Tolerance of Wheat Doubled Haploids to Elevated Levels of NaCl at Germination and Seedling Stages

Genetic variability in salt tolerance of bread wheat could be induced via crossing diverse parents and producing doubled haploid (DH) lines from such crosses. One hundred seventeen DH lines resulted via anther culture technique from the cross between Sakha-8 (salt tolerant old variety) and Line-25 (a high yielding promising line) along with the two parents and two check cultivars (Sakha-93 and Sids-1), making a total number of 121 genotypes, were evaluated at different salinity levels under controlled greenhouse conditions at germination (in petri dishes) and seedling (in pots) stages. The aims were to identify the most tolerant DH lines to elevated levels of salinity and to determine the traits of strong association with salinity tolerance. A factorial experiment based on randomized complete blocks design in three replications was used. Full strength Hoagland solution was added to four saline solutions, namely zero (distilled water + Hoagland solution), 3000, 6000 and 9000 ppm NaCl. Increasing concentration of NaCl caused a gradual and significant decrease for most studied traits. On the contrary, increasing salt level caused a significant increase in mean germination time (MGT) (delay) at 6000 and 9000 ppm, shoot dry weight (SDW) at 3000 ppm and root:shoot ratio (RSR) at 9000 ppm NaCl level. At the highest salinity level (9000 ppm NaCl), the 121 genotypes under study were classified based on their salinity tolerance index (STI) into four categories, i.e., tolerant (T), moderately tolerant (MT), sensitive (S) and very sensitive (VS), with a number of 39, 36, 38 and 8 genotypes, respectively; 28 DH lines showed much higher salinity tolerance than the highest salt tolerant check cultivar in this study (Sakha-93). The relationship between NaCl levels and means of studied traits is of quadratic (curvilinear) nature for all categories ofgenotypes, expect for root dry weight (RDW) of all categories, root fresh weight (RFW) of the two groups S and VS and shoot length (SL) of the group VS, where the relationship was near linear regression. The quadratic regression was in the direction of decrease with increasing of NaCl levels for all studied traits, except for MGT of all wheat categories and RSR of S and VS groups of genotypes, which showed a curvilinear increase. Salinity tolerance trait index (STTI) of T group of genotypes increased by increasing NaCl levels, while STTI of MT, S and VS groups decreased for most studied traits. In general, increasing salinity level increased correlation coefficients among absolute means and each of STTI's and STI for all studied traits. Traits showing strong correlations with STI, high heritability estimates, high expected selection gain and wide phenotypic and genotypic variability were shoot fresh weight (SFW), SDW, RFW and shoot length (SL) at 9000 ppm and RDW and SL at 3000 and 6000 ppm; they were recommended as selection criteria for salinity tolerance.