HANDA, ANILKATWAL, VINAY SINGH2017-02-162017-02-16201047252http://krishikosh.egranth.ac.in/handle/1/5810001191ABSTRACT Investigations were conducted to record the incidence of viruses in apple orchards of the state along with serological detection by employing ELISA, besides indexing of some trees of commercial cultivars of apple. Seventeen apple orchards surveyed in Shimla, Kinnaur and Kullu district of HP revealed the presence of viral infection with an incidence of 5-99 per cent. Both indirect DAC ELISA and direct DAS ELISA assays resulted in detection of ACLSV, ApMV, ASGV and ASPV in apple trees of different commercial cultivars being grown in different orchards. ACLSV, ApMV, ASGV and ASPV were found to be present in serologically detectable limit in leaves, bark and petals parts of an infected plant. However leaf sample drawn during June, bark taken during August and petals taken during April month found to contain highest relative concentration of these viruses based on the OD values obtained in serological reactions. About 50 per cent of the diseased plants revealed the presence of two or more than two viruses, thus indicating prevalence of mixed infection. Out of 115 asymptomatic apple trees of different commercial cultivars selected through viral indexing, 4 trees were found to carry latent infection of ACLSV. Virus tested trees were marked to serve as mother trees for providing budwood use in propagations.eneconomics, biological phenomena, resins, productivity, technological changes, exhibitions, developmental stages, marketing, biological development, selectionThesis