Rhizosphere competence of biocontrol agent Bacillus subtilis strain SRB28 from sorghum

Abstract

Bacillus subtilis SRB28, isolated from sorghum rhizosphere, is a strain known for stimulating sorghum plant growth and antifungal activity against soil-borne fungal pathogens. In this study, the strain was characterized for IAA production and its effects on root development in sorghum. Factors determining rhizosphere competence including root colonization and survival in the sorghum rhizosphere have been assessed. SRB28 produced IAA and influenced the growth of primary root depending on cell concentration. The cells at high concentration (>106 cfu/ml) increased the number of adventitious root and number and length of root hairs in seedlings raised from bacteria treated seed in the presence of tryptophan. The bacteria colonised on sorghum root, formed micro-colonies and survived in the sorghum rhizosphere. The overall results indicated that the B. subtilis SRB28 hold promise as potential biocontrol as well as PGPR for sorghum.