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Cotton Leaf Curl Disease in Pakistan Caused by a Whitefly-Transmitted Geminivirus. S. Hameed, Plant Virology Laboratory; National Agricultural Research Centre, Islamabad-15500, Pakistan. Plant Dis. S. Khalid, Plant Virology Laboratory, and Ehsan-ul-Haq and A. A. Hashrni, Entomological arch Laboratory, National Agricultural Research Centre, Islamabad-15500, Pakistan. Plant Dis. 78:529. Accepted for publication 30 June 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0529C.

In Pakistan, cotton leaf curl disease of cotton (Gossypium hirsutum L.) was first observed in 1967 in Multan, Pakistan. In 1987, the disease reached epidemic proportions in most cotton-growing areas. Symptoms resembling those caused by cotton leaf curl virus (CLCuV) (I), which is transmitted by the whitefly Bemisia tabaci (Gennadius) included upward or downward cupping and shortening of leaves, distortion and thickening of veins, and development of enations on the underside. In a 1992 survey of key districts, the disease was well established in Vehari, Multan, Khanewal, Bahawalpur, and Sahiwal. Incidence of symptomatic plants ranged from 30 to 80% among districts, and B. tabaci occurred in abundance. An infectious agent was isolated by whitefly transmission from field-infected cotton and was subsequently transmitted by grafting and whileflies to cotton, cowpea, okra, and soybean. Symptoms characteristic of CLCuV developed in these experimental hosts. Electron microscopic examination confirmed the presence of geminivirus-like particles (monomers, dimers, and paired dimers) in extracts from symptomatic experimental hosts. Dimers were 15-18 nm in diameter. Triple antibody sandwich (TAS) ELISA was conducted with antibodies specific lo whitefly-transmitted geminiviruses (2). Polyclonal antibodies to African cassava mosaic virus (ex SCRI) and monoclonal antibodies lo Indian cassava mosaic virus (2-HI 2 SCR60) were used to lest inoculated experimental hosts and naturally infected cotton (antibodies provided by B. D. Harrison, Dundee, Scotland). Extracts of these infected plants reacted positively with these antibodies in TAS-ELISA. We conclude that cotton leaf curl disease in Pakistan is caused by a whitefly-transmitted geminivirus with the properties of CLCuV.

References: (1) A. M. Idris. Meded. Fac. Landbouwwet. Rijksuniv. Gent. 55(2a):263, 1990. (2) M. M. Swanson et al. Ann. Appl. Biol. 121:285, 1992.