Symbiotic effectiveness, abiotic stress tolerance and phosphate solubilizing ability of new chickpea root-nodule bacteria from soils in Kununurra Western Australia and Narrabri New South Wales Australia

Abstract

Aims: To assess the symbiotic effectiveness, tolerance to abiotic stress factors and phosphate solubilizing ability of new chickpea root-nodule bacteria. Methods: Symbiotic effectiveness, abiotic stress tolerance and phosphate solubilizing ability of ten new chickpea rhizobial strains collected from soils were evaluated using laboratory and glasshouse experiments. Results: Six of the ten strains were symbiotically efficient with diversity between those and the commercial chickpea strain CC1192. High temperatures significantly affected strain survival in liquid and peat carrier. Peat carrier offered greater protection. Above 37 °C, strain infectivity decreased with no correlation between strain origin and their infectivity after exposure. Three of the new strains and CC1192 produced optimum growth and survival at pH 6.8 and at two lower pH’s of 4.4 and 5.4 were able to neutralize the growth medium while the other seven strains at high pH were able to either neutralize or acidify the growth medium. Strain survival was significantly higher at increased salt concentrations of NaCl compared to CaCl2. At 3% NaCl concentration, 8 strains survived while at 3% CaCl2 only 3 survived. Many strains were resistant to more than one antibiotic. All strains were able to solubilize phosphate. The ratio between the most efficient strain and the least was 3:1. Conclusions: Chickpea rhizobia strains sourced from soils in Narrabri New South Wales and Kununurra in Western Australia differed in expressed traits from the commercial strain CC1192. These unique traits could provide additional tools for rhizobial strain selection to benefit chickpea production in different soil environments.