Physical mapping of the Vrn-A1 and Fr1 genes on chromosome 5A of wheat using deletion lines

Homozygous deletion lines of wheat for 5AL, generated in the variety 'Chine se Spring', were tested for flowering time without vernalization and for fr ost resistance after cold hardening. It was found that the Vrn-A1 gene for vernalization requirement mapped between breakpoints 0.68 and 0.78, whilst the frost resistance gene Fr1 was flanked by deletion breakpoints 0.67 and 0.68. This confirms previous evidence that these genes are linked but are n ot the pleiotropic effect of a single gene. A comparison between the physic al and genetic maps for Vrn-A1 and Fr1 shows that the linear order is ident ical. These results indicate that cytogenetically based physical maps of Vr n-A1 and Fr1 loci, together with genetic maps, could be useful in the furth er study of genome synteny and in elaborating a gene cloning strategy.