Resposta de defesa induzidas por pgpr´s em plantas de arroz de terras altas contra mancha parda causada por bipolaris sp.

Abstract

Brown spot is a common disease in rice, with potential to reduce crop yields in the quality of harvested grains. The objective of this study was to evaluate the efficiency of PGPR (Burkholderia pyrrocinia BRM-32113 and Pseudomonas fluorescens BRM-32111) in the suppression of the brown spot caused by Bipolaris sp. and in the maintenance of the photosynthetic apparatus in rice plants. Rice seeds were microbiolized with suspension of each rhizobacteria (BRM-32111, BRM-32113) and in the control were submerged in water. Sowing was done in six pots per treatment with 5 plants, and at 35 days of age the plants were inoculated with B. oryzae. The rhizobacteria BRM-32111 and BRM-32113 reduced the severity of the brown spot in rice by 74% and 67%, on average reduced by 44% the AACPD. On the other hand, the rhizobacteria induced in plants increased the rate of CO2 assimilation and transpiration by 60%, in 48% the stomatal conductance and in 40% the transpiration. The chlorophyll a (Chl) concentration increased by 38%, chlorophyll b (Chlb) increased by 32% and total chlorophyll (Chl (a + b)) increased by 36%. The quantum efficiency of photosystem II [Y (PII)] was 23% and the non-photochemical extinction coefficient Y (NQP) was the highest in the treated plants. increase was 45% in plants treated with the rhizobacteria in comparison with the control. Therefore, it is concluded that the rhizobacteria P. fluorescens BRM-32111 and B. pyrrocinia BRM-32113 reduce the severity of the brown spot and attenuate the damage of the disease in the photosynthetic apparatus and the chlorosplastídicos pigments of the rice plants and can be evaluated in the field for later insertion in the rice crop management.