Nucleotide Sequence of Citrus Tristeza Virus Seedling Yellows Isolate

Abstract

The complete nucleotide sequence of a seedling-yellows-inducing isolate NUagA of Citrus tristeza virus (CTV) was determined. It consisted of 19302 nucleotides and contained 12 open reading frames (ORF) organized identically to those of previously sequenced isolates. This genome is the largest among the CTV genome sequenced so far ; it is 6 nucleotides (nt), 76 nt, 43 nt, and 63 nt longer than that of T36 (quick decline, Florida), VT (seedling yellows, Israel), T386 (mild, Spain), and SY668 (stem pitting, California), respectively. Sequence comparison of NUagA and the other isolates revealed approximately 90% identities throughout the 3 half of the genome. The 6‘ half of the genome was only about 70% identical to that of T36 but still high at about 90% to those of VT, SY668, and T386. Comparison of amino acid sequences on ORFla encoding polyproteins, the most variable region, reflects the CTV isolate relationship ; NUagA is closely related to VT, SY668, and T385, but distantly related to T36. (Received May 29, 2000 ; Accepted November 16, 2000) Key words : Citrus tristeza virus, seedling yellows, NUagA, Closterovirus, nucleotide sequence