Abstract

The yellow vein mosaic disease is one of the most destructive viral diseases in okra. There are many viruses associated with this disease and it is an important requirement to know about them in order to design resistance strategies. The disease affected samples from different parts of India were used to clone geminiviruses. The sequences were then compared to find out the similarities between them. It was found out that the viruses including associated molecules called as betasatellite share more than 90% identity among each other. Agrobacterium mediated transfer of viral genome is an important method to establish successful viral infection in plants and used to perform infectivity analysis in model plant Nicotiana benthamiana. Agroinfectious constructs harbouring different components of virus were cloned in a way that after infection in plants, virus could successfully replicate inside. Some viral replicative forms were detected by Southern hybridization however symptoms could not be observed. In order to achieve resistance against viral diseases hairpin RNA homologous to viral sequence were cloned. These constructs produced small RNA in planta which was confirmed by Northern hybridization. The okra associated viral genomes were also screened for their counter-defensive strategy against plants, since plants use a mechanism called as RNA silencing as a defence system against viruses. The study revealed that few viral proteins act as mild suppressors of silencing mechanism used by plants.