A la recherche de la phase aquatique de champignons endophytes foliaires de l'epinette noire (Picea mariana)

Fungal foliar endophytes were isolated on agar from black spruce needles (Picea mariana) of the boreal forest in an area delimited by 47°N and 54°N in Quebec for two successive years. While searching for reference specimens, a new species Lophodermium macci on Pinus strobus is described. It is often confused as L. pinastri in herbaria. A modified technique was used to extract DNA from minute fruitbodies on herbaria specimen and new primers were made to amplify the damaged DNA. It provided added evidence to separate L. macci from L. pini-excelsae, its closest morphological taxon.; The endophytes were named using sequences homology of ITS rDNA from GenBank. More than 240 morphotypes were classified in 44 sequence groups. The incidence of the most common foliar endophyte species were 28% for Lophodermium piceae, 17% for Darkera parca, and 9% for Dwayaangam colodena. Eighteen sequence groups were unique to P. mariana and found on one site only. Impacts of climate change and forestry practices on these potential rare endemic species are discussed.; In order to compare these endophytes and the aquatic hyphomycetes, foam from 8 streams of the same forests were sampled. Those fungi were morphologically identified by their detached conidia. A total of 58 species were identified in all streams. Twenty-eight taxa were unique to the North, and five were unique to the South.; Superficially sterilized needles of black spruce were incubated in aerated sterile water in a small glass chamber. A newly described aquatic hyphomycete was isolated and described: Dwayaangam colodena. The ITS rDNA sequence of D. colodena was compared with P. mariana fungal needle endophytes. The third most commonly encountered endophyte in all the area sampled shared an homologous ITS sequence with D. colodena. Both D. colodena and the endophyte isolates produced similar aquatic conidia after 30 days. Without the use of molecular tools, the link between the two phases would have gone unnoticed. It is the first time a conifer foliar fungal endophyte is shown to have an aquatic phase.; This thesis made possible the study and comparison of fungi present in two habitats associated with P. mariana.