Transmission and survival of Acremonium and the implications for grass breeding

Abstract

The transmission and survival of species of the endophyte fungi Acremonium in Festuca arundinacea Schreb. (Fa), Lolium perenne L. (Lp) and Lolium multiflorum Lam. (Lm) as well as in festulolium (Lp/Lm × Fa) hybrids are reviewed. As little work has been specifically conducted on the mode of transfer of the endophyte from the parents to the progeny, this matter is mainly discussed on the basis of research results at Oak Park. Progenies from more than 50 reciprocal intergeneric crosses of infected and non-infected parents were studied. The results confirmed that the transmission of infection was mainly dependent on the presence of endophytic mycelium in the female parent. It was also found that the content of perloline in the host had no effect on the growth of the endophyte. Microscopic observation of leaf sheaths stained with cotton-blue lactophenol confirmed that Acremonium hyphae in Fa, Lp, Lm and hybrids were very similar. However, the presence of pyrrolizidine alkaloids in hybrid festulolium plants from crosses in which Lm or Lp were the female parent suggests the possible existence of Acremonium coenophialum biotypes that infect othern than Fa. The study of progenies from 30 reciprocal sib-crosses revealed some discrepancies among results given by endophyte detection methods (microscopic observation of stained leaf sheaths, enzyme-linked immunosorbent assay and chemical) which demonstrate the limitations of exclusive use of the ELISA test for screening breeding material. The survival of Acremonium spp. in seed and plants in vivo is reviewed with special emphasis on the effects of environmental conditions. Finally, the viability of the endophyte in seeds of ecotypes and cultivars kept in long-term storage in gene banks is discussed in relation to the effects on seeds used in grass breeding programmes.