Diallyl Trisulfide Controls Postharvest Gray Mold and Maintains Tomato Fruit Quality via Direct Antifungal Activity and Host Defense Activation

Abstract

Diallyl trisulfide (DATS), a volatile natural sulfur-containing compound derived from garlic, possesses antifungal and preservative potential. However, its biocontrol efficacy against postharvest gray mold of tomato and the molecular mechanisms underlying fruit quality maintenance remain unclear. In this study, we systematically investigated the inhibitory effect of DATS fumigation on postharvest gray mold, its role in fruit quality maintenance, and the associated molecular mechanisms through in vitro antifungal assays, physiological and biochemical measurements, transcriptome sequencing, and correlation analysis. In vitro experiments showed that DATS at 50 μL L−1 completely inhibited spore germination and germ tube elongation of Botrytis cinerea in a concentration-dependent manner, and disrupted spore membrane integrity (FDA-positive spores dropped from 73.4% to 2.9% at 50 μL L−1). In vivo experiments demonstrated that Bc + DATS treatment completely inhibited lesion development compared to the control Bc, enhanced the activities of superoxide dismutase, catalase and peroxidase (e.g., CAT activity 2.20-fold higher than Bc on day 3), decreased malondialdehyde accumulation (0.65-fold of Bc on day 4), and delayed the declines in total soluble solids, titratable acidity, soluble sugars and vitamin C content (VC content 4.14-fold higher than Bc on day 4). Transcriptomic analysis revealed that DATS treatment up-regulated genes involved in plant hormone signal transduction, ubiquitin-mediated proteolysis, and phenylalanine metabolism, while down-regulating core MAPK kinases and histidine decarboxylase. Correlation analysis demonstrated significant associations between the expression of these pathway genes and antioxidant enzyme activities, vitamin C content, and lesion diameter. Collectively, DATS achieves effective control of postharvest gray mold and maintenance of fruit quality in tomato through direct antifungal activity, synergistic activation of hormone/MAPK signaling, reprogramming of phenylalanine metabolism, and modulation of membrane lipid homeostasis. This study provides a theoretical and practical basis for developing DATS as a green postharvest preservative to reduce food loss and ensure food safety.