First Report of Botrytis cinerea Causing Fruit Rot of Pyrus sinkiangensis in China

Pathogenic fungi shape the fungal community, network complexity, and pathogenesis in kiwifruit

Kiwifruit decay caused by endophytic fungi is affected by exogenous pathogens that trigger changes in fungal community composition and interact with the endophytic fungal community. Four fungal pathogens of kiwifruit were identified. These were Aspergillus japonicus, Aspergillus flavus, Botryosphaeria dothidea, and Penicillium oxalicum. Except for P. oxalicum, the remaining three species represent newly described pathogens of kiwifruit. All four fungal species caused disease and decay in mature kiwifruit. Results of the fungal community analysis indicated that three pathogens that A. japonicus, A. flavus and P. oxalicum were the most dominant, however, other fungal species that did not cause disease symptoms were also present. Positive interactions between fungal species were found in asymptomatic, symptomatic, and infected kiwifruit. The ability of all four pathogens to infect kiwifruit was confirmed in an inoculation experiment. The presence of any one of the four identified pathogens accelerated decay development and limited the postharvest longevity of harvested kiwifruit. Results of the study identified and confirmed the ability of four fungal species to infect and cause decay in harvested kiwifruit. Changes in the structure and composition of the kiwifruit microbiome during the decay process were also characterized. This provides a foundation for the further study of the microbiome of kiwifruit and their involvement in postharvest diseases.

BCB1, a member of the acyl-coenzyme A synthetase family, regulates the morphogenesis and pathogenicity of Botrytis cinerea

Botrytis cinerea is a non-host-specific phytopathogenic fungus capable of infecting numerous cash crops. Here, we analyzed the functions of the Bcb1 gene in B. cinerea, which encodes a membrane protein belonging to the acyl-coenzyme A synthase family. Compared to the wild type, Bcb1-deletion mutants exhibited obvious morphological abnormalities, including slower vegetative growth and reduced melanin production. The absence of Bcb1 causes B. cinerea to form only small and incompletely developed infection cushions and fail to produce spores. The Bcb1 mutants displayed hypersensitivity to the membrane stressor SDS, the cell wall stressor Congo red, and the oxidative stressor H₂O₂ and increased resistance to intracellular osmotic stress caused by KCl compared to the wild-type strain. However, there were no differences in tolerance to extracellular osmotic stress caused by NaCl. The deletion of Bcb1 also caused a reduction in pathogenicity. The qRT‒PCR results showed that the genes Bcpks12 and Bcpks13, which are related to melanin biosynthesis, and Bcpg2, BcBOT2, and cutA, which are related to virulence, were downregulated in ∆Bcb1. These data suggest that BCB1 is important for conidial morphogenesis, and pathogenesis in B. cinerea.