globosa can be regarded as one of the main olive trunk pathogens in South Africa because of its high incidence from olive trunk disease symptoms in established orchards and its high virulence in pathogenicity trials.

Fungal canker agents in apple production hubs of Iran

To identify apple canker casual agents and evaluate their pathogenicity and virulence in apple production hubs including West Azarbaijan, Isfahan and Tehran provinces; samples were collected from symptomatic apple trees. Pathogenic isolates on the detached branches were identified as Cytospora cincta, Diplodia bulgarica, Neoscytalidium dimidiatum and Eutypa cf. lata. E. cf. lata was reported as a potential apple canker causal agent in Iran for the first time based on the pathogenicity test on the detached branches, whereas it caused no canker symptoms in apple trees until 6 months after inoculation. Currently, E. cf. lata seems to be adapted to a single city. C. cincta, D. bulgarica and N. dimidiatum caused canker symptoms in apple trees. “C. cincta” and also “C. cincta and N. dimidiatum” were the most widespread and aggressive apple canker species, respectively, associated with apple canker in Iran. Therefore, they are considered to be the main threat to apple production in Iran and should be carefully monitored. Disease progress curve, area under the disease progress curve and optimum temperatures were determined for mentioned species. It is concluded that the establishment of each species occurs in appropriate areas and times in terms of the optimum temperature for their growth.

Evaluation of Pruning Wound Protection Products for the Management of Almond Canker Diseases in California

Almond trunk and branch canker diseases constitute a major cause of tree mortality in California. Numerous fungal pathogens have been associated with these canker diseases and pruning wounds act as major infection courts. Before this study, there were no products registered in California for the management of these diseases. In this study, fungicidal products including synthetic chemistries, biocontrols, paint, and a sealant were evaluated for preventing fungal pathogen infection via pruning wounds. In four field trials conducted over two dormant seasons, 16 pruning wound treatments were tested using handheld spray applications against five almond canker pathogens, namely Botryosphaeria dothidea, Neofusicoccum parvum, Cytospora sorbicola, Ceratocystis destructans, and Eutypa lata. The fungicide thiophanate-methyl (Topsin M; United Phosphorus, Bandra West, Mumbai, India) provided 82% overall disease prevention against four fungal pathogens. The biological control agent, Trichoderma atroviride SC1 (Vintec; Bi-PA, Londerzeel, Belgium), tested at three application rates, resulted in 90 to 93% protection of pruning wounds in field trials, and for individual pathogens ranged from 81 to 100% protection for the three rates. At the time of this publication, Vintec is being considered for registration as a biological control product for the prevention of almond canker diseases, while Topsin M is recommended to growers for the prevention of almond canker diseases. This research indicates that effective protection of pruning wounds from infection by almond canker pathogens can be achieved with a one-time spray application of thiophanate-methyl or the biocontrol T. atroviride SC1 (recommended 2 g/liter) after pruning.

Discovery of Three Novel Cytospora Species in Thailand and Their Antagonistic Potential

During an ongoing research survey of saprobic fungi in Thailand, four coelomycetous strains were isolated from decaying leaves in Chiang Mai and Phitsanulok Provinces. Morphological characteristics demonstrated that these taxa are typical of Cytospora in forming multi-loculate, entostromatic conidiomata, branched or unbranched conidiophores, with enteroblastic, phialidic conidiogenous cells and hyaline, allantoid, aseptate conidia. Multiloci phylogeny of ITS, LSU, ACT, RPB2, TEF1-α and TUB2 confirmed these taxa are distinct new species in Cytospora in Cytosporaceae (Diaporthales, Sordariomycetes), viz., Cytospora chiangmaiensis, C. phitsanulokensis and C. shoreae. Cytospora chiangmaiensis has a close phylogenetic relationship with C. shoreae, while C. phitsanulokensis is sister to C. acaciae. These three novel species were also preliminary screened for their antagonistic activity against five plant pathogenic fungi: Colletotrichumfructicola, Co. siamense, Co. artocarpicola, Co. viniferum and Fusarium sambucinum. Cytospora shoreae and C. phitsanulokensis showed >60% inhibition against Co. viniferum and F. sambucinum, while C. chiangmaiensis had moderate inhibition activity against all pathogens.

Dieback and decline pathogens of olive trees in South Africa

Trunk disease fungal pathogens reduce olive production globally by causing cankers, dieback, and other decline-related symptoms on olive trees. Very few fungi have been reported in association with olive dieback and decline in South Africa. Many of the fungal species reported from symptomatic olive trees in other countries have broad host ranges and are known to occur on other woody host plants in the Western Cape province, the main olive production region of South Africa. This survey investigated the diversity of fungi and symptoms associated with olive dieback and decline in South Africa. Isolations were made from internal wood symptoms of 145 European and 42 wild olive trees sampled in 10 and 9 districts, respectively. A total of 99 taxa were identified among 440 fungal isolates using combinations of morphological and molecular techniques. A new species of Pseudophaeomoniella, P. globosa, had the highest incidence, being recovered from 42.8 % of European and 54.8 % of wild olive samples. This species was recovered from 9 of the 10 districts where European olive trees were sampled and from all districts where wild olive trees were sampled. Members of the Phaeomoniellales (mainly P. globosa) were the most prevalent fungi in five of the seven symptom types considered, the only exceptions being twig dieback, where members of the Botryosphaeriaceae were more common, and soft/white rot where only Basidiomycota were recovered. Several of the species identified are known as pathogens of olives or other woody crops either in South Africa or elsewhere in the world, including species of Neofusicoccum, Phaeoacremonium, and Pleurostoma richardsiae. However, 81 of the 99 taxa identified have not previously been recorded on olive trees and have unknown interactions with this host. These taxa include one new genus and several putative new species, of which four are formally described as Celerioriella umnquma sp. nov., Pseudophaeomoniella globosa sp. nov., Vredendaliella oleae gen. & sp. nov., and Xenocylindrosporium margaritarum sp. nov.

Cytospora and Diaporthe Species Associated With Hazelnut Canker and Dieback in Beijing, China

Hazelnut (Corylus heterophylla Fisch.) is an important nut crop in China but has been declining owing to the destructive effects of fungal branch canker and dieback. The identification and management of these pathogens are difficult because of the lack of attention to branch canker, insufficient understanding of phylogenetic, and overlapping morphological characteristics of the pathogens. In total, 51 strains were isolated from Chinese wild hazelnut in this study, and three species of Cytospora and two of Diaporthe were identified through morphological observation and multi-locus phylogenetic analyses (ITS, act, rpb2, tef1-α, and tub2 for Cytospora; ITS, cal, his3, tef1-α, and tub2 for Diaporthe). Three new species, Cytospora corylina, C. curvispora, and Diaporthe corylicola, and two known species, Cytospora leucostoma and Diaporthe eres, grew at 5-30°C and a pH of 3.0-11.0, with optimum growth at approximately 25°C and pH 4.0-7.0. Additionally, the effects of six carbon sources on mycelial growth were investigated. This study explored the main pathogenic fungi species of Corylus heterophylla, completed the corresponding database of pathogenic fungi information, and clarified their biological characteristics. Moreover, the results of this study provided a theoretical basis for Corylus heterophylla disease management and prevention in China.

Pleurostoma Decline of Olive Trees Caused by Pleurostoma richardsiae in California

A single fungal pathogen was consistently isolated from symptomatic wood of olive trees (Olea europaea) displaying branch and trunk cankers in superhigh-density orchards in the Sacramento and San Joaquin Valleys of California. Morphological characters of the pathogen included two distinct types of conidia (thick-walled, dark brown, and globose and thin-walled, hyaline, and oblong to ellipsoid) and three types of phialides, indicating a pleurostoma-like fungus. Phylogenetic results of four nuclear loci including the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) and partial sequences of the actin, beta-tubulin, and translation elongation factor 1-α genes confirmed the isolates as Pleurostoma richardsiae. Pathogenicity trials conducted in the field involving 2- to 3-year-old branches of three widely planted oil olive cultivars (Arbequina, Arbosana, and Koroneiki) satisfied Koch's postulates and confirmed the pathogenic nature of this species to cause the decline of olive trees in California. All three cultivars were equally susceptible to Pl. richardsiae, indicating no detectable resistance to the pathogen. Additional isolations from symptomatic hosts including almond, peach, pistachio, and plum, also confirmed this species, suggesting that Pl. richardsiae is widespread in agricultural systems and should be considered an emerging pathogen of fruit and nut crops in California.

The Hidden Diversity of Diatrypaceous Fungi in China

In this study, we investigated the diversity of diatrypaceous fungi from six regions in China based on morpho-molecular analyses of combined ITS and tub2 gene regions. We accept 23 genera in Diatrypaceae with 18 genera involved in the phylogram, and the other five genera are lacking living materials with sequences data. Eleven species included in four genera (viz. Allocryptovalsa, Diatrype, Diatrypella, and Eutypella) have been isolated from seven host species, of which nine novel species (viz. Allocryptovalsa castaneae, A. castaneicola, Diatrype betulae, D. castaneicola, D. quercicola, Diatrypella betulae, Da. betulicola, Da. hubeiensis, and Da. shennongensis), a known species of Diatrypella favacea, and a new record of Eutypella citricola from the host genus Morus are included. Current results show the high diversity of Diatrypaceae which are wood-inhabiting fungi in China.

Assessment of Cytospora Isolates From Conifer Cankers in China, With the Descriptions of Four New Cytospora Species

Cytospora species are widely distributed and often occur as endophytes, saprobes or phytopathogens. They primarily cause canker and dieback diseases of woody host plants, leading to the growth weakness or death of host plants, thereby causing significant economic and ecological losses. In order to reveal the diversity of Cytospora species associated with canker and dieback diseases of coniferous trees in China, we assessed 11 Cytospora spp. represented by 28 fungal strains from symptomatic branches or twigs of coniferous trees, i.e., Juniperus procumbens, J. przewalskii, Picea crassifolia, Pinus armandii, P. bungeana, Platycladus orientalis in China. Through morphological observations and multilocus phylogeny of ITS, LSU, act, rpb2, tef1-α, and tub2 gene sequences, we focused on four novel Cytospora species (C. albodisca, C. discostoma, C. donglingensis, and C. verrucosa) associated with Platycladus orientalis. This study represented the first attempt to clarify the taxonomy of Cytospora species associated with canker and dieback symptoms of coniferous trees in China.

Fungal Pathogens Associated With Canker Diseases of Almond in California

Almond canker diseases are destructive and can reduce the yield as well as the lifespan of almond orchards. These diseases may affect the trunk and branches of both young and mature trees and can result in tree death soon after orchard establishment in severe cases. Between 2015 and 2018, 70 almond orchards were visited throughout the Central Valley of California upon requests from farm advisors for canker disease diagnosis. Two major canker diseases were identified, including Botryosphaeriaceae cankers and Ceratocystis canker. In addition, five less prevalent canker diseases were identified, including Cytospora, Eutypa, Diaporthe, Collophorina, and Pallidophorina canker. Seventy-four fungal isolates were selected for multilocus phylogenetic analyses of internal transcribed spacer region ITS1-5.8S-ITS2 and part of the translation elongation factor 1-α, β-tubulin, and glyceraldehyde 3-phosphate dehydrogenase gene sequences; 27 species were identified, including 12 Botryosphaeriaceae species, Ceratocystis destructans, five Cytospora species, Collophorina hispanica, four Diaporthe species, two Diatrype species, Eutypa lata, and Pallidophorina paarla. The most frequently isolated species were Ceratocystis destructans, Neoscytalidium dimidiatum, and Cytospora californica. Pathogenicity experiments on almond cultivar Nonpareil revealed that Neofusicoccum parvum, Neofusicoccum arbuti, and Neofusicoccum mediterraneum were the most virulent. Botryosphaeriaceae cankers were predominantly found in young orchards and symptoms were most prevalent on the trunks of trees. Ceratocystis canker was most commonly found in mature orchards and associated with symptoms found on trunks or large scaffold branches. This study provides a thorough examination of the diversity and pathogenicity of fungal pathogens associated with branch and trunk cankers of almond in California.

Water Stress Enhances the Progression of Branch Dieback and Almond Decline under Field Conditions

Branch dieback and tree decline have been described as a common complex disease worldwide in woody crops, with Botryosphaeriaceae and Diaporthaceae being considered the most frequent fungi associated with the disease symptoms. Their behaviour is still uncertain, since they are considered endophytes becoming pathogenic in weakened hosts when stress conditions, such as water deficiency occur. Therefore, the main goal of this study was to determine if water stress enhances general decline on weakened almond trees subjected to different irrigation treatments under natural field conditions. In parallel, the occurrence of fungal species associated with almond decline was also determined in relation to disease progression by fungal isolation, and morphological and molecular based-methods. The symptoms of branch dieback and general decline were observed over time, mainly in the experimental plots subjected to high water deficiency. Botryosphaeriaceae were the most consistently isolated fungi, and Botryosphaeria dothidea was the most frequent. Collophorina hispanica was the second most frequent species and Diaporthe and Cytospora species were isolated in a low frequency. Most of them were recovered from both asymptomatic and symptomatic trees, with their consistency of isolation increasing with the disease severity. This work reveals the need to elucidate the role of biotic and abiotic factors which increase the rate of infection of fungal trunk pathogens, in order to generate important knowledge on their life cycle.

Seasonal changes in population structure of the ambrosia beetle Xylosandrus compactus and its associated fungi in a southern Mediterranean environment

Exotic ambrosia beetles are increasing in Europe due to global trade and global warming. Among these xylomycetophagous insects, Xylosandrus compactus (Eichhoff) (Coleoptera: Curculionidae) is a serious threat for several Mediterranean host plants. Carob trees growing in Sicily (Italy) have been extensively attacked by beetles leading to rapid tree decline. Although X. compactus has been found in Europe for several years, most aspects of its ecology are still unknown. We thus studied the population structure and dynamics of X. compactus, together with its twig size preference during a sampling of infested carob trees in south east Sicily. In addition, fungi associated with insects or galleries were isolated and characterized. The results showed that, in this newly-colonized environment and host plant, adult X. compactus overwinters inside twigs and starts to fly and reproduce in mid spring, completing five generations before overwintering in late fall. The mean diameter of carob twigs infested by the beetle varied significantly over the seasons, with the insect tending to infest larger twigs as season progresses. The mean number of adults/gallery was 19.21, ranging from 6 to 28. The minimum temperature significantly affected the overwintering adult mortality. Ambrosiella xylebori and Fusarium solani were the main symbionts associated with the pest in this study. Acremonium sp. was instead recorded for the first time in Europe inside X. compactus galleries. Several other fungi species were also found for the first time in association with X. compactus. Our findings provide useful insights into the sustainable management of this noxious pest.

Endophytic Fungi of Olive Tree

In addition to the general interest connected with investigations on biodiversity in natural contexts, more recently the scientific community has started considering occurrence of endophytic fungi in crops in the awareness of the fundamental role played by these microorganisms on plant growth and protection. Crops such as olive tree, whose management is more and more frequently based on the paradigm of sustainable agriculture, are particularly interested in the perspective of a possible applicative employment, considering that the multi-year crop cycle implies a likely higher impact of these symbiotic interactions. Aspects concerning occurrence and effects of endophytic fungi associated with olive tree (Olea europaea) are revised in the present paper.

High Diversity of Cytospora Associated With Canker and Dieback of Rosaceae in China, With 10 New Species Described

Cytospora canker is a destructive disease of numerous hosts and causes serious economic losses with a worldwide distribution. Identification of Cytospora species is difficult due to insufficient phylogenetic understanding and overlapped morphological characteristics. In this study, we provide an assessment of 23 Cytospora spp., which covered nine genera of Rosaceae, and focus on 13 species associated with symptomatic branch or twig canker and dieback disease in China. Through morphological observation and multilocus phylogeny of internal transcribed spacer (ITS), large nuclear ribosomal RNA subunit (LSU), actin (act), RNA polymerase II subunit (rpb2), translation elongation factor 1-α (tef1-α), and beta-tubulin (tub2) gene regions, the results indicate 13 distinct lineages with high branch support. These include 10 new Cytospora species, i.e., C. cinnamomea, C. cotoneastricola, C. mali-spectabilis, C. ochracea, C. olivacea, C. pruni-mume, C. rosicola, C. sorbina, C. tibetensis, and C. xinjiangensis and three known taxa including Cytospora erumpens, C. leucostoma, and C. parasitica. This study provides an initial understanding of the taxonomy of Cytospora associated with canker and dieback disease of Rosaceae in China.

Olive Twig and Branch Dieback in California Caused by Cytospora oleicola and the Newly Described Species Cytospora olivarum sp. nov

Field surveys conducted throughout California olive-growing regions in 2008 and 2009 resulted in a collection of 101 Cytospora-like isolates from olive twig and branch dieback symptoms. Cytospora isolates were isolated from multiple cvs. in different olive orchards in Fresno, Madera, Merced, Napa, Riverside, Santa Barbara, Sonoma, Tulare, and Ventura counties. Taxonomic studies of macro- and microscopic structures along with multigene phylogenetic analyses of the internal transcribed spacer region, including the 5.8S rDNA (ITS1-5.8S-ITS2), and fragments of the translation elongation factor 1-α, beta-tubulin, and actin genes identified two species, Cytospora oleicola and C. olivarum sp. nov. Pathogenicity studies conducted in mature olive trees cvs. Manzanillo and Sevillano showed both species to be pathogenic and able to cause vascular necrosis and cankers in olive branches. This study adds to the current knowledge on the etiology of olive twig and branch dieback and provides new important information for the development of effective control strategies against canker diseases affecting olive in California.

Dieback of Euonymus alatus (Celastraceae) Caused by Cytospora haidianensis sp. nov. in China

Euonymus alatus (Celastraceae) is widely cultivated in China for its economic value and landscape benefits. Euonymus alatus dieback occurs due to members of Cytospora and has become one of the most severe diseases affecting its cultivation in China. In this study, we examined the causal agent of bough dieback on campuses of University Road, Beijing, China. Among the strains, three were morphologically consistent with Cytospora, showing hyaline and allantoid conidia. Based on phylogenetic analyses of the concatenated actin (ACT), internal transcribed spacer (ITS), RNA polymerase II second largest subunit (RPB2), translation elongation factor 1-alpha (TEF1-α) and beta-tubulin (TUB2) gene sequences, along with morphological and physiological features, we propose C. haidianensis as a novel species. It was confirmed as a causal agent of dieback of E. alatus by pathogenicity tests. Mycelial growth of Cytospora haidianensis occurred at pH values ranging from 3.0 to 11.0, with optimum growth at 8.3, and at temperatures from 5 to 35 °C, with optimum growth at 19.8 °C. We also tested the growth of C. haidianensis in the presence of six carbon sources. Sucrose, maltose and glucose were highly efficient and xylose was the least. The ability of C. haidianensis to grow at 19.8 °C may help to explain its occurrence causing dieback of E. alatus in Beijing during the autumn season.

Fungal diversity notes 1151–1276: taxonomic and phylogenetic contributions on genera and species of fungal taxa

Fungal diversity notes is one of the important journal series of fungal taxonomy that provide detailed descriptions and illustrations of new fungal taxa, as well as providing new information of fungal taxa worldwide. This article is the 11th contribution to the fungal diversity notes series, in which 126 taxa distributed in two phyla, six classes, 24 orders and 55 families are described and illustrated. Taxa in this study were mainly collected from Italy by Erio Camporesi and also collected from China, India and Thailand, as well as in some other European, North American and South American countries. Taxa described in the present study include two new families, 12 new genera, 82 new species, five new combinations and 25 new records on new hosts and new geographical distributions as well as sexual-asexual reports. The two new families are Eriomycetaceae (Dothideomycetes, family incertae sedis) and Fasciatisporaceae (Xylariales, Sordariomycetes). The twelve new genera comprise Bhagirathimyces (Phaeosphaeriaceae), Camporesiomyces (Tubeufiaceae), Eriocamporesia (Cryphonectriaceae), Eriomyces (Eriomycetaceae), Neomonodictys (Pleurotheciaceae), Paraloratospora (Phaeosphaeriaceae), Paramonodictys (Parabambusicolaceae), Pseudoconlarium (Diaporthomycetidae, genus incertae sedis), Pseudomurilentithecium (Lentitheciaceae), Setoapiospora (Muyocopronaceae), Srinivasanomyces (Vibrisseaceae) and Xenoanthostomella (Xylariales, genera incertae sedis). The 82 new species comprise Acremonium chiangraiense, Adustochaete nivea, Angustimassarina camporesii, Bhagirathimyces himalayensis, Brunneoclavispora camporesii, Camarosporidiella camporesii, Camporesiomyces mali, Camposporium appendiculatum, Camposporium multiseptatum, Camposporium septatum, Canalisporium aquaticium, Clonostachys eriocamporesiana, Clonostachys eriocamporesii, Colletotrichum hederiicola, Coniochaeta vineae, Conioscypha verrucosa, Cortinarius ainsworthii, Cortinarius aurae, Cortinarius britannicus, Cortinarius heatherae, Cortinarius scoticus, Cortinarius subsaniosus, Cytospora fusispora, Cytospora rosigena, Diaporthe camporesii, Diaporthe nigra, Diatrypella yunnanensis, Dictyosporium muriformis, Didymella camporesii, Diutina bernali, Diutina sipiczkii, Eriocamporesia aurantia, Eriomyces heveae, Ernakulamia tanakae, Falciformispora uttaraditensis, Fasciatispora cocoes, Foliophoma camporesii, Fuscostagonospora camporesii, Helvella subtinta, Kalmusia erioi, Keissleriella camporesiana, Keissleriella camporesii, Lanspora cylindrospora, Loratospora arezzoensis, Mariannaea atlantica, Melanographium phoenicis, Montagnula camporesii, Neodidymelliopsis camporesii, Neokalmusia kunmingensis, Neoleptosporella camporesiana, Neomonodictys muriformis, Neomyrmecridium guizhouense, Neosetophoma camporesii, Paraloratospora camporesii, Paramonodictys solitarius, Periconia palmicola, Plenodomus triseptatus, Pseudocamarosporium camporesii, Pseudocercospora maetaengensis, Pseudochaetosphaeronema kunmingense, Pseudoconlarium punctiforme, Pseudodactylaria camporesiana, Pseudomurilentithecium camporesii, Pseudotetraploa rajmachiensis, Pseudotruncatella camporesii, Rhexocercosporidium senecionis, Rhytidhysteron camporesii, Rhytidhysteron erioi, Septoriella camporesii, Setoapiospora thailandica, Srinivasanomyces kangrensis, Tetraploa dwibahubeeja, Tetraploa pseudoaristata, Tetraploa thrayabahubeeja, Torula camporesii, Tremateia camporesii, Tremateia lamiacearum, Uzbekistanica pruni, Verruconis mangrovei, Wilcoxina verruculosa, Xenoanthostomella chromolaenae and Xenodidymella camporesii. The five new combinations are Camporesiomyces patagoniensis, Camporesiomyces vaccinia, Camposporium lycopodiellae, Paraloratospora gahniae and Rhexocercosporidium microsporum. The 22 new records on host and geographical distribution comprise Arthrinium marii, Ascochyta medicaginicola, Ascochyta pisi, Astrocystis bambusicola, Camposporium pellucidum, Dendryphiella phitsanulokensis, Diaporthe foeniculina, Didymella macrostoma, Diplodia mutila, Diplodia seriata, Heterosphaeria patella, Hysterobrevium constrictum, Neodidymelliopsis ranunculi, Neovaginatispora fuckelii, Nothophoma quercina, Occultibambusa bambusae, Phaeosphaeria chinensis, Pseudopestalotiopsis theae, Pyxine berteriana, Tetraploa sasicola, Torula gaodangensis and Wojnowiciella dactylidis. In addition, the sexual morphs of Dissoconium eucalypti and Phaeosphaeriopsis pseudoagavacearum are reported from Laurus nobilis and Yucca gloriosa in Italy, respectively. The holomorph of Diaporthe cynaroidis is also reported for the first time.

Discovery of Cytospora species associated with canker disease of tree hosts from Mount Dongling of China

Members of Cytospora encompass important plant pathogens, saprobes and endophytes on a wide range of woody hosts with a worldwide distribution. In the current study, we obtained seven representative isolates from six tree hosts of Betulaceae, Juglandaceae, Rosaceae, Tiliaceae and Ulmaceae in Mount Dongling of China. Based on morphological comparison and phylogenetic analyses using partial ITS, LSU, act, rpb2, tef1-α and tub2 gene sequences, we identified two known species (Cytospora leucostoma and C. pruinopsis) and two novel species (C. coryli and C. spiraeicola). These results represent the first study on Cytospora species associated with canker disease from Mount Dongling of China.

Macrophomina Crown and Root Rot of Pistachio in California

In this study, declining pistachio rootstocks were detected in newly planted commercial pistachio orchards in Kern County, California. Symptoms were characterized by wilted foliage combined with crown rot in the rootstock. From diseased trees, 42 isolates were obtained, and all had similar cultural and morphological characteristics of Macrophomina phaseolina. Analyses of nucleotide sequences of three gene fragments, the internal transcribed spacer region (ITS1-5.8S-ITS2), partial sequences of β-tubulin, and translation elongation factor 1-α (TEF1) confirmed this identification, and 20 representative isolates are presented in the phylogenetic study. Testing of Koch's postulates showed that M. phaseolina, when inoculated to stems and roots of the pistachio rootstocks using mycelial plugs or a microsclerotial suspension, is indeed pathogenic to this host. The widely used clonal University of California Berkeley I (UCBI) rootstock appeared highly susceptible to M. phaseolina, suggesting that this pathogen is an emerging threat to the production of pistachio in California. This study confirmed the association of M. phaseolina with the decline of pistachio trees and represents the first description of this fungus as a crown rot-causing agent of pistachio in California.

Identification of six Cytospora species on Chinese chestnut in China

Chinese chestnut (Castanea mollissima) is an important crop tree species in China. In the present study, Cytospora specimens were collected from Chinese chestnut trees and identified using molecular data of combined ITS, LSU, ACT and RPB2 loci, as well as morphological features. As a result, two new Cytospora species and four new host records were confirmed, viz. C. kuanchengensis sp. nov., C. xinglongensis sp. nov., C. ceratospermopsis, C. leucostoma, C. myrtagena and C. schulzeri.

Identification and Characterization of Neofabraea kienholzii and Phlyctema vagabunda Causing Leaf and Shoot Lesions of Olive in California

California produces over 95% of the olives grown in the United States. In 2017, California's total bearing acreage for olives was 14,570 hectares producing 192,000 tons of olives valued at $186.6 million. During the early spring of 2016, unusual leaf and shoot lesions were detected in olive trees from superhigh-density orchards in the Northern San Joaquin and Sacramento valleys of California. Affected trees displayed numerous leaf and shoot lesions developing at wounds created by mechanical harvesters. The 'Arbosana' cultivar was highly affected by the disease, whereas the disease was sporadic in 'Arbequina' and not found in 'Koroneiki' cultivar. Two fungal species, Neofabraea kienholzii and Phlyctema vagabunda, were found to be consistently associated with the disease, and Koch's postulates were completed. Species identity was confirmed by morphology and molecular data of the partial large subunit rDNA, the internal transcribed spacer region, and partial beta-tubulin region. The disease signs and symptoms are described and illustrated.

Dwiroopa punicae sp. nov. (Dwiroopaceae fam. nov., Diaporthales), associated with leaf spot and fruit rot of pomegranate (Punica granatum)

During a survey of diseases affecting pomegranate in the southeastern USA we identified a unique species of Diaporthales causing leaf spotting and fruit rot. Objectives of this study were to provide a morphological description of the putative new species, use DNA sequence data of three gene loci (LSU, ITS and rpb2) to accurately place the fungus within the Diaporthales, and to prove Koch's postulates. Morphological and phylogenetic comparisons confirmed the fungus to represent a new species and family, for which the names Dwiroopa punicae sp. nov. and Dwiroopaceae fam. nov. are proposed. This is the first report of a species of Dwiroopa being pathogenic to Punica granatum.

Identification and Pathogenicity of Fungal Species Associated with Canker Diseases of Pistachio in California

A survey was conducted during 2015 and 2016 in pistachio orchards throughout the San Joaquin Valley of California to investigate the occurrence of canker diseases and identify the pathogens involved. Cankers and dieback symptoms were observed mainly in orchards aged >15 years. Symptoms of canker diseases included brown to dark brown discoloration of vascular tissues, wood necrosis, and branch dieback. In total, 58 fungal isolates were obtained from cankers and identified based on multilocus phylogenetic analyses (internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, β-tubulin, calmodulin, actin 1, and translation elongation factor 1α) representing 11 fungal species: Colletotrichum karstii, Cytospora californica, Cytospora joaquinensis, Cytospora parapistaciae, Cytospora pistaciae, Diaporthe ambigua, Didymella glomerata, Diplodia mutila, Neofusicoccum mediterraneum, Phaeoacremonium canadense, and Schizophyllum commune. Pathogenicity tests conducted in the main pistachio cultivars Kerman, Golden Hills, and Lost Hills using the mycelium-plug method indicated that all fungal species were pathogenic to Pistacia vera. All species tested caused cankers in pistachio branches, although virulence among species varied from high to moderate. Overall, N. mediterraneum and Cytospora spp. were the most widespread and virulent species associated with canker diseases of pistachio in California.

Cytospora (Diaporthales) in China

Members of the genus Cytospora are often reported as endophytes, saprobes or phytopathogens, primarily causing canker diseases of woody host plants. They occur on a wide range of hosts and have a worldwide distribution. Although several species have in the past been reported from China, the vast majority are not known from culture or DNA phylogeny. The primary aim of the present study was thus to clarify the taxonomy and phylogeny of a large collection of Cytospora species associated with diverse hosts in China. Cytospora spp. were collected in northeast, northwest, north and southwest China, indicating that the cold and dry environments favour these fungi. In this paper, we provide an assessment of 52 Cytospora spp. in China, focussing on 40 species represented by 88 isolates from 28 host genera. Based on a combination of morphology and a six-locus phylogeny (ITS, LSU, act1, rpb2, tef1-α and tub2), 13 new species and one new combination are introduced. The majority of the species investigated here appear to be host-specific, although further collections and pathogenicity studies will be required to confirm this conclusion.