Endophytic bacteria nano-formula: A promotor for plant growth and systemic acquired resistance against sheath blight disease on rice

Abstract

Sheath blight disease significantly affected growing rice crop and caused yield losses. This study identified two endophyte bacterial isolates, Bacillus subtilis, and Pseudomonas brassicacearum subsp. Neoaurantiaca, significantly inhibit Rhizoctonia solani AG1 IA mycelial growth. Further, the analysis of the culture filtrate for the two identified bacteria recorded a set of bioactive components that have antifungal activity and enhance plant growth. We prepared a novel nano-formula using the advantages of nano natural charcoal (NCNPs) as an organic matter and enriched with alginate to improve the nano-formula porosity and keep the viability of the loaded bacteria up to 18 months. Two methods (soil application and root dipping) were used to evaluate the impact of bacteria nano-formula on rice growth and rice sheath blight (ShB) disease under artificial inoculation with R. solani at greenhouse conditions. The root dipping with P. brassicacearum NCNPs alginate (PBNF-R) and B. subtillus NCNPs alginate (BSNF-R) recorded the highest performance in the rice growth traits, and a high control level of the rice ShB disease by decreasing relative lesion height and percent disease index. In addition, PBNF-R and BSNF-R increase the defense-related enzyme production in the plant cell (peroxidase, polyphenol oxidase, and phenylalanine ammonia‐lyase) and, consequently, the plant immunity. Moreover, both upregulate the gene expression levels of OsNPR1, OsWRKY45, OsPR10, and OsAOS2, which are related to the plant defense mechanism. Finally, here we introduce the first application of bacteria nano-formula as a safe environmental approach to control the rice ShB disease, promoting growth and thousand-grain weight in rice.