Nitrogen fixation, plant growth and yield enhancements by diazotrophic growth-promoting bacteria in two cultivars of chickpea ( Cicer arietinum L.)

Abstract

A total of 11 rhizobia-like-bacteria, isolated from the nodules of chickpea, were characterized for nitrogen fixation potential and growth promoting ability. All the isolates nodulated chickpea, amplified nifH gene and fixed nitrogen but, four isolates (ICKM-9, ICKM-15, ICS-31 and ICS-32) were found to fix nitrogen more than 4.0 nmoles of ethylene g−1 fresh weight of nodules h−1. Under field conditions, seeds of chickpea varieties ICCV 2 and JG 11, when treated with the bacteria, enhanced the nodule number (up to 46% and 46%), nodule mass (up to 76% and 50%), shoot mass (up to 21% and 42%) and grain yield (up to 27% and 25%), respectively, over the un-inoculated control. At the harvest, organic carbon (up to 7% and 24%), total nitrogen (up to 11% and 19%) and available phosphorous (up to 14% and 29%) were found enhanced, respectively, in the rhizosphere of ICCV-2 and JG-11 treated with bacteria over the un-inoculated control. All the isolates produced plant growth-promoting traits including indole acetic acid, β-1,3-glucanase, hydro cyanic acid (except ICKM-17 and ICS-31) and siderophore (except ICS-31). The 16 S rDNA gene sequences of bacterial isolates of ICKM-1, ICKM-4, ICKM-7, ICKM-9, ICKM-12, ICKM-14, ICKM-15, ICKM-17, ICS-30, ICS-31 and ICS-32 showed maximum identity with Pantoea dispersa, Chryseobacterium indologenes, Pseudomonas geniculata, Stenotrophomonas pavanii, P. geniculata, P. geniculata, Stenotrophomonas maltophilia, Chryseobacterium sp., P. geniculata, Chryseobacterium indologenes and Stenotrophomonas acidaminiphila, respectively. This study indicates nodule-associated bacteria could be a valuable pool for improving nitrogen fixation and crop yields in chickpea.