GmSALT3, Which Confers Improved Soybean Salt Tolerance in the Field, Increases Leaf Cl- Exclusion Prior to Na+ Exclusion But Does Not Improve Early Vigor under Salinity

Abstract

Soil salinity reduces soybean growth and yield. The recently identified GmSALT3 (Glycine max salt Tolerance-associated gene on chromosome 3) has the potential to improve soybean yields in salinized conditions. Here we evaluate the impact of GmSALT3 on soybean performance under saline or non-saline conditions. Three sets of near isogenic lines (NILs), with genetic similarity of 95.6–99.3% between each pair of NIL-T and NIL-S, were generated from a cross between two varieties 85–140 (salt-sensitive, S) and Tiefeng 8 (salt-tolerant, T) by using marker-assisted selection. Each NIL-T; 782-T, 820-T and 860-T, contained a common ~1000 kb fragment on chromosome 3 where GmSALT3 was located. We show that GmSALT3 does not contribute to an improvement in seedling emergence rate or early vigor under salt stress. However, when 12-day-old seedlings were exposed to NaCl stress, the NIL-T lines accumulated significantly less leaf Na+ compared with their corresponding NIL-S, while no significant difference of K+ concentration was observed between NIL-T and NIL-S; the magnitude of Na+ accumulation within each NIL-T set was influenced by the different genetic backgrounds. In addition, NIL-T lines accumulated less Cl- in the leaf and more in the root prior to any difference in Na+; in the field they accumulated less pod wall Cl- than the corresponding NIL-S lines. Under non-saline field conditions, no significant differences were observed for yield related traits within each pair of NIL-T and NIL-S lines, indicating there was no yield penalty for having the GmSALT3 gene. In contrast, under saline field conditions the NIL-T lines had significantly greater plant seed weight and 100-seed weight than the corresponding NIL-S lines, meaning GmSALT3 conferred a yield advantage to soybean plants in salinized fields. Our results indicated that GmSALT3 mediated regulation of both Na+ and Cl- accumulation in soybean, and contributes to improved soybean yield through maintaining a higher seed weight under saline stress.

Halotolerant rhizobacteria Pseudomonas pseudoalcaligenes and Bacillus subtilis mediate systemic tolerance in hydroponically grown soybean (Glycine max L.) against salinity stress

“…This indicates that Na + transportation from roots to shoots was accelerated when NaCl concentration was increased. A negative correlation between Na + concentration and salt tolerance was also observed by [61] in soybean. In the PGPR inoculated plants, less leakage of K + and less uptake of Na + was observed than stressed plants.…”

Translating knowledge about abiotic stress tolerance to breeding programmes

“…Following the phenotyping of these rice lines, techniques such as genome‐wide association studies (GWAS) and QTL mapping can be used to identify genes underpinning novel traits in stress tolerance (Kumar et al ., ). In soybean, fine mapping of a QTL for shoot Na + exclusion and salt tolerance derived from a bi‐parental population that varied in these traits was used to identify the gene responsible ( SALT3 ) (Guan et al ., ), and the presence of this gene improves soybean yield under saline field conditions (Liu et al ., ). The same gene associated with salt tolerance was also identified through whole‐genome sequencing in wild soybean (Qi et al ., ).…”

“…The same gene associated with salt tolerance was also identified through whole‐genome sequencing in wild soybean (Qi et al ., ). The natural variation of this allele across soybean landraces, breeding lines and wild soybean indicated that presence of the allele conferring improved salt tolerance is associated with the distribution of plants in saline areas of China (Guan et al ., ), but interestingly induces no yield penalty under non‐saline conditions (Liu et al ., ,b). Markers developed from this research are now being used by soybean breeders to select for enhanced salt tolerance in their lines.…”

“…The article focuses on translation of research into cereal breeding as cereals represent the major food crops, but other examples are given when appropriate. Emerging areas not covered in this review which have prospects for further improving crop stress tolerance include exploiting epigenetics through breeding for epi‐allelles (Liu et al ., ,b; Zhang et al ., ) and the use of rhizospheric and endophytic organisms to improve stress tolerance to complement breeding programmes (Munns and Gilliham, ).…”

Plant Trans-Golgi Network/Early Endosome pH regulation requires Cation Chloride Cotransporter (CCC1)

“…These proteins were shown to fulfil important roles in protein sorting to the vacuole, sorting of the auxin transporter PIN5, and potassium homeostasis; and the respective double or triple knockouts exhibit severely stunted growth (Bassil et al, 2011; Fan et al, 2018; Zhu et al, 2018; Wang et al, 2019). The cation proton exchanger CHX20 localises to the endomembrane system and was shown to be important for osmoregulation of stomatal guard cells (Sze et al, 2004; Padmanaban et al, 2007) and the ER localised soybean CHX protein, GmSALT3, was shown to be important for salinity tolerance (Guan et al, 2014; Liu et al, 2016). Lastly, the TGN/EE localised chloride proton antiporter CLC-d was shown to be important for pathogen resistance (Guo et al, 2014).…”