Description
All begomovirus species causing cotton leaf curl disease have geminate particles, approximately 18-20 nm in diameter and 30 nm long and a circular, single-stranded DNA genome. All except Cotton leaf crumple virus have a monopartite genome, with all viral products required for replication, systemic movement and whitefly transmission encoded on a single DNA component of c. 2.75 kB (DNA A). The genome of CLCrV is bipartite. Two smaller, circular, single-stranded DNA molecules, named DNA 1 and DNA β, are associated with a range of monopartite begomoviruses from the Old World including the cotton leaf curl viruses. These molecules are regarded as satellite molecules as they depend on the helper begomovirus to support one or more stages of their infection cycle (movement and insect transmission for both molecules and, additionally, replication in the case of DNA β). DNA β is symptom-modulating and typical cotton leaf curl disease symptoms only develop when this molecule is present: in the absence of DNA β, the concentration of viral DNA (DNA A) is low and the symptoms of infection very mild. DNA β has a single open reading frame (βC1 ORF), which encodes a suppressor of RNA silencing. DNA 1 is homologous to the DNA-R component of the nanoviruses and encodes a master replication initiator (M-Rep) protein but its presence does not alter symptom expression. (Corresponding author: Dr Andrew Geering 2007) The plant resistance to against CLCuV was descriped by Ali(1997, 1999) that the CLCuV resistanve was controlled by single dominate gene, and could be transferred to any cultivar by using back cross technique.
Read more about this topic: Cotton Leaf Curl Virus
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