Bread Wheat With High Salinity and Sodicity Tolerance

Abstract

Soil salinity and sodicity are major constraints to global cereal production, but breeding for tolerance has been slow. Narrow gene pools, over-emphasis on the sodium (Na+) exclusion mechanism, little attention to osmotic stress/tissue tolerance mechanism(s) in which accumulation of inorganic ions such as Na+ is implicated, and lack of a suitable screening method have impaired progress. The aims of this study were to discover novel genes for Na+ accumulation using genome-wide association studies, compare growth responses to salinity and sodicity in low-Na+ bread Westonia with Nax1 and Nax2 genes and high-Na+ bread wheat Baart-46, and evaluate growth responses to salinity and sodicity in bread wheats with varying leaf Na+ concentrations. The novel high-Na+ bread wheat germplasm, MW#293, had higher grain yield under salinity and sodicity, in absolute and relative terms, than the other bread wheat entries tested. Genes associated with high Na+ accumulation in bread wheat were identified, which may be involved in tissue tolerance/osmotic adjustment. As most modern bread wheats are efficient at excluding Na+, further reduction in plant Na+ is unlikely to provide agronomic benefit. The salinity and sodicity tolerant germplasm MW#293 provides an opportunity for the development of future salinity/sodicity tolerant bread wheat.

A Grain of Salt

“…Together they suggest that HKT1’s are critically important for maintaining fitness under saline conditions. Our data, supported by recent evidence that shoot Na + accumulation in certain bread wheat genotypes is not negatively associated with plant salinity tolerance 38, 39 , question this conclusion for barley. Here we show that biomass yield (and by inference photosynthesis) is maintained in lines such as Maris Mink (HvHKT1;5 HAP3 ) that have levels of grain (and leaf) Na + content that would be expected to significantly impact yield.…”

A single nucleotide substitution in TaHKT1;5‐D controls shoot Na+ accumulation in bread wheat

“…It appears that although TaHKT1;5-D has a key role in Na + exclusion, salinity tolerance in bread wheat may not necessarily be entirely related to the plants ability to maintain a low shoot Na + concentration. The lack of a relationship between shoot Na + concentration and salinity tolerance in bread wheat has been observed in other studies (Genc et al, 2019;Genc, McDonald, & Tester, 2007). When Na + or Cl − is accumulated to a high concentration in shoot tissue, cells are able to compartmentalize ions in vacuoles to avoid accumulating toxic concentration of Na + and/or Cl − in the cytosol, thus maintain sensitive metabolic processes (Flowers et al, 2015;Munns et al, 2016;Munns & Tester, 2008).…”

“…Breeding of salt-tolerant bread wheat cultivars has focused on selecting genotypes with improved shoot Na + exclusion (Ashraf & O'leary, 1996;Poustini & Siosemardeh, 2004). However, selection based on shoot Na + exclusion is not always correlated with increased salinity tolerance in bread wheat (Genc et al, 2013;Genc et al, 2019).…”

Determination of the most important characteristics in bread wheat grain yields under salinity stress

“…Salinity problem is a major constraint to the global cereal production but breeding for tolerance and exploring the most characteristics of wheat under salinity stress has been slow (Genc et al 2019). Although rising salinity levels more than 3.5 dS m − 1 for all seedling characteristics studied result in a substantial decrease.…”