Evaluation of Yeast Potential in the Biological Control of Colletotrichum orbiculare in Cucumber

This work aimed to evaluate the effect of the yeasts Candida albicans, Pichia guilliermondii, Rhodotorula glutinis, Saccharomyces cerevisiae and Zygoascus hellenicus in the control of anthracnose in cucumbers. The influence of volatile and non-volatile compounds on mycelial growth and the effect of cell suspension and culture filtrate on conidial germination were evaluated. In a greenhouse, yeasts were tested on cucumber cotyledons, one cotyledon being treated and the other not; afterwards both cotyledons were challenged with C. orbiculare. The severity of the disease in both cotyledons was assessed by determining biological control and resistance induction. The production of volatile compounds from the yeasts R. glutinis and C. albicans reduced the pathogen growth by 90.7 and 90.0%, respectively. The production of non-volatile compounds stimulated the pathogen development. Conidia germination was affected when exposed to cell suspension of all tested isolates, ranging from 43 to 75%. For the culture filtrate from Z. hellenicus, it reduced the conidia germination by 11.4%. In the in vivo test, on the treated cotyledon, the yeasts Z. hellenicus, R. glutinis and S. cerevisiae reduced the anthracnose severity by 52.5, 50.0 and 42.5%, respectively.