Investigation of soybean advanced lines and parental varieties under non-stress and under water stress conditions

Soybean (Glycine max L.) is one of the most important oil seeds and its importance refer to its role in providing the essential fats needed to complete the human food pyramid similar to other oilseeds. In Iran, after cotton and canola, the highest cultivated land is dedicated to soybeans. The yield of plants such as soybeans is significantly reduced due to environmental stresses, especially drought stress. Thus the aim of the present study was an investigation of soybean advanced lines and parental varieties under non-stress and under water stress conditions to compare different genotypes and identification of more tolerant lines to water stress.

Plant materials consisted of 30 soybean genotypes including three parental varieties Sahar, Williams, Katoul and 27 advanced lines. The lines were derived from parental varieties Sahar×K778, Sahar×Hamilton, Sahar×Gorgan3, Sahar×Williams, Williams×Katoul, Hamilton×Katoul, Sahar×Katoul, Williams×K778, Williams×Hamilton, Gorgan3×Williams. The plants were cultivated in a filed with a total area of 400 m2 at Ezberam, Siahkal (N 37°1.3′8 ̋N, 49°54′10.5 ̋E) in the Guilan province of Iran in spring and summer 2016 as randomized block complete design under normal and water stress conditions with three replications. A total of 14 traits were measured including plant height, number of nodes, first pod height from ground, number of branches, total weight of plant, number of pods, weight of total pods, number of filled pods, weight of filled pods, pod length, number of seeds per pod, number of total seeds, weight of total of seeds and 100- seed weight.

The combined analysis of variance revealed genotypes difference and genotype×conditions interaction were significant (p<0.01) for all of the traits except pod length that indicated high diversity among soybean genotypes and different responses of genotypes to normal and water stress conditions for measured traits. According to the cluster analysis Ward method, all genotypes were assigned to three groups under normal condition. The first group consist of five advanced lines Williams×Katoul3123, Williams×Katoul(4), Williams×Hamilton(2), Sahar×Hamilton(4), Gorgan3×Williams(2) and Katoul had higher mean based on all of agronomic and yield traits such as number and weight of pods, weight of total seeds and 100- seed weight than other genotypes. Under water stress condition genotypes were classified into three groups that third group consisting of four lines Sahar×Katoul(4), Williams×Hamilton(1), Williams×K778(3) and Williams×Katoul(4) had higher performance based on important yield traits including number of pod, weight of pod, number and weight of filled pods, number of seeds per pod, number of seeds in plant, total weight of seeds in plant and 100- seed weight than other genotypes.

According to comparisons mean, Gorgan3×Williams(2) had the highest weight of total pods (94.4gr), number of branches (14.11), number and weight seeds in plant (284.22 and 66.98 gr respectively) and 100-seed weight (35.74gr) under normal condition and the highest weight of total pods (63.28 gr), weight of filled pods (61.91gr), number and weight seeds in plant (236.44 and 44.11gr respectively) and 100-seed weight (33.67gr) belonged to Williams×Katoul(4). Also according to cluster analysis to comparing soybean genotypes under normal and water stress conditions, Williams×Katoul(4) in both groupings, belonged to the better group, indicating that the line was superior to other lines and its parents in terms of total traits. Totally, advanced lines performed better than their parents, especially under water stress condition. Also according to principal component analysis and biplot of two first PC, Gorgan3×Williams(2) under normal condition and Williams×Katoul(4) under both of conditions were better than other lines and parental varieties.