Ergopeptine Alkaloid Production by Endophytes in a Common Tall Fescue Genotype
The fungal endophyte, Acremonium coenophialum Morgan-Jones & Gams, is present in many tall fescue (Festuca arundinacea Shreb.) pastures. It imparts fitness-related traits to the tall fescue plant but produces ergopeptine alkaloids, which may be the cause of fescue toxicosis in grazing livestock. Inasmuch as the endophyte provides the plant with added vigor, development of endophyte-infected tall fescue populations that are incapable of producing ergopeptine alkaloids may be a solution to providing a sustainable nontoxic grass base for livestock producers. Our objective was to study changes in ergopeptide alkaloid production in a common tall fescue genotype that was infected by two different endophyte isolates that express different levels of alkaloids when in their host plants. Endophytefree tall fescue Genotype PDN2 explants were cultured in vitro to obtain 28-d-old calli. Endophytes EDN2 and EDNll isolated from infected PDN2 and another plant genotype PDN11 were cultured and inserted into germinating somatic embryos by placing pieces of mycelium into slits at the base of the noninfected embryonic PDN2 explant. Both endophyte-infected and -free plants were regenerated from callus culture. Regenerated plants with each reinfected endophyte were grown with their endophyte-infected naturally occurring forms to compare endophyte behavior within a common plant genotype under greenhouse conditions. The PDNll plant with its naturally occurring endophyte was a high alkaloid producer while PDN2 was a low alkaloid producer. When the endophytes EDNll and EDN2 were reinfected into noninfected individuals of PDN2, the resulting plants were low alkaloid producers. These data suggest that the plant plays a major role in controlling the expression of the genetic potential of endophytes for ergopeptine alkaloid production.
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