Yeasts with potential biocontrol of Colletotrichum gloeosporioides in avocado (Persea americana Mill. cv. Hass) and characterization of Yamadazyma mexicana mechanisms

Anthracnose caused by species of Colletotrichum can result in avocado pre and postharvest losses. This disease has been controlled with synthetic fungicides that produce toxicological risks, the development of resistant pathogens, and consumer demand for fungicide-free foods. Due to this concern, antagonistic yeasts can be used as a natural alternative to control anthracnose. This study aimed to isolate and identify yeast strains from avocado fruits with the potential to control this pathogen and to evaluate the action mechanisms of the most promising yeast. Twenty-three yeasts were isolated from the avocado fruit epicarp. Seven yeasts showed in vitro antagonistic activity with inhibition of mycelial growth from 60.1 to 87.2%, and inhibition of spore germination from 95.3 to 100%. Yamadazyma mexicana LPa14 exhibited the best antagonist activity with a severity reduction of 63.63% and incidence of 60%. It also showed the ability to survive in hostile conditions of low water activity and high temperature with 64.29 and 93.45% of viability at a_w 0.96 and 0.98 at 38 °C, respectively. The mechanisms of action of Y. mexicana LPa14 included colonization in the wounds of avocado fruit, competition for nutrients, adherence to the hyphae and spores of the pathogen, biofilm formation, and production of volatile organic compounds (VOCs). The main VOCs identified were alcohols (isopentan-1-ol, ethanol, 2-phenylethanol, 2-methyl-1-butanol) and esters (ethyl acetate and isopentyl acetate). This study demonstrated that Y. mexicana LPa14 is a viable biocontrol candidate for C. gloeosporioides and could be used as a suitable alternative to control preharvest and postharvest anthracnose disease in avocado fruits.