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Nucleic Acid Probes for Detection and Strain Discrimination of Cucurbit Geminiviruses. Jane E. Polston, Department of Plant Pathology, University of California, Riverside, CA 92521, Current address: Department of Entomology, University of California, Riverside 92521; J. Allan Dodds(2), and Thomas M. Perring(3). (2)Department of Plant Pathology, University of California, Riverside, CA 92521; (3)Department of Entomology, University of California, Riverside, CA 92521. Phytopathology 79:1123-1127. Accepted for publication 14 June 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1123.

A nucleic acid spot hybridization assay was developed for detection of cucurbit geminiviruses in plant tissue extracts. With a probe composed of four unique full-length DNA geminiviral genome components cloned from squash infected with two variants of squash leaf curl virus (SLCV), viral nucleic acid could be detected in various infected hosts representing nine genera from four plant families. The least amount of virus that could be detected by the spot hybridization assay was 300400-fold less than that by enzyme-linked immunosorbent assay (ELISA). The limit of detection of purified SLCV was 3.2 pg of viral nucleic acid (17 pg of virus). A unique restriction fragment from each of the four genome components was identified (19). Two biologically different strains could be differentiated with these cloned fragment probes and mixtures of these two strains could be detected in experimentally infected plants. All four SLCV genome components were detected in field-collected squash plants. The genome components of both strains could be found in the same plant; however, in some plants the two genome components of one strain and only one of the other strains could be detected.