Department of Plant Pathology, University of Agricultural Sciences, GKVK, Bangalore-560065, India

Background and objectives
Pumpkin (Cucurbita moschata) is a common vegetable grown in South India. During the years 1994-96 our surveys in Karnataka and Tamil Nadu States have revealed the presence of yellow vein mosaic disease in pumpkin. Symptoms consist of yellow vein mosaic on leaves, reduction in leaf size and stunting. In the past decade both the prevalence and distribution of whitefly-transmitted viruses have increased and the impact has been devastating [1]. We report evidence that the yellow vein mosaic disease of pumpkin is due to a whitefly-transmitted geminivirus. We describe its host range, vector and serological relationships, and show that its epitope profile differs from the profiles of geminiviruses from cassava, okra and tomato.

Results and conclusions
A culture of pumpkin yellow vein mosaic virus (PYVMV) was transmitted by whiteflies (Bemisia tabaci) to five plant species: Cucurbita maxima (winter squash), C. moschata (pumpkin), C. pepo (summer squash), Lagenaria siceraria (bottle gourd), Nicotiana tabacum cv. White Burley and N. tabacum cv. Xanthi. PYVMV was transmitted from pumpkin to pumpkin by adult B. tabaci after an acquisition access period of 30 min, could be inoculated in 10 min, had a minimum latent period of 6 h and was retained by viruliferous insects for up to 8 days. A network of serological relationships exists among whitefly-transmitted geminiviruses [2]. PYVMV reacted with 1/8 monoclonal antibodies (MAbs) to African cassava mosaic, 4/9 to Indian cassava mosaic and 1/3 to okra leaf curl (Ivory Coast) geminiviruses in triple antibody sandwich ELISA (TAS-ELISA). The epitope profile of PYVMV differed from the profiles of ACMV, ICMV, OLCV and ToLCV. Well preserved geminate virus particles (30x20 nm) were found in immunosorbent electron microscopy with antisera to squash leaf curl geminivirus in extracts of pumpkin leaves infected with PYVMV. The results present unequivocal evidence for the occurrence of whitefly-transmitted geminivirus in pumpkin in south India. B. tabaci failed to transmit acalypha yellow mosaic, cotton leaf curl, croton yellow vein mosaic, dolichos yellow mosaic, horsegram yellow mosaic, Indian cassava mosaic, malvastrum yellow vein mosaic, tobacco leaf curl and tomato leaf curl geminiviruses to pumpkin.

1. Brown JK, 1994. FAO Plant Protection Bulletin 42, 3-32.
2. Harrison BD, Muniyappa V, Swanson MM et al., 1991. Annals of Applied Biology 118, 299-308.