R.F. Lee - University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred 33850

Two plasmids  with cDNA inserts representing different regions of the citrus tristeza virus (CTV) genome were used to compare five biologically distinct isolates of CTV. One of the plasmids (D2)  hybridized strongly with all of the isolates. The other (D1) plasmid hybridized strongly with four of the isolates. A fifth isolate, which caused severe symptoms, hybridized weakly, if at all, with DI. Similar results were obtained using total plant RNA, RNA extracted from purified and partially purified virus preparations, or dsRNA preparations. Virion RNA of two CTV isolates, HT and VT, used as probes for hybridization with restriction patterns of the D1 CTV clone revealed DNA fragments that carry strain specific sequences.