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

Abstract

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.

Field and postharvest application of microencapsulated Yamadazyma mexicanaLPa14: anthracnose control and effect on postharvest quality in avocado (Persea americana Mill. cv. Hass)

“…Since, the fresh yeast cells were simultaneously free and exposed to adverse factors such as rain, high temperature, and UV radiation, which contributed to a decrease in their survival and field persistence. 12 Based on this knowledge, the WPC, SA, and AG encapsulation materials provided thermoprotection and photoprotection. 25,26 Due to these properties, the microencapsulated yeast presented greater cell survival compared to fresh yeast.…”

“…However, the population of microencapsulated yeast was higher than the fresh cells. Since, the fresh yeast cells were simultaneously free and exposed to adverse factors such as rain, high temperature, and UV radiation, which contributed to a decrease in their survival and field persistence 12 …”

“…A weakness of the postharvest application of BCAs is that field‐established infections such as quiescent infection caused by Colletotrichum gloeosporioides , are not controlled 11 . This concern requires that the application of BCAs must be carried out in the preharvest phase 12 …”

“…11 This concern requires that the application of BCAs must be carried out in the preharvest phase. 12 The application of yeasts in the field can allow early colonization of the fruit epicarp and prevent the establishment of the quiescent fungus Colletotrichum gloeosporioides. However, in the field, the yeasts have difficulties withstanding hostile environmental conditions such as high temperatures, low RH, and ultraviolet (UV) radiation.…”