JARIAL, KUMUDSHARMA, ARPANA2020-11-232020-11-232020-08-30https://krishikosh.egranth.ac.in/handle/1/5810155562Effect of sowing dates on the development of bacterial leaf spot in bottle gourd and pumpkin was studied and it was found that disease severity decreased with delay in date of sowing from mid May to end of June (27th June) or mid July (17th July) in both the crops. A high disease severity was recorded in early sown (17 May and 7 June) crops. From the diseased samples of bottle gourd and pumpkin collected from field, the causal bacterium was isolated on nutrient sodium chloride agar as circular, yellow, mucoid colonies having 1-5 mm diameter. Both the isolates tested positive for Esculin hydrolysis as well as protein digestion tests and negative for Gram’s reaction. Pathogenicity test on leaves of healthy seedlings of bottle gourd and pumpkin with respective isolates resulted in incubation periods of 46h and 48h, respectively However, in case of cross pathogenicity of the pathogen isolates, an incubation period of 70h and 72h was recorded in case of bottle gourd and pumpkin isolate on pumpkin and bottle gourd, respectively and the identity of the pathogen was confirmed as Xanthomonas cucurbitae. Development of bacterial spot of bottle gourd and pumpkin was favoured by temperature ranging between 30-35ºC and relative humidity more than 80 per cent. The plants of bottle gourd and pumpkin at the age of 10, 20, and 30 days were more susceptible to infection as compared to the older plants (40, 50 and 60 days old) which exhibited the presence of adult plant resistance in both the crops against X. cucurbitae. Out of nine chemicals tested in vitro against both bottle gourd and pumpkin isolates of X.cucurbitae, only streptocycline, captan, copper oxycloride and copper hydroxide alone as well as in combinations exhibited antibacterial activity. Out of seven plant extracts tested, plant extract of Eucalyptus hybrida was found to be inhibitory towards X. cucurbitae. A chemical combination comprising of streptocycline (100ppm) + captan (2500ppm) proved effective in controlling the pathogen and disease both under in vitro and pot house conditions, respectively.EnglishThesis