Lysinibacillus fusiformis LF-E2 as a plant growth-promoting bioinoculant for improved rice growth

Abstract

Plant growth-promoting bacteria (PGPB) are crucial for sustainable agriculture, but their effectiveness varies between endophytic and rhizosphere bacteria due to differing ecological and climatic conditions. This study investigated the PGP potential of two bacterial strains, Bacillus subtilis (BS-R) and Lysinibacillus fusiformis (LF-E), as a bioinoculant to promote biocatalytic processes in rice cultivation, isolated from the rhizosphere and endophytic niches of traditional red rice (Sivappu Kavuni), on the widely cultivated rice variety TN1 (Oryza sativa L.) to elucidate their mode of action. In vitro analyses revealed that both strains demonstrated promising PGP traits, including the synthesis of indole-3-acetic acid (IAA), phosphate solubilization, siderophore production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and hydrogen cyanide (HCN) production. Seed priming with these bacterial strains significantly enhanced seed germination and growth parameters. Among the treatments, Lysinibacillus fusiformis LF-E2 outperformed the control and BS-R strains. LF-E2 promoted early germination (within 23 h), improved seed vigor (1764), increased plant height (47.38 cm), and enhanced root (17.72 cm) and shoot (29.66 cm) lengths. Additionally, LF-E2 increased biomass and yield traits, such as a higher tiller number (64.6), panicles (19), grains per panicle (165), and grain weight (32.602 g per 1000 grains). LF-E2 also elevated levels of total soluble proteins (TSP, 2.334 mg/g FW), total phenolic content (TPC, 27.402 mg/g DW), and chlorophyll (5.6432 mg/g FW) in rice leaves. These findings highlight the potential of LF-E2, as a bioinoculant, improving rice growth and productivity, and offering a sustainable approach to enhancing agricultural outcomes.