Evaluation of infection with endophytes in seeds of forage species with different levels of ploidy

Many C3 grasses establish mutualistic associations with endophytic fungi Neotyphodium spp. Lolium multiflorum Lam. natural diploid populations of the Pampa region present high levels of infection whereas commercial cultivars, mainly tetraploid, exhibit low or no infection. In the genus Bromus , no information is available about this association in polyploid populations. The incidence of Neotyphodium spp. endophytes in diploid and tetraploid commercial cultivars of L. multiflorum , as well as in natural hexaploid populations of genus Bromus , was analysed. Observed infection was higher in diploid populations of L. multiflorum than in tetraploid populations. No infection was detected in Bromus spp. Various factors such as the production and handling of commercial seeds, the interaction of endophytes with ploidy level, and the genetic manipulation of seeds are discussed as the possible causes for the differences observed between natural and improved annual ryegrass and brome populations, and between diploid and tetraploid annual ryegrass.