Study the effect of drought stress on oil percent, protein percent and fatty acids composition of soybean grain

In order to assess the effect of drought stress on seed chemical compositions and determine a stage In order to assess the effect of drought stress on seed chemical compositions and determine a stage that drought stress has the most effect on seed compositions, an experiment was conducted as a split factorial based on complete randomized block design in three replications in agriculture faculty of Tarbiat Modares University in 2014. Four treatments of drought stress were exerted as withholding irrigation at flowering stage, pod formation, seed filling stage, and control (without stress). The other treatments were two soybean cultivars (Williams and L17) and the seeds resulted from three planting dates in Moghan in a last year (10 May, 10 June and 10 July). The measured traits included fatty acids percent, oil and protein percent of soybean grain. The results indicated that effect of drought stress was significant on oil and protein percent and also fatty acids except palmitic acid. The lowest percent of oil (19.29% ) and the highest percent of protein (37.36 %) were obtained by drought stress at seed filling stage. The highest percent of oleic acid (25.75%) and the lowest linolenic acid (5.98%) was observed in Williams at drought stress at seed filling stage. Regarding that the main purpose of soybean planting in Iran is oil production and drought stress at seed filling stage has negative effect on oil content, so irrigation in this stage of reproductive growth is necessary to achieve desirable oil yield.