INTRODUCTION Pumpkin (Cucurbita moschata Duch. Ex Poir) is an important vegetable crop in India and is grown extensively throughout the year in different parts of the country. It is one of the most popular summer vegetables grown on commercial scale. The crop is also extensively grown in United States of America, Mexico and China. In India, it is mainly grown in Odisha, Uttar Pradesh, Madhya Pradesh, West Bengal, Chhattisgarh, Karnataka, Tamil Nadu, Kerala and Bihar. In India, pumpkin is cultivated over an area of 67640 ha, with a total production of 1508990 mt and the productivity is about 22.31 mt/ha (Anon., 2016). The crop is cultivated over an area of 1480 ha in Karnataka with the production of 64870 tonnes and productivity of 25.74 t/ha. In Karnataka the major pumpkin growing districts are Hassan, Mandya, Kolar, Haveri, Koppal, Bagalkot, Kolar, Chikkaballpur (Anon., 2006). The fruits are having creamy orange color flesh and almost all parts of plant are edible. The fruit contains protein 1.0 g, moisture 91.5 per cent, fat 0.1 g, carbohydrate 6.5g, energy 26 k cal, cholesterol 0 mg, dietary fiber 0.5 g, Vitamin A (7384 mg/100g, Vitamin C (9.0 mg/100g), Vitamin E (1.06 mg/100g), riboflavin 0.110 g, potassium 340 mg, phosphorous 44 mg, iron 0.8 mg and magnesium 12 mg for 100 g edible portion. Because of its high carotene content and good keeping quality, it is considered as vegetable of immense value. The crop has been reported to be affected with a number of diseases. Among them viral diseases are known to cause severe yield losses. Pumpkin Yellow Vein Mosaic Disease (PYVMD) is an important disease infecting the plants at all stages of growth and is responsible for the distortion and mottling of fruits, which is unmarketable (Nath, 1994). The casual virus is designated as “Pumpkin Yellow Vein Mosaic Disease” (PYVMD) and occurrence of this disease was first reported by Varma (1955) from New Delhi; Capoor and Ahmad (1975) from Pune, Maharashtra; Bharghava and Bharghava (1977) from Uttar Pradesh; Ghosh and Mukhyopadhyay (1979) from West Bengal; Latha and Gopalkrishnan (1993) from Kerala; Babhitha (1996), Jayashree et al. (1999) and Muniyappa et al. (2003) from Karnataka. In 1990 a severe epidemic of leaf curl in muskmelon (Cucumis melo L.) and yellow vein mosaic in pumpkin, caused by begomoviruses, appeared in northern India (Varma, 1990). This epidemic was caused due to increase in whitefly populations early in the cucurbit-growing season. Since then, disease caused by begomoviruses have emerged as a major constraint in the production of a variety of cucurbits in India (Varma and Giri 1998; Muniyappa et al., 2003; Varma and Malathi, 2003). Two species of geminiviruses, with bipartite genome, causing PYVM have been reported from India. Tomato leaf curl New Delhi virus-India (Maruthi et al., 2007) has been reported from North India and squash leaf curl China virus-India, from South India. Later, bipartite Squash leaf curl Palampur virus was also reported to be associated with PYVM (Jaiswal et al., 2011). Most of the viruses causing yellow vein mosaic in crop pants belong to genus begomovirus. Taking the severity of the disease in the field in to consideration the work on survey, symptomatology and host range of PYVMV was taken up. MATERIAL AND METHODS A roving survey was conducted during 2016-17 to determine the prevalence of incidence of mosaic disease in major pumpkin growing districts of Southern Karnataka (Chikkaballapura, Kolar, Bengaluru Rural and Tumkuru). Plants were observed for the typical symptoms viz., yellowing of veins, mosaic symptoms, mottling etc. For each one acre of field five randomly selected sites (10m × 10m) were selected and the average disease incidence was calculated using the following formula. Per cent disease incidence (PDI) = To study the host range for PYVMD and to determine the natural reservoirs of PYVMD, the different plants belong to family solanaceae like tomato, brinjal, chilli, capsicum and cucurbitaceae like bottle gourd, ridge gourd, bitter gourd, watermelon, cucumber, muskmelon and other crops like tobacco, okra, french bean, soya bean, green gram, black gram and also the other weed hosts, which were found in and around the field were inoculated by using viruliferous whiteflies as described by Sohrab (2005). The plants were kept in insect proof net house and observed for symptom expression and the symptoms were recorded. Later the details on date of inoculation, days for symptom expression and number of plants infected and per cent transmission also was recorded. RESULTS AND DISCUSSION The survey was undertaken in four different districts in southern Karnataka. In Kolar district, the percent disease incidence was ranged from 16.30 to 38.10 per cent and in Chikkaballapura district the percent disease incidence was ranged from 14.50 to 22.60 per cent, in Tumkuru district the per cent disease incidence was ranged from 12.70 to 36.30 per cent, and in Bengaluru district the per cent disease incidence was ranged from 12.70 to 28.10 percent (Table 1, Fig. 1 and Plate 1). The disease incidence was varied from taluk to taluk in different districts. This difference may be attributed to different climatic factors, vectors activity, different cultivars and different cultivation practices followed. It may also be due to variation in plant protection practices followed by the farmers, low quality seeds. The similar work was carried out by Namrata (2012), conducted roving survey, pumpkin plants exhibited different kinds of symptoms such as severe yellow-vein mosaics accompanied by leaf curl and stunted growth. The incidence of symptomatic plants varied between fields at different locations and it was ranged from 40 to 80 per cent in monocropping system. Rekha et al. (2005) conducted survey in pumpkin-growing areas of Karnataka to assess the incidence and severity indicated that PYVMD incidences ranged from 45 to 100% in Kunigal and Nagamangala taluks of Tumkur and Mandya districts. Therefore, the natural incidence of pumpkin yellow vein mosaic virus disease would vary from field to field in the surveyed area. The symptoms of disease started occurring on 11th day of inoculation and symptoms includes the development of yellow vein mosaic. The diseased plants show vein yellowing, later coalesces to form chlorotic patches. Infected plants stunted in growth and flowers drop prematurely, greatly reducing yields. The entire plants will become yellow vein mosaic in 24-30 days (Plate 2). Similar symptoms of stunted growth, vein yellowing, chlorotic patches, premature flower drop were reported by Muniyappa et al. (2003). To identify the natural reservoirs and those susceptible to virus, the host range study of the virus was conducted. Twenty two different plant species belong to family solanaceae like tomato, brinjal, potato, chilli, capsicum and cucurbitaceous crops like bottle gourd, ridge gourd, bitter gourd, watermelon, cucumber, muskmelon and other crops like tobacco, okra, french bean, soya bean, green gram, black gram and also the weed species like Acalypha indica L., Euphorbia geniculata Orteg., Chenopodium amaranticolor, Datura metel L. Parthenium hysterophorus L. from among these only three plant species viz., Luffa acutangula (L.) Roxb.] (ridge gourd), Cucumis pepo L.(squash), Legenaria segeraria (Molina.) Standl. (bottle gourd) have showed virus infection. None of the other plant species including weed species were showed any symptoms (Table 2 and Plate 2). Among the different plant species only three plant species viz., Luffa acutangula (L.) Roxb.] (ridge gourd), Cucumis pepo L. (squash), Legenaria siceraria (Molina.) Standl. (bottle gourd) have showed virus infection (Plate 2). None of the other plant species including weed species were showed any symptoms. This showed that the virus mainly confined to important cucurbitaceous species only. Similarly Muniyappa et al. (2003), studied forty-three crop plants, including 11 ornamental and 13 weed species belonging to 16 families to test their susceptibility to PYVMD. Of all the plants tested few cucurbits viz., summer squash (100%), winter squash (100%), bottle gourd (96%) and N. tabacum, varieties like White Burley and Xanthi., were infected with 7 % and 42% respectively.