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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #42404


item Szabo, Les

Submitted to: Canadian Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Rust fungi cause some of the most destructive diseases of small grain crops. Rust fungi are notorious for their ability to overcome resistant cereal varieties by evolving new pathogenic races. Understanding their genetics is one of the keys to learning how to better combat these important pathogens. Unfortunately, the unique biology of rust fungi makes them much more difficult than most fungi to study genetically. Knowledge gained from research on other fungi can accelerate progress in genetic studies of rust fungi if those fungi are closely related through common ancestry. We analyzed these evolutionary relationships among a diverse group of fungi including rust and smut fungi by comparing both molecular and morphological data. Our results show that the rusts are only distantly related to smut fungi. The use of molecular and morphological data complement each other and can be used in concert to identify characters that bias the results, such as characters that have evolved more than once.

Technical Abstract: To obtain an understanding of the relationship of the basidiomycetes, especially those with horizontally partitioned metabasidis, and of the evolution of structural characters, members of nine orders and an additional four genera of simple septate fungi (Auriculariales sensu lato) were studied using cladistic analysis of light microscopic and ultrastructural characters. Comparisons were made with the nucleotide sequence from the 5' end of the nuclear large subunit ribosomal RNA gene analyzed with several algorithms, including parsimony and maximum likelihood. Morphological and molecular analyses support similar phylogenetic conclusions, but polarization of some morphological characters was difficult without guidance from molecular data. The Uredinales are shown to be an advanced taxon arising from the simple septate Auriculariales sensu lato, and some characters that they share with the ascomycetes result from convergent evolution. The simple septate Auriculariales consist of more than one clade, and the related gasteroid Pachnocybe ferruginea possesses numerous derived light microscopic characters, including holobasidia.