مطالعه ژنتيكي ويژگي‌هاي مختلف در ژرم پلاسمي از برخي گراس‌ها و آناليز ژنتيكي حافظه تنش خشكي و شوري در فسكيوي بلند

Grasses are key components of rangelan‎ds, forage systems, an‎d urban green spaces, an‎d they play an important role in ecosystem stability an‎d forage production. Their performance depends on genetic diversity, reproductive traits, an‎d the ability to adapt to environmental stresses. This dissertation aimed to eva‎luate genetic diversity in grasses an‎d to examine the genetic an‎d physiological mechanisms of drought an‎d salinity stress memory in tall fescue (Festuca arundinacea) through four complementary studies. In the first study, 78 genotypes from 18 grass species, together with one commercial cultivar, were eva‎luated over six years. The SIIG composite index effectively combined multiple traits an‎d showed that species superiority varied depending on the breeding objective; thus, F. arundinacea an‎d the commercial cultivar Sportivo exhibited superior performance in persistence an‎d turf quality, whereas Paspalum dilatatum performed better in persistence an‎d forage production. Among them, F. arundinacea displayed a more balanced combination of major traits an‎d indices, indicating a more multifunctional nature. Analysis of seed production traits revealed significant variation among species in resource allocation strategies. Accordingly, high-yielding species such as F. arundinacea, species with high seed number such as Poa pratensis, an‎d large-seeded species such as P. dilatatum may be used to increase total seed yield, improve reproductive capacity, an‎d enhance seedling establishment in breeding programs, respectively. In the second study, genetic analysis of 24 half-sib families of tall fescue an‎d their parents showed that traits related to turf quality an‎d seed characteristics were under moderate to high genetic control, making direct selec‎tion effective. In contrast, dry forage yield was more strongly affected by the environment an‎d therefore requires indirect selec‎tion indices. Biplot analysis identified genotypes 21M an‎d 15L an‎d families 25L, 23M, an‎d 21M as multifunctional genetic materials, while genotypes 25M, 11M, an‎d 1E an‎d families 25M an‎d 3M were identified as suitable can‎didates for improving turf quality. In the third an‎d fourth studies, the effects of drought an‎d salinity stress memory were eva‎luated in selfed an‎d open-pollinated genotypes. A significant interaction between stress memory an‎d pollination type was observed. In open-pollinated genotypes, induction of drought an‎d salinity stress memory (Study 3) led to increased photosynthetic pigment content, enhanced antioxidant system activity, an‎d improved root-to-shoot ratio, whereas in selfed genotypes, drought stress memory (Study 4) mainly improved photosynthetic pigments an‎d root growth. Overall, selfing led to inbreeding depression an‎d reduced several physiological an‎d root traits. Estimation of genetic parameters in open-pollinated populations under drought stress memory treatments showed that many root an‎d physiological traits had desirable heritability, with additive gene effects playing a predominant role, indicating the effective potential of phenotypic selec‎tion in breeding programs. Based on multivariate analyses an‎d the STI an‎d YSI indices, genotype 11M an‎d families 3LOP, 15LS1, an‎d 12LS1 were identified as superior can‎didates for stress-oriented breeding programs an‎d the development of synthetic varieties. Overall, this research highlights the importance of genetic diversity, stress memory, an‎d multivariate approaches in developing stable an‎d resilient grass genotypes under changing climatic conditions.

محمد مهدي مجيدي

مجيد طالبي

علي محمد ميرمحمدي ميبدي , ابوذر سورني , احسان شهبازي