CONICET | Buscador de Institutos y Recursos Humanos

Tall fescue is probably the most important forage grass in temperate regions worldwide. Its natural association with fungal endophytes (Epichloë) usually makes it unsuitable for livestock feeding due to toxic alkaloids. Since the symbiosis increases stand persistence and productivity, current breeding strategies involve re-inoculation with non-toxic or novel endophytes. As a vertically transmitted microorganism, the endophyte presence in the seed potentially affects aspects of seed behavior relevant for farmers and seed companies. We conducted a set of experiments aimed at understanding the effects of the fungal endophyte AR584 on several aspects of seed functioning of two tall fescue cultivars [INIA Aurora (LE14-84)§ and Taita£]. Specifically, we studied seed ageing, and germination responses to alternating and constant temperatures and water availability. Germination was evaluated under two alternating temperatures (10º-20º; 15º-25º; 12/12h), four constant temperatures (5º, 15º, 20º and 25º), and four water potentials (0, -0.5, -1.0 and -1.5MPa; PEG6000). Response to constant temperature and water availability was characterized by the thermal-time and hydro-time models, respectively. Endophyte presence only reduced seed longevity in Taita cultivar. In both cultivars, rate of seed germination was lower in endophyte-infected seeds than in endophyte-free seeds, except for Aurora at 5ºC which showed an opposite response. Base water potentials was less negative in endophyte-infected seeds of both cultivars, resulting in lower rate and total germination as water limitation was higher. Our results show that the differential response of cultivar seeds to the inoculated endophyte must be considered to predict seed and endophyte viability decay under storage and also to select for the best ?cultivar by endophyte? combination for a given ecological condition.