QTL mapping for salt tolerance in barley at seedling growth stage

Barley (Hordeum vulgare L.), an important food and fodder crop, is potentially tolerant to salinity. To identify quantitative trait loci (QTLs) controlling salt tolerance, the population of 162 recombinant inbred lines (RILs) derived from F8 generation of Arigashar (an extremely salt tolerant Iranian six-rowed barley landrace) crossed with Igri (a salt semi-sensitive two-rowed cultivar) were evaluated. The growth of shoots, roots, and coleoptiles, and root numbers are four important growth characteristics severely affected by salt stress at seedling growth stages. A linkage map was constructed using 106 AFLP and SSR markers spanning six barley chromosomes including 2(2H), 3(3H), 4(4H), 7(5H), 6(6H), and 1(7H). Out of totally 26 detected QTLs, 17 QTLs were found effective for salt tolerance at 250 and 350 mM NaCl which localized on chromosomes 2H, 3H, 4H, 6H, 7H, and linkage group L1, whereas considering equivalent overlapped QTLs with a pleiotropic effect led to detection of totally 9 distinctive QTLs (QClgH2.1b, QSdgH2.1b, QSlgH2.1c, QNrgH2.1b, QTwgH2.2c, QSdg3Hb, QSlg4Hb1, QClg4Hb, and QSlg6Hc2) effective for salinity tolerance. 2(2H), 4(4H), and 6(6H) were major chromosomes harboring QTLs which effectively controlled salt tolerance in the IgrixArigashar population. An interesting QTL, QTwg4Hc, was localized on chromosome 4H in the XE41-M61 marker distance that controls several traits including shoot and coleoptile lengths and shoot fresh mass under salt stress. A dense marker cluster around a resistance gene could offer a starting point for positional cloning.