Influence of pesticide-treated seeds on survival of Mesorhizobium sp. Cicer, symbiotic efficiency and yield in chickpea

Abstract

Chemical seed protectants are used to reduce the adverse effects of seedling fungal pathogens or insect attack on legume pastures and crops. Chickpea seeds are also frequently treated with Mesorhizobium sp. Cicer inoculant to promote effective symbiotic nitrogen fixation (SNF), which seems to be a cost effective measure. The population of viable Mesorhizobium sp. Cicer on seeds of chickpea declined with time of storage (4°C) in pesticide treated and untreated chickpea seeds in vitro. A significant reduction in chickpea rhizobia was observed in seed treatment with Captan followed by Endosulfan and Chlorpyrifos. In a field experiment during the winter season 2006–2008, no difference in the emergence count of chickpea plants was observed. Treatments inoculated with Mesorhizobium sp. Cicer alone or along with Captan, Chlorpyrifos or Endosulfan showed improved plant growth and symbiotic parameters (plant height, nodulation, leghaemoglobin content, and nitrogen content) in comparison with the uninoculated control treatment. Significantly higher grain yield (9.6%) was observed in the treatment inoculated with Mesorhizobium sp. Cicer alone as compared to the uninoculated control. A non-significant difference in grain yield among treatments where Mesorhizobium sp. Cicer along with a mixture of fungicide and insecticides was applied was observed in contrast to the Mesorhizobium sp. Cicer treatment. In conclusion, the recommended rates of fungicide and insecticides as seed treatment were not detrimental to chickpea-Mesorhizobium sp. Cicer symbiosis, hence they can be safely used to obtain higher productivity.