Identification of Two Distinct Strains of Watermelon Mosaic Virus 2 Affecting Cucurbits in Texas. V. H. Chala, Director, Estación Napo, Apartado 2600, Quito, Ecuador. C. W. Harrison, and R. S. Halliwell. Henderson County Junior College, Athens, TX; and Professor, Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843. Plant Dis. 71:750-752. Accepted for publication 22 December 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0750.

Two distinct strains of watermelon mosaic virus 2 (WMV-2) were isolated in Texas. One strain, designated isolate M, was obtained from the wild cucurbit Melothria pendula, and the other, isolate S, was isolated from zucchini squash (Cucurbita pepo). Neither isolate caused symptomatic infections of the differential hosts garden pea Pisum sativum (cultivar Alaska) or Nicotiana benthamiana, thus distinguishing them both from WMV-2 and zucchini yellow mosaic virus (ZYMV). Isolate S caused a systemic infection on Phaseolus vulgaris (cultivar Black Turtle 2), whereas isolate M did not, thus distinguishing them from each other. Isolates S and M were characteristic of WMV-2 in that they both produced typical cytoplasmic inclusions, had modal lengths of 755 and 775 nm, respectively, and protein capsid subunits of 3.2 × 10⁴ daltons. Antisera produced to S and M reacted in sodium dodecyl sulfate (SDS) immunodiffusion tests with WMV-2, S, and M antigens but not with ZYMV antigens.