Cotton leaf crumple and cotton leaf curl are distinct geminiviruses
Two important viral diseases of cotton are caused by cotton leaf crumple and cotton leaf curl geminiviruses. Cotton leaf crumple was first reported in United States from California (1954) and then Arizona (1960). It is also present in Mexico. The disease causes floral distortion, hypertrophy of veinal tissues leading to downward curling of leaves, foliar mosaic, vein clearing, vein distortion. Cotton leaf curl was first reported in Africa (1963). It is present in several countries in Africa and also in Pakistan, India and the Philippines. The disease causes vein distortion, thickening and enations on the underside of the leaves, reduction of flower numbers. Recently, severe epidemics have occurred in Pakistan, where losses reached 100% in early infected cotton fields.
Genetic studies have shown that these two viruses belong to geminivirus subgroup III (transmitted by Bemisia tabaci), that they are distantly related and distinct geminiviruses. When compared with other geminiviruses, cotton leaf crumple appears more closely related to New World geminiviruses (such as Abutilon mosaic, sida golden mosaic, bean dwarf mosaic, tomato mottle geminiviruses), whereas cotton leaf curl is more closely related to the Old World geminiviruses (such as ageratum yellow vein, tomato leaf curl, African cassava mosaic, tomato yellow leaf curl geminiviruses).
Nadeem, A.; Weng, Z.; Nelson, M.R.; Xiong, Z. (1997) Cotton leaf crumple and cotton leaf curl virus are two distantly related geminiviruses.
Molecular Plant Pathology on-line.