Molecular markers flanking citrus tristeza virus resistance gene from Poncirus trifoliata (L.) Raf

Two segregating populations for citrus tristeza virus (CTV) resistance derived from Poncirus trifoliata var 'Flying Dragon' by self-pollination and pollination to Citrus medica L. var ethrog 'Arizona' were inoculated with a common CTV isolate. The presence of virus was checked by the Double Antibody Sandwich Enzyme-Linked Assay and Direct Tissue Blot Immunoassay at 3, 6, and 12 months after inoculation. Seven RAPDs were found linked to the CTV resistance gene by bulked segregant analysis. The closest linked RAPDs were cloned to obtain linked codominant RFLPs and to increase the precision of the genetic distance estimation. The CTV resistance gene seems to be located between cW18 and cK16. Differences in genetic distances among progenies are large and can be explained by genome-wide reduction in the recombination of progeny derived from male versus female gametes.