Taxonomic placement for mycelia sterilia in endophytic fungal research: a molecular approach

摘要

Traditionally a culture-dependent process has been employed in most of the endophyte studies so far1,2. Mycelia sterilia have been isolated as endophytes mainly from a vast range of host plants despite modifications in artificial media and different incubation conditions to sporulate3– 5. The importance of these sterile mycelia may be answers to the famous question of ‘where are the missing fungi’6. Mycelia sterilia cannot be given taxonomic status and are not comparable among hosts or sites. In order to appreciate the considerable diversity, mycelia sterilia have been generally categorized as sterile fungi7, or morphotypes based on similar cultural characteristics8,9. Grouping this way is a useful but limited tool, as comparisons cannot be made with other studies and a few studies have used molecular techniques to identify these morphospecies further10. However, morphotypes do not reflect species phylogeny and isolates included in a morphotype could comprise distantly related taxa or different morphotypes belonging to the same species11, and may disregard diversity when compared with taxonomic groups based on molecular data and will split and lump taxonomic groups with nearly equal frequency12. Therefore molecular techniques are considered promising methods to find new endophytic fungi. Fungal ITS sequences are now routinely used in phylogenetic studies as well as in the detection and identification of fungi13. Potentially successful methods include extracting entire host DNA with various methods to sequence individual taxa such as DNA cloning14, DGGE15 and T-RLFP