Evaluation of drought stress effects on important agronomic traits, protein and oil content of soybean genotypes

Soybean is an annual self-fertilized crop, belonging to leguminous family and glycine genus, with 40 chromosomes. Soybean is the most important oil crop worldwide since the composition of oil and protein which plays a significant role in public health. Soybean seeds have an average of 40 percent protein and 20 percent oil. Iran import more than 90% of edible oil annually. With 50 hectares of lands under soybean cultivation, Golestan province is the largest soybean cultivation area in Iran. The limitation of water is one of the serious problems in most cultivated lands. In order to solve this problem, relying on the genetic potential and identify drought tolerant varieties are most quick and economic ways. In this regard, pay attention to oil and protein content was quick valuable, which was considered in this study well. In order to evaluate the amount of oil and protein content as well as some related traits under drought stress conditions of soybean genotypes experiment carried out by using split plot format in randomized complete block design with three replications. Main factor was time-course of irrigation included three levels: FC irrigation (control), irrigation after50mm evaporation form a class evaporation pot, irrigation after 100mm evaporation form a class evaporation pot and irrigation after 150mm evaporation form a class evaporation pot. In each irrigation soil moisture to field capacity was reached. Water stress at the time of establishment of the plants began. Sub factor included 10 soybean genotypes: DPX, SARI, williams, Sahar, WE6, L17, HT2, Ds2, PE10 and DW1. Measured traits were included grain oil and protein content, grain yield, plant height, number of sub branches, number of pods, number of seed per pod, seed weight, and dry matter. The percentage of dry matter yield per plant were measured based. At the end of the growing period, to determine the percentage of protein and oil seed samples were taken from each treatment. The results showed that the grain yield and yield components had a significant positive correlation and its value fell under drought stress condition. The reduction of dry matter, seed weight and plant height was higher than other traits. The results of this study showed that the drought had negative impact on yield components which eventually comes to reduce of grain yield. In general, drought stress treatment at each level had more deteriorate effect on susceptible genotypes. Considering the significant positive correlation between seed yield and one thousand seeds weight and significant reduce seed weight in both stress levels (100 and 150 treatment), we can say that a lot of grain yield reduction was due to weight loss. In the meantime, more tolerant and better show for cultivation in areas with water shortages is more suitable. Interestingly, the amount of protein increased by effect of drought condition in most genotypes. It was the same for oil content just for 50mm drought treatment, while significant reduction occurred at 100mm and 150mm drought treatments. There was negative correlation between oil and protein content. PE10 and DS2 had the highest grain yield and sari variety had the lowest grain yield.