Tall fescue ( Festuca arundinacea ) is a valuable turf grass which benefits from a symbiotic relationship with endophytic fungi of Neotyphodium . Endophytes confer many desirable traits to their host plants such as improved performance and resistance to various biotic and environmental stresses. These acquired traits are affected by the genotype of fungi, genotype of host plant and the interaction between them. Finding a favorite mutualistic complex and exploiting it, is in need to maintain the genetic identity of the fungi during generations of symbiosis with host plant. In order to examine the genetic stability of Neotyphodium in transferring to the next generation of the plant and its relationship with the genotype of the host plant, two crosses between genotypes of tall fescue and one cross between two genotypes of meadow fescue were conducted. Considering reciprocal crosses, 6 cross groups were obtained. Endophytes were isolated from parental host plants and three offsprings of each cross and by applying AFLP molecular marker, genetic diversity was evaluated. 8 primer combinations were examined on 23 fungal samples and 264 polymorphic bands were produced. Based on clustering that was made by Dice similarity coefficient and average linkage method (UPGMA) in all crosses offspring isolates were located in the same group with their maternal parent isolate. The close similarity between offspring isolates and their maternal parent isolates, indicates that transferring of the fungi has been happened via maternal parent and the genetic material of the fungi has not been changed in subsequent generations. Also, the different amount of genetic stability of the fungi in different host genotypes reveals the effect of host genotype on Neotyphodium genetic stability.
