Meetei, Ng. TombisanaBhattacharjee, Saumika2023-04-112023-04-112019https://krishikosh.egranth.ac.in/handle/1/5810196283Capsicum spp. is curtailed as one of the wider known spice crops hailing around the world with at least twenty five known cultivated varieties. Dalle Khursani (Capsicum annum) an indigenous variety of the foothills and slopes of Sikkim and Darjeeling is famously used for its powder and pickles owing to its high degree of pungency through the chemical Capsaicinoids. Capsicum like its counter crops is to a larger extent susceptible to the second largest destructible pathogens i.e. viruses. Among which the name of Cucumber mosaic virus draws remarkable attention as being a source of extensive yield losses and deteriorated fruit quality. The present study was taken with the following objectives: i) Molecular characterization of virus infecting Dalle Khursani based on coat protein gene sequence ii) Production of virus free plants by in-vitro meristem tip culture Cucumber mosaic virus (CMV) was visually detected in the field based on its symptoms and later confirmed through molecular techniques. RT-PCR using CMV coat protein gene specific primers CPTALL 5’ and CPTALL 3’ were utilized to confirm the presence of the virus. The PCR product with the expected size of 950 bp was sent for sequencing and the sequence obtained on database search using BLAST confirmed to belong to coat protein of CMV. The phylogenetic study with other CP gene reference sequences showed the isolate to cluster with other CMV belonging to subgroup IB whereas the reference sequence of CMV subgroup IA and II clustered separately thus indicating the present CMV isolate to belong to subgroup IB. For the production of virus free plants, shoot tips from confirmed infected plants were used as source of explants for meristem tip culture. Meristems of 0.1- 0.5 mm were dissected from the infected shoot tips and cultured in 29 media concentrations all set with five different plant growth regulators i.e. BAP, KIN, TDZ , NAA and IBA in addition to the presence of a control. Of the 29 combinations, 20 showed signs of regeneration wherein the concentrations of TDZ particularly 5 μM TDZ gave the best performance in terms of shoot length (2.82 ± 0.09 cm), number of shoots (2.81 ± 0.31) and percentage of response to survivability (88.83%). The in vitro explants bearing roots were transferred to artificial soil for hardening and 75% were recorded to survive. Leaf samples from the in vitro generated plants along with the control were once again subjected to the norms of molecular methods to confirm the presence/absence of CMV. Absence of bands confirmed the regeneration of virus free plantlets.EnglishThesis