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Co-inoculation of nitrogen-fixing and phosphate-solubilizing bacteria to promote growth, yield and nutrient uptake in chickpea

Wani, P. A., Khan, M. S., Zaidi, A.
Acta agronomica Academiae Scientiarum Hungaricae 2007 v.55 no.3 pp. 315-323
Azotobacter, Mesorhizobium, ammonia, bacteria, biomass, chickpeas, chlorophyll, field experimentation, grain protein, hydrogen cyanide, indole acetic acid, nitrogen content, nitrogen fixation, nutrient uptake, pH, protein content, roots, seed yield, shoots, siderophores, solubilization, sowing, tricalcium phosphate
A total of 32 bacterial isolates including <i>Mesorhizobium</i> (N=10), <i>Azotobacter</i> (N=12) and phosphate-solubilizing bacteria (N=10) were isolated and tested for siderophore, HCN, ammonia, indole acetic acid production and phosphate solubilization <i>in vitro</i> . The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates, <i>M. ciceri</i> RC3 and <i>A. chrococcum</i> A4 displayed 35 and 14 μg ml <sup>−1</sup> of IAA, respectively, whereas <i>Bacillus</i> produced 19 (<i>Bacillus</i> PSB1) and 17 μg ml <sup>−1</sup> (<i>Bacillus</i> PSB10) of IAA in Luria Bertani broth. The diameter of the P solubilization zone varied between 4 (<i>Bacillus</i> PSB1) and 5 mm (<i>Bacillus</i> PSB10) and a considerable amount of tricalcium phosphate (7 and 8 μg ml <sup>−1</sup> by <i>Bacillus</i> PSB1 and <i>Bacillus</i> PSB10, respectively) was released in liquid medium, with a concomitant drop in pH. The effects of N <sub>2</sub> -fixing and PS bacteria on the growth, chlorophyll content, seed yield, grain protein and N uptake of chickpea plants in field trials varied considerably between the treatments. Nodule number and biomass were significantly greater at 90 days after sowing (DAS), decreasing by 145 DAS. Seed yield increased by 250% due to inoculation with <i>M. ciceri</i> RC3 + <i>A. chroococcum</i> A4 + <i>Bacillus</i> PSB10, relative to the control treatment. Grain protein content ranged from 180 (<i>Bacillus</i> PSB1) to 309 ng g <sup>−1</sup> (<i>M. ciceri</i> RC3 + <i>A. chroococcum</i> A4 + <i>Bacillus</i> PSB10) in inoculated chickpea. The N contents in roots and shoots differed considerably among the treatments.