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 and 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 mapped in a Nipponbare×Kasalath cross, and FLTQ1, a novel QTL identified by analysis of 78 F₃ families derived from a cross of ‘IR20’ב63–83’. Possible relationships between Vrn-A1 and rice QTL are discussed. Analysis of the chromosome 5A deletion lines showed evidence for a second, more proximal flowering-time effect located between deletion breakpoints 0.56 and 0.64. The proximal part of chromosome 5A is homoeologous to rice chromosome 9, on which two QTL were detected in the ‘IR20ב63–83’ cross. The possible relationship between these effects is also discussed. Received: 23 December 1997 / Accepted: 12 January 1998