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The ATP-binding cassette (ABC) superfamily is involved in numerous complex biological processes. However, the understanding of ABCs in plant pathogen defense, particularly against Botryosphaeria dothidea , remains limited. In this study, we identified MdABCI17 that plays a positive role in apple resistance to B. dothidea . Overexpression of MdABCI17 significantly enhanced the resistance of apple calli and fruits to B. dothidea . Our findings revealed that the jasmonic acid (JA) content and the expression of genes associated with JA biosynthesis and signal transduction were higher in stable MdABCI17- overexpressing apple calli than that of wild-type after inoculation with B. dothidea . Similar results were obtained for apple fruits with transient overexpression of MdABCI17 . Our research indicates that MdABCI17 enhances apple resistance to B. dothidea through the JA signaling pathway. We further determined that MdABCI17 plays a crucial role in the apple’s response to JA signaling. Moreover, exogenous methyl jasmonate (MeJA) treatment significantly enhanced the effectiveness of MdABCI17 in boosting apple resistance to B. dothidea . We proposed a positive feedback regulatory loop between MdABCI17 -mediated apple resistance to B. dothidea and JA signal. In summary, our study offers new insights into the role of ABC superfamily members in the control of plant disease resistance.

Many mycoviruses have been accurately and successfully identified in plant pathogenic fungus Botryosphaeria dothidea. This study discovered three mycoviruses from a B. dothidea strain SXD111 using high-throughput sequencing technology. A novel hypovirus was tentatively named Botryosphaeria dothidea hypovirus 1 (BdHV1/SXD111). The other two were known viruses, which we named Botryosphaeria dothidea polymycovirus 1 strain SXD111 (BdPmV1/SXD111) and Botryosphaeria dothidea partitivirus 1 strain SXD111 (BdPV1/SXD111). The genome of BdHV1/SXD111 is 11,128 nucleotides long, excluding the poly (A) tail. A papain-like cysteine protease (Pro), a UDP-glucose/sterol glucosyltransferase (UGT), an RNA-dependent RNA polyprotein (RdRp), and a helicase (Hel) were detected in the polyprotein of BdHV1/SXD111. Phylogenetic analysis showed that BdHV1/SXD111 was clustered with betahypovirus and separated from members of the other genera in the family Hypoviridae. The BdPmV1/SXD111 genome comprised five dsRNA segments with 2396, 2232, 1967, 1131, and 1060 bp lengths. Additionally, BdPV1/SXD111 harbored three dsRNA segments with 1823, 1623, and 557 bp lengths. Furthermore, the smallest dsRNA was a novel satellite component of BdPV1/SXD111. BdHV1/SXD111 could be transmitted through conidia and hyphae contact, whereas it likely has no apparent impact on the morphologies and virulence of the host fungus. Thus, this study is the first report of a betahypovirus isolated from the fungus B. dothidea. Importantly, our results significantly enhance the diversity of the B. dothidea viruses.

During September of 2020, Fruit suspected to be rot were observed on Choerospondias axillaris grown in an plantation in Yichun, Jiangxi, China. Approximately 10% of the fruit was discovered to be infected. The morphological features of the fungal isolate was identical to the features of Botryosphaeria dothidea . Phylogeny of concatenated sequences of the ITS, SSU, LSU and TUB2 genes were used to identify the causative agent as B.dothidea . Pathogenicity tests confirmed that this fungal species is the causal agent to C. axillaris. To the best of our knowledge, this is the first report of B. dothidea on C. axillaris in China and the world.

Apple fruit ring rot (FRR), caused by Botryosphaeria dothidea, is a worldwide disease that impacts Asian apple production regions. However, no substantial progress has thus far been made toward the mapping of candidate genes or the development of effective genetic makers. In this five-year study, the resistance of 1,733 F1 hybrids from the cross ‘Jonathan’ × ‘Golden Delicious’ was phenotyped by non-wounding inoculation with four B. dothidea isolates. We first conducted systematic comparison of different analytic strategies for bulk segregant analysis by re-sequencing (BSA-Seq) and obtained suitable one for outbreeding species such as Malus. Forty-six quantitative trait loci (QTL) for resistance/susceptibility to the four isolates, including one QTL ‘hotspot’ on chromosome 14, were identified via BSA-Seq. Using integrated multi-omics strategies including RNA-sequencing, parental re-sequencing, BSA-Seq and meta-analysis of RNA-sequencing, fifty-seven candidate genes and corresponding functional mutations from the QTL were predicted. Functional mutations located on the candidate genes were validated using kompetitive allele-specific PCR in hybrids and Malus germplasm accessions with extremely resistant/susceptible phenotypes. Ten effective markers for apple ring rot were developed. The results provide an example of rapid candidate gene mapping for complex traits in outbreeding species.

Botryosphaeria dothidea is, globally, one of the most economically important phytopathogenic fungi worldwide, causing the canker and dieback of fruit trees. An increasing number of viruses infecting B. dothidea have lately been reported, several of which could confer hypovirulence. In this study, isolated from strain ZM170285-1 of B. dothidea, a novel double-stranded RNA (dsRNA) mycovirus, tentatively named Botryosphaeria dothidea partitivirus 2 (BdPV2), was identified well. The BdPV2 harbored three dsRNA segments (1–3) with lengths of 1751, 1568, and 1198 bp, which encoded an RNA-dependent RNA polymerase (RdRp), a capsid protein (CP), and a hypothetical protein of unknown function, respectively. BLASTp searches revealed that the predicted protein sequences of dsRNA1 and dsRNA2 had the highest identities (74.95% and 61.01%) with the corresponding dsRNAs of Penicillium stoloniferum virus S (PsV-S), whereas dsRNA3 shared the highest identity (32.95%) with the dsRNA3 of Aspergillus ochraceous virus 1 (AoV1). Phylogenetic analysis indicated that BdPV2 belonged to the Gammapartitivirus genus and Partitiviridae family. To our knowledge, this is the first report of a Gammapartitivirus in B. dothidea.

Pear ring rot disease, mainly caused by Botryosphaeria dothidea , is widespread in most pear and apple-growing regions. Mycoviruses are used for biocontrol, especially in fruit tree disease. BdCV1 ( Botryosphaeria dothidea chrysovirus 1) and BdPV1 ( Botryosphaeria dothidea partitivirus 1) influence the biological characteristics of B. dothidea strains. BdCV1 is a potential candidate for the control of fungal disease. Therefore, it is vital to explore interactions between B. dothidea and mycovirus to clarify the pathogenic mechanisms of B. dothidea and hypovirulence of B. dothidea in pear. A high-quality full-length genome sequence of the B. dothidea LW-Hubei isolate was obtained using Single Molecule Real-Time sequencing. It has high repeat sequence with 9.3% and DNA methylation existence in the genome. The 46.34 Mb genomes contained 14,091 predicted genes, which of 13,135 were annotated. B. dothidea was predicted to express 3833 secreted proteins. In bioinformatics analysis, 351 CAZy members, 552 transporters, 128 kinases, and 1096 proteins associated with plant-host interaction (PHI) were identified. RNA-silencing components including two endoribonuclease Dicer, four argonaute (Ago) and three RNA-dependent RNA polymerase (RdRp) molecules were identified and expressed in response to mycovirus infection . Horizontal transfer of the LW-C and LW-P strains indicated that BdCV1 induced host gene silencing in LW-C to suppress BdPV1 transmission. To investigate the role of RNA-silencing in B. dothidea defense, we constructed four small RNA libraries and sequenced B. dothidea micro-like RNAs ( Bd -milRNAs) produced in response to BdCV1 and BdPV1 infection. Among these, 167 conserved and 68 candidate novel Bd -milRNAs were identified, of which 161 conserved and 20 novel Bd -milRNA were differentially expressed. WEGO analysis revealed involvement of the differentially expressed Bd -milRNA-targeted genes in metabolic process, catalytic activity, cell process and response to stress or stimulus. BdCV1 had a greater effect on the phenotype, virulence, conidiomata, vertical and horizontal transmission ability, and mycelia cellular structure biological characteristics of B. dothidea strains than BdPV1 and virus-free strains. The results obtained in this study indicate that mycovirus regulates biological processes in B. dothidea through the combined interaction of antiviral defense mediated by RNA-silencing and milRNA-mediated regulation of target gene mRNA expression.

Branch and trunk canker diseases have become prevalent on nut crops in Iran. During 2015 to 2018, extensive field surveys were conducted on 58 almond, 43 pistachio and 80 walnut orchards in Iran to study fungal pathogens associated with symptomatic trees. One hundred and fifty-six representative fungal isolates were selected and identified based on morphological characteristics and by phylogenetic comparison of DNA sequence data. Fungal species found were Collophorina hispanica, Pleurostoma richardsiae, nine species of Phaeoacremonium (namely P. angustius, P. cinereum, P. italicum, P. fraxinopennsylvanicum, P. minimum, P. parasiticum, P. scolyti, P. tuscanum and P. viticola), 11 species of Botryosphaeriaceae (namely Botryosphaeria dothidea, Diplodia gallae, D. mutila, D. seriata, Dothiorella plurivora, Do. sarmentorum, Do. viticola, Lasiodiplodia citricola, L. mahajangana, L. theobromae and Neofusicoccum parvum), four species of Diatrypaceae (namely Cryptosphaeria pullmanensis, Diatrype whitmanensis, Eutypella citricola and E. vitis) and two non-identified Eutypella spp. (Eutypella sp. 1 and Eutypella sp. 2). Some of these species represent new reports in Iran and/or are reported for the first time in their respective hosts. Pathogenicity tests demonstrated that most of these fungi were pathogenic to inoculated almond, pistachio and walnut shoots. Therefore, more importance should be given to fungal trunk pathogens in Iran, and specific management strategies should be included within the nut crops IPM management programs, with the aim of improving their sustainability.

Paenibacillus polymyxa is a plant growth-promoting rhizobacterium that has immense potential to be used as an environmentally friendly replacement of chemical fertilizers and pesticides. In the present study, Paenibacillus polymyxa SK1 was isolated from bulbs of Lilium lancifolium. The isolated endophytic strain showed antifungal activities against important plant pathogens like Botryosphaeria dothidea, Fusarium oxysporum, Botrytis cinerea, and Fusarium fujikuroi. The highest percentage of growth inhibition, i.e., 66.67 ± 2.23%, was observed for SK1 against Botryosphaeria dothidea followed by 61.19 ± 3.12%, 60.71 ± 3.53%, and 55.54 ± 2.89% against Botrytis cinerea, Fusarium fujikuroi, and Fusarium oxysporum, respectively. The metabolite profiling of ethyl acetate fraction was assessed through the UHPLC-LTQ-IT-MS/MS analysis, and putative identification was done with the aid of the GNPS molecular networking workflow. A total of 29 compounds were putatively identified which included dipeptides, tripeptides, cyclopeptides (cyclo-(Leu-Leu), cyclo(Pro-Phe)), 2-heptyl-3-hydroxy 4-quinolone, 6-oxocativic acid, anhydrobrazilic acid, 1-(5-methoxy-1H-indol-3-yl)-2-piperidin-1-ylethane-1,2-dione, octadecenoic acid, pyochelin, 15-hydroxy-5Z,8Z,11Z, 13E-eicosatetraenoic acid, (Z)-7-[(2R,3S)-3-[(2Z,5E)-Undeca-2,5-dienyl]oxiran-2-yl]hept-5-enoic acid, arginylasparagine, cholic acid, sphinganine, elaidic acid, gossypin, L-carnosine, tetrodotoxin, and ursodiol. The high antifungal activity of SK1 might be attributed to the presence of these bioactive compounds. The isolated strain SK1 showed plant growth-promoting traits such as the production of organic acids, ACC deaminase, indole-3-acetic acid (IAA), siderophores, nitrogen fixation, and phosphate solubilization. IAA production was strongly correlated with the application of exogenous tryptophan concentrations in the medium. Furthermore, inoculation of SK1 enhanced plant growth of two Lilium varieties, Tresor and White Heaven, under greenhouse condition. In the light of these findings, the P. polymyxa SK1 may be utilized as a source of plant growth promotion and disease control in sustainable agriculture.

Botryosphaeria dothidea is a major postharvest causal agent of soft rot in kiwifruit. Methyl jasmonate (MeJA) is an important plant hormone that participates as a plant defense against pathogens from a signal molecule. However, the impact and regulatory mechanism of MeJA on the attenuation of kiwifruit fungal decay remains unknown. This work investigated the effects of exogenous MeJA on the enzyme activity, metabolite content and gene expression of the phenylpropanoid and jasmonate pathways in kiwifruit. The results revealed that MeJA inhibited the expansion of B. dothidea lesion diameter in kiwifruit ( Actinidia chinensis cv. ‘Hongyang’), enhanced the activity of enzymes (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, 4-coumarate: coenzyme A ligase, cinnamyl alcohol dehydrogenase, peroxidase and polyphenol oxidase), and upregulated the expression of related genes ( AcPAL , AcC4H , Ac4CL , and AcCAD ). The accumulation of metabolites (total phenolics, flavonoids, chlorogenic acid, caffeic acid and lignin) with inhibitory effects on pathogens was promoted. Moreover, MeJA enhanced the expression of AcLOX , AcAOS , AcAOC , AcOPR3 , AcJAR1 , AcCOI1 and AcMYC2 and reduced the expression of AcJAZ . These results suggest that MeJA could display a better performance in enhancing the resistance of disease in kiwifruit by regulating the phenylpropanoid pathway and jasmonate pathway.

Background The MYB transcription factor family is one of the largest transcriptional factor families in plants and plays a multifaceted role in plant growth and development. However, MYB transcription factors involved in pathogen resistance in apple remain poorly understood. Results We identified a new MYB family member from apple, and named it MdMYB30. MdMYB30 was localized to the nucleus, and was highly expressed in young apple leaves. Transcription of MdMYB30 was induced by abiotic stressors, such as polyethylene glycol and abscisic acid. Scanning electron microscopy and gas chromatograph–mass spectrometry analyses demonstrated that ectopically expressing MdMYB30 in Arabidopsis changed the wax content, the number of wax crystals, and the transcription of wax-related genes. MdMYB30 bound to the MdKCS1 promoter to activate its expression and regulate wax biosynthesis. MdMYB30 also contributed to plant surface properties and increased resistance to the bacterial strain Pst DC3000. Furthermore, a virus-based transformation in apple fruits and transgenic apple calli demonstrated that MdMYB30 increased resistance to Botryosphaeria dothidea . Our findings suggest that MdMYB30 plays a vital role in the accumulation of cuticular wax and enhances disease resistance in apple. Conclusions MdMYB30 bound to the MdKCS1 gene promoter to activate its transcription and regulate cuticular wax content and composition, which influenced the surface properties and expression of pathogenesis-related genes to resistance against pathogens. MdMYB30 appears to be a crucial element in the formation of the plant cuticle and confers apple with a tolerance to pathogens.