A.S.ByadgiHemavati Ranebennur2016-10-242016-10-242005http://krishikosh.egranth.ac.in/handle/1/81644Papaya ring spot virus disease is a major limiting factor for cultivation of papaya where cucurbits are suspected as source of survival and spread. In present investigation, a roving survey was conducted in seven districts of Karnataka viz., Dharwad, Belgaum, Bijapur, Bagalkot, Gadag, Bellary and Haveri to know the incidence of PRSV on papaya and also on cucurbits grown in and around papaya orchards. Various symptoms like mosaic, vein clearing, blistering, mottling, shoestring stunting, ringspots on both stem and fruit and malformation of fruits were observed in papaya. Cucurbits viz Luffa acutangla, Momordica charantia, Cucumis sativus, C. maxima, C. melo, C. anguira and Citrullus vulgaris, were found growing in and around papaya orchards as volunteers, twined and intercropped with papaya in some orchards. Symptoms of mosaic, chlorotic spot, vein clearing and mottling were observed in these cucurbits In vitro mechanical, insect and seed transmission studies were carried out using thirteen cucurbits and two Chenopodium sp. All the in vitro studied samples and field-collected samples were subjected to DAS ELISA and back inoculation to papaya. The virus readily transmitted by mechanical and aphid vectors from papaya to cucurbits and vice versa. Among the cucurbits tested Luffa acutangula, Cucurbita maxima, Cucumis sativus, C. anguira, C. melo and Momordica charantia were found positive in mechanical, insect and field collected samples in both DAS ELISA and back inoculation to papaya. Where as Cucurbita pepo and C.moschata, were found positive in insect and mechanical transmission, but were not found in fields. Benincasa hispida, Lagenaria siceraria, Cucumis metuliferus and Trichosanthes anguira gave negative reaction in all the samples tested. While, Citrullus vulgaris gave positive in in vitro studies but negative in field-collected samples. No samples were found positive in seed transmission. The studies on management of PRSV in cucurbits using insecticides and botanicals revealed ineffectiveness of any of the insecticides tried in inhibiting vectors and hence spread of virus. However Spraying of Nimbicidine 4 ml/l reduced the aphid colonization and further spread of the disease. Application of Boron @1.5 g/l delayed the occurrence of the disease for a considerable period. The studies revealed that the cucurbits can play a significant role in survival and spread of PRSV to papaya. Prevention of growing cucurbits in and around papaya orchards can reduce the incidence and spread of the disease.Plant PathologyThesis