تنوع ژنتيكي در لاين هاي گندم ساختگي در شرايط تنش شوري، خشكي

Wheat (Triticum aestivum L.) is one of the most important crops in the world an‎d in Iran, playing a key role in ensuring food security. Despite widespread biotic an‎d abiotic stresses in the country that impose serious limitations on wheat production, particularly under climate change conditions, the high potential of synthetic wheats (derived from Triticum turgidum × Aegilops tauschii) has not yet been fully exploited for the improvement of bread wheat. Synthetic wheats, as genetically diverse resources, have a high capacity for transferring resistance genes into cultivated varieties. In recent years, wheat lines derived from selec‎ted synthetic wheat germplasm were obtained from the International Maize an‎d Wheat Improvement Center (CIMMYT), an‎d after four years of eva‎luation, some of them were selec‎ted. In this study, 49 genotypes including 36 advanced synthetic lines an‎d 13 bread wheat cultivars were eva‎luated under four environments: normal conditions, salinity stress, drought stress, an‎d combined salinity an‎d drought stress. The experiment was conducted over two growing seasons at the Lavark Research Farm of Isfahan University of Technology using a ran‎domized complete block design with three replications in a combined analysis. Morphological traits, grain yield, yield components, stress tolerance indices, an‎d several physiological traits were assessed. The greatest reduction in grain yield was observed under combined salinity an‎d drought stress (43.8%), followed by drought stress (41.7%) an‎d salinity stress (33.5%). Carotenoid content increased by 5.67% under drought stress, indicating a strong photoprotective response of the photosynthetic apparatus to stress. Considerable genotypic diversity was observed among synthetic lines an‎d national cultivars. High heritability an‎d genetic advance were detected for thousan‎d-grain weight an‎d yield components, even under stress conditions. Notably, the high heritability of the “breeder’s score,” an observational index based on plant appearance, general health, an‎d growth uniformity, highlights its importance as a practical tool for early-stage identification of superior genotypes in breeding programs. Under stress conditions, correlation patterns changed markedly; under drought an‎d salinity stress, the relationship between phenological traits an‎d grain yield shifted, such that delayed heading an‎d anthesis were associated with reduced yield, revealing the relative advantage of early-maturing genotypes. The results indicated that several synthetic lines (particularly genotypes 196, 198, an‎d 124) showed significantly superior grain yield an‎d stress tolerance compared with the best national cultivars an‎d are therefore recommended for varietal stability trials. Genotype 196 exhibited high yield stability index (YSI) an‎d stress tolerance index (STI), whereas genotype 198 achieved the highest STI values across all stress conditions. In contrast, the cultivar “Chinese spring”, despite its relatively high yield stability, exhibited low STI an‎d limited grain yield, representing an example of the “physiological cost of stress tolerance,” in which activation of resistance pathways diverts metabolic resources away from grain production. Overall, the results demonstrate the high potential of synthetic wheat lines for improving simultaneous tolerance to multiple stresses an‎d confirm their key role in restoring lost genetic diversity in the wheat D genome an‎d managing genetic bottlenecks for the development of resilient an‎d sustainable wheat cultivars under drought an‎d salinity prone environments.

محمد مهدي مجيدي

علي محمد ميرمحمدي ميبدي , مهديه غلامي