Characterization of Endophytic Microorganisms of Rice (Oryza sativa L.) Potentials for Blast Disease Biocontrol and Plant Growth Promoting Agents

Abstract

One hundred twenty-five endophytic microorganisms were isolated from the roots, stems, and leaves of four prominent rice cultivars growing in temperate regions. Their potential to combat rice blast disease and promote plant growth was investigated. The dual culture tests highlighted the strong antagonistic activity of five fungal (ranging from 89%–70%) and five bacterial (72%–61%) endophytes. Subsequent examination focused on volatile compounds produced by selected isolates to counter the blast pathogen. Among these, the highest chitinase (13.76 µg mL⁻¹) and siderophore (56.64%), was exhibited by <i>Aspergillus flavus</i>, and the highest HCN production was shown by <i>Stenotrophomonas maltophilia</i> (36.15 µM mL⁻¹). In terms of growth promotion traits, <i>Aspergillus flavus</i> and <i>Enterobacter cloacae</i> excelled in activities viz, phosphorous solubilization, ammonia production, auxin and gibberellic acid production, and nitrogen fixation. The Identity of these endophytes was confirmed through molecular analysis as Trichoderma afroharzianum, <i>Trichoderma harzianum</i>, <i>Penicillium rubens</i>, <i>Aspergillus flavus</i>, <i>Stenotrophomonas rhizophila</i>, <i>Stenotrophomonas maltophilia</i>, <i>Bacillus cereus</i>, <i>Enterobacter cloacae</i>, and <i>Bacillus licheniformis</i>. Under greenhouse conditions, the highest disease control was shown by isolate <i>Bacillus licheniformis</i> and <i>A. flavus</i> with an inhibition of 79%, followed by <i>S. rhizophila</i> (77%) and <i>T. afroharzianum</i> (73%). The overall results of this study showed that <i>Bacillus licheniformis</i> and <i>Stenotrophomonas rhizophila</i> have great potential to be used as bio-stimulant and biocontrol agents to manage rice blast disease.