Screening and characterization of rhizobacterial strains of Bacillus spp. isolated from rhizosphere of cauliflower (Brassica oleracea var. botrytis L.)

A total of 40 isolates were isolated from different rhizospheric soil and roots of cauliflower from the vicinity of three districts (Kangra, Hamirpur and Bilaspur) of Himachal Pradesh belonging to sub temperate Himalayan location. Thereafter, these isolates were screened and characterized for their plant growth promotion and biocontrol properties as per standard methods. Out of 40, only 5 isolates (MK2, MK4, MK5, MK7 and MK9) showed maximum plant growth promoting attributes like P- solubilization, N- fixation etc. All the five isolates solubilized tricalcium phosphate under in vitro conditions however, MK5 and MK7had highest phosphate solubilizing efficiency of 172.21 and 166.67% were recorded.Production of IAA, HCN and siderophore demonstrated in broth assay were other important plant growth promoting characters. The isolates produced diffusible and volatile compounds that inhibited the growth of three soil borne phytopathogens namely Fusariumsp., Rhizoctonia solani and Pythium sp. The carrier based formulations of these isolates resulted in increased plant growth in bioassays. The isolate MK5 showed maximum homology (99%) with Bacillus subtilis (HQ594544) and isolate MK7 showed homology (100%) with Bacillus pumilus (GU290547) by 16S rRNA analysis.   Key words: Bacillus sp., cauliflower, Plant growth promoting rhizobacteria (PGPR), P-solubilization, biocontrol.