Interactive effects of Epichloë fungal and host origins on the seed germination of Achnatherum inebrians

Cool-season grasses have developed a symbiotic relationship with Epichloë endophytes. In many environments, Epichloë endophytes have been shown to be mutualistic symbionts of plants by increasing the fitness of their host against abiotic or biotic stresses. The effects of Epichloë endophytes on other fitness-correlated plant characteristics are less intensively studied, and the results are usually variable and contradictory. In this study, we evaluated the effects of endophyte infection on seed germination in Achnatherum inebrians from four origins. Our results indicate that the germination rate of the seeds collected from alpine regions was higher at low temperatures than that of seeds with desert and arid grassland origins. By contrast, a higher germination percentage was detected in seeds with desert and arid grassland origins than in those with alpine origins in higher temperatures. Epichloë endophyte infection affects the cardinal temperatures of seeds from different origins. Endophyte-infected seeds have a lower base temperature and a higher ceiling temperature than their endophyte-free counterparts. The value of the base temperature was higher in seeds with alpine grassland origins than in those with desert and arid grassland origins. However, the ceiling temperature was higher in seeds with desert and arid grassland origins than in those with alpine grassland origins. Consequently, future experiments should consider the effects of endophytes on seed germination and seedling recruitment in suboptimal climatic conditions.