Evaluation of salinity tolerance of some durum wheat genotypes at germination and seedling growth stage using multivariate selection indices

Introduction Durum wheat (Triticum turgidum L. var. durum) is the second most crucial wheat and the tenth main crop globally. Salinity stress prevents water absorption from the soil and disturbs the ionic balance of the cell. As a result, metabolic processes such as seed germination, seedling growth, flowering, and seed formation are inhibited. The purpose of this study is to the evaluation of the effects of salinity stress on the germination and seedling growth of different durum wheat genotypes, as well as to identify and select tolerant genotypes using multivariate selection indices such as the ideal genotype selection index (IGSI) and the multi-trait genotype–ideotype distance index (MGIDI). Materials and methods In this research, 50 different durum wheat lines and genotypes were prepared by the Agricultural Research, Education and Extension Organization of Iran and were evaluated in terms of tolerance to salinity in the germination stage, as a factorial experiment, based on a completely randomized design with three replications. Salinity levels included 0, 75, 150, and 300 mM sodium chloride concentrations. After one day, counting the number of germinated seeds was started daily. Based on the data obtained from counting the germinated seeds, various parameters of seed germination, including coefficient of the velocity of germination (CVG), germination index (GI), average germination duration (MGT), average daily germination (MDG) and final germination percentage (FGP) were calculated. In addition, after ten days, the characteristics such as root and shoot length and dry weight of root and shoot were measured for each genotype. Also, using the seedling height and dry weight, and the seed germination percentage, the seedling vigor was calculated. The MGIDI index of the studied genotypes was calculated based on factor scores of the first three factors with eigenvalues greater than one in factor analysis based on principal component analysis (PCA). The IGSI index also was calculated considering all the traits. Results and discussion The analysis of variance showed significant differences (p < 0.01) between salinity levels and between genotypes in terms of all traits. But, the interaction effect of salinity × genotype was not significant for all studied traits. The comparison of the salinity levels showed that the germination components and the length and weight of the root and shoot decreased by increasing salinity levels. Factor analysis based on principal component analysis (PCA) showed that in normal conditions and salinity (150 mM NaCl) stress conditions, the first three factors with eigenvalues greater than one explained 83.89 and 84.97 percent of the total variance among the traits, respectively. According to the MGIDI index, under normal conditions based on the selection intensity of 30%, genotypes G30, G39, G51, G19, G14, G2, G31, G34, G5, G48, G7, G26, G1, G23, and G33 have the lowest values and were favorable. In 150 mM salinity condition, genotypes G9, G2, G29, G5, G12, G47, G30, G1, G31, G10, G34, G41, G13, G49, and G16 were the best genotypes with the lowest MGIDI values. According to the IGSI index in the 150 mM salinity level, genotypes G5, G29, G2, G30, G23, G9, G12, G1, G10, G41, G47, G34, G48, G16, and G13 have the highest values (between 0.60 to 0.80) were considered as desirable genotypes. On the contrary, genotypes G43, G46, G4, G26, G15, G19, G8, G14, G35, G44, G24, and G42, having IGSI values less than 0.40, were considered weak genotypes in this condition. Conclusion In this study, IGSI and MGIDI indices were used to evaluate the response of different durum wheat genotypes to salinity using all studied traits. In general, the results of the present research showed a considerable genetic diversity among the studied durum wheat genotypes in terms of salinity tolerance at the germination stage, which can be used in the breeding programs of this valuable crop. Also, the IGSI and the MGIDI indices were effective in identifying superior genotypes based on all the studied traits. Using these indices in breeding programs to select desirable genotypes can be fruitful and effective.