Soybean [Glycine max (L.) Merr.] is a major agricultural crop widely used for providing human and animal food owing to its high protein and oil content. For this reason, they have been consumed in Asia and world greatly and demand is ever increasing. Soybean is classified as a moderately salt-sensitive crop and its production is greatly affected due to increasing salinity stress. About 8 % of the world’s total land is salt-affected. In Korea, around 9 % of total agricultural land (approximately 130,000ha) was reclaimed since 1960's. In order to meet the demand for soybean and to solve arable land shortage problem, it is unavoidable to cultivate soybean in salt-affected soils. Fortunately, soybean germplasm has been shown to have salt-tolerant phenotypes, which have been used to identify the salt-tolerant genes. GmCHX1, a novel ion transporter, is one of the genes known to confer salt tolerance in soybeans. Present study was conducted to understand the effects of sequence variations of GmCHX1, on salt tolerance in wild and cultivated soybeans. A total of 1026 (301 lines of G. max and 725 lines of G. soja) lines were phenotyped for salt tolerance in greenhouse conditions. At the V1-V2 growth stage, the plants were treated with 100mM NaCl solution for two weeks and thereafter the response was measured depending on leaf scorch score (1-health, 3-mid, 5-dead). About 20 lines found to show tolerance to saline conditions and were selected for sequence analysis of GmCHX1. Most of the haplotypes detected in this study corresponded with the haplotype patterns in previous studies. However, several lines showed different patterns of polymorphism in the coding region, suggesting that sequencing of more lines and analysis for the polymorphism in GmCHX1 is needed in order to identify new haplotypes that could confer greater salt tolerance.

Soybeans [Glycine max (L.) Merr.] are frequently exposed to unfavorable environments during growing seasons and water is the most important factor limiting for the production system. The purpose of this study was to determine the leaf water potential changes by irrigation, and to evaluate the relationships of leaf water potential, growth and yield in soybeans. Three soybean cultivars, Hwangkeumkong, Shinpaldalkong 2, and Pungsannamulkong, were planted in growth chamber and field with irrigated treatments. Leaf water potential of three soybean cultivars was positively correlated with leaf water content during vegetative and reproductive growth stages in growth chamber and field experiments. Leaf water potentials measured for three soybean cultivars under growth chamber were higher than those of under field conditions. Higher leaf water potential with irrigated plots under field was observed compared to conventional plots during reproductive growth stages. Leaf water potentials of three soybean cultivars were continually decreased during reproductive growth stages under field and there was no significant difference among them. Number of leaves, leaf water content, pod dry weight, number of seeds and seed dry weight with irrigated plots were higher than those of conventional plots. The results of this study suggested that leaf water potential could be used as an important growth indicator during the growing season of soybean plants.