Abstract

Citrus yellow mosaic badna virus (CMBV) is known to infect citrus cultivars in nature. CMBV isolates infecting two citrus cultivars, acid lime and pummelo were investigated. It was found that all the isolates share very high homology amongst themselves. The genetic variability of CMBV within and among different host showed that CMBV population, within a single host-plant is generally closely related, however, the populations among different hosts are quite diverse and more so in case of the CMBV infecting Pumello. The study on Sri Lankan cassava mosaic virus (SLCMV) covered two aspects. First, the putative CP and Rep promoter regions were compared with the known constitutive promoter Cauliflower mosaic virus (CaMV) 35S. it was observed that they show transient activity both in eukaryotic (BY2) and prokaryotic cells (Agrobacterium). The CP promoter region, however, was found to drive almost similar level of expression compared to the CaMV 35S promoter. The expression driven by Rep promoter was almost negligible. In transformed plants, the promoter fragments were found to have very low activity. Mentha is an important crop in the northern part of the country, and India is the largest producer of menthol oil. Because of the prevalence of typical geminivirus-like symptoms and whiteflies in the fields, a geminivirus was suspected to be involved in the disorder. In this study the geminivirus shared maximum sequence identity with Tomato leaf curl virus. In addition, two satellite DNAs, namely, a DNA β and a DNA II were also associated with this virus. DNA β was homologous to DNA β associated with cotton leaf curl disease and DNA II was a new molecule. The infectivity of virus was also demonstrated in artificial and natural host after mechanical and whitefly inoculation, respectively.