ارزیابی عملکرد دانه برخی ارقام گندم با استفاده از شاخص‌های تحمل به تنش

Introduction: Drought stress is one of the most significant limiting factors in agricultural production. Numerous quantitative indices have been proposed to assess plant drought tolerance. These indices, which compare plant performance under both stress and non-stress conditions, are valuable tools for evaluating drought-resistant plant varieties.
Materials and methods: Eight wheat cultivars were evaluated in the Dashestan region of Bushehr Province to assess the impact of drought stress on yield using drought stress indices. The trial was conducted on two adjacent fields, utilizing two irrigation regimes and implementing a 50% drought stress. The experiment was arranged in a randomized complete block design with three replicates during the 2023-2024 growing season. The grain yield per plant was measured using the standard method. After confirming the normality of the data distribution with the Kolmogorov-Smirnov test, an analysis of variance was conducted using SAS software (version 9.4). To conduct correlation analysis, principal component analysis, and create scatter plots of the data, R software was employed. Furthermore, a biplot analysis was performed based on the results of the principal component analysis.
Results: The analysis of variance indicated that the imposition of drought stress significantly decreased the grain yield per plant across all cultivars. Under irrigated conditions, Chamran (18.29 g/plant) and Mehrgan (17.96 g/plant) demonstrated the highest grain yields. Conversely, under drought stress, Koohdasht (11.90 g/plant) and Aftab (8.70 g/plant) yielded the most significant amounts. Various drought tolerance indices, including TOL, MP, HM, STI, YI, GMP, SSI, YSI, and RSI, were utilized to evaluate the drought tolerance of the cultivars. Correlation analysis revealed a negative relationship between grain yield and the indices TOL, MP, GMP, HM, and STI under well-watered conditions. Furthermore, a negative correlation was also observed between yield and both TOL and SSI. The 3D plot analysis utilizing the studied indices indicated that the cultivars Karim, Dehdasht, and Savarez are not well-suited for cultivation in the Dashtestan region of Bushehr. The Koohdasht cultivar was situated in Region C, adjacent to Region A, as illustrated in the diagram. This positioning suggests that it can endure stress while also thriving under irrigated conditions. Factor analysis of the stress indices revealed the identification of two components that collectively accounted for 99.8% of the total variation. These components were designated as 'yield adaptation to stress' and 'yield adaptation to irrigation'. The biplot of drought tolerance indices indicated that the Karim cultivar was situated in close proximity to the SSI vector, further confirming the cultivar's sensitivity to drought stress. Additionally, the correlation between yield under drought stress and the harmonic mean (HM), relative stress index (RSI), and yield index (YI) suggests that these indices can be considered for cultivar selection in stress conditions.
Conclusion: The results indicated that drought stress significantly reduced grain yield across all wheat cultivars. Chamran and Mehrgan cultivars exhibited the highest yields under well-watered conditions, whereas Koohdasht and Aftab cultivars demonstrated superior performance under various levels of drought stress compared to other cultivars. There was a negative correlation between grain yield and the indices TOL, MP, GMP, HM, and STI under well-watered conditions. Furthermore, a negative correlation was also observed between yield and both TOL and SSI under stress conditions. Due to their sensitivity to drought stress, the cultivars Karim, Dehdasht, and Savarez are unsuitable for cultivation in the Dashtestan region of Bushehr. Performance, harmonic, and relative stress indices are recommended for the selection of drought-tolerant cultivars.