K. T. Rangaswamy

Detection and characterisation of a begomovirus associated with leaf curl disease of ornamental croton (Codiaeum variegatum)

Summary A leaf curl disease was observed on croton (Codiaeum variegatum L.), a popular ornamental plant in botanical, home, and office gardens in and around Bengaluru, South India. Diseased plants showed typical symptoms of vein thickening, severe inward curling and a reduction in leaf size, and stunting. The pathogen responsible was transmitted to healthy croton plants by grafting of infected scions, and through the whitefly vector, Bemisia tabaci, suggesting that the disease was caused by a begomovirus. The association of a begomovirus with the disease was further confirmed by the amplification of viral DNA fragments of ca. 520 bp and 575 bp derived from the coat protein (CP) gene of DNA-A using degenerate primers and total DNA extracted from infected, but not from healthy croton plants. The 575 bp fragment corresponding to the core region of the CP gene was cloned and sequenced. Phylogenetic analysis of the core CP sequence grouped the croton-infecting begomovirus, which we tentatively called croton leaf curl virus (CrLCuV), with Ageratum yellow vein virus (AJ810825), with which it shared the highest nucleotide identity (95%). The core CP sequence was similar (90 – 95%) to many other begomoviruses from the Indian sub-continent that infect tomato, tobacco, cotton, and papaya. Thus, its precise taxonomic denomination will require sequencing of the complete ssDNA viral genome.