Expression of Russian wheat aphid (Homoptera: Aphididae) resistance in genotypes of tall fescue harhoring different isolates of Acremoniurn endophyte

Abstract

Experiments were conducted to compare the expression of Russian wheat aphid, Diuraphis noxia (Mordvilko), resistance in 2 genotypes of tall fescue grass, Festuca arundinacea Schreb., harboring different isolates of the endophytic fungus Acremonium coenophialum Morgan-Jones & Gams. Aphids did not select endophyte-free over endophyte-infected tiller sections in laboratory tests. In a laboratory population growth test, aphid numbers declined for 2 d on all endophyte-free plants and then increased. Aphid mortality was 100% on all infected plants after 4 d. Thus, antibiosis resistance to D. noxia was not specific to tall fescue genotype or to Acremonium isolate. In a field plot, numbers of Russian wheat aphids were significantly higher on endophyte-free tall fescue. Using these results, and results of other studies involving Acremonium-enhanced resistance to D. noxia in tall fescue and other host grasses, the potential for using D. noxia to screen grass germplasm for Acremonium fungi is discussed.