Abstract
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 yiel