Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2005
Publication Date: 9/30/2005
Citation: Rao, S., Alderman, S.C., Takeyasu, J. 2005. The botanophila-epichloë association in cultivated festuca in oregon: evidence of simple fungivory. Entomologia Experimentalis et Applicata. v. 115. p. 427-433.
Interpretive Summary: Choke, caused by the fungus Epichloë, is a disease of grasses which results in lower seed yields. Fungal growth on the surface of grass stems relies on a specific fly (Botanophila sp.) for fertilization. This study indicates that in cultivated fine fescue seed production fields in Oregon, the fly forages on the fungus, but that rates of fungal fertilization are low. This is the first report of B. lobata on E. fesctucae in Oregon.
Technical Abstract: The Botanophila (Diptera: Anthomyiidae)-Epichloë (Ascomycetes: Clavicipitaceae) interaction in cultivated Festuca spp. (fine fescue) in Oregon in western USA was investigated. Epichloë spp. are endophytic fungi of grasses in the subfamily Pooideae that develop a felt-like stroma on the surface of grass culms and a dense mycelium within the culms that typically prevents seed head emergence, resulting in suppression of seed yields. The disease is referred to as choke. Studies on Epichloë spp. on wild grasses indicate that the fly-fungus interaction reflects obligatory mutualism. Female flies benefit Epichloë by transferring spermatia between stromata of opposite mating types during oviposition, resulting in fungal fertilization and development of perithecia which serve as food for Botanophila larvae. We surveyed 19 cultivated fields of Festuca spp., and observed choke caused by the exotic E. festucae in ten. Perithecia were observed in only four fields, and on only 1.0 to 2.6% of stromata. Perithecial development was also low, and rarely covered 50% of the stromal surface. Despite the absence or the low numbers of fertilized stromata, Botanophila was present in all choke-infested fields. Infestation levels ranged from 2.5 to 70.7% based on examination of 175-200 stromata from each field. Botanophila larvae completed development and exited from unfertilized stroma. The average puparium weight (0.0037g) indicated that fly fitness was not affected by development on unfertilized stroma. Only 8 (=2%) of the 450 stromata with Botanophila had perithecia. This is the first report of the Botanophila-E. festucae association in Oregon, and of Botanophila larvae developing successfully on unfertilized Epichloë stroma. The study indicates that in cultivated fine fescue fields in Oregon, Botanophila forages on E. festucae, but fly development is not dependent on fertilized stroma of Epichloë.