COMPARATIVE MAPPING OF THE WHEAT CHROMOSOME 5A VRN-A1 REGION WITH RICE AND ITS RELATIONSHIP TO QTL FOR FLOWERING TIME

The vernalization gene Vrn-A1 on chromosome 5A is the predominant gene determining the spring/winter habit difference in bread wheat. Vrn-A1 was physically mapped using a set of deletion lines which located it to the region of chromosome 5A flanked by deletion breakpoints 0.68 an d 0.78. This interval was shown to be homoeologous to a region of rice chromosome 3 that contains the flowering-time QTL Hd-6, previously ma pped in a Nipponbare x Kasalath cross, and FLTQ1, a novel QTL identifi ed by analysis of 78 F-3 families derived from a cross of 'IR20' x '63 -83'. Possible relationships between Vrn-A1 and rice QTL are discussed . Analysis of the chromosome 5A deletion lines showed evidence for a s econd, more proximal flowering-time effect located between deletion br eakpoints 0.56 and 0.64. The proximal part of chromosome 5A is homoeol ogous to rice chromosome 9, on which two QTL were detected in the 'IR2 0 x '63-83' cross. The possible relationship between these effects is also discussed.