Physiological mechanisms and transcriptomic analysis of the disease resistance in pear fruit induced by Debaryomyces...

Debaryomyces hansenii, an antagonistic yeast, effectively suppresses postharvest pathogens in various across fruit and vegetable commodities. However, the specific mechanisms underlying its ability to trigger defense responses in pear fruits remain poorly understood. This study investigated the physiological and molecular mechanisms associated with D. hansenii-induced disease resistance in pear fruits. The results showed that D. hansenii significantly inhibited Penicillium expansum, rapidly colonized on wound and surfaces at 20 °C, and competitively excluded pathogens by monopolizing carbon sources and spatial niches. Physiological analyses revealed that D. hansenii enhanced the activity of resistance-related enzymes (Polyphenol oxidase, Phenylalanine ammonia-lyase, and Peroxidase) and increased secondary metabolite content (total phenols and flavonoids) while reducing Malondialdehyde (MDA) levels. Moreover, this yeast induced the activity of antioxidant enzymes (Superoxide dismutase, Catalase, and Ascorbate peroxidase) in pears, which synergistically scavenged reactive oxygen species (ROS) to maintain redox homeostasis. Transcriptomic analysis demonstrated that D. hansenii activates five key pathways, triggering the expression of genes involved in the biosynthesis of defense-related antimicrobial compounds. Additionally, it activates calcium signaling-MAPK-WRKY cascades, thereby upregulating defense-related genes such as PR1. Notably, critical genes (AOS and OPR2) in the jasmonic acid (JA) signaling pathway were significantly upregulated. This study is the first to elucidate the synergistic role of D. hansenii in enhancing postharvest disease resistance in pear fruits through multidimensional mechanisms. This study provides a theoretical foundation for the development of efficient and safe biocontrol technology.