Isolation and sequence analysis of cotton infecting begomoviruses

Abstract

Cotton is an important cash crop of Pakistan which is severely suffered from a leaf curl disease called cotton leaf curl disease. Studies had shown that a number of begomoviruses collectively called cotton leaf curl viruses (CLCVs) are responsible for leaf curl disease. Some of the important viruses in this group are Cotton leaf curl Multan virus, Cotton leaf curl Kokhran virus, Cotton leaf curl Burewala virus, Cotton leaf curl Rajasthan virus, and Cotton leaf curl Allahabad virus. In this study diseased cotton plants were screened for the presence of cotton-infecting begomoviruses. Amplified viruses were cloned and sequenced. Sequence analysis showed that Cotton leaf curl Burewala virus (CLCuBuV) is the causal organism of cotton leaf curl disease and this result is the affirmation of previous findings that, unlike first epidemic of the cotton leaf curl disease when a group of begomoviruses were affecting the cotton crop, there is a single virus CLCuBuV damaging the economically important crop of the country. Pairwise sequence comparison showed that sequences of isolates obtained in this study have maximum 98.9% to 99.55% homogeneity to published sequences of CLCuBuV. Surprisingly one of the isolates lacks an intact Rep, which is invariably present in begomoviruses.