Abstract
Salt stress inhibits soybean growth and reduces gain yield. Genetic improvement of salt tolerance is essential for sustainable soybean production in saline areas. In this study, we isolated a gene (Ncl) that could synchronously regulate the transport and accumulation of Na+, K+, and Cl− from a Brazilian soybean cultivar FT-Abyara using map-based cloning strategy. Higher expression of the salt tolerance gene Ncl in the root resulted in lower accumulations of Na+, K+, and Cl− in the shoot under salt stress. Transfer of Ncl with the Agrobacterium-mediated transformation method into a soybean cultivar Kariyutaka significantly enhanced its salt tolerance. Introgression of the tolerance allele into soybean cultivar Jackson, using DNA marker-assisted selection (MAS), produced an improved salt tolerance line. Ncl could increase soybean grain yield by 3.6–5.5 times in saline field conditions. Using Ncl in soybean breeding through gene transfer or MAS would contribute to sustainable soybean production in saline-prone areas.
Highlights
Genetic variation for salt tolerance has been described in soybean[1,4,5,6], The salt tolerance of partial soybean germplasm conserved in the GRIN, USDA has been evaluated
RT-PCR analysis showed that the level of transcription of Glyma03g32900 was higher in the salt-tolerant line NILs18-T than in the salt-sensitive line NILs18-S (Fig. 1b)
Because BLAST homology search showed that Ncl belonged to the Na+/H+ antiporter gene family, we expected to observe Na+ and K+ regulation by Ncl as observed in the studies of Qi et al.[12] and Guan et al.[20]
Summary
Genetic variation for salt tolerance has been described in soybean[1,4,5,6], The salt tolerance of partial soybean germplasm conserved in the GRIN, USDA has been evaluated. The high level of variation in soybean germplasm, including wild and cultivated soybean species, suggest that genetic improvement of salt tolerance is feasible. The salt tolerance QTL, in which the tolerant allele was from a wild soybean accession PI 483463, was recently mapped within a 658-kb region between SSR03_1335 and SSR_1359 on chromosome 310. Glyma03g32900 (GmSALT3), which associated with limiting the accumulation of sodium ion, was identified as a candidate causal gene underlying the QTL on chromosome 3 from a Chinese commercial soybean cultivar, Tiefeng 8, by using fine mapping method[20]. Map-based cloning or positional cloning strategies have been successfully used in the isolation of genes underlying QTLs of environmental stress tolerant traits such as salt[25], submergence[37], and phosphorus deficiency[38] tolerances in crops. The near isogenic lines (NILs) carrying the tolerant allele of the QTL could increase soybean grain yield by 3.6–5.5 times in saline field conditions
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