Clones of cotton leaf curl geminivirus induce symptoms atypical of cotton leaf curl disease

The causative agent of cotton leaf curl disease has previously been shown t o be transmissible by the whitefly Bemisia tabaci (Gennadius) and a begomov irus (Geminiviridae) was shown to be associated with the disease. This viru s was provisionally called cotton leaf curl virus (CLCuV) although no causa l relationship between virus and disease was shown. In the present study fu ll-length clones of CLCuV, equivalent to the DNA A component of bipartite b egomoviruses, were obtained. The clones of CLCuV were systemically infectio us to both Nicotiana benthamiana and cotton. Infected plants did not exhibi t symptoms characteristic of cotton leaf curl disease, producing mild leaf curling, yellowing and some stunting. Efforts to identify a second genomic component were not successful. These findings suggest that the begomovirus, CLCuV, is not or not the sole cause of cotton leaf curl disease. The trans mission of cotton leaf curl disease by B. tabaci, however, may indicate tha t the begomovirus plays a part in the transmission of the disease. The impl ications of these findings are discussed.