Evaluation of salinity tolerance of the fifth generation (M5) of bread wheat lines using some indices of stress tolerance

The basis of breeding programs is the presence of genetic diversity. The role of nuclear radiation to create genetic diversity has been well documented. Mutations induced by irradiation with gamma rays has had a significant role in improving the lot of important agronomic traits in plants. Salinity stress every year affects crops in large areas of the country. Since crops' yield is reduced due to the salt toxicity, hence the production and introduction of high yielding salinity tolerant varieties can minimize the phenomenon effect. In order to determine some stability indices related to wheat grain yield the fifth generation (M5) under salinity conditions, 15 selected lines from the fourth generation (M4) with two parents' genotypes (‘Arg’ and ‘Bam’) and two genotypes produced in Yazd region (‘Sivand’ and ‘Narin’) were planted under both conditions of non-stress )2 dsm-1) and salinity stress )10 dsm-1) in research field of the National Salinity Research Center (NSRC) in Yazd province. Each plot included two rows in 1 m long with a row spacing of 20 cm. During the growing season, to determine the soil salinity in the root growth zone the soil sampling was carried out to a depth of 0-90 cm. The average salinity under conditions of non-stress and stress was obtained 2.3 and 9.7 dsm-1, respectively. Analysis of variance for a complete random block design was performed on grain yield, yield components and sodium and potassium ions traits and the Comparison of means was conducted by least significant difference (LSD) test. Tolerant indices of mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), Stress stability index (SSI), Tolerance index (TOL) were calculated to investigation salinity. Also, Pearson correlation, stability analysis and cluster analysis was performed The results of analysis of variance for grain yield and yield components showed the genetic diversity among lines. Line two (Arg-200 gray, 246.67 g m-1) and one (Bam-150 gray, 165.55g m-1) had the highest grain yield, K+ and K+/NA+ ratio and the lowest and NA+ ions under both conditions. Also, lines tolerant to salinity had a lower level of NA+, high level of K+ and a higher K+/NA+ ratio under salinity stress conditions to sensitive lines. Regarding the positive and significant correlation between grain yield in both conditions and indices of MP, GMP and STI, the indices were selected as the most desirable tolerance indices. According to three-dimensional graph Fernandez were introduced that lines one, two and eight as the most tolerant lines to salinity stress. The experiment results showed, indices of MP, GMP and STI are the most suitable indices for selection of lines tolerant to salinity. Lines one, two and eight had high grain yield under both conditions. So, according to the results lines one, two and eight can be introduced as stable lines and with high yield under salinity stress conditions and the fifth generation and it is recommended to introduce these three lines for cultivation in the sixth generation.