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Bromus auleticus is a winter wild species with promissory characteristics for domestication as forage that inhabits temperate‐warm grasslands from a wide region from South America. Populations from regions with different environmental conditions are considered as ecotypes and are associated with different seedborne Epichloë fungal endophytes. Association with Epichloë provides B. auleticus with increased growth capacity and resistance against pathogens. The seeds mature at the end of spring and germinate in autumn, remaining dormant during wet and warm summer. As the persistence of Epichloë endophytes in the seed is highly sensitive to temperature and humidity, we studied how the endophytes modulate seed germination in response to these factors in two B. auleticus ecotypes named La Pampa (LP) and El Palmar (EP). We also studied how environmental factors during germination affect endophyte survival. In the LP ecotype, adapted to coldest temperatures in autumn, Epichloë improved final germination under alternating temperatures, but had no effects on germination inhibition imposed by low water availability. In the EP ecotype, adapted to warm humid summer and autumn, the endophyte promoted germination at constant 25°C and alternating 15/25°C temperatures, and prevented germination at low water potentials. At 30°C, seed germination was inhibited and whereas seeds remained viable, endophyte survival was significantly lowered. The effect of Epichloë on B. auleticus seed germination was ecotype‐specific: promoting germination at alternating temperatures in La Pampa ecotype or at high temperatures in El Palmar ecotype, while inhibiting it at low water availabilities, could be an endophyte‐mediated ecotypic strategy minimising endophyte mortality and increasing seedling establishment. [ABSTRACT FROM AUTHOR]

Context. Tall fescue (Schedonorus arundinaceus) is one of the most important cultivated forage grasses in temperate regions but its association with some Epichloë fungal endophytes usually makes it unsuitable for livestock feeding due to toxic alkaloids. However, re-inoculation of plants with non-toxic endophytes can result in positive effects for livestock feeding. Aims. Assess the effects of the non-toxic AR584 endophyte on seed viability and germination in two tall fescue cultivars. Methods. The effects of AR584 endophyte (presence/absence) and tall fescue cultivar (INIA Aurora/Taita) were evaluated on seed viability and germination responses across a range of temperature and water availability regimes. Response to constant temperature and water availability was characterised by the thermal-time and hydro-time models, respectively. Key results. Under accelerated aging conditions, endophyte presence reduced seed viability in cultivar Taita. For both cultivars, endophyte-infected seeds showed a lower germination rate than endophyte-free seeds, except for INIA Aurora under low incubation temperatures. Also, endophyte-infected seeds in both cultivars displayed lower germination rates and final germination as the water potential was lowered. Conclusions. A strong cultivar-by-endophyte interaction for seed germination indicates the need to understand how specific cultivarendophyte combinations best fit a given environmental condition, as defined by temperature and water availability. Implications. The information we present can be valuable not only for farmers who have to decide what to cultivate but also for seed companies that have to preserve seed quality. [ABSTRACT FROM AUTHOR]