Performance studies of free-living tomato (Lycopersicon exculentum L.) rhizospheric Bacillus for their multiple plant growth promoting activity

Abstract

The present investigation is based on the study of the diversity of Bacillus spp. isolated from tomato rhizosphere and their evaluation as plant growth promoter. A total of twenty eight rhizospheric gram positive rod-shaped bacteria (DPNSB-1 to DPNSB-28) were isolated on nutrient agar and confirmed as Bacillus spp. on the basis of phenotypic characterization. Carbon source utilization pattern based on BIOLOG and 16S rDNA-RFLP analysis of these isolates using three tetra cutter restriction enzymes (AluI, HaeIII and MspI) was employed for diversity studies. All the 28 strains deliberated with multiple plant growth promotion (PGP) attributes such as production of Indole acetic acid (IAA), siderophore, ammonia, HCN and phosphate solubilization. The diversity pattern followed amongst isolates was based on carbon utilization profiling, which revealed 9 distinct clusters ranging from 10 to 50%, whereas RFLP based resulted into pattern 5 determined distinct clusters with a range of 10 to 70%. However, all the isolates were endowed with variable range of PGP activities. Among them, DPNSB-2, DPNSB-11 and DPNSB-28 produced significant levels of IAA production 503.65, 687.94 and 845.28 µg mg -1 respectively. While 19 (67%) isolates were capable of solubilizing phosphate, 13 (46%) isolates produced siderophore, 21 (75%) isolates produced Ammonia and 20 (71%) were produced HCN. The positive isolates appeared attractive for exploring their plant growth- promoting activity and may be useful for control of Fusarium wilt in tomato field.