Photoprotector adjuvants to enhance UV tolerance of yeast strains for controlling mango decay using pre-harvest spraying.

Post-harvest mango decay is caused by multiple pathogens in tropical conditions but concerns regarding the risk of food contamination by fungicides established biocontrol as a promising alternative. However, occurrence of quiescent infections requires pre-harvest applications of biocontrol agents (BCA), exposing them to harmful UV radiation effects. The objective of this work was to evaluate UV sensitivity of yeast BCA strains previously selected against multiple pathogens that cause mango decay and evaluate suitable UV protectants. In a first bioassay conducted exposing yeast suspensions sprayed on glass plates, it was verified that Saccharomyces sp. ESA47 and Pichia kudriavzevii CMIAT171 were highly sensitive to UV, while Saccharomyces cerevisiae ESA45 had a slightly lower mortality. A bioassay using fragments of mango peels evaluated UV protection from increasing concentrations of starch, dextrin, casein, benzophenone, and cinnamic acid derivative compounds. Results showed that starch and isoamyl p-methoxycinnamate (NHE-1000) resulted in higher survival for yeast strains in doses of 10.0 and 1.0 g kg−1, respectively. Application of the yeast BCA in a semi-commercial mango orchard resulted in a significant reduction of post-harvest disease incidence and severity. Field application of the yeasts in technical grade preparations containing both UV protectants enhanced the control efficiency by 52.5, 31.9, and 37.7% for ESA45, ESA47, and CMIAT171, respectively