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Plant microbiomes harbour beneficial microorganisms crucial for sustainable crop protection strategies. This study identified keystone taxa in rice rhizosphere microbiomes through 16S rRNA amplicon-based metagenomic analysis followed by isolation, and evaluation of the efficiency of antagonistic bacteria against Rhizoctonia solani, the causal agent of sheath blight disease (SBD) in rice. Bacillus and Actinobacteria were identified as dominant keystone genera in rice rhizosphere. Based on these insights, cultivation media were used to specifically target and culture these keystone taxa, resulting in a total of 223 bacterial isolates that were subsequently screened for antagonistic activity. Four antagonistic isolates exhibiting >70% inhibition were selected (SR2KB2.1, SR2KB6.1, SR3KB3.6, and SR3KB6.4). These isolates produced cell wall-degrading enzymes, volatile organic compounds, and various plant growth-promoting substances. A synthetic microbial consortium (SynComKU-B1) constructed from these isolates demonstrated 87% SBD suppression under greenhouse conditions, comparable to chemical fungicides, while significantly enhancing plant biomass (39.02 ± 8.81 g versus 28.10 ± 4.48 g in untreated plants). Furthermore, when combined with fertiliser, SynComKU-B1 significantly increased wet weight (115.85 ± 6.76 g) compared to rice alone (102.08 ± 7.09 g) and rice with SynComKU-B1 without fertiliser (102.87 ± 5.26 g), indicating effective mineral solubilisation and growth promotion capabilities. These findings suggest that SynComKU-B1 shows promise as a sustainable biocontrol agent, offering a possible environmentally friendly alternative to chemical fungicides, while possibly enhancing both disease resistance and plant fitness in rice agroecosystems.
Sakdapetsiri et al. (Thu,) studied this question.