ASPECTOS BIOQUÍMICOS E FISIOLÓGICOS EM SOJA INFECTADA POR Heterodera glycines EM RESPOSTA AO AGENTE DE BIOCONTROLE Bacillus velezensis GF267

Abstract

The present study aimed to evaluate biochemical and physiological aspects of soybeans infected with Heterodera glycines and treated with Bacillus velezensis isolate GF267. Two experiments were conducted in the greenhouse: one to evaluate the effect of GF267 on infection and reproduction of the pathogen, in addition to the physiological aspects (liquid photosynthesis, electron transport rate, water use, transpiration, internal concentration ratio and external leaf CO2 (Ci/Ca) and stomatal conductance); and another to evaluate the activity of enzymes related to plant defense: lipoxygenase (LIPOX), phenylalanine ammonia lyase (FAL), β 1,3-glucanase (GLU), chitinase (CHI) and catalase (CAT). The treatments consisted of the application or not of GF267 (1x109 Colony Forming Unit - CFU/mL) through soybean seed cultivar Desafio RR, and with or without inoculation of H. glycines (4000 eggs/plant) 10 days after sowing, at total of 4 treatments. For physiological aspects, the evaluations occurred at 0, 10, 30 and 50 days after inoculation, with 6 replications. At 60 days after sowing, the occurrence of penetration and quantification of the number of females/g of root, cysts/cm3 of soil, eggs/10 females and eggs/10 cysts was evaluated. For biochemical aspects, leaf tissue collections for evaluation occurred at 0, 48, 96, 144, 192 and 240 hours after inoculation with H. glycines, with 5 replicates for each treatment and collection time. In both experiments, the design was completely randomized. Treatment with GF267 reduced the number of females/g of root, cysts/cm3 of soil and the number of eggs/10 cysts. Among the evaluated parameters of physiological aspect, at 20 days after inoculation, plants treated with GF267 had greater efficiency in the use of water. And at 50 days after inoculation, plants treated with GF267 showed less transpiration, higher Ci/Ca ratio and better water use efficiency. Regarding the biochemical aspects, plants treated with GF267 did not increase GLU, CHI and CAT activity, only for LIPOX and FAL. For LIPOX, plants with GF267 inoculated and not, had a significant increase between 96 and 192 hours after inoculation. For FAL, plants with GF267, inoculated showed increased activity in 0 and 192 hours, and those not inoculated in 96 hours after inoculation. The isolate GF267 from B. velezensis was able to reduce the population of H. glycines, in addition to increase the activity of the enzymes LIPOX and FAL, both related to the defense of the plant against phytopathogens, under greenhouse conditions.