Characterization of a new citrus viroid species tentatively termed Citrus viroid OS

A new viroid was obtained from a viroid sample, named 'OS', collected from a citrus plant. The viroid consists of 330-331 nucleotides, contains the ce ntral conserved region (CCR) characteristic of the genus Apscaviroid, and h as the highest sequence similarity (only 68%) with Citrus III viroid (CVd-I II) among known viroids. This viroid, by itself, caused only mild petiole n ecrosis and characteristically very mild leaf bending in Arizona 861-SI Etr og citrons (Citrus medica L.), the degree of which differed from that induc ed by other citrus viroids. This viroid could be a new citrus viroid specie s belonging to the genus Apscaviroid;or convenience, it was tentatively nam ed Citrus viroid OS (CVd-OS) after the original sample, CVd-OS has chimeric features related to other viroids. In particular, CVd-OS has high sequence similarity with CVd-III and Apple dimple fruit viroid in the putative cent ral and terminal left domains, including a duplicative sequence from the lo wer CCR of the genus Pospiviroid in the left terminus. Further, CVd-OS shar es high sequence similarity with Citrus exocortis viroid (CEVd) in the lowe r strand of the putative variable and terminal right domains, including the sequence identical to that of the right termini of CEVd and of Citrus IV v iroid.