Survival efficacy and potential of Mesorhizobium Ciceri for enhancing the growth and yield of imidacloprid-treated chickpea (Cicer arietinum)

Chickpea relies on inoculation with N2-fixing bacteria to fulfill its N requirement. The efficacy of the inoculation process hangs on the success of association between N2-fixing bacteria and Chickpea plants. Seed treatment with insecticides may kill the inoculated bacteria and result in poor establishment and upshot of the symbiosis. Survival efficacy of four rhizobial (Mesorhizobium ciceri) strains (CRI14, CRI20, CRI34 and CRI35) selected on the basis of preliminary study, was evaluated at increasing concentration of imidacloprid (0-200 μg L). Amongst four inoculated strains, the strain CRI20 and CRI35 showed better survival in the presence of Imidacloprid when compared to rest of two. Strain CRI35was able to tolerate insecticide above the recommended dose whereas the strain CRI20 showed relatively less growth at high concentration. So, for as the efficacy of these strains was concerned pertaining to improvement in growth of imidacloprid treated chickpea it was tested in a pot trial. Chickpea seeds were treated with recommended dose of imidacloprid and then inoculated with respective rhizobial strains as per experimental plan. Un-inoculated treated and untreated seeds were also used for comparison. The pots were arranged according to completely randomized design in two sets having three replications each. At flowering, plants from one set were uprooted and data regarding nodulation was recorded, whereas, the data regarding growth and yield parameters was calculated from other set at maturity. The results showed that inoculation not only improved nodulation but also caused a significant increase in growth and yield. Rhizobial strain CRI35 performed better than the other which might be due to its better growth promoting traits in addition to its ability to tolerate insecticide. Therefore, it is suggested to use only those rhizoidal strains that could tolerate agrochemicals and survive well in the rhizosphere and would consequently nodulate legume plants more efficiently.