NUCLEOTIDE-SEQUENCE OF A HOP STUNT VIROID VARIANT ISOLATED FROM CITRUS GROWING IN TAIWAN

The 303 nucleotide sequence of HSVd-citrus(T), a hop stunt viroid (HSV d) variant present in Etrog citron growing in Taiwan, was determined f rom cDNAs amplified by the polymerase chain reaction, HSVd-citrus(T) i s very similar to several HSVd isolates previously recovered from citr us or cucumber, and exhibits microsequence heterogeneity at positions 154 and 181. Phylogenetic analysis using maximum parsimony grouped HSV d-citrus(T) with seven other isolates from citrus and cucumber in a la rge cluster of ''citrus-type'' isolates. A similar analysis revealed m arked differences in both the extent and distribution of sequence vari ation among naturally occurring isolates of potato spindle tuber viroi d.