MATING COMPATIBILITY AND PHYLOGENETIC-RELATIONSHIPS AMONG 2 NEW SPECIES OF EPICHLOE AND OTHER CONGENERIC EUROPEAN SPECIES

Epichloe species are endophytic symbionts of grasses which may differ in the relative importance of their sexual or asexual life cycles. Sex ual reproduction of the fungus by stroma-formation prevents host flowe ring (choke) and thus is highly antagonistic, whereas asexual reproduc tion through clonal propagation in host seeds does not affect host fit ness. Stroma-forming Epichloe endophytes from Bromus erectus and non-s tromal strains from B. benekenii and B. ramosus were recognized as a d istinct mating population (MP) based on complete sexual compatibility among strains and intersterility between other MPs established by mati ng tests. This biological species represents the only documented case of highly antagonistic strains interfertile with highly mutualistic st rains. A second distinct MP of Epichloe was evident on Brachypodium sy lvaticum including both stroma-forming and non-stromal isolates. These two MPs were further characterized by distinct morphologies of fruiti ng structures, allozyme divergence, beta-tubulin gene phylogeny, and h ost preferences, and were described as new species: E. bromicola assoc iated with Bromus spp. and E. sylvatica with Bp. sylvaticum. Additiona l mating tests among Epichloe from several, previously unexamined, hos ts including Brachypodium pinnatum, Calamagrostis villosa, Festuca spp ., Phleum pratense, and Paa spp., expanded the known host ranges of th ree other European species, E. typhina, E. festucae and E. baconii. Ge netic variability of all five European species and gene diversity of h ost subpopulations were analysed based on allozyme data from a total o f 497 Epichloe isolates. Average gene diversity (H-s) within MPs range d from 0.09 to 0.36 with E. typhina being the most diverse, and G(ST) values, a measure for between subpopulation differentiation, ranged fr om 0.73 to 0.90 indicating that genetic isolation of endophytes on man y host grasses is likely.