Molecular evidence for the anamorph—teleomorph connection in Cordyceps sinensis

Abstract

Cordyceps sinensis, the caterpillar fungus in traditional Chinese medicine, has been intensively collected from nature in recent years. As a result, the establishment of the anamorph of this species has become important for large-scale culture to meet increasing demand for medicinal use and to ease exploitation of natural populations. To establish a reliable connection between the teleomorph and anamorph stages, the ITS nrDNA sequences were sequenced from both the stroma of the telemorph and cultures of the anamorph. Observations of microcyclic conidiation were also made on germinated ascospores and compared with the anamorph in culture. Hirsutella sinensis was confirmed as the anamorph of C. sinensis by both DNA sequences and microcyclic conidiation. Two recently described species, C. multiaxialis and C. nepalensis, were shown to share identical or almost identical ITS sequences with C. sinensis. These minor variations were considered to be within the range of variation exhibited within a species, but representing different populations. Sequences from other Cordyceps species included in this study exhibited considerable differences from each other. Therefore, these three entities are probably conspecific, and the names should be regarded as synonymous. The morphological characters used in the description of the two new species are discussed. It is suggested that ITS sequences provided useful information on establishing the anamorph—telemorph connection and assisting in the delimitation of species within Cordyceps.