Response of soybean cultivars to salinity stress

A factorial experiment based on completely randomized design (CRD) with three replications was conducted in 2007, to evaluate grain filling (four harvests), yield and yield components of three soybean cultivars under a non-saline (control) and three saline (3, 6 and 9 dS/m NaCl) conditions in the greenhouse. Six seeds were sown in each pot filled with 900 g perlite, using 144 pots. After emergence, seedlings were thinned and 4 plants were kept in each pot. Grain filling rate and duration and consequently maximum grain weight decreased with increasing salinity. Grain filling rate also varied among cultivars and was positively associated with maximum grain weight. However, variation in grain filling duration had little effect on final grain weight of soybean cultivars. Mean number of pods and grains per plant and mean grain weight and grain, oil and protein yields per plant under non-saline conditions were considerably higher than those under saline conditions. Although grain yield of soybean cultivars was statistically similar, grain yield of Zan was about 11% less than that of L 17 and Williams. L 17 produced more, but smaller grains per plant, compared with other cultivars. However, Williams produced the largest grains, particularly under salinity stress. Decreasing oil and protein yields per plant with increasing salinity were mainly attributed to the large reductions in grain yield per plant under saline conditions. It was concluded that soybean is a sensitive plant to salinity stress and both environment and genotype are responsible for the variation in yield and yield components of this crop.