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Molecular Plant Pathology

A Genotype-Based System for Identification and Classification of Mycoplasmalike Organisms (MLOs) in the Aster Yellows MLO Strain Cluster. I.- M. Lee, USDA-ARS, MPPL, Beltsville, MD 20705; R. E. Davis(2), T.-A. Chen(3), L. N. Chiykowski(4), J. Fletcher(5), C. Hiruki(6), and D. A. Schaff(7). (2)(7) USDA-ARS, MPPL, Beltsville, MD 20705; (3)Department of Plant Pathology, Cook College, Rutgers University, New Brunswick, NJ 08903; (4)Plant Research Center, Agriculture Canada, Ottawa Ontario, Canada K1A 0C6; (5)Department of Plant Pathology, Oklahoma State University, Stillwater, OK 74078; (6)Department of Plant Science, University of Alberta, Edmonton Alberta, Canada T6G 2P5, Present address: Department of Plant and Soil Science, University of Delaware, Newark 19717. Phytopathology 82:977-986. Accepted for publication 23 May 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-977.

Fifteen mycoplasmalike organism (MLO) strains from North America and Europe, including aster yellows (AY), tomato big bud (BB), clover phyllody (CPh), chrysanthemum yellows (CY), and unknown MLOs, were studied. These MLOs are among those previously identified, on the basis of dot hybridizations, as members of the AY MLO strain cluster. Restriction fragment length polymorphism (RFLP) analyses revealed that all 15 strains can be classified into three genomic types: type 1 (typified by eastern AY MLOs), type II (e.g., western AY and CY MLOs), and type III (e.g., CPh MLO). Four key DNA probes (pAY9N, pBB88, pBB101, and pCN1-25) were designated for use in RFLP analyses for the identification of strains in the AY MLO strain cluster and the differentiation of the types within this cluster. This classification is consistent with results from monoclonal antibody typing and polymerase chain reaction analysis, but not with classifications based solely on biological properties.