Systemic resistance and growth promotion of chili pepper induced by an antibiotic producing Bacillus vallismortis strain BS07

Abstract

In the present study, the ability of plant growth-promoting rhizobacterium (PGPR), Bacillus vallismortis strain BS07 (BS07) was evaluated as one of the potential biocontrol agents against multiple pathogens in chili pepper. Under greenhouse conditions, chili pepper seedlings treated with BS07 or chemical control, benzothiadiazole (BTH) by soil drench suppressed the soft rot incidence significantly by reducing the percent disease lesion area per leaf disk compared to negative control. The treatment with BS07 or BTH induced plant resistance against phytophthora blight caused by Phytophthora capsici upon pathogen challenge. There was a greater reduction of anthracnose infection caused by Colletotrichum acutatum on matured fruits in BS07 or BTH treated plants when compared to untreated control. Under field conditions, percent of soft rot incidence and disease severity of phytophthora blight were significantly reduced in BS07 and BTH treated plants when compared to untreated control. In the case of anthracnose disease, the significant reduction of disease was observed during the two years on matured fruits, when compared to untreated control. The study also clearly showed that there was a significant increase of fruit yield in BS07 treated plants, and it has also been observed that BS07 treated plants showed higher chlorophyll content in the fresh leaves compared to untreated control. Reverse transcriptase (RT)-PCR analyses of Arabidopsis thaliana leaves revealed up-regulation of PR1a gene expression in Col-0, while there was no expression in Nag-G plants treated with BS07 suspensions. This suggests that the systemic resistance might be evolved by the mechanism of salicylic acid (SA) dependent pathway.