Mechanisms of action of the yeast Debaryomyces nepalensis for control of the pathogen Colletotrichum gloeosporioides in mango fruit

The yeast Debaryomyces nepalensis was evaluated for effectiveness against Colletotrichum gloeosporioides in mangoes (Mangifera indica L.) cv. 'Tainong No. 1', and possible mechanisms of action involved in the inhibition were identified. The results showed that D. nepalensis could survive in mango wounds and produce a hydrolytic enzyme (β-1,3-glucanase). Scanning electron microscopy showed that the yeast produced biofilms on the mango surface and yeast cells attached to each other and became embedded in the pathogen hyphal walls. In addition, D. nepalensis competed for nutrients (FeCl3) and competed for space with the pathogen (p < 0.05). Morever, D. nepalensis enhanced defense-related enzymes of wounded mangoes, including peroxidase, β-1,3-glucanase, chitinase and phenylalanine ammonia-lyase. In addition, gas chromatographic-mass spectrometry (GC-MS) analysis of volatile compounds (VOCs) produced by the yeast showed that VOCs can play important roles over short distances in the suppression of C. gloeosporioides. The solid-phase microextraction (SPME) coupled with GC-MS technique analysis revealed phenylethyl alcohol (29.62% relative peak area, RA) as the dominant VOC mainly produced by D. nepalensis, and it had a significant inhibitory effect on fungal mycelia. According to the results obtained here, the combination of different mechanisms of action of the yeast increases their ability to control C. gloeosporioides. The use of antagonistic yeast to control C. gloeosporioides may contribute to the integrated management of disease caused by this pathogen.