# Bacillus velezensis Enhances Rice Resistance to Brown Spot by Integrating Antifungal and Growth Promotion Functions

## TL;DR

A Neotropical strain of Bacillus velezensis helps rice resist brown spot disease by both fighting the fungus and boosting plant growth.

## Contribution

A native Bacillus velezensis strain is shown to uniquely combine antifungal and growth-promoting traits for rice protection.

## Key findings

- Ba. velezensis reduced disease severity by 60% and increased seedling vigor by 51% in greenhouse tests.
- Genome analysis revealed antifungal gene clusters for polyketides and lipopeptides in Ba. velezensis.
- The rice cultivar 'Predileta' showed the strongest response to Ba. velezensis treatment under high disease pressure.

## Abstract

Brown spot, caused by the seedborne fungus Bipolaris oryzae, remains a major constraint in rice production. Here, we used in vitro and in vivo assays to evaluate the biocontrol potential of three Bacillus strains (Ba. cereus OQ725688.1, Ba. velezensis OP938696.1, and Ba. subtilis OP937353.1) against Bi. oryzae in two rice cultivars (“Rubelita” and “Predileta”). Ba. cereus showed the highest in vitro mycelial inhibition (≈95%), whereas Ba. velezensis was the most effective under greenhouse conditions, reducing disease severity by up to 60% and increasing seedling vigor by 51% compared with infected controls. “Predileta” showed the strongest response to bacterial treatment, maintaining severity scores below 2 even under high inoculum pressure. Functional assays confirmed that all strains displayed amylolytic, catalase, and phosphate-solubilizing activities, with Ba. velezensis uniquely expressing strong cellulase and protease activities. Genome analysis of Ba. velezensis OP938696.1 revealed multiple biosynthetic gene clusters for antifungal polyketides and lipopeptides. These integrated biochemical and genomic traits demonstrate the novelty and potential of this Neotropical strain as a multifunctional agent capable of suppressing Bi. oryzae while enhancing rice seedling performance. Incorporating such a native strain into seed and soil management offers a sustainable strategy for rice protection in Neotropical systems.