Submitted to: Entomologica Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1996
Publication Date: N/A
Interpretive Summary: Over the last 20 years increased global concern about the use of conventional chemical insecticides on food crops has broadened the research agenda in the USDA-Agricultural Research Service and other organizations to find new control methods that are specific, effective and environmentally safe. Plant and microbial germplasm stored in the seed repositories of the USDA-ARS National Plant Germplasm System may be a valuable source of new and more environmentally safe chemicals for insect management applications. Indeed, research has shown that increased insect resistance in forage and turf grasses from USDA-ARS seed repositories is associated with the presence of microbes (called endophytic fungi) in these grasses. The basis of this insect resistance is the production of specific chemicals by the endophyte-infected grasses. Today, seed companies worldwide market turf grasses infected with endophytes for biological control of insect pests. This manuscript describes the discovery of endophytic fungi in a food crop relative (wild barley) and summarizes their role in protecting wild barley from aphid attack. This research is important because it 1) underscores the importance of plant and microbial genetic resources in USDA-ARS seed repositories and 2) offers the scientific community a new source of endophytic fungi to strengthen the defensive capabilities of economically important grass species.
Technical Abstract: Laboratory experiments were conducted to compare the expression of Diuraphis noxia (Homoptera: Aphididae) resistance in four plant introduction (PI) lines of wild barley (Hordeum) infected with different species of strains of endophytic fungi (tribe Balansieae, family Clavicipitaceae, Neotyphodium formerly Acremonium ). Aphid densities were significantly lower on endophyte-infected plants of P1314696 (H. bogdanii) and PI440420 (H. brevisubulatum subsp. violaceum), 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 PI269406 and PI4404413 (H. bogdanii) 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 PI314696 and PI440420 previously reported in the literature, and underscore the potential importance of endophytic fungi in conferring insect resistance in wild barley.