Unveiling the potential of rice rhizospheric microbes and indigenous organic sources for the management of rice blast

Abstract

The rice blast incited by Pyricularia oryzae caused immense losses and left rice production in a predicament situation globally. Blast can be effectively controlled with synthetic fungicides. However, their indiscriminate use causes resistance among the pathogens coupled with environmental pollution issues. Exploitation of microbe-based alternatives for the management of plant diseases diminishes public concerns on the ill effects of pesticide usage in crops. Under this scenario the present investigation was designed to envisage the potential rhizosphere microflora from native rhizosphere soil samples collected from rice growing regions of three different agro-climatic zones of (North Telangana Zone, Central Telangana Zone and Southern Telangana Zone) for the sustainable management of rice blast in Telangana state. We observed varied level of antagonism against Pyricularia oryzae under in vitro conditions. Seeds treated with native effective rhizospheric microflora exhibited significantly higher seed vigour index ranging from 1940.7 to 2183.6 compared to control. Further, these effective rhizospheric microbes were identified through cultural and morphological characteristics as well as by the sequencing internal transcribed spacer (ITS) and 16S rRNA gene sequences analysis for bacteria and fungi as Bacillus cereus, Bacillus xiamenensis, Bacillus subtilis and Trichoderma asperellum respectively. Later, bio-efficacy tests were carried out in the field during the 2 years of Kharif 2019 and 2021 by spraying the combinations of the antagonists in association with indigenous organic sources (Panchagavya, Beejamrutham and Vermiwash) and non-chemical sources such as Butter milk and Neem oil on healthy rice plants to assess disease inhibition under natural conditions. Results obtained from present investigation on the field bio-efficacy studies showed significant improvement in the seedling's growth with 83.36 cm plant height, 10.40 no of panicles with an average yield of 8583.33 kg ha−1, when compared to control during 2019 and 2021 with lower AUDPC and r value. Our findings indicate that the native rhizospheric microflora in association with indigenous organic sources can be used as potential alternative strategy for the management of rice blast in Telangana region of India. The knowledge gathered from the present study can be used to develop strategies for maintaining soil quality and crop conservation to increase crop productivity with less dependency on chemical approaches.