Fungal endophytes of the genera Neo~yphodium and Epich/oc systemicaIly infect several grasses. One of the most relevant aspects of the grass-endophyte interaction is the production of secondary compounds (alkaloids) which are toxic to both vertebrate and invertebrate herbivores. To daLe, ergovaline is the most abundant ergot alkaloid which has been found in several endophyte infected grasses. This alkaloid seems to be responsible for livestock disorders such as reduced weighL gain or reduced concepLion rates which are part of a syndrome referred to as fescue toxicosis. High rates ol' cndophyte infection have been reporLed in Fes/l/ca al"lllldinacea and Fes/uca rubra populaLions from semiarid dehesa pasLures, in Lhe province of Salamanca (Spain). These pasLure cOInmuniLies are rich in plant species and Lhe abundance of F. rubra is greaLer Lhan Lhat of F. u/"lIndinacea. [n the present work, ergovaline conLenl was deLermined in seeds produced by inl'ecLed plants of F. arundinocea and F. ruhra. The resulLs indicated the oceurrence of ergovaline in boLh infected grasses. The concenLraLion varied beLween species and ecotypes wiLh higest values in F. arundinacea.

We are grateful to J.e. Estévez and M. Hernández for technical assistance. Ergovaline standard sample was generously provided by Dr. Forrest Smith, Auburn University. This work was financed by the Spanish "Comisión Interministerial de Ciencia y Tecnología" (CICYT, project AGF96-0423) and "Junta de Castilla y León" (project CSI3/ 98). B.R.Vázquez de Aldana was supported by a Research Contract from the Spanish "Ministerio de Educación y Cultura".

Resumen del trabajo presentado en el 18th General Meeting of the European Grassland Federation, celebrado en Aalborg (Dinamarca), del 22 al 25 de mayo de 2000