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Identification of Leptosphaeria korrae by Cloned DNA Probes. N. A. Tisserat, Associate professor, Department of Plant Pathology, Kansas State University, Manhattan 66506-5502; S. H. Hulbert, and A. Nus. Assistant professor, and research assistant (NAT), respectively, Department of Plant Pathology, Kansas State University, Manhattan 66506-5502. Phytopathology 81:917-921. Accepted for publication 25 March 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-917.

Leptosphaeria korrae was identified by a unique banding pattern of EcoRI-digested total DNA that was fractionated by gel electrophoresis and stained with ethidium bromide. Discrete and intensely stained bands of DNA that migrated at 1.1, 1.3, and 2.4 kb were noted on 38 isolates of L. korrae, but not in 26 other fungal species. DNA fragments were isolated from the 1.1- and 1.3-kb bands of EcoRI-digested DNA and were cloned. Two clones, pLK66 and pLK88, hybridized to multiple-sized EcoRI fragments of L. korrae, and occurred at an estimated 10–100 copies per genome. The two clones did not cross-hybridize. The clone pLK88 was specific to L. korrae and hybridized to DNA of the fungus isolated from 200 mg (wet weight) of infected Kentucky bluegrass and bermudagrass roots and from 1 µg of lyophilized mycelium. DNA hybridization techniques with pLK88 as a probe provide ways of identifying L. korrae, an ectotrophic, root-infecting fungus of turfgrasses, and of detecting the pathogen in root tissue.