Abstract

Cassava, an important source of starch in the tropical countries, is affected by various diseases, principal among them being the mosaic disease caused by single-stranded DNA geminiviruses. Two geminiviruses, Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV) are found in mosaic affected cassava plants in India. Both ICMV and SLCMV are bipartite geminiviruses with two circular molecules as the genome, DNA-A and DNA-B. The infectivities of ICMV and SLCMV DNAs were studied in Nicotiana benthamiana, N. tanacum, Arabidopsis thaliana and cassava were studied by agroinoculation. ICMV and SLCMV DNAs (both DNA-A and DNA-B) were converted into partial dimers, cloned in binary plasmids for this purpose. Agroinoculation of these constructs resulted in leaf curling (upward and downward) in N. benthamiana, stunting in N. tabacum for SLCMV, but mild leaf deformation and stunting for ICMV. No significant symptoms appeared in A. thaliana and cassava, although the viral DNA could be detected by PCR amplification.