MOLECULAR MARKERS FLANKING CITRUS TRISTEZA VIRUS-RESISTANCE GENE FROMPONCIRUS-TRIFOLIATA (L) RAF

Two segregating populations for citrus tristeza virus (CTV) resistance derived from Poncirus trifoliata var 'Flying Dragon' by self-pollinat ion and pollination to Citrus medica L. var ethrog 'Arizona' were inoc ulated with a common CTV isolate. The presence of virus was checked by the Double Antibody Sandwich Enzyme-Linked Assay and Direct Tissue Bl ot Inmunoassay at 3, 6, and 12 months after inoculation. Seven RAPDs w ere found linked to the CTV resistance gene by bulked segregant analys is. The closest linked RAPDs were cloned to obtain linked codominant R FLPs and to increase the precision of the tic distance estimation. The CTV resistance gene seems to be located between cW18 and cK16. Differ ences in genetic distances among progenies are large and can be explai ned by genome-wide reduction in the recombination of progeny derived f rom male versus female gametes.