Endophytic Yeasts as Biocontrol Agents for Common Bean White Rot Disease Caused by Sclerotinia sclerotiorum

Common bean white-rot disease, caused by Sclerotinia sclerotiorum, is widespread and destructive, leading to economic losses. Endophytic yeasts have shown effectiveness in controlling fungal phytopathogens due to their diverse biological activities and broad-spectrum antifungal properties, making them promising candidates for application. From 11 endophytic yeasts isolated from 75 Phaseolus vulgaris plant samples, two superior yeast isolates, Cryptococcus albidus and Saccharomyces cerevisiae were selected for both in-vitro and in-vivo trials. During the in-vitro phase, three biocontrol methods were employed: dual culture technique and volatile and non-volatile assays. Among these methods, C. albidus demonstrated the greatest ability to suppress S. sclerotiorum growth in the dual culture setup, achieving an inhibition rate of 48.57%. For volatile metabolites assay, both C. albidus and S. cerevisiae effectively inhibited the pathogen's growth, with rates of 53.38% and 44.24%, respectively. For the non-volatile metabolites assay, two isolates again showed the highest suppressive effects on S. sclerotiorum, with inhibition rates of 60.93% and 54.49%, respectively. Growth-chamber trials demonstrated yeast’s effectiveness in controlling pathogens on host plants. C. albidus reduced disease incidence by 43.7%, while S. cerevisiae reduced it by 31.2%. Additionally, trials showed enhanced plant growth parameters, as indicated by increases in height, and dry and fresh weight. These findings suggest that P. vulgaris plants may develop resistance against S. sclerotiorum through biological protection provided by endophytic yeasts, which could serve as novel and effective biocontrol agents.