Variability assessment and construction of infectious clone of Indian Apple Scar Skin Viroid

Apple scar skin viroid (ASSVd) is widely distributed and economically important pome-fruit infecting viroid belonging to the genus Apscaviroid. It causes huge economic losses to the apple industry. Apple fruits with dappling, scarring, cracking and deformation symptoms were noticed during survey of apple growing regions of Himachal Pradesh, India. ASSVd was detected from four isolates showing dappled fruits. Molecular characterization of the viroid was done. Ten clones each from five isolates were sequenced out of which seven new sequence variants of ASSVd were found. Four of the clones were 330 nucleotides (nt) long and the other eight had an additional nucleotide. The clones showed significant sequence variability (94-100%) with each other. Variability was more common in the pathogenic domain of the viroid genome. Present isolates grouped with some Chinese and Korean isolates in phylogenetic analysis. The study reports seven new sequence variants of ASSVd and also gives a first molecular evidence of a viroid infection (ASSVd) in apple from India. Infectious clone of ASSVd were constructed for in vitro mutagenic studies.