Incidence of Fungal endophyte in the preferred grass Hordeum comosum associated to environmental stress gradients in Patagonia.

CASAS, C.; DEL TORO, C.; DELIENS, E.; CASABELLA, M.P.; GARCÍA-MARTÍNEZ, G.C.; NAGAHAMA, N.; VIGNALE, V.M.; IANNONE, L.J.; SCHNYDER, H. ; GUNDEL, P.E.

Ciudad de Buenos Aires

Simposio; 5 th International Symposium of Forage Breeding; 2015

Natural grasslands sustain animalproduction in semiarid environments. In central-west Patagonia wild grassspecies are the main forage resource for wool producing sheep. Grazing managementhas impoverished the vegetation communities reducing preferred species. Understandingthe underlying controls of species distribution and abundance is needed for communityrestoration and quality forage production. Certain grass species form symbioticassociations with fungal endophytes, related to host fitness improvements suchas herbivory resistance and drought tolerance. We studied the incidence ofEpichloë fungal endophytes in Hordeum comosum populations, a perennial grassthat is highly preferred forage to sheep. We defined 32 sites along fourwest-east transects from extreme humid to extreme arid conditions (1200 - 150mm. year-1, 5500 km²) in central Patagonia. In each site, we estimated thecover of H. comosum and we collected a total of eight plants per site todetermine the endophyte incidence. We found similar curve shapes for H. comosumcover and endophyte incidence in relation to mean annual precipitation, waterbalance (precip-evapotransp), and the Aridity Index of Martonne[(precip/(temp+10)]. Interestingly, H. comosum cover was described by aquadratic curve with a peak at around 500 mm. year-1 annual precipitation.Meanwhile, endophyte incidence was highly variable at extreme arid and, thisvariability tended to decrease when annual precipitation increased. Theendophyte incidence reached values of 100% above 600 mm.year-1 annualprecipitation. This suggests that aridity limits both, host species and endophytepersistence; while in less arid and humid conditions, the endophyte persistsbut it may not prevent the host species declining likely due to herbivorypressure or the intra-specific competition.