Avaliação da levedura rizoférica Torulaspora globosa como indutora de resistência sistêmica em milho contra o patógeno Fusarium verticillioides

Abstract

In maize, one of the most consumed vegetables in the world, numerous applications of agrochemicals are used to control phytopathogens that cause damage to human health and the environment. Among the main diseases affecting the crop, the fungus Fusarium verticillioides is responsible for causing root, stem and ear rot, in addition to causing damage to stored grains. Plants, naturally exposed to environmental stresses, have defense mechanisms that remain inactive or latent until triggered by adverse conditions. One of these mechanisms is known as Induced Systemic Resistance (ISR). Chemical agents such as acetylsalicylic acid (ASA) or biological agents such as plant growth promoting microorganisms (PGPM) can be used to trigger ISR. Although several works show the potentialities of ISR by PGPB, the study of the action of yeasts responsible for such mechanisms is still not completely elucidated. Considering the above, this study aimed to evaluate the capacity of the rhizospheric yeast Torulaspora globosa (strain 6S01) to trigger ISR in maize, in order to promote an immune response to the phytopathogen F. verticillioides. Therefore, maize plants were grown in pots, in a greenhouse, where they received the following treatments (at planting and from 4 days after emergence, every two days, for 11 days, totaling 7 applications): control (saline solution 0.85%), ASA solution (100mg/L), yeast cells (1x105 cells/ml) and yeast metabolites (filtered from the yeast growth medium for 48 hours). Treatments were applied with a spray bottle (5 ml/plant). After finishing the application of treatments, the plants were inoculated with 1ml of suspension of spores of the pathogen F. verticillioides (1x106 spores/ml). Ten days after fungus inoculation, the plants were analyzed for the degree of severity of symptoms of rot, plant development and activity of enzymes related to the plant defense system. The results show that, with the application of T. globosa yeast cells, systemic resistance was induced in maize plants, similarly to the use of ASA. The inoculation of yeast cells provided infected plants with less symptoms of rot and with greater activity for enzymes related to plant resistance. Therefore, it is concluded that the species of T. globosa (strain 6S01) has great potential to be used in agriculture as a plant protection agent, contributing to the decrease in the use of fungicides in the field and maintenance of plant productivity under conditions of stress.