|Van Berkum, Peter|
Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2002
Publication Date: N/A
Interpretive Summary: Species in the Leptosphaeria complex of microscopic fungi cause many of the most destructive diseases in agricultural crops. The fungi are traditionally characterized by morphological features that are sometimes obscure, making classification of these organisms difficult. In addition, there has been no consensus using morphological, ecological, or molecular apporaches as to the phylogenetic significance of these traits. The identification of a pathogen is important in order to be able to develop appropriate disease control strategies, to make predictions about the potential destructiveness and the disease-causing capacity of the fungus, and to determine it's relatedness to other pathogens. In this study, we clarified the phylogenetic relatedness of members of the Leptosphaeria complex and determine the taxonomic significance of host, geographic origin, and asexual stages. Through new molecular technologies and DNA sequencing of specific rDNA regions, the phylogeny of sixty-two isolates was inferred, using two methods of analysis. The fungi clustered into three well-supported groups, and we concluded that asexual stage, host, and select ecological traits are phylogenetically significant.
Technical Abstract: The objectives of this study were to determine the phylogenetic relationships of taxa in Leptosphaeria and Phaeosphaeria and to evaluate the phylogenetic significance of morphological characters of the teleomorph and anamorph, host, and ecology. The sequences of the entire ITS region including the 5.8s rDNA, of 62 isolates representing 57 species were analyzed and the estimated phylogeny inferred using parsimony analysis. Isolates clustered into three well-supported groups. Based on the results of this study, we consider Phaeosphaeria to be a genus distinct from Leptosphaeria sensu stricto, however the relationships between the species in the Phaeosphaeria clade are not well-resolved. We conclude that peridial wall morphology and anamorph characteristics are phylogenetically significant as are the host and some ecological traits.