Nucleic Acid Hybridization Based Diagnosis DNA-A components of different WTGs share high nucleotide sequence

The nomenclature of papaya viruses has been a source of confusion, primarily because symptomatology has been used extensively for describing papaya viruses. Although the literature is confusing and causal viruses for each of the diseases are not well identified, it appears that papaya viral diseases can generally be grouped as ring spot, mosaic and leaf curl, associated with poty, potex and geminivirus respectively. PAPAYA LEAF CURL DISEASE Papaya leaf curl disease was first recorded in India in 1930's and shown to be transmitted by the whitefly Bemisia tabaci. The disease was characterized by typical leaf curl symptoms produced on many crop plants, by whitefly transmitted geminiviruses (WTGs). Papaya leaf curl disease is of moderate incidence and widely distributed in India. Our observation of papaya fields indicated that there has been continuous increase in the incidence of papaya leaf curl disease resulting into severe economic losses. Since whitefly is known to transmit geminiviruses and typical leaf curl symptoms on many crops are found to be associated with geminiviruses, initially on the basis of leaf curl symptoms and whitefly transmission the possible involvement of a geminivirus in papaya leaf curl disease was suspected. Till the present work was taken up there were no reports on the detection or identification of the causal agent of papaya leaf curl disease. So, keeping in view the economic importance of the papaya leaf curl disease, an attempt was made to develop methods for the detection and identification of the causal agent. A preferred choice for the detection of the causal agent suspected to be geminivirus was nucleic acid based diagnostics primarily on account of symptoms and transmission studies. Geminiviruses are difficult to isolate and purify due to their fragile nature. Consequently generating antibodies against these viruses for immunodiagnostic purpose is not easy. Therefore, in order to detect the casual agent of papaya leaf curl disease, which was