Biological control of Botrytis cinerea on tomato plants by the use of epiphytic yeasts Candida guilliermondii strains 101 and US 7 and Candida oleophila strain I-182: I. in vivo studies

Candida guilliermondii (strains 101 and US 7) and C. oleophila (strain I-182) were screened for biocontrol activity (BA) against Botrytis cinerea, both in vitro and in a bioassay, using stem portions and atomized aqueous pathogen suspensions. Yeast C. guilliermondii strains 101 and US 7 significantly reduced disease incidence, when applied simultaneously with the pathogen, whereas C. oleophila strain I-182 and isolated epiphytic yeasts had no BA against B. cinerea. When tomato stem portions were inoculated with yeasts (strains 101 and US 7) 24 h before pathogen challenge, the BA significantly improved. Addition of exogenous nutrients significantly reduced BA of both yeast strains, indicating that nutrient competition may be involved in their mode of action. In vivo application of both C. oleophila (strain I-182) and C. guilliermondii (strains 101 and US 7) gave significant control of B. cinerea, even though strain I-182 had been ineffective in the stem assay. These results suggest that yeasts selected for the biocontrol of postharvest diseases have the potential to control diseases of whole plants.