Differentiation of Strains in the Aster Yellows Mycoplasmalike Organism Strain Cluster by Serological Assay with Monoclonal Antibodies. I. -M. Lee, Molecular Plant Pathology Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705. R. E. Davis, and H.-T. Hsu. Molecular Plant Pathology Laboratory; and Florist and Nursery Crops Laboratory, Plant Sciences Institute, ARS, U.S. Department of Agriculture, Beltsville, Maryland 20705. Plant Dis. 77:815-817. Accepted for publication 19 April 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0815.

Monoclonal antibodies (MAbs) raised against the tomato big bud (BB) mycoplasmalike organism (MLO), a member of the aster yellows (AY) MLO strain cluster, were employed in dot immuno-binding assays. The MAbs reacted only with strains in the AY MLO cluster, and not with any of several other MLOs not affiliated with the AY MLO strain cluster. However, reactions with MLOs in the AY cluster varied by strain. All MAbs reacted with BB and several MLO strains previously termed “aster yellows,” including NAY (eastern AY), OKAY1 (Oklahoma strain), NJAY (New Jersey strain), and AY27 (Alberta strain); but none of the MAbs reacted with certain other strains of AY MLO, including strains termed SAY3 (western AY), OKAY3 (Oklahoma strain), NYAY (New York strain), and MNAY (Minnesota strain). Thus, the BB MLO-MAbs distinguished a group of interrelated MLO strains within the AY MLO strain cluster. This serogroup corresponds to the type I subcluster in the AY MLO strain cluster, previously identified on the basis of nucleic acid dot hybridizations and restriction fragment length polymorphism analyses.