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

Abstract

A total of 32 bacterial isolates includingMesorhizobium(N=10),Azotobacter(N=12) and phosphate-solubilizing bacteria (N=10) were isolated and tested for siderophore, HCN, ammonia, indole acetic acid production and phosphate solubilizationin vitro. The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates,M. ciceriRC3 andA. chrococcumA4 displayed 35 and 14 μg ml−1of IAA, respectively, whereasBacillusproduced 19 (BacillusPSB1) and 17 μg ml−1(BacillusPSB10) of IAA in Luria Bertani broth. The diameter of the P solubilization zone varied between 4 (BacillusPSB1) and 5 mm (BacillusPSB10) and a considerable amount of tricalcium phosphate (7 and 8 μg ml−1byBacillusPSB1 andBacillusPSB10, respectively) was released in liquid medium, with a concomitant drop in pH. The effects of N2-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 withM. ciceriRC3 +A. chroococcumA4 +BacillusPSB10, relative to the control treatment. Grain protein content ranged from 180 (BacillusPSB1) to 309 ng g−1(M. ciceriRC3 +A. chroococcumA4 +BacillusPSB10) in inoculated chickpea. The N contents in roots and shoots differed considerably among the treatments.