Selection of advanced bread wheat genotypes for tolerance to end-season drought stress using MGIDI and IGSI multi-trait selection indices

IntroductionDrought stress is the most critical cause of wheat yield reduction in semi-arid regions. Drought affects wheat yield somewhat during the growing season, but yield reduction predominantly occurs during the reproductive and grain-filling stages. This research aimed at the identification of end-season drought stress-tolerant wheat genotypes based on tolerance and sensitivity indices using the ideotype genotype selection index (IGSI) and the multi-trait genotype–ideotype distance index (MGIDI) multi-trait selection indices.Materials and methodsIn this study, 18 bread wheat genotypes and two control cultivars were evaluated based on a randomized complete block design with three replications under two conditions: full irrigation and end-season drought stress. The experiment was conducted at the Ardabil Agricultural Research Station during the 2021-2022 season. The genotypes were sown in plots of 2.5 m × 3 m with a row spacing of 20 cm. The full-irrigation treatment received 100% of the crop's water requirement, while in the drought stress treatment, the irrigation stopped after heading. Standard agronomic practices were followed throughout the growing season and data on traits such as yield were recorded. Tolerance and stress indices, including tolerance index (TOL), mean productivity (MP), stress tolerance index (STI), modified stress tolerance index (MSTI), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), yield index (YI), yield stability index (YSI), and yield reduction percentage (YRP) were calculated. Statistical analysis was performed using ANOVA, and the means were compared using the least significant difference (LSD) test at the 5% probability level. Additionally, IGSI and MGIDI selection indices were also determined to evaluate the drought tolerance of the genotypes.Results and discussionThe experiment results indicated that based on lower YRP, TOL, and SSI indices, genotypes 11, 5, 9, and 10 were selected as tolerant genotypes. Nevertheless, genotypes 12, 2, 1, and 6 were superior based on higher STI and Harm indices. Also, genotypes 12, 1, 11, and 3 were best in the k2STI and YI indices. Additionally, genotypes 14, 4, 2, and 6 were tolerant based on the k1STI index, genotypes 11, 9, 5, and 10 in the YSI index, genotypes 2, 12, 14, and 4 in the MP index, and genotypes 12, 2, 4, and 1 in the GMP index. Using the multivariate selection indices of the IGSI and MGIDI, genotypes 11, 5, 1, and 12, with the highest IGSI value and the lowest MGIDI value, are among the genotypes with high end-season drought stress tolerance. This was confirmed through heat map cluster analysis and bi-plot diagram in principle components analysis. Also, genotypes 20, 16, and 19, having the lowest value of IGSI and the highest MGIDI, showed higher sensitivity to drought stress. The comparison of the means of the selected genotypes with the total means showed that these genotypes under the end-of-the-season drought stress conditions performed better in stress conditions (with higher Ys) and had less yield reduction compared to the average of other genotypes.ConclusionThe ideotype genotype selection index (IGSI) and the multi-trait genotype–ideotype distance index (MGIDI) for different genotypes based on the quantitative indices of tolerance and stress show that genotype 11, having a high value of IGSI and the lowest value of MGIDI is the most tolerant to end-season drought stress. The genotypes 5, 1, and 12 were ranked next. Based on these results, it is clear that different genotypes exhibit varying levels of drought tolerance based on the indices evaluated. Overall, the results of this experiment provide valuable insights into the potential for improving drought tolerance in wheat through the selection of tolerant genotypes using IGSI and MGIDI indices. The selected genotypes can be further evaluated for their agronomic and physiological traits to confirm their suitability for cultivation in drought-prone areas.