Thind, S.K.Yesmin Kaur2019-09-132019-09-132019http://krishikosh.egranth.ac.in/handle/1/5810127748Foot rot of citrus caused by Phytophthora spp. is major threat to flourishing citrus industry across the world. During surveillance, maximum disease incidence was recorded in Fazilka and minimum in Sangrur districts of Punjab. Among different agro-climatic zones of Punjab, maximum incidence was recorded in arid-irrigated zone and minimum in central zone. The disease incidence was more on Grapefruit and less on Kinnow cultivars of citrus. Oat meal agar medium was best for growth of Phytophthora. The causal agent of the disease was identified as Phytophthora nicotianae on the basis of morphological and molecular characters. Phytophthora survival was highest in irrigated and inoculated soil planted with Rough lemon seedlings and diminished in unirrigated bare soil after 15 months of inoculation. The population was maximum at 0-8 inches depth and was positively correlated with the plant root density. Maximum population was recorded in the months of July-September with temperature of 28.0-32.5 °C and relative humidity of 71.5 to 75.0 per cent. Leaf baiting was found best for detecting Phytophthora population after 24 hours with 1:1 soil and water ratio. A set of seventeen SSR primers generated 67 to 100 per cent polymorphism. Metalaxyl resistant isolate of Phytophthora showed reduced sensitivity to Ridomil Gold 68 WP at 1, 10 and 50 μg/ml with ED50 value of 30.0 μg/ml. Ridomil Gold 68 WP, Profiler 71.1 WG and Curzate M8 72 WP were found effective in vitro and in vivo against Phytophthora. Profiler 71.1 WG and Curzate M8 72 WP were also effective against metalaxyl resistant isolate.ennullThesis