First report of the identification of Moroccan watermelon mosaic virus in papaya in Democratic Republic of Congo

摘要

Pawpaw is the major cash crop in North Kivu, Democratic Republic of Congo, where it is grown for latex and exported to Europe for papaverine production. Since 1997, a disease has gradually spread throughout North Kivu, seriously affecting latex yields. As field production declined, this has been offset by expansion into new areas of forest; in turn this has a serious environmental impact on the fragile ecosystems of the equatorial highlands. Plants are affected at all ages and all local pawpaw cultivars are susceptible to the disease. Leaf symptoms ranged from yellow mosaic patterns to deformation and shoestrings as the disease progressed. Oily streaks in petioles and variations in shape and size of the ring spots on the fruits were also seen. Within the trunk, pink discolouration and tumour-like growth appeared, which eventually became brown and necrotic. In the final disease stage, plants resembled a pole with a tuft of small leaves at the apex and the internal trunk became fibrous. The isolated pathogen was identified as Moroccan watermelon mosaic virus (MWMV). This is thought to be the first record of MWMV both in pawpaw and in the DRC.