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Title: CRYPTIC SPECIATION IN GIBBERELLA SUBGLUTINANS

Author
item STEENKAMP, EMMA - U OF PRETORIA, S AFRICA
item WINGFIELD, BRENDA - U OF PRETORIA, S AFRICA
item Desjardins, Anne
item MARASAS, WALTER - PROMEC, S AFRICA
item WINGFIELD, MICHAEL - U OF PRETORIA, S AFRICA

Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2002
Publication Date: 6/1/2002
Citation: STEENKAMP, E.T., WINGFIELD, B.D., DESJARDINS, A.E., MARASAS, W.F., WINGFIELD, M.J. CRYPTIC SPECIATION IN GIBBERELLA SUBGLUTINANS. MYCOLOGIA. 2002. v. 96. pp. 1032-1043.

Interpretive Summary: Populations of the fungus Fusarium subglutinans that are associated with different host plants, such as maize, teosinte, and pine, cannot be distinguished on the basis of their morphology. The DNA sequence analysis in this paper indicates that F. subglutinans strains from teosinte, the wild relative of maize, are not related to strains from pine with pitch canker disease, but are closely related to strains from maize that do not cause pitch canker. Therefore, it is highly unlikely that the pitch canker disease of pine can be caused by strains of F. subglutinans from teosinte.

Technical Abstract: Fusarium species that form part of the Gibberella fujikuroi complex have been classified using either a biological, morphological or phylogenetic species concept. Most problems with the taxonomy of Fusarium species in this complex are experienced when the morphological species concept is applied. To solve this problem, the morphological species concept has often been applied in combination with the biological species concept. However, the most accurate identifications are obtained when the phylogenetic species concept has been used. Results from recent studies have suggested discordance between the biological and phylogenetic species concepts. A group of F. subglutinans isolates, apparently belonging to G. fujikuroi mating population E, could be sub-divided into more than one phylogenetic lineage. The aim of this study was to determine whether it represented species divergence or intraspecific diversity within mating population E. For this purpose, we included 29 F. subglutinans isolates belonging to the E-mating population that were collected from a wide geographic range. DNA sequence data for six nuclear regions in each of these isolates were obtained and used in phylogenetic concordance analyses. These analyses showed that the E-mating population of the G. fujikuroi complex is divided into two reproductively isolated groups, designated Groups 1 and 2. The lack of shared polymorphisms bewteen Groups 1 and 2 further suggested that they represent separate species. The taxonomy of all fungi previously identified as belonging to the E-mating population using the biological species concept should, therefore, be re-evaluated. We also suggest that the biological species concept should be used with caution when dealing with these and similar fungi.