Combined application of brassinosteroid and Metschnikowia pulcherrima against controls Botrytis cinerea on grape berries

Abstract:

[Background] The yeast for biocontrol is characterized by rapid growth, strong stress resistance, and absence of antibiotic production. However, their biocontrol effects are easily influenced by environmental conditions. Brassinosteroid (BR) regulates the balance between plant growth and stress response and efficiently controls the occurrence of gray mold (Botrytis cinerea) on grape berries. [Objective] To investigate the effect and mechanism of Metschnikowia pulcherrima combined with BR in controlling B. cinerea on grape berries, and to provide a theoretical basis for the development and application of new biocontrol agents. [Methods] The berries of ‘Red Globe’ grape were treated with M. pulcherrima P01C004 (Y), P01C004+BR (YBR), and P01C004+brassinazole (YBZ), respectively. The spore suspension of B. cinerea was inoculated on the grape berries 6 h after the Y, YBR, and YBZ treatments. The efficiency of disease control, the activities of antioxidant enzymes, and the content of 13 phenolic compounds were evaluated 7 days after the inoculation of B. cinerea. qRT-PCR was performed to quantify the expression of the genes related to BR signaling pathway and pathogenesis under different treatments. [Results] Compared with Y treatment, YBR increased the control efficiency against B. cinerea by 23.64% and significantly improved the activities of polyphenol oxidase in grape berries. YBR significantly increased the content of chlorogenic acid, protocatechin, caffeic acid, epicatechin, and apigenin, and activated the rapid synthesis of phenols 2 days after inoculation. YBR activated the BR signaling pathway and up-regulated the expression levels of genes VvBZR1 and VvPR1 at the time point of 48 h, which sustained the plant immunity and induced strong defense responses of grape berries to the pathogen. [Conclusion] The combined application of M. pulcherrima and BR triggered multiple defense mechanisms of grape and improved the control efficiency against B. cinerea on grape berries, demonstrating a promising prospect in the postharvest disease control.