Leveduras e seus efeitos no manejo biológico de antracnose em soja e na promoção de crescimento vegetal

Abstract

Yeasts have proven to be a promising and sustainable strategy for disease management and plant growth promotion in agricultural systems. Therefore, the objective was to evaluate the potential of yeasts in the biological control of anthracnose and the effect of these yeasts on growth promotion in soybean plants. To this end, in vitro assays were performed to evaluate the effects of eight yeast species on mycelial growth and spore germination of Colletotrichum truncatum. In a greenhouse, assays were conducted to verify the effect of these yeasts on reducing the severity of anthracnose in soybeans, as well as the possible mechanisms related to plant defense involved. Finally, an assay was performed to analyze the growth promotion of soybean plants when treated with the yeasts. It was found that none of the eight yeasts interfered with the mycelial growth of C. truncatum. Candida albicans showed an average of 42.5% inhibition of conidia germination. The other yeasts did not inhibit the germination of C. truncatum conidia. Yeasts also did not reduce the severity of anthracnose in soybean plants under the assay conditions. However, Rhodotorula glutinis and Pichia pini were able to induce defensive metabolism in soybean plants, acting through different mechanisms of action, but not against C. truncatum under the assay conditions. R. glutinis increased polyphenol oxidase enzyme activity by 200%. P. pini induced β-1,3-glucanase enzyme activity by 98% after the presence of the pathogen. However, Sporidiobolus johnsonii, Zygoascus hellenicus, R. glutinis, and Rhodotorula aurantiaca induced promising increases in different agronomic variables related to plant growth. S. johnsonii increased the total number of trifoliate leaves by 31%, the number of flowers by 164%, the number of vegetative/reproductive branches by 45%, the shoot dry mass by 45%, the root volume by 114%, and the root fresh mass by 121%. Meanwhile, Z. hellenicus increased the number of vegetative/reproductive branches by 42%, the root volume by 90%, and the root fresh mass by 80%. R. glutinis showed a 31% increase in the number of vegetative/reproductive branches and a 37% increase in shoot dry mass, and R. aurantiaca also showed a 28% increase in the number of vegetative/reproductive branches. It is concluded that the yeasts in the assay were not efficient in controlling C. truncatum under the tested conditions; however, they were able to promote resistance mechanisms and contribute to plant growth in soybean plants.