Interactive effects of fungal endophyte infection and host genotype on growth and storage in Lolium perenne

Summary • The effect of infection by the fungal endophyte Neotyphodium lolii, host genotype and their interaction on growth and storage traits, and regrowth following defoliation, were investigated in the forage grass Lolium perenne. • Ramets of infected (+E) and noninfected (–E) genotypes of Lolium perenne cv. Yorktown III were glasshouse grown for 12 wk after which all plants were defoliated. Half the plants were harvested for total nonstructural carbohydrate (TNC) analysis, the remainder grew for an additional 4 wk before harvesting. • Effects of endophyte infection on tiller numbers, leaf area and TNC were highly dependent on host genotype at the time of defoliation. Leaf mass, tiller base mass, and specific leaf area after regrowth were highly dependent on genotype by endophyte interactions. Regrowth rates were influenced by host genotype, but not by endophytes. Leaf area regrowth rate was negatively correlated with TNC across genotypes, but only in –E plants. • The marked host genotype–endophyte infection interactions detected in this L. perenne population indicates that, for many growth and storage traits, endophyte infection can impact microevolutionary change. However, there is no overriding consistently positive effect of the endophyte on growth or storage in L. perenne before or after defoliation. If there is a metabolic cost to harboring endophytes, it was not detected here.