Induction of defense response against Colletotrichum capsici in chili fruit by the yeast Pichia guilliermondii strain R13

Pichia guilliermondii strain R13, a yeast isolated from Thai rambutan, has been shown to suppress the fungal pathogen Colletotrichum capsici in harvested chili. Its multiple modes of action include nutrient competition, tight attachment to the fungus, and hydrolytic enzyme secretion. This study investigated the ability of the P. guilliermondii strain R13 to induce resistance against C. capsici in chili fruit. The pretreatment of chili with the yeast antagonist, physically separated from the fungus by known distances, significantly reduced disease incidence and lesion diameter caused by C. capsici. Compared to the controls, the yeast treatment also significantly enhanced the activities of phenylalanine ammonia-lyase, chitinase, and β-1,3-glucanase, and the accumulation of capsidiol phytoalexin in chili tissue. Scanning electron micrographs showed that the morphology of C. capsici spores and hyphae were abnormal and that the pathogen had restricted growth on chili tissue adjacent to the yeast-inoculated sites. The results indicate that the induction of resistance may be another mechanism by which the yeast antagonist suppresses C. capsici.