EFFECTS OF CURATIVE YEASTS ON B. cinerea SPORE GERMINATION IN LOW NUTRIENT CONCENTRATION MEDIUM

NALLY M. C; FLORES C; PESCE, V.M; ASSAF RODRIGUEZ, L.A; TORO M.E; CHULZE, S.N; VAZQUEZ F

Santa Cruz

Simposio; XVII International Botrytis Symposium; 2016

Biocontrol using microbial antagonists is one of the most promising alternatives for reducing fungicides in fruit. When infection on fruits has been occurred curative antagonists can be used or preventive antagonists before disease occur. Yeasts are particularly suitable as antagonistic agents. There are several studies reporting the preventive activity of yeasts and their modes of action. Even so there are few studies about yeasts with curative activity and there are not studies about their antifungal modes. It might be proposed that the mechanisms of action of preventive yeasts are consistent with the mechanisms of curative yeasts. Substrate competition is one of the main biocontrol strategies of action reported between preventive yeasts and fungi. This competition occurs over scarce resources. During 2014, 18 yeasts antagonistic of B. cinerea were isolated in San Juan and characterized as curative. The objective of this work was to evaluate substrate competition between curative yeasts and B. cinerea strains. Material and Methods: 1-Microorganisms: Eighteen yeasts (13 Saccharomyces and 5 non-Saccharomyces) and two B. cinerea strains B14-B15. 2- Evaluation of curative yeasts activity on fungal spore germination in medium with low nutrient concentration: Yeast suspension (106 cells∙mL-1), 100μL of sterile 0.5°Bx grape must and 25μL of fungal suspension (104 spores∙mL-1) were inoculated on sterile excavated slides. They were incubated at 25°C during 24h. One hundred spores of each excavated slide were observed to determine the percentage of germinated spores. Results: Spore germination of B. cinerea B14 was significantly inhibited by two biocontrol yeasts (S. cerevisiae BSc27, H. vinae BHv86). B. cinerea B15 was significantly inhibited by four yeasts (S. cerevisiae BSc102, BSc60, BSc97and BHv86). These yeasts reduced the spore germination between 8 and 33%. BSc102 and BSc27 were the isolates that more inhibited the spore germination of the two B. cinerea strains assayed (33%). We concluded that substrate competition could be an antifungal mechanism of Saccharomyces and Hanseniaspora curative yeasts against B. cinerea strains.