Effect of microbial inoculants and nitrogen levels on oil content and fatty acid composition in winged bean [Psophocarpus tetragonolobus L. (DC)] seed

Abstract

A field experiment was carried out at research farm of Tirhut College of Agriculture, Dholi, Muzaffarpur, Bihar in year 2015-16 on sandy loam soil to study the effect of inoculation and nitrogen levels on oil content and fatty acid composition in matured seed of winged bean. The experiment was laid out in Randomized Block Design comprising twelve treatments with three replications. Effect of different treatment combinations had significant effect on oil content over control. Seed oil content obtained marked variations with application of PGPR inoculant and a decrease in oil content had been observed with use of higher dose of nitrogen. The maximum oil content (26.41%) was recorded in seed treatment with both Rhizobium and PGPR inoculants without use of nitrogen whereas, the maximum free fatty acid content (3.87%) was recorded in treatment where seeds were inoculated with Rhizobium and no application of nitrogenous fertilizer followed by 0 kg Nha-1 + PGPR inoculation (3.80%) and 20 kg Nha-1 + no inoculation (3.74). On the other hand, winged bean oil contained high amount of oleic acid (31.9 to 36.20%), linoleic acid (33.46 to 38.50%) of major unsaturated fatty acid. The highest amount of oleic (monounsaturated fatty acid) and linolenic acid were recorded with treatment of 40 kg Nha-1 + no inoculation (38.50%) and 0 kg Nha-1 + Rhizobium + PGPR inoculation (38.50%) respectively. Maximum saturated fatty acid content (29.51%) was recorded in treatment of 40 kg Nha-1 + PGPR, however minimum value (22.61%) was obtained with application of 40 kg Nha-1 and without inoculation of either PGPR or Rhizobium.