Fungal Endophytes of Wild Barley and their Effects on Diuraphis noxia Population Development
Laboratory experiments were conducted to compare the expression of Diuraphis noxia (Mordvilko) (Homoptera: Aphididae) resistance in four plant introduction (PI) lines of wild barley (Hordeum) infected with different species or strains of endophytic fungi (tribe Balansieae, family Clavicipitaceae, Neotyphodium gen. nov. [formerly Acremonium]). Aphid densities were significantly lower on endophyte-infected plants of PI 314696 (H. bogdanii Wilensky) and PI 440420 (H. brevisubulatum subsp. violaceum (Boissier & Hohenacker)), compared with densities on endophyte-free plants of both PI lines in population growth experiments. This endophyte-associated resistance was the result of antibiosis effects or starvation. In other experiments, endophyte-free plants of PI 269406 and PI 440413 (H. bogdunii) were not superior to endophyte-infected conspecifics as host plants of D. noxia. Our results demonstrate the.influence of host plant species/genotype and endophyte species/strain on expression of aphid resistance, provide an explanation of the high levels of D. noxia resistance in PI 314696 and PI 440420 previously reported in the literature, and underscore the potential importance of endophytic fungi in conferring insect resistance in wild barley.