Molecular taxonomy and population genetics of Lophodermium on Pinus sylvestris in Scotland

Abstract

Endophytes are organism s w hich infect plants asym ptom atically for at least part of their life cycle. The vast m ajority of endophytes are ascom ycete fungi. They show high species diversity and are often closely related to econom ically im portant pathogens. There is some evidence that endophytes protect their host from pathogen and herbivores. Little is know n about the evolutionary relationship betw een potentially m utualistic endophytes and related pathogens and how these tw o groups differ in population biology and genetics. The Lophoderm ium /Pinus sylvestris endophyte/host system is ideal for investigating these questions since native pine forests harbour closely related Lophoderm ium species w hich range from endophytic (L. pinastri, L. conigenum) to parasitic (L. seditiosum). C urrent taxonom y recognises only one species, L. pinastri, fruiting on senescent needles. H ow ever there are recent indications that this taxon includes cryptic species. In this thesis m olecular approaches w ere used to clarify the taxonom y of Lophodermium on Scots pine. Genealogical Concordance Phylogenetic Species Recognition based on ACTIN and ITS sequences revealed three cryptic species w ithin L. pinastri two of w hich w ere w idely distributed. The existence of these taxa w as supported by AFLP genetic m arker analysis and differences in culture grow th rate. A nalysis of Inter-SSR m arkers revealed that L. seditiosum and L. conigenum are both out-crossing species and that unlike one of the cryptic L. pinastri species, their populations are genetically differentiated. Im plication of the discovery of cryptic L. pinastri species and opportunities offered by the clarification of the taxonom y of Lophodermiumon Scots pine are discussed.