Momordica charantia is a Weed Host Reservoir for Papaya ringspot virus Type P in Jamaica

Papaya rinsgpot virus type P (PRSV), a member of the genus Potyvirus in the family Potyviridae, is primarily transmitted by aphids in a nonpersistent manner (2). The virus is geographically widespread but has a narrow host range within the plant families Caricaceae, Chenopodiaceae, and Cucurbitaceae (2). The first reported epidemic of PRSV in Jamaica was during the late 1980s (1). Since then, the virus has spread across the island and is recognized as a potential problem for continued production of papaya (Carica papaya L.). In the summers of 1999 and 2000, prominent vein clearing symptoms were observed on leaves of a common weed, cerasee (Momordica charantia L.), in papaya orchards of western Jamaica. This weed, a climbing annual in the Cucurbitaceae family used in a variety of local herbal preparations, was found to be growing on fences or the ground along the periphery of the orchards. Leaf samples were collected and tested for PRSV by double-antibody sandwich (DAS)-ELISA with polyclonal antibodies (Agdia Inc, Elkhart, IN). In addition, crude sap extracts from 12 cerasee leaf samples that were diluted 1:20 were mechanically inoculated onto six plants each of cerasee and papaya. Within 2 weeks, vein clearing symptoms were observed on cerasee and symptoms (vein clearing followed by mosaic development and leaf distortions) typical of PRSV infection were obtained on papaya (2). All original leaf samples and inoculated plants tested positive in DAS-ELISA. In subsequent vector transmission tests, 10 healthy cerasee or papaya seedlings were inoculated with aphids (Aphis gossypii) that were previously permitted to feed on PRSV-infected papaya or cerasee. High rates of virus transmission were achieved in three tests from cerasee to papaya (77 to 83%), papaya to cerasee (90 to 93%), and cerasee to cerasee (60 to 70%). Total RNA from papaya samples was subjected to reverse transcriptase-PCR using primers to the capsid protein gene (3). A single fragment of the expected size (approximately 996 bp) was amplified and sequenced and showed high nucleotide identity (90.3 to 91.4%) with previously reported PRSV type P from Jamaica (GenBank Accession No. DQ104823), Cuba (GenBank Accession No. DQ089482), Florida (GenBank Accession No. AF196839), Brazil (GenBank Accession No. AF344650), and Hawaii (GenBank Accession No. S46722). To our knowledge, this is the first report of the natural occurrence of PRSV on a weed host in Jamaica. Because of its widespread distribution and