Species of the fungus genus Alternaria are economically important in plant disease, food toxicology, medical mycology, and ecology, yet this large genus has not been comprehensively studied using modern tools of DNA analysis. A workable taxonomic system is critically needed that will ensure consistent and reliable identification of species and promote advanced studies in comparative biology. Toward this end, the principal objectives of collaborative work by Barry Pryor at University of Arizona and Tobin Peever at Washington State University are to: 1) establish evolutionary relationships among Alternaria species based upon comparison of DNA sequences from several genes, 2) re-examine and establish new criteria for delimiting Alternaria species based upon comparison of DNA among populations within species, and 3) evaluate morphological characters that critically define species validated by DNA analysis. Embedded within these objectives are additional goals of creating taxonomic identification keys based upon morphological characters that can be used by research, industry, and regulatory professionals, and developing an on-line database for the dissemination of data generated from these and other related studies. This database will serve as a world-wide resource for the advancement of contemporary research on Alternaria and related fungi. The scope of the proposed research is both timely and comprehensive in regard to the evolution of asexually-reproducing fungi, of which Alternaria is a key representative. In general, taxonomy for most organisms is based primarily on the development and characteristics of sexual structures, which normally have proven to be consistent with evolutionary relationships based upon DNA analyses. Thus, one of the primary limitations in the study of asexual fungi is the lack of sexual structures; only recently have studies begun to examine and contrast the characteristics of asexual fungi with data derived from DNA analysis. However, these studies seldom address intra-specific variation among populations, which is critical for delimiting the boundaries between species. Within Alternaria, a considerable range of inter- and intra specific diversity exists in asexual characters. Moreover, the occurrence of many Alternaria species over large geographic areas provides an ideal opportunity for comprehensive studies on intra-specific variation. Thus, the diversity in morphological traits encompassed within Alternaria provides a fertile ground for testing hypotheses relating to the evolutionary significance of asexual characters, and for comparing morphology-based taxonomy with DNA-based taxonomy of asexual fungi. The effective integration of the asexual fungi into a common evolutionary framework with the sexual fungi is a widely recognized goal of mycological research worldwide. A comprehensive study of Alternaria will contribute significantly to this objective. More importantly, the diversity and evolution of species within the asexual lineage of Alternaria positions this study as a foundation for future research into evolutionary processes that shape asexual fungal lineages and asexual organisms in general.
