01209naa a2200181 a 450000100080000000500110000800800410001910000140006024500920007426000090016652007180017570000180089370000230091170000150093470000150094970000150096477300480097916485432000-01-10       1998    bl ---       0--  u    #d1 aLOPEZ, C.  aMolecular variability of the 5 - and 3 - terminal regions of citrus tristeza virus RNA.  c1998  aIsolates of citros tristeza virus (CTV) differ widely in their biological properties. These properties may depend on the structure of viral RNA populations comprising the differnt isolats. As a first approach to study the molecular basis of the biological variability. we have compared the sequences of multiple cDNA clones of the two terminal regions of the RNA from different CTV isolates. The polymorphism of the 5' untranslated region (UTR) allowed the classification of the sequences into three groups, with intragroup sequence indenty higher than 88% and intergroup sequence identitu as low as 44%. The variability of an open reading frame (ORF) la segment adjacent to the 5' UTR supports the same grouping.1 aAYLLON, M. A.1 aNAVAS-CASTILLO, J.1 aGUERRI, J.1 aMORENO, P.1 aFLORES, R.  tPhytopathologygv.88, n.7, p.685-691, 1998.