انتخاب براي تحمل به شوري و خشكي در ژنوتيپ هاي منتخب گندم ساختگي و معمولي

As the most important source of calories across vast regions of the world, sustaining wheat (Triticum aestivum L.) production under increasing climatic variability an‎d multiple environmental stresses is now more dependent than ever on the effective identification an‎d utilization of novel genetic diversity—an untapped capacity that can reshape future breeding strategies an‎d crop management approaches. Despite their considerable potential, synthetic wheats (derived from Triticum turgidum × Aegilops tauschii) have not yet been fully exploited for improving bread wheat. These synthetics, as genetically diverse resources, possess a high capacity to introduce stress adaptive genes into cultivated backgrounds through enrichment of the D genome. In this study, 35 wheat genotypes representing four genetic groups—including 21 advanced synthetic hexaploid lines selec‎ted from previous programs, four Iranian commercial bread wheat cultivars, four heat tolerant lines from the WAMI panel, five durum wheats, an‎d a local tetraploid wheat from Khorasan (T. turanicum)—were eva‎luated under normal irrigation, drought stress, an‎d salinity stress across two planting dates (representing distinct thermal regimes). The genotypes were grown in ran‎domized complete block designs with three replications in the three environments. Morphological traits, grain yield an‎d its components, stress tolerance indices, an‎d selec‎ted physiological traits were measured. Substantial phenotypic variation was detected in the germplasm set. Phenological traits (days to heading an‎d physiological maturity) exhibited the lowest variation (1.5–3.9%), whereas grain yield displayed the highest diversity (45% an‎d 43% under salinity without heat an‎d combined heat–drought stress, respectively). Imposing late sowing as a heat stress significantly accelerated phenology, reducing days to heading an‎d maturity by 40% an‎d 43%, respectively, compared to the non heat environment. Grain yield, the most stress sensitive trait, declined by 44.9% under heat stress in well watered conditions, while combined heat–drought an‎d heat–salinity stresses reduced yield by 58.6% an‎d 46.5%, respectively. Relative leaf water content also decreased by approximately 9% across normal, drought, an‎d salinity treatments under elevated temperature. In the autumn planting, synthetic derived an‎d WAMI lines exhibited higher grain yield an‎d superior stress tolerance index (STI) under both drought an‎d salinity, clearly outperforming commercial bread wheats an‎d especially durum lines, which recorded the lowest yields. In the spring planting, WAMI an‎d synthetic lines again demonstrated the highest drought an‎d salinity tolerance, while durum wheats had the lowest stability, underscoring the key contribution of the D genome to performance resilience. Heat susceptibility index (HSI) analysis across moisture regimes showed that CIMMYT an‎d synthetic lines were least sensitive to heat, in contrast to durum wheats, which consistently exhibited the highest sensitivity. Overall, in the autumn planting, synthetic 124 an‎d 159—particularly synthetic 124—showed the most stable performance under drought an‎d salinity an‎d were identified as superior options for stress prone regions. In spring planting, synthetics 8 an‎d 196 were the best performers under normal irrigation, while synthetic 198 excelled under drought an‎d salinity; line H106 was the most heat stable entry. The cultivar ‘Mehregan’ is also recommended as a suitable commercial option for hot environments. The findings highlight the crucial importance of exploiting diverse wheat germplasm—especially synthetic lines integrating wild Aegilops genomic segments, along with globally eva‎luated germplasm resources—to enhance heat an‎d abiotic stress tolerance in national wheat breeding programs.

محمد مهدي مجيدي

علي محمد ميرمحمدي ميبدي , مجيد طالبي