Draft genome sequences for four isolates of the hemp (Cannabis sativa) fungal pathogen Neofusicoccum parvum

Four isolates of Neofusicoccum parvum, collected from diseased hemp (Cannabis sativa) plants over a period of 2 years and shown to be pathogenic on C. sativa, were examined in this study. Their genome sizes ranged between 42.8 and 44.4 Mb, with 16,499 ± 72 predicted genes across the four isolates.

First Report of Neofusicoccum parvum causing leaf spot on Camellia japonica in China

Camellia japonica is an important garden landscape plant in southern China. In April 2022, leaf spot symptoms were observed at the camellia garden of Jiaying University (24°32'83″N, 17 116°12'31″E) in Meizhou city, Guangdong Province, China. The initial symptoms were grayish brown spots on the leaves, as the disease progressed, the lesions were enlarged and affected the whole leaf and eventually led to the loss of its ornamental value. The disease incidence was above 15%. Leaf pieces (5 × 5 mm) from 3 diseased Camellia leaves were sterilized in 75% ethanol for 1 min, then in 1% NaOCl for 1 min; and rinsed three times with sterile water. Leaf pieces were inoculated on potato dextrose agar (PDA) medium and incubated at 25 °C. Three days later, fungal colonies initially showed a white aerial mycelium, turning gray after 5 days, and dark gray after 7 days of incubation. Conidia were single-celled, hyaline, ellipsoidal and without septa. Dimensions of conidia (n≥50) were 14.27 to 20.65 × 4.28 to 6.56 μm. The morphological characteristics matched the genus Neofusicoccum (Pavlic et al. 2009). For molecular identification, the rDNA internal transcribed spacer (ITS1, 5.8S and ITS2) region, translation elongation factor 1-alpha (tef1-α), and beta-tubulin (tub2) of a representative isolate SC6-2 were amplified using the primer pairs ITS1/ITS4, EF1/EF2 and BT2a/-BT2b, respectively (Golzar and Burgess，2011). The sequences obtained were deposited in GenBank (accession nos. PP064173, PP479650 and PP082457 for ITS, tef1-α and tub2, respectively). Nucleotide BLAST analysis showed a 99.81% homology with N. parvum (519/520 bp, OQ509869; 519/520 bp, KF294003; 518/519 bp KF293989) for ITS, 100% homology with N. parvum (398/398 bp, MN318108; 398/398 bp, MK294085; 398/398 bp, MH936021) for tub2, and >99% homology with N. parvum (259/259 bp, 100%, MW390561; 263/265 bp, 99.25%，MN175952; 263/265 bp, 99.25%, MK781982) for tef1-α. The combined phylogenetic analyses (ITS, tef1-α, and tub2) showed that the sequence of the tested isolate and the corresponding sequence of N. parvum (CMW9081, SHSJ1-2) in GenBank grouped in the same branch of the phylogenetic tree. Based on morphological characters, DNA sequencing, and the phylogenetic tree, it can be determined that the pathogen was Neofusicoccum parvum. Inoculation on Camellia leaves was performed to confirm pathogenicity. Nine healthy camellia leaves were pin-pricked with a sterile needle and inoculated with mycelial plugs of isolate SC6-2. Nine other healthy leaves were pin-pricked and inoculated with noncolonized PDA plugs as control leaves. The inoculated leaves were maintained on water agar solid medium at 25°C. To keep a high-humidity environment the inoculation sites were covered by moistened cotton for 2 days. The experiment was repeated three times. Five days after inoculation, all the inoculated leaves showed similar symptoms to those observed in the field, whereas control leaves were asymptomatic for 6 days. The fungal isolates recovered from inoculated leaves were morphologically identical to the N. parvum isolates originally recovered from symptomatic leaves collected in the field, fulfilling Koch's postulates. Neofusicoccum parvum is an aggressive pathogen that causes severe disease on important tree and woody species (Liddle et al. 2019). It has been reported that N. parvum can infect the leaves and branches of grapes (Otoya-Martinez et al. 2023), dieback on Camellia japonica (Pintos, et al. 2012), Brazilian pepperwood (Bertetti et al. 2022), mango (Giancarlo et al. 2023) and other plants. To our knowledge, this is the first report of N. parvum causing leaf spot on Camellia japonica in China.

First Report of Neofusicoccum parvum Causing Fruit Rot on Psidium guajava in China

Guava (Psidium guajava L.), a nutrient-rich and economically significant fruit, is extensively cultivated in southern China. In six continuous years (from 2018 to 2023), dark-purple rotted guava with sunken lesion were observed on guava trees (variety 'Zhenzhu', aged over 5 years) in Dongguan and Panyu districts, Guangdong Province. Annually, the incidence of fruit rot disease in the affected fields reached 30% to 50% and significantly reduced the yield and quality of harvest guava. The initial symptoms on the epicarp of the fruits were black, needle-like dots that rapidly spread, causing partial or complete fruit rot within two to three weeks. To identify the causative agent, six symptomatic fruits were collected from two different orchards. Samples of 0.5 cm³ were excised from the lesion margins of each fruit. These samples were surface-sterilized with 70% ethanol for 30 seconds, followed by 0.2% NaClO for 2-3 minutes, and rinsed in sterile water three times. The samples were then cultured on potato dextrose agar (PDA) at 25°C for five days. This process yielded eight fungal isolates with similar morphological. Initially, the colonies were white with dense aerial mycelium becoming dark gray after 4 to 5 days. The mycelia were septate and branched. No spores were observed on PDA. To induce spore formation, the isolates were cultured on water agar for 20 days. This process led to the production of hyaline, aseptate, ellipsoid conidia, which were thin-walled, smooth-surfaced, and measured 3.7-5.1 × 1.6-2.2 μm (n = 100). Three isolates, including at least one from each orchard (Np1, Np2, Np3), were selected for further analysis. Genomic DNA was extracted using Axygen MAG-FRAG-I-50 (Axygen Bio-Tek). The internal transcribed spacer of rDNAs (ITS), beta-tubulin (tub2), the nuclear ribosomal large subunit (LSU), and translation elongation factor 1-α (tef1-α) gene regions were amplified using the primers ITS1/4, Bt2a/Bt2b, LR5/LR0R, and EF1-728F/EF1-986R (Golzar and Burgess 2011) and sequenced. Sequence analysis using MEGA 7.0 (Kumar et al., 2018) revealed 100% similarity among the isolates. BLAST searches of the ITS, tub2, LSU, and tef1-α sequences (accession nos. MN907637, MT537938, MT528156, MT537939) showed the highest nucleotide similarities (99.24 to 100%) to Neofusicoccum parvum strains (Crous et al. 2006). A phylogenetic tree was constructed with MEGA 7.0 based on the nucleotide sequence tub2 using the maximum likelihood method. Pathogenicity tests on 10 healthy guava fruits using mycelium-inoculated and control fruits confirmed the causative agent. The inoculated fruits, maintained at 25°C under a 12-h light/dark cycle, exhibited symptoms identical to the field infections within four to seven days, while control fruits remained symptomless. The fungus, reisolated from the inoculated fruits, was morphologically identical to the original isolates, fulfilling Koch's postulates. In conclusion, based on molecular, morphological, and pathogenic analysis, N. parvum as the causal agent of the fruit rot disease on guava. Previously, N. parvum has been reported in association with fruit rot on Eriobotrya japonica and Juglans regia (Zhai et al. 2019; Chen et al. 2019). To our knowledge, this is the first report of N. parvum affecting guava in China.

First Report of Neofusicoccum parvum Causing Seedpod Blight on Lotus (Nelumbo nucifera) in China

Lotus (Nelumbo nucifera Gaertn.) is a widely cultivated plant in China, and the fruit lotus variety has a high economic value attributed to the exquisite flavor of its fresh seeds. During the summer of 2023, an unidentified blight was observed affecting lotus seedpods in Jiande City, Zhejiang province, with approximately 65% of seedpods impacted in a 130-hectare area. The initial symptoms included dark purple spots on the lotus seedpod surface, which gradually expanded over time. After 5 to 7 days, the entire seedpod turned black, withering, and rendering the lotus seeds inedible. To identify the causal agent, tissues from symptomatic seedpods were excised and disinfected in 75% ethanol for 60 s, and washed twice in sterile distilled water. The disinfected symptomatic tissues (5 × 5 mm) were plated on potato dextrose agar (PDA), incubated at 25 ℃, transferred hyphal tips to obtain pure isolates after 3 days. Fungal colonies exhibiting Botryosphaeriaceae morphology were isolated from 33% of the samples (n = 15). Pure cultures were grown on PDA for both morphological and molecular identification. The colonies displayed a white aerial mycelium, turning olivaceous grey after 7 days. Pycnidia were produced within 3 weeks on PDA with added sterilized healthy lotus seedpod pieces on the surface. Conidia were hyaline, unicellular, ellipsoidal, 12.65 to 20.72 × 3.92 to 9.38 μm in size (mean 16.67 × 6.24 μm, n = 100). To determine the fungal species, genomic DNA was extracted from one representative isolate (ZJUP1112-1), to amplify four gene loci through polymerase chain reactions (PCR): rDNA internal transcribed spacer (ITS) with primers ITS1/ITS4, rDNA large subunit (LSU) with LR0R/LR5, the translation elongation factor 1-alpha gene (tef1) with EF1-728F/EF1-986R, and β-tubulin gene (tub2) with Bt2a/Bt2b. The PCR products were Sanger sequenced in Zhejiang Shangya biotechnology co., LTD, and the resulting sequences were assembled and deposited in GenBank (ITS: OR740546; LSU: OR740547; tef1: OR776996; tub2: OR776997). BLAST searches indicated the highest nucleotide sequence identity with the reference strains of Neofusicoccum parvum CMW 9081 (ITS: 98.8%, AY236943; LSU: 100%, AY928045; tef1: 99.6%, AY236888; tub2: 99.3%, AY236917). Multi-locus phylogenetic analyses revealed that isolate ZJUP1112-1 formed a highly supported clade with N. parvum. Pathogenicity tests were performed on healthy lotus seedpods using mycelial plugs (5 mm diameter) from actively growing colonies of ZJUP1112-1 that were placed onto the front and side of the seedpods (6 each). Controls received PDA plugs. Treated seedpods were wrapped with parafilm and incubated at 25 ℃ and the experiment was repeated three times. After 5 days, dark purple lesions were observed on the inoculated seedpods, whereas controls remained symptomless. The same isolate was recovered from the margin of resulting lesions and confirmed by morphology, thus fulfilling Koch's postulates. N. parvum is a polyphagous pathogen causing blights and fruit rot on multiple economically important fruit crops, such as cacao (Puig et al. 2019), walnut (Chen et al. 2019), pistachio (Lopez-Moral et al. 2020), chestnut (Seddaiu et al. 2021), blueberry (Spetik et al. 2023) and mango (Polizzi et al. 2022), among others. To the best of our knowledge, this is the first report of N. parvum causing seedpod blight on lotus seedpods in China, which contributes to a better understanding of the pathogens affecting this plant species in China.

First Report of Postharvest Fruit Rot Caused by Neofusicoccum parvum on Prunus salicina (Nai Plum) in China

Nai plum (Prunus salicina var. cordata cv. Younai) is one of the most popular fruit crop in South China. In July 2023, a fruit rot of nai plum with about 5 % disease incidence was observed in a fruit market of Changsha city, Hunan Province, China. Initially, small, brown lesions appeared randomly on the fruit surface, with disease progression, the lesions gradually expanded and developed into soft rot. To isolate possible fungi from rotten fruits, small pieces (2 × 2 mm) from the periphery of 10 infected fruits were surface-sterilized using 70% ethanol for 10 s, rinsed three times in sterile distilled water, air dried, and then placed onto potato dextrose agar (PDA) plates and incubated at 28℃ for three days. Emerging colonies were subcultured by hyphal tip transfer on fresh PDA. A total of ten isolates with similar morphology were obtained. Fungal colonies were initially white, gradually turning gray and eventually becoming black, and aerial hyphae were dense and fluffy. Conidia were hyaline, single celled, ellipsoidal to fusiform, and range from 12.7 to 20.0 μm long (avg. 16.9 ± 2.39 μm) × 5.3 to 7.3 μm wide (avg. 6.3 ± 0.82 μm). These morphological characteristics of these isolates matched those of Neofusicoccum parvum (Phillips et al. 2013). To future confirmation of the identify, the internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (TEF1-a), and beta-tubulin TUB2) genes of two representative isolates (JXNP1 and JXNP2) were amplified and sequenced using primer sets ITS5/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999; Phillips et al. 2013), and BT2A/BT2B (Glass and Donaldson 1995), respectively. The sequences of both isolates were deposited in GenBank for the ITS (accession nos. OR899331 and OR899332), TEF1-a gene (accession nos. OR909890 and OR909891) and TUB2 gene (accession nos. OR909892 and OR909893). BLAST analysis showed 99-100% identity with the ex-type strain of N. parvum (CMW9081) for ITS, TEF1-a and TUB2. A maximum likelihood phylogenetic tree was constructed using IQtree web server based on combined ITS, TEF1-a and TUB2 data set. The phylogenetic tree revealed that two isolates clustered with N. parvum in a clade with 90% bootstrap support. Based on morphological and molecular data analysis, the isolates were identified as N. parvum. To confirm the pathogenicity, five healthy nai plum fruits were wounded by using a sterile needle after surface sterilization with 75% ethanol, then a 5-mm-diameter mycelial disc of isolate JXNP1 was taped to the wound, the control fruits were taped with sterile agar plugs. All fruits were incubated at 25 ℃ with 80% humidity. After five days, typical naturally occurring fruit rot symptoms appeared on the fruits which inoculated with N. parvum, whereas control fruits remained asymptomatic. To fulfill Koch's postulates, the pathogen was re-isolated from the inoculated fruits and comfirmed as N. parvum by morphological and molecular analysis. Previous studies reported that N. parvum caused fruit rot on various common fruits in China, including loquat, kiwifruit and citrus (Lei et al. 2013; Zhai et al. 2019; Zhou et al. 2013). To our knowledge, this is the first report of N. parvum causing postharvest fruit rot on nai plum in China. This finding provides critical insights for the management of the high-risk disease on plum in China.

Detecting and identifying pathogens and antagonistic bacteria associated with Ginkgo biloba leaf spot disease

Background

Leaf spot disease severely impacts Ginkgo biloba (G. biloba) yield and quality. While microbial agents offer effective and non-toxic biological control for plant diseases, research on controlling leaf spot disease in G. biloba is notably scarce.

Methods

The pathogenic fungi were isolated and purified from diseased and healthy leaves of G. biloba, Subsequent examinations included morphological observations and molecular identification via PCR techniques. A phylogenetic tree was constructed to facilitate the analysis of these pathogenic fungi, and Koch's postulates were subsequently employed to reaffirm their pathogenic nature. The antagonistic experiment was employed to select biocontrol bacteria, and subsequently, the isolated biocontrol bacteria and pathogenic fungi were inoculated onto healthy leaves to assess the inhibitory effects of the biocontrol bacteria.

Results

Two pathologies responsible for the leaf spot disease on G. biloba were identified as Botryosphaeria dothidea and Neofusicoccum parvum via the analysis of phylogenetic tree and the application of Koch's Postulates. Additionally, we isolated two strains of biocontrol bacteria, namely Bacillus velezensis and Bacillus amyloliquefaciens. Their average inhibitory zones were measured at 4.78 cm and 3.46 cm, respectively. The inhibition zone of B. velezensis against N. parvum was 4 cm. B. velezensis showed a stronger inhibitory effect compared to B. amyloliquefaciens on the development of lesions caused by B. dothidea via leaf culture experiment.

Conclusion

This research reports, for the first time, the presence of B. dothidea as a pathogenic fungus affecting G. biloba. Moreover, the biocontrol bacteria, B. velezensis and B. amyloliquefaciens, exhibited the capability to effectively inhibit the growth and reproduction of B. dothidea, indicating their promising potential as environmentally friendly biocontrol resources.

Exploring Factors Conditioning the Expression of Botryosphaeria Dieback in Grapevine for Integrated Management of the Disease

Species from the Botryosphaeriaceae family are the causal agents of Botryosphaeria dieback (BD), a worldwide grapevine trunk disease. Because of their lifestyle and their adaptation to a wide range of temperatures, these fungi constitute a serious threat to vineyards and viticulture, especially in the actual context of climate change. Grapevine plants from both nurseries and vineyards are very susceptible to infections by botryosphaeriaceous fungi due to several cuts and wounds made during their propagation process and their entire life cycle, respectively. When decline becomes chronic or apoplectic, it reduces the longevity of the vineyard and affects the quality of the wine, leading to huge economic losses. Given the environmental impact of fungicides, and their short period of effectiveness in protecting pruning wounds, alternative strategies are being developed to fight BD fungal pathogens and limit their propagation. Among them, biological control has been recognized as a promising and sustainable alternative. However, there is still no effective strategy for combating this complex disease, conditioned by both fungal life traits and host tolerance traits, in relationships with the whole microbiome/microbiota. To provide sound guidance for an effective and sustainable integrated management of BD, by combining the limitation of infection risk, tolerant grapevine cultivars, and biological control, this review explores some of the factors conditioning the expression of BD in grapevine. Among them, the lifestyle of BD-associated pathogens, their pathogenicity factors, the cultivar traits of tolerance or susceptibility, and the biocontrol potential of Bacillus spp. and Trichoderma spp. are discussed.

The fungal metabolite 4-hydroxyphenylacetic acid from Neofusicoccum parvum modulates defence responses in grapevine

In a consequence of global warming, grapevine trunk diseases (GTDs) have become a pertinent problem to viticulture, because endophytic fungi can turn necrotrophic upon host stress killing the plant. In Neofusicoccum parvum Bt-67, plant-derived ferulic acid makes the fungus release Fusicoccin aglycone triggering plant cell death. Now, we show that the absence of ferulic acid lets the fungus secrete 4-hydroxyphenylacetic acid (4-HPA), mimicking the effect of auxins on grapevine defence and facilitating fungal spread. Using Vitis suspension cells, we dissected the mode of action of 4-HPA during defence triggered by the bacterial cell-death elicitor, harpin. Early responses (cytoskeletal remodelling and calcium influx) are inhibited, as well as the expression of Stilbene Synthase 27 and phytoalexin accumulation. In contrast to other auxins, 4-HPA quells transcripts for the auxin conjugating GRETCHEN HAGEN 3. We suggest that 4-HPA is a key component of the endophytic phase of N. parvum Bt-67 preventing host cell death. Therefore, our study paves the way to understand how GTDs regulate their latent phase for successful colonisation, before turning necrotrophic and killing the vines.

Duplex Real-Time PCR Assays for the Simultaneous Detection and Quantification of Botryosphaeriaceae Species Causing Canker Diseases in Woody Crops

Woody canker diseases caused by fungi of the Botryosphaeriaceae family are producing increasing losses in many economically important woody crops, including almond. To develop a molecular tool for the detection and quantification of the most aggressive and threatening species is of main importance. This will help to prevent the introduction of these pathogens in new orchards and to conveniently apply the appropriate control measures. Three reliable, sensitive and specific duplex qPCR assays using TaqMan probes have been designed for the detection and quantification of (a) Neofusicoccum parvum and the Neofusicoccum genus, (b) N. parvum and the Botryosphaeriaceae family and (c) Botryosphaeria dothidea and the Botryosphaeriaceae family. The multiplex qPCR protocols have been validated on artificially and naturally infected plants. Direct systems to process plant materials, without DNA purification, allowed high-throughput detection of Botryosphaeriaceae targets even in asymptomatic tissues. These results validate the qPCR using the direct sample preparation method as a valuable tool for Botryosphaeria dieback diagnosis allowing a large-scale analysis and the preventive detection of latent infection.

First report of Neofusicoccum parvum causing stem blight and dieback of highbush blueberry in the Czech Republic

Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips is a cosmopolitan pathogen causing dieback of multiple diverse woody hosts including highbush blueberry (Vaccinium corymbosum L.). This fungus can survive inside colonized plants without causing any symptoms for several years. Once the endophytic lifestyle is switched to the parasitic one, the symptoms of dieback can rapidly occur (bronze leaves, necroses under the bark, apoplexy) and the plant usually declines within a few weeks (Slipper and Wingfield 2007). In August 2022, blueberry plants displaying symptoms described above were observed in a production orchard located in Hovorany, the Czech Republic. Around 3 % of 1000 observed plants were symptomatic. In order to identify the pathogen, leaves, stems and roots of three diseased plants were collected, sectioned into small pieces (5 × 5 mm), surface sterilized (60 s in 75% ethanol, followed by 60 s in 1% sodium hypochlorite and rinsed three times using sterile distilled water), plated on potato dextrose agar (PDA) supplemented with 0.5 g/liter of streptomycin sulfate (PDAS) (Biosynth, Staad, Switzerland) and incubated at 25°C for 2 weeks at dark. Newly developed mycelia were immediately transferred to fresh PDA plates and purified by single-spore or hyphal-tip isolation. In total 33 fungal isolates were obtained. All the 33 isolates shared similar morphology and resembled Botryosphaeriaceae spp. Colonies on PDA (7 d at 25°C) were felty, white to iron grey in the centre. Conidiomata were observed on sterile pine needles on 2 % water agar (WA) at 25°C under near-UV light after 2 wks (110-220 × 60-175 μm). Conidia (n=30) were cylindrical to ellipsoidal, hyaline, 0(-1)-septate, (3.8-8.1 × 2-3 μm). Two representative isolates were deposited at the Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands (CBS 149846 and CBS 149847). The partial internal transcribed spacer (ITS) regions, beta-tubulin gene (tub2) and translation elongation factor 1-alpha (tef) gene were amplified from genomic DNA of both isolates following primers and protocols previously described (Eichmeier et al. 2020). Newly generated sequences were deposited in NCBI GenBank (acc. nos. ITS: OQ376566, OQ376567; tub2: OQ401701, OQ401702 and tef: OQ401699, OQ401700), being >99% identical (ITS 483/484 nt, tub2 426/430 nt and tef 230/232 nt) with the ex-type ITS (AY236943), tub2 (AY236888) and tef (AY236917) sequences of N. parvum strain CMW9081. Phylogenetically, newly obtained isolates grouped with ex-type and another three cultures of N. parvum in the three gene-based phylogenetic tree with strong 98/1.0 (BP/PP) support. To confirm pathogenicity, one-year-old canes of ten two-year-old V. corymbosum plants grown in pots were wounded by a 5 mm diam cork borer, and a 5-mm mycelial plug of a 7-day-old culture of both (CBS 149846 and CBS 149847) strains (five plants per strain) was inserted into the wound. Ten plants were inoculated with sterile PDA plugs and served as controls. Wounds were covered by sterile wet cotton, sealed with Parafilm® and inoculated plants were maintained in a growth chamber at 20 °C with 12/12 h light/dark period. Within two weeks, inoculated shoots changed colour from green to dark brown and exhibited dark necroses under the bark; after one month inoculated plants declined, while controls remained symptomless. The pathogen was reisolated from the inoculated plants with 100 % re-isolation rate, and its identity confirmed by sequencing ITS region. The experiment was repeated. Neofusicoccum parvum causing dieback of highbush blueberry was already reported from Australia, California, Chile, China, Italy, Mexico, Portugal and Uruguay (Rossman et al. 2023). Pecenka et al. (2021) reported a presence of another pathogen - Lasiodiplodia theobromae (Pat.) Griffon & Maubl. from the same plantation. This suggests that stem blight and dieback of highbush blueberry is caused by more than one Botryosphaeriaceae spp. as it was previously proved by Xu et al. (2015). To the best of our knowledge, this is the first report of stem blight and dieback of highbush blueberry caused by N. parvum in the Czech Republic.

Natamycin Has an Inhibitory Effect on Neofusicoccum parvum, the Pathogen of Chestnuts

This research aimed to investigate natamycin's antifungal effect and its mechanism against the chestnut pathogen Neofusicoccum parvum. Natamycin's inhibitory effects on N. parvum were investigated using a drug-containing plate culture method and an in vivo assay in chestnuts and shell buckets. The antifungal mechanism of action of natamycin on N. parvum was investigated by conducting staining experiments of the fungal cell wall and cell membrane. Natamycin had a minimum inhibitory concentration (MIC) of 100 μg/mL and a minimum fungicidal concentration (MFC) of 200 μg/mL against N. parvum. At five times the MFC, natamycin had a strong antifungal effect on chestnuts in vivo, and it effectively reduced morbidity and extended the storage period. The cell membrane was the primary target of natamycin action against N. parvum. Natamycin inhibits ergosterol synthesis, disrupts cell membranes, and causes intracellular protein, nucleic acid, and other macromolecule leakages. Furthermore, natamycin can cause oxidative damage to the fungus, as evidenced by decreased superoxide dismutase and catalase enzyme activity. Natamycin exerts a strong antifungal effect on the pathogenic fungus N. parvum from chestnuts, mainly through the disruption of fungal cell membranes.

Effects of Cultivar Susceptibility, Branch Age, and Temperature on Infection by Botryosphaeriaceae and Diaporthe Fungi on English Walnut (Juglans regia)

Botryosphaeriaceae and Diaporthe fungi have been described as the main causal agents of branch dieback and shoot blight of English walnut (Juglans regia L.). To date, the effects of biotic and abiotic factors on disease development on this host are still poorly understood. Thus, the main goal of this study was to evaluate the effects of cultivar, shoot-branch age, and temperature on infection by Botryosphaeriaceae and Diaporthe fungi on English walnut. The susceptibility of eight commercial cultivars was evaluated against three Botryosphaeriaceae and two Diaporthe species. For the remaining experiments, shoots or branches of 'Chandler' were used. An initial experiment evaluating two inoculation methods was conducted, with inoculation with a mycelial plug being more consistent and useful than conidial suspension inoculation. Cultivar susceptibility varied depending on the fungal species, with 'Chandler' being among the most tolerant cultivars for shoot infection. One-year-old shoots were significantly more sensitive for both Neofusicoccum parvum and Diaporthe neotheicola in comparison with 2- to 4-year-old branches. The effect of temperature on shoot infection was evaluated under 5, 10, 15, 20, 25, 30, and 35°C. Lesion development was significantly higher for N. parvum isolates than for D. neotheicola isolates at all temperatures evaluated, with optimum temperature of shoot infection being ∼26°C for N. parvum and ∼21°C for D. neotheicola.

Unveiling the Secretome of the Fungal Plant Pathogen Neofusicoccum parvum Induced by In Vitro Host Mimicry

Neofusicoccum parvum is a fungal plant pathogen of a wide range of hosts but knowledge about the virulence factors of N. parvum and host-pathogen interactions is rather limited. The molecules involved in the interaction between N. parvum and Eucalyptus are mostly unknown, so we used a multi-omics approach to understand pathogen-host interactions. We present the first comprehensive characterization of the in vitro secretome of N. parvum and a prediction of protein-protein interactions using a dry-lab non-targeted interactomics strategy. We used LC-MS to identify N. parvum protein profiles, resulting in the identification of over 400 proteins, from which 117 had a different abundance in the presence of the Eucalyptus stem. Most of the more abundant proteins under host mimicry are involved in plant cell wall degradation (targeting pectin and hemicellulose) consistent with pathogen growth on a plant host. Other proteins identified are involved in adhesion to host tissues, penetration, pathogenesis, or reactive oxygen species generation, involving ribonuclease/ribotoxin domains, putative ricin B lectins, and necrosis elicitors. The overexpression of chitosan synthesis proteins during interaction with the Eucalyptus stem reinforces the hypothesis of an infection strategy involving pathogen masking to avoid host defenses. Neofusicoccum parvum has the molecular apparatus to colonize the host but also actively feed on its living cells and induce necrosis suggesting that this species has a hemibiotrophic lifestyle.

Mixed infections of fungal trunk pathogens and induced systemic phenolic compound production in grapevines

As grapevines mature in California vineyards they accumulate chronic wood infections by the Ascomycete fungi that cause trunk diseases, including Botryosphaeria dieback (caused by Diplodia seriata and Neofusicoccum parvum) and Esca (caused by Phaeomoniella chlamydospora). It is thought that such mixed infections become localized to separate internal lesions/cankers of the permanent, woody structure of an individual vine, but nonetheless the fungi all colonize the same vascular system. In response to infection by one pathogen, the host may initiate systemic biochemical changes, which in turn may affect the extent of subsequent infections by other pathogens. To test this hypothesis, we measured changes in phenolic compounds in the wood and lesion lengths of the pathogens, during sequential co-inoculations with different or identical pair-wise sequences of infection by D. seriata, N. parvum, or P. chlamydospora. Prior fungal infections only affected the development of subsequent D. seriata infections. Effects of fungal infections on phenolic compounds were variable, yet initial infection by D. seriata was associated with significantly higher concentrations of most phenolic compounds distally, compared to all other initial inoculation treatments. It was hypothesized that pre-existing phenolic levels can slow initial lesion development of fungal trunk pathogens, especially for D. seriata, but over time the pathogens appeared to overcome or neutralize phenolic compounds and grow unimpeded. These results demonstrate that effects of one fungal trunk pathogen infection is generally unable to distally affect another long-term, albeit shifts in host phenolics and other plant defenses do occur.

Comparative Transcriptomics and Gene Knockout Reveal Virulence Factors of Neofusicoccum parvum in Walnut

Neofusicoccum parvum can cause stem and branch blight of walnut (Juglans spp.), resulting in great economic losses and ecological damage. A total of two strains of N. parvum were subjected to RNA-sequencing after being fed on different substrates, sterile water (K1/K2), and walnut (T1/T2), and the function of ABC1 was verified by gene knockout. There were 1,834, 338, and 878 differentially expressed genes (DEGs) between the K1 vs. K2, T1 vs. K1, and T2 vs. K2 comparison groups, respectively. The expression changes in thirty DEGs were verified by fluorescent quantitative PCR. These thirty DEGs showed the same expression patterns under both RNA-seq and PCR. In addition, ΔNpABC1 showed weaker virulence due to gene knockout, and the complementary strain NpABC1c showed the same virulence as the wild-type strain. Compared to the wild-type and complemented strains, the relative growth of ΔNpABC1 was significantly decreased when grown with H2O2, NaCl, Congo red, chloramphenicol, MnSO4, and CuSO4. The disease index of walnuts infected by the mutants was significantly lower than those infected by the wild-type and complementary strains. This result indicates that ABC1 gene is required for the stress response and virulence of N. parvum and may be involved in heavy metal resistance.

First Report of Brown Leaf Spot Caused by Neofusicoccum parvum on Photinia × fraseri Dress (Christmas berry) in China

Christmas berry (Photinia × fraseri Dress), known as red tip photinia, is an important landscape color plant in South China (Zhu et al., 2021). In summer 2021, brown leaf spots of Christmas berry were observed with an incidence of 45-70% on the campus of Nanchang Institute of Technology, Jiangxi Province (28°41'32.61"N, 116°1'53.75"E), China. These spots have a negative influence on the photosynthetic activity and severely reduce the ornamental value of these plants. Lesions originally occurred on the margins or tips of the leaves as red patches (Figure 1 A) and then developed into irregular reddish-brown necrotic spots with yellow halos (Figure 1 B) that finally were grey lesions with dark brown ring circles surround with yellow halos (Figure 1 C). Ten leaf samples with typical symptoms from five plants were collected. The tissue between the healthy and necrotic area (ca. 5 mm × 5 mm) was cut with a sterile scalpel and surface sterilized in 70% alcohol for 45 s, followed by 2% NaClO for 2 min and washed in sterile deionized water three times, The sterilized leaf parts were placed on potato dextrose agar (PDA) and incubated at 25℃ for 3 to 5 days. A total of 28 fungal isolates were obtained from ten symptomatic leaves, which were classified into five species by morphological characteristics. Neofusicoccum was the genus with the highest isolation frequency (50%). For pathogenicity tests, healthy leaves of Christmas berry were surface-sterilized, wounded using a sterile needle and inoculated with mycelial plugs (6 mm in diameter) on the left site of the leaves. Five representative isolates were chosen and ten leaves were used for every isolate. The controls on the same leaves on the right side of the leaves were treated with sterile PDA plugs. All samples were placed in an artificial climate box (RH 90±3%, 27±1℃, 12 h light) for 3 days. Only the leaves inoculated with isolate NH7 showed dark brown leaf spots (Figure 1 D). The control leaves and those inoculated with the other four isolates remained symptomless. To confirm pathogenicity, mycelial plugs of isolate NH7 were applied on punctured leaves of Christmas berry in the field as the artificial climate box (Figure 1 E-H). Inoculation with a sterile PDA plug served as control. All the leaves were covered with plastic bags for 48 h to maintain high relative humidity. Seven days later, symptoms similar to those observed in the field developed on all leaves inoculated with isolated NH7, while the controls remained symptomless. To fulfill Koch's postulates, fungal isolates were reisolated from symptomatic leaves and identified by morphological and molecular characteristics. The colony of isolate NH7 developed aerial hyphae, which had a grey center surrounded by grey-white hyphae (Figure 1 I). Conidia were aseptate, primarily fusiform and measured 11.1-19.8 × 3.2-7.1 µm (n = 50) (Figure 1 J). For further confirmation of the identity, five genes, including ITS (White et al., 1990), RPB2 (Pavlic et al., 2009), tub2 (Glass & Donaldson, 1995), and tef1 (Carbone & Kohn, 1999) were sequenced. The sequences were deposited in GenBank (OL584411 for ITS, OL606622 for ACT, OL694623 for tub2, OM141481 for RPB2 and OM141482 for tef1), Based on the phylogenetic tree analysis using IQ-TREE, isolate NH7 clustered with Neofusicoccum parvum (Figure 2). N. parvum has been reported to cause leaf spot disease on different plants including Myristica fragrans (Jayakumar et al., 2011), Ginkgo biloba (Mirhosseini et al., 2014), Vitis heyneana (Wu et al., 2015), rubber tree (Liu et al., 2017) and Geodorum eulophioides (Du et al., 2021). To our knowledge, this is the first report of N. parvum causing leaf spot disease on Christmas berry in China. As one of the most widely planted ornamental shrubs in China, the detailed knowledge of the pathogens targeting Christmas berry is critical.

First Report of Neofusicoccum parvum Causing Leaf Spot on coral trees (Viburnum odoratissimum) in China

Coral trees (Viburnum odoratissimum), as a class of evergreen shrubs, are mainly planted in landscapes in numerous cities in China. During September 2020, the author investigated four major parks in Hefei (Bao Park, Hefei Botanical Garden, Luzhou Park and Peninsula Park) and the campus of Anhui Agricultural University (approximately 0.5 ha) (31°49'21.30″N, 117°13'18.25″E). The results showed that the incidence rate of leaf spot disease reached 60% among approximately 100,000 coral trees planted in these areas. Coral trees begin to show leaf spots in August. In early stages of coral trees infection, the symptoms appeared as small brown spots ranged in length from 2 to 3 millimeters on the leaves. After the disease patches expand and darken, the coral leaves eventually wither and fall, which seriously affects its viewing and admiring value. To identify the fungal pathogen, the five-point sampling method was used to take typical similar leaf samples from 5 regions, and 6 samples were taken from each site, so a total of 150 samples were obtained. Fragments of sample leaves were surface-sterilized with 1% NaClO, plated on potato dextrose agar, and incubated at 25 °C in the dark. A total of 275 strains were obtained from 150 samples. According to the morphological characteristics, 275 strains were purified and divided into four types. Four representative strains (MI1, K1, F1, D1) were selected from four types for further pathogenicity testing and identification. The pathogenicity test was conducted in triplicate by inoculating wounded leaves of 1-year-old potted V. odoratissimum with 20μL of a conidial suspension (106 conidia/mL). The control was inoculated with sterile water. The specimens were placed in a growth chamber while maintaining 90% relative humidity and 28℃. After five days, the characteristic lesions were observed only on inoculated MI1 spore suspension leaves. The same fungus was reisolated from the lesions, thus fulfilling Koch's postulates. The pathogenic fungi accounted for 60% of all strains. Fungal colonies were circular and had abundant white aerial mycelium, and colonies changed from white to pure black after maturity. Conidia were fusiform (16-17×5-6 μm), thin-walled, transparent, and without diaphragms. Molecular identification was performed by partially sequencing the internal transcribed spacer (ITS) gene, the translation elongation Factor 1-alpha(EF1-alpha) gene, and the β-tubulin (TUB2) gene by using the primers ITS1/ITS4 (White et al. 1990), EF1-728F (Alves et al. 2008)/EF1-986R (Carbone & Kohn 1999), and Bt2a/Bt2b (Glass & Donaldson 1995), respectively. The obtained ITS sequence (MW767713) showed 99% identity with N. parvum CMW28429 (KU997429.1), the EF1-alpha sequence (MZ398261) showed 99% identity with N. parvum isolate A4 (FJ528597.1), and the TUB2 sequence (MZ398260) showed 99% identity with N. parvum isolate BO52 (KU554657.1). By combining the sequences of individual fragments of each fungus in the order ITS, EF1-alpha and TUB2, MEGA 6.0 was used to analyze the sequence of kinship by using the maximum likelihood method, and the repeat value of bootstraps was 1000. A polygenic phylogenetic tree analysis based on multilocus alignment (ITS, EF1-alpha and TUB2) was constructed with some strains of Botryosphaeriaceae species. The results of the phylogenetic tree showed that MI1 and N. parvum clustered into a branch. To our knowledge, this is the first report of N. parvum causing leaf spot on V. odoratissimum in China.

Insights of the Neofusicoccum parvum-Liquidambar styraciflua Interaction and Identification of New Cysteine-Rich Proteins in Both Species

Neofusicoccum parvum belongs to the Botryosphaeriaceae family, which contains endophytes and pathogens of woody plants. In this study, we isolated 11 strains from diseased tissue of Liquidambar styraciflua. Testing with Koch's postulates-followed by a molecular approach-revealed that N. parvum was the most pathogenic strain. We established an in vitro pathosystem (L. styraciflua foliar tissue-N. parvum) in order to characterize the infection process during the first 16 days. New CysRPs were identified for both organisms using public transcriptomic and genomic databases, while mRNA expression of CysRPs was analyzed by RT-qPCR. The results showed that N. parvum caused disease symptoms after 24 h that intensified over time. Through in silico analysis, 5 CysRPs were identified for each organism, revealing that all of the proteins are potentially secreted and novel, including two of N. parvum proteins containing the CFEM domain. Interestingly, the levels of the CysRPs mRNAs change during the interaction. This study reports N. parvum as a pathogen of L. styraciflua for the first time and highlights the potential involvement of CysRPs in both organisms during this interaction.

Cultivar Contributes to the Beneficial Effects of Bacillus subtilis PTA-271 and Trichoderma atroviride SC1 to Protect Grapevine Against Neofusicoccum parvum

Grapevine trunk diseases (GTDs) are a big threat for global viticulture. Without effective chemicals, biocontrol strategies are developed as alternatives to better cope with environmental concerns. A combination of biological control agents (BCAs) could even improve sustainable disease management through complementary ways of protection. In this study, we evaluated the combination of Bacillus subtilis (Bs) PTA-271 and Trichoderma atroviride (Ta) SC1 for the protection of Chardonnay and Tempranillo rootlings against Neofusicoccum parvum Bt67, an aggressive pathogen associated to Botryosphaeria dieback (BD). Indirect benefits offered by each BCA and their combination were then characterized in planta, as well as their direct benefits in vitro. Results provide evidence that (1) the cultivar contributes to the beneficial effects of Bs PTA-271 and Ta SC1 against N. parvum, and that (2) the in vitro BCA mutual antagonism switches to the strongest fungistatic effect toward Np-Bt67 in a three-way confrontation test. We also report for the first time the beneficial potential of a combination of BCA against Np-Bt67 especially in Tempranillo. Our findings highlight a common feature for both cultivars: salicylic acid (SA)-dependent defenses were strongly decreased in plants protected by the BCA, in contrast with symptomatic ones. We thus suggest that (1) the high basal expression of SA-dependent defenses in Tempranillo explains its highest susceptibility to N. parvum, and that (2) the cultivar-specific responses to the beneficial Bs PTA-271 and Ta SC1 remain to be further investigated.

Neofusicoccum parvum Causing Stem and Branch Blight Disease of Zanthoxylum bungeanum in Sichuan, China

The Chinese pepper Zanthoxylum bungeanum Maxim is a special economically important species and a traditional spice in China. It is widely used in medicine, food, timber, tourism, soil and water conservation. In April 2019, A stem and branch blight disease of Z. bungeanum was discovered in Muli, Puge and Yanyuan counties, in Liangshan Prefecture (27°15'20″-27°19'38″N, 101°44'58″-102°04'10″E), causing approximately 15% yield loss in the three counties. Among all fields in Muli County, approximately 41.38%, 10.79% and 2% of Chinese peppers exhibited mild, moderate and severe branch blight, respectively. The symptoms started to occur from March to April. First, red-brown spots on the base of the stem, branches or main trunks of young trees observed but were not obvious. In May, the spots became gray-brown to dark brown ovals and gradually expanded into long strips (Figure 1a, b). When the spots surrounded the branches, the branches above them withered and died, and the spots gradually expanded downward. Around June or July, scattered black dot-shaped fruiting bodies were observed on the lesion. The branches of infected trees were sampled systematically by cutting the branch at the junction of infected and healthy areas in 5×5 mm sections. Each sample was surface-sterilized with 3% NaClO and 75% alcohol for 60 s before being rinsed three times with sterilized distilled water. The sterile filter paper was used to dry the tissue, and the samples were cultured on potato dextrose agar (PDA) amended with streptomycin sulfate (50 μg/ml). Plates were incubated at 25°C in the dark. From the five isolates obtained, four exhibited the morphology described by Yu et al. (2015) for Neofusicoccum parvum. The colonies were white fluffy at first and grew fast (Figure 1c). After five days, the colony diameter reached 75.2-84.8 mm, produced yellow pigment and the mycelium in the middle of the colony began to turn gray (Figure 1d). and the entire colony turned dark gray 7-8 days post culturing as observed previously (Javier-Alva et al. 2009) and formed a black fruiting body at 20 days (Figure 1e). The width of the mycelium measured 2.3-4.8 µm, and with the diaphragm (Figure 1f). The spores were round or fusiform, colorless, transparent, smooth, thin-walled, and measured 6.3-10.6×3.1-5.2 µm (Figure 1g, h), similar to N. parvum (Yu et al. 2013). For molecular identification, DNA was extracted from the mycelia of four fungal isolates using a plant genomic DNA extraction kit (Solarbio, Beijing). Polymerase Chain Reaction (PCR) was performed with the primers ITS1/ITS4 (White et al. 1990), EF446F/EF1035R (Inderbitzin et al. 2005), BTF/BTR2 and HspF3/HspR (Inderbitzin et al. 2010) for the ribosomal internal transcribed spacer region (ITS), elongation factor-1alpha (EF1-alpha), beta-tubulin (TUB) and heat shock protein (HSP) genes, respectively. BLAST searches in the GenBank database indicated that the ITS, TUB, HSP and EF-1α sequences had 100%, 99.0%, 99.7% and 99.7% identity to N. parvum, respectively. Representative sequences were deposited in GenBank (ITS: MT355871; TUB: MT409397; EF-1α: MT409399; HSP: MT460413). A pathogenicity test was performed using N. parvum on ten 2-year-old potted Z. bungeanum plants at 22-28°C and 60% humidity indoors. The conidial suspension (1×107 conidia/ml) collected 25 days old PDA cultures with 0.05% tween buffer was used for inoculation by brushing the wounded area of branch scratched by epidermis with a piece of sandpaper. Ten plants in pots were inoculated with sterile water and served as controls. Thirty days post-inoculation, the plants showed the same symptoms as the original diseased plants, and the controls remained asymptomatic. N. parvum was re-isolated from the infected tissues and identified by morphological characteristics and DNA sequence analysis. The pathogenicity test was repeated three times with similar results, confirming Koch's postulates. This fungus is an important pathogen on a variety of woody hosts, and represents a serious problem in the vineyards worldwide (Mélanie, et al. 2017). To our knowledge, this is the first report of N. parvum causing stem and branch blight of Z. bungeanum trees in China.

Identification and Pathogenicity of Diplodia, Neofusicoccum, Cadophora, and Diaporthe Species Associated with Cordon Dieback in Kiwifruit cultivar Hayward in Central Chile

Dieback symptoms associated with fungal trunk pathogens cause significant economic losses for farmers of kiwifruit and other woody fruit trees worldwide. This study represents the first attempt to identify and characterize the fungal trunk pathogens associated with cordon dieback disease of kiwifruit in central Chile. Field surveys were conducted throughout the main kiwifruit-growing regions in central Chile to determine the incidence and characterize the fungal trunk pathogens associated with cordon dieback of kiwifruit cultivar Hayward through morphological, molecular, and pathogenicity studies. A total of 250 cordon samples were collected and isolations were performed on 2% acidified potato dextrose agar (APDA) plus antibiotics and Igepal. The incidence of kiwifruit cordon dieback ranged between 5% and 85% in all surveyed areas in central Chile. A total of 246 isolates were isolated and identified using culture and morphological features belonging to three fungal taxa: Diaporthaceae spp. (Diaporthe ambigua and D. australafricana; n = 133 isolates); Botryosphaeriaceae spp. (Diplodia seriata and Neofusicoccum parvum; n = 89 isolates); and Ploettnerulaceae spp. (Cadophora luteo-olivacea and C. malorum; n = 24 isolates). These were identified using phylogenetics studies of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2) of the rDNA, part of the β-tubulin gene (tub2), and part of the translation elongation factor 1-α gene (tef1-α). Isolates of N. parvum and D. seriata were the most virulent, causing internal brown lesions and dieback symptoms in attached green shoots, attached lignified canes, and young inoculated kiwifruits. This report is the first to describe D. seriata and C. luteo-olivacea associated with kiwifruit cordon dieback in Chile. It presents the first description of N. parvum causing kiwifruit dieback worldwide.

Characterization of the Mycovirome of the Phytopathogenic Fungus, Neofusicoccum parvum

Neofusicoccum parvum is a fungal plant-pathogen belonging to the family Botryosphaeriaceae, and is considered one of the most aggressive causal agents of the grapevine trunk disease (GTD) Botryosphaeria dieback. In this study, the mycovirome of a single strain of N. parvum (COLB) was characterized by high throughput sequencing analysis of total RNA and subsequent bioinformatic analyses. Contig annotations, genome completions, and phylogenetic analyses allowed us to describe six novel mycoviruses belonging to four different viral families. The virome is composed of two victoriviruses in the family Totiviridae, one alphaendornavirus in the family Endornaviridae, two mitoviruses in the family Mitoviridae, and one narnavirus belonging to the family Narnaviridae. The presence of the co-infecting viruses was confirmed by sequencing the RT-PCR products generated from total nucleic acids extracted from COLB. This study shows that the mycovirome of a single N. parvum strain is highly diverse and distinct from that previously described in N. parvum strains isolated from grapevines.

Early Season Symptoms on Stem, Inflorescences and Flowers of Grapevine Associated with Botryosphaeriaceae Species

Botryosphaeria dieback caused by several Botryosphaeriaceae species is one of the most important grapevine trunk diseases affecting vineyards worldwide. These fungi cause wedge-shaped perennial cankers and black streaking of the wood and have also been associated with intervein leaf chlorosis, dried or mummified berries, and eventually, the death of the plant. Early season symptoms may sometimes be disregarded by growers, being mistaken with symptoms from other diseases such as downy mildew or botrytis rot. Currently, few studies are available to determine what species may be causing these early season symptoms in grapevines. During the 2018 season, during the flowering period, grapevine samples showing necrosis on green shoots, dried inflorescences, and flowers, were collected in vineyards throughout the central regions of Portugal. Isolations were performed from symptomatic organs, and twenty-three isolates of Botryosphaeriaceae were selected. An analysis of the ITS and part of the translation elongation factor 1-α sequences was performed, revealing that the two main species apparently responsible for these symptoms were Diplodia seriata and Neofusicoccum parvum. In pathogenicity tests conducted on 1-year-old plants grown under controlled conditions in a greenhouse and on field-grown clusters, symptoms were reproduced, confirming the pathogenic behavior of the selection of isolates.

First Report of Neofusicoccum parvum Causing Leaf Spot on Geodorum eulophioides in China

Geodorum eulophioides Schltr. is a critically endangered orchid listed in the International Union for Conservation of Nature (IUCN) Red List of threatened species. At present, only two natural populations were found in China. It has important scientific and ornamental values because of its uniqueness. During the summer of 2019, a black leaf spot disease occurred on G. eulophioides, in Yachang Orchid National Nature Reserve (E106°13'32″，N24°44'19″) in Guangxi province, China. More than 60% of leaves of these plants were infected. The disease symptoms initially appeared as small yellow circular spots, which enlarged into irregular brown spots (6 to 9 cm length and 3 to 5 cm width). In later stages of the disease development, the center of the spots became dark brown with a clear edge and surrounded by a yellow halo. In severe infections, the spots coalesced covering the entire leaf. Six symptomatic leaves were collected from three infected plants, surface sterilized in 75% ethanol for 15 s and 0.1% HgCl2 for 4 min, and subsequently washed three times with sterile water, then plated onto potato dextrose agar (PDA), and incubated at 28℃ for three days. Eighteen fungal cultures with similar morphological characteristics were obtained from the infected tissues. Colonies were initially white, then turned dark grey after nine days. To induce sporulation, isolates were grown on 2% water agar and incubated under UVA light at 28℃ for nine days. Three isolates were selected for morphological characterization. Conidia were hyaline, unicellular, nonseptate, ellipsoidal to fusiform, externally smooth, thin-walled, and ranged from 10.7 to 16.6 μm (avg. 13.8 μm) × 4.1 to 6.7 μm (avg. 5.1 μm) (n=50). The isolate DBL-1 was selected as a representative for molecular identification. Genomic DNA was extracted and used for PCR to amplify the rDNA internal transcribed spacer region (ITS), translation elongation factor 1-alpha gene (EF1-α), and beta-tubulin gene (TUB2), using the primer pairs ITS1/ITS4 (White et al., 1990), EF1-728F/EF1-986R（Alves et al. 2008；Carbone & Kohn, 1999）, and T1/T2 (O'Donnell et al., 1997), respectively. The obtained ITS sequence (GenBank Accession No. MN918440), EF1-α sequence (MN963815), and TUB2 sequence (MN963816) showed >99% homology with several GenBank sequences of Neofusicoccum parvum (JX513636, KU997497 for ITS, KU997261, MH252401 for EF1-α, and KJ841779, MK412882 for TUB2, respectively). Based on morphological characteristics of the asexual morph and maximum likelihood analyses of a combined rDNA-ITS, EF1-α and TUB2 gene sequences, was identified as N. parvum. Pathogenicity test was performed using isolate DBL-1 by inoculating 3 leaves of G. eulophioides plants. The test was repeated three times. Each leaf was wounded using a sterile needle, and a mycelial plug (6 mm diameter) harvested from the periphery of a 3-day-old colony grown on PDA was placed on each wound. Plants were then covered with plastic bags to maintain high relative humidity of 90% and kept at 28℃ in a greenhouse under natural daylight conditions. An equal number of leaves on the same plant were inoculated using sterile PDA plugs and served as mock inoculated controls. After three days, all the inoculated leaves showed black spot symptoms resembling those observed in the field, whereas controls remained symptomless. The fungus was re-isolated from the symptomatic leaves, thus completing Koch's postulates. N. parvum has been reported to cause leaf spot disease on Myristica fragrans (Jayakumar, et al., 2011), Ginkgo biloba (Mirhosseini, et al., 2014), Vitis heyneana (Wu, et al., 2015), and Hevea brasiliensis (Liu et al., 2017), respectively. To the best of our knowledge, this is the first report of N. parvum causing leaf spot disease on G. eulophioides in China. The disease control measures and in-situ conservation method need to be strengthened to protect this rare species.

Five Fungal Pathogens Are Responsible for Bayberry Twig Blight and Fungicides Were Screened for Disease Control

Bayberry (Myrica rubra) is a commercial fruit in China. For the past seven years, twig blight disease has been attacking bayberry plantations in Shantou City, Guangdong Province, China, leading to destructive damage and financial loss. In this study, five fungal species associated with twig dieback and stem blight were identified based on morphological characteristics combined with multilocus sequence analysis (MLSA) on the internal transcribed spacer (ITS) region, partial sequences of β-tubulin (tub2), translation elongation factor 1-α (tef1-α), large subunit ribosomal RNA (LSU) and small subunit ribosomal RNA (SSU) genes, which are Epicoccum sorghinum, Neofusicoccum parvum, Lasiodiplodia theobromae, Nigrospora oryzae and a Pestalotiopsis new species P. myricae. P. myricae is the chief pathogen in fields, based on its high isolation rate and fast disease progression after inoculation. To our knowledge, this is the first study reporting the above five fungi as the pathogens responsible for bayberry twig blight. Indoor screening of fungicides indicates that Prochloraz (copper salt) is the most promising fungicide for field application, followed by Pyraclostrobin, 15% Difenoconazole + 15% Propiconazole, Difenoconazole and Myclobutanil. Additionally, Bacillus velezensis strain 3–10 and zeamines from Dickeya zeae strain EC1 could be used as potential ecofriendly alternatives to control the disease.

Antifungal Agents Based on Chitosan Oligomers, ε-polylysine and Streptomyces spp. Secondary Metabolites against Three Botryosphaeriaceae Species

Grapevine trunk diseases (GTDs) are a major threat to the wine and grape industry. The aim of the study was to investigate the antifungal activity against Neofusicoccum parvum, Diplodia seriata, and Botryosphaeria dothidea of ε-polylysine, chitosan oligomers, their conjugates, Streptomyces rochei and S. lavendofoliae culture filtrates, and their binary mixtures with chitosan oligomers. In vitro mycelial growth inhibition tests suggest that the efficacy of these treatments, in particular those based on ε-polylysine and ε-polylysine:chitosan oligomers 1:1 w/w conjugate, against the three Botryosphaeriaceae species would be comparable to or higher than that of conventional synthetic fungicides. In the case of ε-polylysine, EC₉₀ values as low as 227, 26.9, and 22.5 µg·mL^-1 were obtained for N. parvum, D. seriata, and B. dothidea, respectively. Although the efficacy of the conjugate was slightly lower, with EC₉₀ values of 507.5, 580.2, and 497.4 µg·mL^-1, respectively, it may represent a more cost-effective option to the utilization of pure ε-polylysine. The proposed treatments may offer a viable and sustainable alternative for controlling GTDs.

Bacillus subtilis PTA-271 Counteracts Botryosphaeria Dieback in Grapevine, Triggering Immune Responses and Detoxification of Fungal Phytotoxins

Plant pathogens have evolved various strategies to enter hosts and cause diseases. Particularly Neofusicoccum parvum, a member of Botryosphaeria dieback consortium, can secrete the phytotoxins (-)-terremutin and (R)-mellein during grapevine colonization. The contribution of phytotoxins to Botryosphaeria dieback symptoms still remains unknown. Moreover, there are currently no efficient control strategies of this disease, and agro-environmental concerns have raised increasing interest in biocontrol strategies to limit disease spread in vineyards, especially by using some promising beneficial bacteria. Here, we first examined in planta the biocontrol capacity of Bacillus subtilis PTA-271 against N. parvum Np-Bt67 strain producing both (-)-terremutin and (R)-mellein. We then focused on the direct effects of PTA-271 on pathogen growth and the fate of pure phytotoxins, and explored the capacity of PTA-271 to induce or prime grapevine immunity upon pathogen infection or phytotoxin exposure. Results provided evidence that PTA-271 significantly protects grapevine cuttings against N. parvum and significantly primes the expression of PR2 (encoding a β-1,3-glucanase) and NCED2 (9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis) genes upon pathogen challenge. Using in vitro plantlets, we also showed that PTA-271 triggers the expression of salicylic acid- and jasmonic acid-responsive genes, including GST1 (encoding a glutathione-S-transferase) involved in detoxification process. However, in PTA-271-pretreated plantlets, exogenous (-)-terremutin strongly lowered the expression of most of upregulated genes, except GST1. Data also indicated that PTA-271 can detoxify both (-)-terremutin and (R)-mellein and antagonize N. parvum under in vitro conditions. Our findings highlight (-)-terremutin and (R)-mellein as key aggressive molecules produced by N. parvum that may weaken grapevine immunity to promote Botryosphaeria dieback symptoms. However, PTA-271 can efficiently attenuate Botryosphaeria dieback by enhancing some host immune responses and detoxifying both phytotoxins produced by N. parvum.

Secreted proteins produced by fungi associated with Botryosphaeria dieback trigger distinct defense responses in Vitis vinifera and Vitis rupestris cells

Grapevine trunk diseases (Eutypa dieback, esca and Botryosphaeria dieback) are caused by a complex of xylem-inhabiting fungi, which severely reduce yields in vineyards. Botryosphaeria dieback is associated with Botryosphaeriaceae. In order to develop effective strategies against Botryosphaeria dieback, we investigated the molecular basis of grapevine interactions with a virulent species, Neofusicoccum parvum, and a weak pathogen, Diplodia seriata. We investigated defenses induced by purified secreted fungal proteins within suspension cells of Vitis (Vitis rupestris and Vitis vinifera cv. Gewurztraminer) with putative different susceptibility to Botryosphaeria dieback. Our results show that Vitis cells are able to detect secreted proteins produced by Botryosphaeriaceae, resulting in a rapid alkalinization of the extracellular medium and the production of reactive oxygen species. Concerning early defense responses, N. parvum proteins induced a more intense response compared to D. seriata. Early and late defense responses, i.e., extracellular medium alkalinization, cell death, and expression of PR defense genes were stronger in V. rupestris compared to V. vinifera, except for stilbene production. Secreted Botryosphaeriaceae proteins triggered a high accumulation of δ-viniferin in V. vinifera suspension cells. Artificial inoculation assays on detached canes with N. parvum and D. seriata showed that the development of necrosis is reduced in V. rupestris compared to V. vinifera cv. Gewurztraminer. This may be related to a more efficient induction of defense responses in V. rupestris, although not sufficient to completely inhibit fungal colonization. Overall, our work shows a specific signature of defense responses depending on the grapevine genotype and the fungal species.

Mourvèdre) after Inoculation with the Botryosphaeria Dieback Pathogens Neofusicoccum parvum and Diplodia seriata and Their Relationship with Flowering

As a result of the increasing economic impact of grapevine trunk diseases on viticulture worldwide, efficient and viable control strategies are urgently needed. However, understanding both plant-pathogen interactions and plant physiological changes related to these diseases is fundamental to such an achievement. In this study, we analyzed the effect of inoculation with the Botryosphaeria dieback fungal agents, Neofusicoccum parvum and Diplodia seriata, with and without inflorescence removal at the onset of G stage (separated clusters), I stage (flowering) and M stage (veraison). A measure of lesion size and real-time reverse-transcription polymerase chain reaction-based analysis were carried out. The results clearly show the importance of inflorescences in the development of lesions associated with Botryosphaeria dieback pathogens inoculated on green stems of adult vines, especially at the onset of flowering. At flowering, the biggest necroses were observed with the inflorescences present, as well as an activation of the studied defense responses. Thus, an ineffective response to the pathogen could be consistent with a possible metabolic reprogramming linked to the host phenophase.

Isolation of Neofusicoccum parvum from withered grapes: strain characterization, pathogenicity and its detrimental effects on passito wine aroma

AIMS

There is scarce information on the occurrence of several fungi that infect withered grapes to produce passito wine. Isolation and characterization of Neofusicoccum parvum strains and evaluation of their effects on withered grape and wine were carried out.

METHODS AND RESULTS

Nine isolates were phenotypically characterized by colony morphology and genetically discriminated by molecular methods. Two representative strains were identified as N. parvum according to the phylogenetic analysis of internal transcribed spacer (ITS), and a part of translation elongation factor 1-alfa (TEF) and β-tubulin DNA sequences. The pathogenicity of both strains on grape berries varied according to the inoculation and incubation conditions. Under withering conditions, infected berries showed browning and shrivelling and some berries showed pycnidial development on the surface. The infection affected laccase, esterase, β-glucosidase and tannase on grape juice as well as the content of several aroma molecules on resulting wines. Strain-specific effects on wine composition were also observed.

CONCLUSIONS

Neofusicoccum parvum occurred in withered grapes and was able to infect grapes under withering condition changing the aroma wine.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reports for the first time the N. parvum isolation in fruit-drying rooms and indicates its important role on postharvest grape infection.

Phytotoxic metabolites from Neofusicoccum parvum, a pathogen of Botryosphaeria dieback of grapevine

Liquid chromatography-diode array screening of the organic extract of the cultures of 13 isolates of the fungus Neofusicoccum parvum, the main causal agent of botryosphaeria dieback of grapevine, showed similar metabolites. One strain was selected for further chemical studies and led to the isolation and characterisation of 13 metabolites. Structures were elucidated through spectroscopic analyses, including one- and two-dimensional NMR and mass spectrometry, and through comparison to literature data. The isolated compounds belong to four different chemical families: five metabolites, namely, (-)-terremutin (1), (+)-terremutin hydrate (2), (+)-epi-sphaeropsidone (3) (-)-4-chloro-terremutin hydrate (4) and(+)-4-hydroxysuccinate-terremutin hydrate (5), belong to the family of dihydrotoluquinones; two metabolites, namely, (6S,7R) asperlin (6) and (6R,7S)-dia-asperlin (7), belong to the family of epoxylactones; four metabolites, namely, (R)-(-)-mellein (8), (3R,4R)-4-hydroxymellein (9), (3R,4S)-4-hydroxymellein (10) (R)(-)-3-hydroxymellein (11), belong to the family of dihydroisocoumarins; and two of the metabolites, namely, 6-methyl-salicylic acid (12) and 2-hydroxypropyl salicylic acid (13), belong to the family of hydroxybenzoic acids. We determined the phytotoxic activity of the isolated metabolites through a leaf disc assay and the expression of defence-related genes in Vitis vinifera cells cv. Chardonnay cultured with (-)-terremutin (1), the most abundant metabolite. Finally, analysis of the brown stripes of grapevine wood from plants showing botryosphaeria dieback symptoms revealed the presence of two of the isolated phytotoxins.