Mining of rice rhizobacteria to control false smut and improve plant growth in rice (Oryza sativa L.)

Oryza sativa (Rice) is one of the most cultivated staple food crops in India. The crop is affected by Rice False Smut (RFS) caused by Ustilaginoidea virens (UV), which leads to a substantial reduction in the crop yield, and the mycotoxins released pose a health risk. In the present study, bacterial strains were isolated from rhizosphere soil samples collected from the eastern regions of Uttar Pradesh, India. A total of 105 isolates were screened for their antagonistic activity against U. virens and the best four among them were selected and identified using 16S rRNA sequencing. Three isolates were identified as Bacillus subtilis, and one as Bacillus amyloliquefaciens. Additionally, plant growth promoting (PGP) traits such as siderophore production, IAA production, phosphate solubilization, HCN production etc. were assessed. To assess the biocontrol activity and PGP properties in rice a talc-based bioformulation was prepared using bacterial isolates. The control of UV infection was tested on rice variety HKR-126 involving 10 treatments with screened isolates. Enhanced germination was recorded in all bacterial treatments of UV infected seeds. Greenhouse experiments were also carried out to evaluate the biocontrol efficiency until the harvest stage, as well as plant growth in different stages. Collectively, the results suggested that biopriming with talc-based formulations consisting of B. subtilis and B. amyloliquefaciens can serve as an alternative to fungicides to control the severity of UV disease in susceptible rice varieties, along with improving overall plant growth and fitness.