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Seven bacterial isolates screened from rhizosphere of common bean growing at Uttarakhand Himalaya showed potential plant growth promoting (PGP) and antagonistic activities. Based on 16S rRNA gene sequence the isolate BPR7 was identified as Bacillus sp. BPR7. The strain BPR7 produced IAA, siderophore, phytase, organic acid, ACC deaminase, cyanogens, lytic enzymes, oxalate oxidase, and solubilized various sources of organic and inorganic phosphates as well as potassium and zinc. Strain BPR7 strongly inhibited the growth of several phytopathogens such as Macrophomina phaseolina, Fusarium oxysporum, F. solani, Sclerotinia sclerotiorum, Rhizoctonia solani and Colletotricum sp. in vitro. Cell-free culture filtrate of strain BPR7 also caused colony growth inhibition of all test pathogens. PGP and antifungal activities of Bacillus sp. BPR7 suggest that it may be exploited as a potential bioinoculant agent for P. vulgaris.

Bacterial isolates having antifungal and good plant growth-promoting attributes were isolated from chirpine (Pinus roxburghii) rhizosphere. An isolate, Bacillus subtilis BN1 exhibited strong antagonistic activity against Macrophomina phaseolina, and other phytopathogens including Fusarium oxysporum and Rhizoctonia solani. It was characterized and selected for the present studies. BN1 resulted in vacuolation, hyphal squeezing, swelling, abnormal branching and lysis of mycelia. The cell-free culture filtrate of BN1 inhibited the growth of M. phaseolina. Pot trial study resulted in statistically significant increase in seedling biomass besides reduction in root rot symptoms in chir-pine seedlings. BN1 treatment resulted in 43.6% and 93.54% increases in root and shoot dry weights respectively, as compared to control. Also, 80-85% seed viability was recorded in treatments receiving BN1 either alone or in the presence of M. phaseolina, compared to 54.5% with M. phaseolina. Bioinoculant formulation study suggested that maximum viability of bacteria was in a sawdust-based carrier. B. subtilis BN1 produced lytic enzymes, chitinase and b-1,3-glucanase, which are known to cause hyphal degradation and digestion of the cell wall component of M. phaseolina. In the presence of M. phaseolina, population of B1 was 1.5 9 10 4 c.f.u. g -1 root after one month, which increased to 4.5 9 10 4 c.f.u. g -1 root in three months. Positive root colonization capability of B. subtilis BN1 proved it as a potent biocontrol agent.

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The bacterial strain Mesorhizobium loti MP6, isolated from root nodules of Mimosa pudica induced growth and yield of Brassica campestris. The isolate MP6 secreted hydroxamate type siderophore in Chrom-Azurol Siderophore (CAS) agar medium. Production of hydrocyanic acid (HCN), indole acetic acid (IAA) and phosphate solubilizing ability was also recorded under normal growth conditions. Root hair curling was observed through simple glass-slide technique. In vitro study showed a significant increase in population of M. loti MP6 in rhizosphere due to root exudates of B. campestris. In dual culture technique the strain showed a strong antagonistic effect against Sclerotinia sclerotiorum, a white rot pathogen of Brassica campestris. The growth of S. sclerotiorum was inhibited by 75% after prolonged incubation. Efficient root colonization of mustard seedlings was confirmed by using a streptomycin-resistant marker M. loti MP6 strep+ . The M. loti MP6 coated seeds proved enhanced seed germination, early vegetative growth and grain yield as compared to control. Also, a drastic decline (99%) in the incidence of white rot was observed due to application of M. loti MP6.