Detection of Chrysanthemum Yellows Mycoplasmalike Organism by Dot Hybridization and Southern Blot Analysis. Assunta Bertaccini, Istituto di Patologia Vegetale, Universita degli Studi, Bologna, Italy 40126. Robert E. Davis, Ing-Ming Lee, Maurizio Conti, Ellen L. Dally, and Sharon M. Douglas. Microbiology and Plant Pathology Laboratory, ARS-USDA, Beltsville, MD 20705; Istituto di Fitovirologia Applicata, Consiglio Nazionale delle Ricerche, Torino, Italy 10135; Microbiology and Plant Pathology Laboratory, ARS-USDA, Beltsville, MD 20705; and Connecticut Agricultural Experiment Station, New Haven 06504. Plant Dis. 74:40-43. Accepted for publication 11 July 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/PD-74-0040.

Chrysanthemum yellows (CY) mycoplasmalike organism (MLO) was detected in plants of Catharanthus roseus (periwinkle), Chrysanthemum frutescens, and Chrysanthemum carinatum by dot hybridizations of biotinylated cloned DNA probes to nucleic acid extracts from infected plants. Probes containing DNA fragments from an eastern U.S. aster yellows (AY) MLO or from a Connecticut periwinkle little leaf (O-1) MLO hybridized with nucleic acid extracted from CY-diseased but not healthy plants. Of five probes used in Southern blot analyses, one probe containing extrachromosomal DNA from O-1 MLO hybridized with extrachromosomal but not chromosomal DNA of CY MLO. Three probes containing chromosomal DNA of AY MLO and one containing chromosomal DNA of O-1 MLO hybridized with chromosomal DNA of CY MLO. The nucleotide sequence homologies between the probes and nucleic acid of CY MLO are evidence for genetic relatedness of a European MLO and American MLOs and provide diagnostic tools for CY MLO detection.