First and third authors: School of Biological Sciences, The Flinders University of South Australia, Sturt Road, Bedford Park 5042, Australia; and second author: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany
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Accepted for publication 22 November 2006.
The causal agent of barley scald, Rhynchosporium secalis, is a haploid anamorphic ascomycete with no known sexual stage. Nevertheless, a high degree of genetic variation has been observed in fungal populations on commercial barley cultivars and parasexuality has been suggested to contribute to this variation. In order to test whether asexual genetic exchange can occur, isolates of R. secalis were transformed to hygromycin B resistance or phleomycin resistance. Mixtures of transformants were co-inoculated either on agar or in planta and screened for the occurrence of dual-antibiotic-resistant colonies. No dual-antibiotic-resistant colonies resulted from mixing transformants of different fungal isolates. In contrast, with transformants originating from the same fungal isolate, asexual exchange of markers was demonstrated on agar plates and in planta. This is the first definitive evidence of asexual genetic exchange in R. secalis.
© 2007 The American Phytopathological Society