Preharvest Botrytis cinerea infection accelerates postharvest spike-stalk browning in 'Munage' grape

Munage grape (Vitis vinifera L. cv. Munage.) is a unique cultivar found in southern Xinjiang, China. Spike-stalk browning in this species has become more common in recent years, and negatively impacting fruit shelf life and market value, thereby causing severe economic losses during storage. To understand the underlying mechanisms of Botrytis cinerea-induced spike-stalk browning in Munage grape, we analyzed the transcrip-tome and phenolic substances so a response to fungal infection using RNA-sequencing (RNA-seq) coupled with Liquid Chromatography Mass Spectrometry (LC-MS) analysis. Morphological and physiological obser-vations showed that the browning degrees and phenolic enzyme activities of phenylalanine ammonia-lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) in B. cinerea-infected spike-stalk were significantly higher than those of in controls' during the entire storage period. According to the omics profiles, phenylpro-panoid and flavonoid biosynthesis pathways were the major pathways induced by B. cinerea infection. The genes encoding enzymes responsible for the synthesis of basic phenolic acids, including phenylalanine ammonia-lyase 2 (PAL2), cinnamate 4-hydroxylase (C4H), 4-coumarate: CoA ligase (4CL), shikimate O-hydroxycinnamoyl transferase (HCT), caffeic acid 3-O-methyltransferase (COMT) and cytochrome P450 84A1 (F5H) were up-regulated 3 to 8 folds in response to B. cinerea infestation, accompanied by abundant accumu-lation of phenols such as 3,4-dihydroxybenzoic acid, trans-cinnamic acid, 4-hydroxy-3,5-dimethoxycinnamic acid and salicylic acid. Several flavonoid compounds with antioxidant activity (vitexin, (+)-dihydrokaemp-ferol, luteolin, naringenin and apigenin) accumulated in the inoculated spike-stalk as stress-response signals. These results contribute to elucidate the underlying mechanisms of B. cinerea induced spike-stalk browning on Munage grapes and provide theoretical guidance for prevention and control measures to reduce the inci-dence of gray mold after harvest.(c) 2023 SAAB. Published by Elsevier B.V. All rights reserved.