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Title: Variable Performance of Bird Cherry-Oat Aphid on Neotyphodium-infected Wild Tall Fescue from Tunisia

item Waldron, Blair

Submitted to: International Symposium on Fungal Endophytes of Grasses
Publication Type: Proceedings
Publication Acceptance Date: 2/1/2007
Publication Date: 3/25/2007
Citation: Clement, S.L., Elberson, L.R., Waldron, B.L., Quisenberry, S.S. 2007. Variable Performance of Bird Cherry-Oat Aphid on Neotyphodium-infected Wild Tall Fescue from Tunisia pgs. 337-340. 6th International Symposium on Fungal Endophytes of Grasses.

Interpretive Summary: Cattle suffer from fescue foot and toxicosis when they graze on tall fescue grass harboring naturally occuring fungi (Neotyphodium grass endophytes) that produce high amounts of toxic alkaloid chemicals. Research has shown that removal of the fungus can render tall fescue nontoxic to grazing animals. However, without the fungus, tall fescue is less able to withstand drought conditions and resist insect attack. Fortunately, scientists have discovered 'nontoxic' strains of fungal endophytes that do not produce mammalian toxins but provide protection against environmental stresses, including insect attack. For continued development of nontoxic tall fescue cultivars for stress resistance, scientists require a large supply of nontoxic strains of grass endophytes. This article for an international symposium on grass endophytes shows that tall fescue from North Africa and stored in the seedbank at the USDA-ARS Plant Introduction Station, Pullman, Washington is a good source of diverse endophyte strains. The existence of diverse strains was discovered after a series of experiments documented the peformance of a common aphid pest of grasses (bird cherry-oat aphid) on different tall fescue - fungal endophyte associations in the Pullman seedbank. This aphid reacts differently to different alkaloids produced by fungal endophytes, so its death and survival on different tall fescue - endophyte associations revealed the presence of diverse endophyte strains. Broadly speaking, this research is important because it highlights the importance of preserving and evaluating microbial germplasm in the U.S. National Plant Germplasm System for sustaining American agriculture.

Technical Abstract: The extent of Neotyphodium based resistance in wild fescue to bird cherry-oat aphid (Rhopalosiphum padi) was determined by quantifying densities of this aphid on a series of Neotyphodium – infected (E+) and uninfected (E-) tall fescue entries. Little or no aphid survival was observed on plants from E+ ‘Kentucky 31’ tall fescue and three E+ wild tall fescue accessions (16079, 15978, 16075) from Tunisia. By contrast, E+ plants from three Tunisia accessions (16036, 16044, 16085) supported populations of R. padi. These results suggest that wild tall fescue from Tunisia harbor diverse Neotyphodium endophtyes. They also support previous observations by entomologists that the magnitude of insect (including aphids) resistance in E+ grasses varies with the host genotype and Neotyphodium strain involved in the interaction.