Investigations on a new bacterial disease of bottle gourd in sub-tropical zone of Himachal Pradesh Jarial Kumud, Dogra Balbir, Mandradia R. K., Kumar Sunil, Sharma Deepa, Gupta A.K.* Dr Y S Parmar University of Horticulture & Forestry Regional Horticulture & Forestry Research Station, Bhota/Neri, Hamirpur – 177 001 *Department of Mycology and Plant Pathology, Dr Y S Parmar University of Horticulture and Forestry, Nauni, Solan – 173 230 Abstract Bottle gourd (Lagenaria siceraria syn. L. vulgaris) crop was found to be attacked by a new bacterial disease in Himachal Pradesh. The symptoms of the disease appeared initially on leaves as small marginal chlorotic spots, which increased in size towards the centre of the leaf. Later, the necrotic areas developed in the chlorotic zone. The symptoms on stem/vine, tendrils and floral parts developed as water soaked areas which ultimately turned into necrotic spots. In severe conditions, amber coloured ooze came out of the vines and this ooze was also visible when the vine was split into two pieces. Finally, the vine completely turned necrotic and died. In case of attack on female flowers, a rot was observed on the stigma and ovary of the flower resulting in no fruit formation. The symptoms on young fruits appeared as water soaked spots which ultimately led to complete rotting of the fruit. On mature fruits, the symptoms developed as small faded spots on fruit peel which later cracked and amber coloured ooze appeared on the spots. In severe cases, the fruits were deformed and got covered with cracks which finally rot. Survey conducted at 64 locations of five districts of the State revealed the variation of disease severity from 12.50 to 78.33 per cent causing around 10.07 to 70.61 per cent yield losses at different locations. The pathogenicity of the isolated bacterium was proved and it was identified as Xanthomonas cucurbitae (Bryan) Dowson on the bases of morphological, cultural, biochemical and Gramís staining assays and the disease was identified as bacterial spot of bottle gourd. The bacterium was found to produce symptoms on cucumber, pumpkin and summer squash in addition to bottle gourd after artificial inoculation on their leaves and fruits with bacterial suspension (104 cfu/ml) where incubation periods ranged between 3–6 and 5–8 days on leaves and fruits, respectively. In vitro evaluation of chemicals by paper disc method revealed good inhibition of the bacterium with streptocycline (200, 150, 100 and 50 ppm), mancozeb (2000 and 1500 ppm), copper oxychloride (2000 ppm) and zineb (2000 ppm). These investigations constitute the first record of the disease on bottle gourd from Himachal Pradesh. Top Keywords Bacterial spot, bottle gourd, Lagenaria siceraria, L. vulgaris and Xanthomonas cucurbitae. Top |