Achieving maximum efficiency of Mungbean yellow mosaic India virus infection in mungbean by agroinoculation

Mungbean is one of the important food legumes in the Indian-sub-continent. Yellow mosaic disease, caused by Mungbean yellow mosaic virus and Mungbean yellow mosaic India virus (MYMIV) poses a severe threat to its production. Agroinoculation has been the most preferred way to test the function of genomic components of these viruses. However, the available inoculation methods are not as efficient as whitefly transmission, thereby limiting their usage for screening and biological studies. We hereby report an efficient and reproducible agroinoculation method for achieving maximum (100%) efficiency using tandem repeat infectious agro-constructs of DNA A and DNA B of MYMIV. The present study targeted wounding of various meristematic tissues of root, shoot, parts of germinating seeds and also non-meristematic tissue of stem to test the suitable tissue types for maximum infection. Among the various tissues selected for, the inoculation on the epicotyl region showed maximum infectivity. Further, to enhance the infectivity of MYMIV, different concentrations of acetosyringone, incubation time and Agrobacterium cell density were also standardized. The incubation of wounded sprouted seeds in 1.0 OD of agroculture containing repeat construct of MYMIV for 2-4 h without acetosyringone followed by sowing in soil showed maximum infection of MYMIV within 10-12 days on the first trifoliate leaf. This standardized method is reproducible and has potential to screen germplasm lines and will be useful in mungbean biological/virological studies and breeding programmes.