Advancing rice breeding for drought tolerance: a comprehensive study of traditional and mutant lines through agronomic performance and drought tolerance indices.

Background: Drought stress is a critical challenge to rice production, necessitating the development of drought-tolerant genotypes. This study aimed to evaluate the drought tolerance of rice genotypes, including traditional parental lines (Hashemi, Khazar, Fajr, and Tarom Mahalli) and their corresponding mutant lines, under normal and drought stress conditions. Methods: Agronomic traits such as plant height, spike number, spike length, seed fertility, and yield were analyzed under both conditions. The performance of these genotypes was further assessed using drought tolerance indices. Statistical methods including cluster analysis and principal component analysis (PCA) were applied to identify the most resilient genotypes. Results: Mutant lines demonstrated superior drought resilience compared to their parental counterparts. Specifically, genotypes like TM-230-VE-7-5-1, TM-B-2-1-E, and HM-250-7-6 exhibited higher yields and better stability of key traits under stress conditions. Cluster analysis and PCA emphasized the strong performance of TM-230-VE-7-5-1, which emerged as the most drought-tolerant genotype, excelling across various drought tolerance indices. Conclusions: The selected mutant lines, particularly TM-230-VE-7-5-1, showed significant potential for breeding programs aimed at improving drought tolerance in rice. These findings have substantial implications for enhancing rice production in drought-prone regions, contributing to sustainable agricultural practices. [ABSTRACT FROM AUTHOR]