VIEW ARTICLE

Etiology

Purification, Serology, and Vector Relationships of Squash Leaf Curl Virus, a Whitefly-Transmitted Geminivirus. S. Cohen, Visiting scientist, Volcani Institute of Agricultural Research, Bet-Dagan, Israel; J. E. Duffus(2), R. C. Larsen(3), H. Y. Liu(4), and R. A. Flock(5). (2)(3)(4)Research plant pathologist, research associate, and research associate, USDA-ARS, U.S. Agricultural Research Station, Salinas, CA 93915; (5)Entomologist, Imperial County Agriculture Department, El Centro, CA 92243. Phytopathology 73:1669-1673. Accepted for publication 13 July 1983. 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, 1983. DOI: 10.1094/Phyto-73-1669.

A complex of whitefly-borne disease agents has been isolated from field cucurbits in the southwestern desert of the USA. One component of the complex, squash leaf curl virus (SLCV) alone caused severe stunting and leaf curl symptoms on leaves of all cultivars of Cucurbita maxima, C. moschata, and C. pepo that were tested, and a green mosaic and leaf distortion of Phaseolus vulgaris. The virus was purified by differential centrifugation after clarification of leaf extracts with chloroform. Virus yields reached 130 μg per 100 g of plant material. The A_{260/280 nm} ratio was 1.5. Infectivity, assayed by Bemisia tabaci fed through membranes, was associated with the occurrence of predominantly geminate particles (22 x 38 nm), which, however, were not completely separated from monomers, trimers, and tetramers. SLCV is circulative in B. tabaci with a relatively long latent period. A high frequency of transmission following the latent period is associated with apparent harmful effects of the virus on the vector. SLCV may multiply in the whiteflies. Serological studies demonstrated that SLCV is related to cassava latent virus, but not to four other geminiviruses.