Cytospora chrysosperma is a common opportunistically parasitic fungus that mainly infects forest trees, severely restricting the development of the fruit and forest industry. Surfactin is a secondary metabolite produced by Bacillus species and exhibits antifungal activity; Although the core antifungal mechanism of surfactin against plant pathogens has been extensively studied, our study found that surfactin can target the tricarboxylic acid cycle of C. chrysosperma. This study aimed to investigate the potential mechanism underlying the inhibitory effect of surfactin on C. chrysosperma. The results showed that surfactin had a significant inhibitory effect on C. chrysosperma, with a half-maximal effective concentration of 0.787 ± 0.045 mg/mL and a minimum inhibitory concentration of 2 mg/mL. Morphological observations revealed that surfactin significantly disrupted the morphology and ultrastructure of C. chrysosperma hyphae. FDA/PI staining indicated that surfactin affected the cell membrane integrity of C. chrysosperma, while DCFH-DA fluorescent staining and antioxidant enzyme activity assays demonstrated the accumulation of reactive oxygen species in hyphal cells following surfactin treatment. Additionally, the reduction in adenosine triphosphate content, as well as the decreased activities of ATPase and succinate dehydrogenase, suggested that energy production might be inhibited. Finally, MDC staining showed the occurrence of autophagosomes in C. chrysosperma hyphae after surfactin treatment, which may lead to hyphal death. Transcriptome analysis revealed that surfactin impaired the normal biosynthesis of the C. chrysosperma cell membrane and interfered with the tricarboxylic acid cycle by binding to citrate synthase, resulting in intracellular energy metabolism disorders. This study provides new insights into the potential mechanism by which surfactin inhibits hyphal growth of C. chrysosperma.

Grapes are one of the widely cultivated fruits, with high nutritional value and economic value. The widespread occurrence of grape virus diseases has seriously affected the development of the grape industry. The grapevine varieties “Merlot”, “Cabernet Sauvignon”, “Syrah”, “Chardonnay”, “Welsch Riesling ”, and “Riesling Weiss” were used as materials for screening grapevines carrying the viroid GYSVd1 by RT-PCR. Principal component analysis (PCA) was employed to systematically assess the physicochemical indexes of both grape berries and wine in order to determine the extent of the influence of GYSVd1 on the quality of grape berries and wine. The results demonstrated that GYSVd1 infection significantly compromised both berries and wine quality across the tested cultivars, albeit with distinct varietal susceptibility patterns. Regarding berries’ quality, the negative impact of GYSVd1 followed this decreasing order: Merlot > Chardonnay > Welsch Riesling > Syrah > Riesling Weiss > Cabernet Sauvignon. Similarly, for wine quality, the negative impact exhibited the following gradient: Welsch Riesling > Riesling Weiss > Chardonnay > Cabernet Sauvignon > Syrah > Merlot. There were significant differences in the amount of sugar, acid and phenolic substances between GYSVd1-infected and -uninfected grapevines, but no significant differences in berry weight, berry shape index, and alcohol content. GYSVd1 affected the quality of berries and wine mainly by regulating the contents of sugar, acid, and phenolic substances.

Cotton verticillium wilt caused by Verticillium dahliae severely restricts global cotton production. Mycovirus–induced hypovirulence provides a promising strategy for sustainable disease management. In this study, V. dahliae isolates from Xinjiang were screened by virome sequencing and RT–PCR, and strain 121–11C–1 co–infected with Verticillium dahliae partitivirus 1 (VdPV1) and Verticillium dahliae magoulivirus 1 (VdMoV1) was identified. Virus–free isogenic strains were obtained via single–conidium purification, verifying that both viruses can be vertically transmitted through fungal conidia. Dual–culture assays uncovered a novel, previously unreported horizontal transmission dependency between the two viruses: VdPV1 achieves horizontal transmission only with the assistance of VdMoV1, whereas VdMoV1 can transmit independently or co–transmit with VdPV1. Biological and pathogenicity assays demonstrated that both viruses significantly inhibit mycelial growth, reduce conidial production and attenuate fungal virulence. Notably, dual infection induced a significantly stronger hypovirulent phenotype than single infection. These findings elucidate the transmission dynamics of VdPV1 and VdMoV1, expand the repertoire of hypovirulent mycoviruses in V. dahliae, and provide evidence that viral co–infection enhances fungal attenuation, offering potential applications for biological control of cotton Verticillium wilt.

This study investigates the roles of grapevine berry inner necrosis virus (GINV) and grapevine yellow speckle viroid 1 (GYSVd1) in regulating the soluble sugar and organic acid metabolism of grape berries and wine. The contents of soluble sugar and organic acid components and the activity and expression levels of critical enzymes of the soluble sugar acid metabolism pathway were measured in ‘Welschriesling’ grape berries and wine carrying the virus GINV, the viroid GYSVd1, and a mixed infection of both GINV and GYSVd1 (GINV + GYSVd1), respectively. The results show that the virus GINV and the viroid GYSVd1 decreased the soluble sugar and increased the organic acid in berries and wine. GINV decreased glucose content and increased malic acid content by regulating AI, NADP-IDH, PEPC, and NAD-MDH activity, as well as VvHT4, VvSWEET10, VvPEPC, and VvMDH expression levels. GYSVd1 decreased glucose content and increased malic acid content by regulating AI and CS activity and VvHT4, VvSWEET15, and VvPEPC expression. The results suggest that the viroid GYSVd1 negatively impacts berries and wine more than the virus GINV. Moreover, in the mixed infection with GINV + GYSVd1, the negative effects of GINV and GYSVd1 on soluble sugars do not seem to be observed.