Cucumber mosaic virus (CMV) is belongs to genus of cucumovirus in the family of Bromoviridae; fast increasing plant pathogen
infecting more than 1200 species from 100 families of monocot and dicots. Tomato is very prone to CMV; causing various
symptoms such as shoestring, yellowing and mottling of leaves, and ultimately deformation of tomato fruit that leads to huge
economic losses. In present study we have collected the Tomato plant showing characteristics symptom of the CMV from the
Koshi region namely, Kishanganj, Purnia and Katihar district of Bihar; diagnosed through direct antigen coating- Enzyme linked
imminosorbent assay (DAC-ELISA) as well as Dot immunobinding assay. Twenty four samples were found positive towards the
CMV antisera out of 168 collected suspected samples. The remaining 144 field samples were negative against CMV antisera, it
may be due other biotic and abiotic stress. The Incidence of the CMV was varying from 12% to 17 % in Koshi region of Bihar.