Cotton Leaf Curl Disease -a High Risk Exotic Viral Pathogen of Cotton

Cotton leaf curl disease (CLCuD) complex (8 or more species) is a damaging disease of cotton that causes leaf curling, leaf-like enations, stunting of the plant, and reduced yield and fiber quality. Losses during epidemic years have reached 50-80% of the crop in Pakistan. Species of the cotton leaf curl complex are endemic in Africa, Pakistan, and northwestern India. Since 1990, Pakistan and India have experienced outbreaks that have led to two major epidemics caused by Cotton leaf curl Multan virus (CLCuMV), for which disease resistant germplasm was developed, leading to disease control for approximately five years, and the emergent resistance breaking 'Burewala' virus (CLCuBV) that overcame resistance in varieties developed to combat CLCuMV. With increased international transport of leaf curl infected ornamentals and vegetable seedlings, there is great concern that leaf curl viruses will be introduced into cotton growing areas of Australia and the Americas. Already, Cotton leaf curl Gezira virus, endemic to Africa, has been introduced into Pakistan, and may have spread into the Middle East on ornamentals, while CLCuMV from Pakistan/India has established in China and the Philippines. This growing concern has led to the need for worldwide virus surveillance in cotton and internationally traded plants that serve as virus hosts, requiring the development of affordable diagnostics for laboratory and field platforms to track the virus complex and aid in early detection to support management practices.