Optimization of the Extraction Process and Application of Bacterial Extracts in the Control of Brown Spot and Leaf Blast in Rice Culture

Abstract

Abstract The objective of this work was to optimize the extraction process and application of bacterial extracts of Bacillus sp. and Serratia sp. in leaf blast control (Magnapothe oryzae) and brown spot (Bipolaris oryzae) in rice culture. The work was divided into three stages: 1) Bacterial obtaining extracts through liquid-liquid extraction 2) Antagonistic capacity of bacterial extracts to M. oryaze and B. oryae 3) Suppression of brown spot (A1) and leaf blast (A2) in greenhouse. The bacterial isolates in present study were identified as Bacillus sp. (BRM32110) and Serratia marcescens (BRM32113). The crude extract of both isolates at different extraction times 6, 16, 24, 48 and 72 hours reduced the growth of colonies of M. oryzae and B. oryzae by up to 92% and 28%, respectively. The extracts that showed highest inhibition of colony growth were those obtained after 6 and 16h of incubation and were selected for subsequent assays. These, for both isolates were able to reduce conidia germination by up to 91% and apressorium formation of M. oryzae by up to 93%. In green house, A1 the treatment that stood out was the extract of Bacillus sp. (16h) with 6.7% of leaf area affected and in A2 the treatment S. marcescens extract (16h) stood out with only 7.6% of leaf area affected with brusone when compared to control. The use of extracts of Bacillus sp. and Serratia marcescens was efficient in reducing the severity of brown spot and leaf blast in rice crop.