Nutritional requirements for growth of fungal endophytes of grasses

Abstract

Fifteen isolates of fungal endophytes of grasses were studied for their ability to metabolize different sources of carbon and nitrogen. These endophytes had been isolated from 12 different species of Poaceae and included Clavicipitaceae with or without a teleomorph (genera Epichloë and Neotyphodium, respectively) and species belonging to the genus Acremonium sensu stricto (Acremonium chilense-like). Pectin and cellulose as carbon sources and tryptophan and methionine as nitrogen sources appeared to support poorly the growth of most isolates. Hexoses, disaccharides, complex nitrogen sources, asparagine, and glutamine supported growth of all isolates. The isolates of genus Neotyphodium were characterized by limited growth whatever the substrate, the inhibition of their growth by high concentrations of glucose and fructose, and their inability to assimilate pentoses (xylose, arabinose) and nitrates. The isolates of genus Epichloë showed better growth than those of the previous group and their growth was not inhibited by high concentrations of glucose, but they were also unable to use pentoses. The Acremonium chilense-like isolates showed rapid growth and were distinguished by their ability to use the pentoses and nitrates. In contrast, they showed relatively poor growth on methionine and alanine as nitrogen sources. They showed the most rapid growth on high concentrations of glucose or fructose.Key words: carbon sources, nitrogen sources, Neotyphodium, Epichloë, Acremonium, grass endophytes.