Selection of salinity-tolerant durum wheat genotypes at germination stage using MGIDI and IGSI multi-trait selection indices

IntroductionDurum wheat (Triticum turgidum L. var. durum) or hard wheat, is the second most important wheat crop species. Since durum wheat is mainly cultivated under dryland conditions in the Mediterranean region, its yield is strongly affected by abiotic stresses, especially drought and salinity. Salinity stress causes osmotic stress and disrupts the ionic balance of the cells and plant physiologic processes such as seed germination and seedling growth. This study was conducted to identify durum wheat salinity tolerant genotypes at germination stage using multi-trait selection indices such as multi-trait genotype-ideotype distance index (MGIDI) and the ideal genotype selection index (IGSI). Materials and methodsThe plant materials of this research were 50 different durum wheat genotypes, which were evaluated for salinity tolerance at germination stage. The experiment was conducted as a factorial in a completely randomized design with three replications. To create salinity stress, sodium chloride (NaCl) was used at three levels including 0 (control), 150 mM (~15 dS.m-1), and 300 mM (~30 dS.m-1) concentrations. To evaluate the salinity tolerance of the studied genotypes, quantitative stress tolerance indices were first calculated based on root (radicle) and shoot (plumule) dry weight under non-stress conditions (Yp) and average salinity levels (Ys) for each genotype. Then according to the results of factor analysis based on principal component analysis (PCA), the MGIDI index was calculated using the factor scores of the first two factors with eigen values greater than one. The IGSI index for each genotype was also calculated using all stress tolerance indices. Research findingsThe results of factor analysis based on principal component analysis (PCA) showed that the first two factors with eigen values greater than one explained 99.6 of the total variance. The calculation of the MGIDI index based on the factor scores of the studied genotypes showed that in average salinity stress conditions, genotypes 6, 23, 5, 30, 34, 29, 31, 2, 10, 39, 13, 9, 47, 12, 52, 48, and 1 with lower values of MGIDI (between 0.90 and 2.50) and higher values of IGSI (between 0.65 and 0.80) were the best genotypes in term of salinity tolerance. In contrast, genotypes 46, 43, 19, 26, 4, 15, 42, 38,11, and 37 with the lower values of IGSI and the higher values of MGIDI, were considered as weak and sensitive genotypes to salinity. The coefficient of determination (R2) between these two indices for all genotypes was 92%, indicating a high correlation between these two indices and the selection of same genotypes. ConclusionThe results of the present study showed that there was a significant genetic diversity among the studied durum wheat genotypes for salinity tolerance at the germination stage, which can be used in the breeding programs of this valuable crop. IGSI and MGIDI indices were also effective in identifying superior genotypes based on all stress tolerance indices. Therefore, these indices can be recommended to select salinity tolerant genotypes based on different traits in breeding programs.