Papaya plants with virus-disease-like symptoms were observed in back yards and commercial groves in Multan, Pakistan. Leaves of the diseased plants displayed downward curling and thickened, dark green veins. Leaf-like enations grew from the base of the diseased leaves. These symptoms are similar to those of cotton leaf curl disease. In addition, diseased papayas were stunted and distorted. Leaf extracts from 3 diseased and 2 healthy papayas were tested in enzyme-linked immunosorbent assay against antibodies to geminiviruses. SCRI-52 and SCRI-60, two monoclonal antibodies to Indian cassava mosaic virus (2), reacted positively (more than 7× healthy background) with the diseased samples but not with the healthy ones. Total nucleic acids from the papaya samples were used as templates in polymerase chain reaction with primers F500 and R1800 (1), which are capable of amplifying a region of DNA A component of the whitefly-transmitted geminiviruses. A DNA fragment of approximately 1.4 kb was amplified from the nucleic acids of the diseased but not the healthy papayas. Under high stringency conditions (1), cloned DNA A fragments of both cotton leaf curl virus and cotton leaf crumple virus cross-hybridized with the amplified DNA fragment, but the hybridization signals were much weaker than those of the homologous hybridization. This is the first report of the papaya leaf curl disease in Pakistan. These data demonstrated that a geminivirus may be the causative agent of this papaya disease. We are currently determining the relationship between the geminivirus infecting papaya and cotton leaf curl virus.

References: (1) A. Nadeem et al. Mol. Plant Pathol. (On-line: /1997/0612nadeem). (2) M. M. Swanson et al. Ann. Appl. Biol. 211:285, 1992.