Endosymbiosis and population differentiation in wild and cultivated Lolium perenne (Poaceae)

Abstract

Premise of the study: Endophytic fungi are common inhabitants of cool-season grasses that can affect host growth and reproduction. One prerequisite for the expected coevolution between symbionts is that there exist variable effects of the endosymbiont on its host in different environments. Here, the impact of endophytes (Neotyphodium lolii) on survival, growth, and reproduction of wild populations of Lolium perenne from its native range (Italy, Morocco, Turkey, Tunisia) and two United States cultivars was explored. Methods: Two unmanaged, common gardens 30 m apart in New Jersey, USA, were planted with endophyte-infected and uninfected plants of the six populations in August 2008. Plants were scored for tiller number and lengths, and survival in October and December 2008 and May and September 2009; flowering tillers (spikes) were counted in spring 2009. A greenhouse experiment was designed to assess tiller production and growth of four populations. Key results: There were significant effects of population and garden on tiller number and lengths but no detectable effects of endophytes. Populations from Italy and Morocco and the two US cultivars grew well in one garden, but Tunisian plants grew the least in either garden. Overwinter survival and postflowering survival were unaffected by endophytes. Spike production was strongly influenced by population. Although populations varied, there were no differences in growth between infected and uninfected plants in the greenhouse. Conclusions: Due to the absence of unambiguous endophyte-mediated effects on growth and reproduction of these differentiated populations, putative coevolutionary relations between the endosymbiont and its native host species remain obscure in this grass - endophyte system. © 2011 Botanical Society of America.