Adarsh, M V creator Smitha Bhasi (Guide) text Vellayani Department of Molecular Biology and Biotechnology, College of Agriculture 2023 monographic Xl,58p. The study entitled “In-vitro chemotherapy for inducing tolerance towards Tomato Leaf Curl New Delhi virus in bitter gourd (Momordica charantia L.)” was conducted at the Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, Thiruvananthapuram during 2022-23. The objective of the study was the evaluation of in-vitro treatment with antiviral compounds, viz., Ribavirin, Virus–Ex and extracts of Bougainvillea spectabilis for inducing tolerance towards Begomovirus- ToLCNDV in bitter gourd (Momordica charantia L.). The explants namely seed of bitter gourd variety Preethi was collected from, Instructional farm, College of agriculture, Vellayani. Seeds were subjected to hot water treatment at 55°C for 15 minutes, followed by washing in 0.2% bavistin for 15 minutes and kept in dark for inducing germination. 91.2% germination was noticed in 3 days. The germinated seeds were grown in Murashige and Skoog (MS) medium supplemented with 2ppm BA and 20ppm concentration of various antiviral compounds viz., Ribavirin (Treatment 1), Virus-Ex (Treatment 2), extract of Bougainvillea spectabilis (Treatment 3) along with control. Percentage of culture establishment was found to be maximum (65.25%) in ribavirin treated plants followed by virus ex and bougainvillea. 20 days old in-vitro grown plants were hardened in coir pith compost and the biometric observations were taken and compared. Significant increase in plant height and number of leaves over control was noticed in treatment using ribavirin and virus ex respectively. DNA was isolated from 20 day old (hardened) treated and control plants prior to whitefly transmission and were confirmed to be virus free using PCR. Whitefly mediated artificial inoculation of virus in hardened plants (25 day old) was done and the plants were maintained inside insect proof cage for symptom development. Symptoms were observed in control plants after 10 days of whitefly transmission. Further PCR was performed to confirm the presence/absence of Begomovirus. Absence of virus in treatments with ribavirin and virus ex were 59 confirmed in PCR. Treatment using extracts of bougainvillea did not show any symptoms but confirmed positive in molecular detection. The control plants which developed symptoms was found positive in PCR. Peroxidase assay (Lobenstein and Linsey method) showed maximum increase in activity (3-fold) in plants treated with ribavirin followed by extracts of bougainvillea (2-fold) three days after whitefly transmission. Biometric observations on 35th day viz., plant height, number of leaves and leaf area were found higher in all the treatments compared to control, out of which treatment using ribavirin was found to be highly significant for all the parameters. To conclude, the present study in bitter gourd could confirm the antiviral activity of ribavirin and virus ex towards Begomovirus through whitefly mediated transmission test and molecular detection using PCR. BSc- MSc Molecular Biology and Biotechnology Chemotherapy Tomato leaf Bitter gourd Momordica charanita L 660.6 ADA/IN PG https://krishikosh.egranth.ac.in/handle/1/5810224599 https://krishikosh.egranth.ac.in/handle/1/5810224599