Tall fescue (Festuca arundinacea) is one of the forages that is commonly used in cold regions as pasture and forage. Tall fescue has gametophytic self-incompatibility. Previous studies reported self-incompatibility in the host endophyte infected genotypes, 75B+ and 75C+, by Epichloe fungi, was low and, in some case, eliminated. In the Fist study, we investigated the effect of endophyte infection on genetic variances of forty full-sib families of tall fescue with their ten male parents, free from endophyte, and two female parents (75B and 75C) with both endophyte-infected (E+) and non-infected (E-) counterparts over two years. In addition, the effect of endophyte infection on selfing ratio and seed production via selfing was eva‎luated between endophyte-infected progenies and their non-infected counterparts. Genetic compatibility between the host and fungus was also eva‎luated by leaf sheath endophyte intensity (LSEI) and seed endophyte infection percentage (SEI %) indices. The results showed that genetic compatibility between the host and endophyte was different between two infected female genotypes and their progenies. Compatibility parameters, leaf sheaths endophyte intensity, and seed endophyte infection rate were higher in 75B+ than in 75C+. Plant traits’ genetic variances were estimated higher among full-sib endophyte infected progenies of 75B+ compared to non-infected counterparts. On the contrary, the genetic variances of plant traits were lower in full-sib endophyte-infected progenies of 75C+ compared to E- counterparts. It seems that higher compatibility in host-endophyte interaction leads to a higher estimate of genetic variances after outcrossing. However, when symbiosis between two partners is not fully compatible, genetic variances among low-performed progenies of a host plant may also be covered by the symbiosis. Therefore, genetic compatibility between the host and the endophytic fungus must be investigated before breeding programs of tall fescue. In the second study, the yield stability of progenies was eva‎luated based on all eva‎luated traits, in the third and second experimental years. As experimental materials, single plants with the highest and lowest seed yield and self-seeding ratio in the second year in each of the four families were selected. The results revealed that 75B+ hybrid progenies had higher yield stability, not only than 75B- family hybrids, but also form 75C+ and 75C- progenies. Also, EI progenies, 75C+, showed lower stability than EF genotypes, 75C-. The results showed that the presence of endophytes, particularly when there is high compatibility between the host and the fungus, not only lead to increasing plant yield but also potentially enhances the stability of forage and seed production. These positive effects are expected to continue in the next years. Also, in several studies it has been reported that EI leads to yield increase and stability of genotypes. However, contrasting findings have been reported in other studies, suggesting no significant effect of endophytes one plant yield and stability. Therefore, the stability of forage seed yields, is critical in breeding programs aimed at providing animal feed. In the third study, plant hormones, GA3, IAA and ABA, were eva‎luated in selected single plants of each EI and EF families. The results showed that GA3 and IAA hormones in all four families have a direct effect on increasing the forage yield, and if there is compatibility between the plant and endophyte, its concentration increases. Also, IAA hormone displayed a positive correlation with seed related traits such ad seed yield and selfing ratio in all families, and its concentration was increased in the 75B+ family, which has high compatibility indices. Also, ABA hormone had a direct correlation with forage related yield traits.

اقافخر ميرلوحي فلاورجاني , محمدرضا سبزعليان دستجردي

محمد مهدي مجيدي , مصطفي قناديان

قدرت اله سعيدي , سعد اله هوشمند كوچي , لادن طلايي