A DNA Fragment Mapped within the Submicroscopic Deletion of Ph1, a Chromosome Pairing Regulator Gene in Polyploid Wheat

Bread wheat is an allohexaploid consisting of three genetically related (homoeologous) genomes. The homoeologous chromosomes are capable of pairing but strict homologous pairing is observed at metaphase 1. The diploid-like pairing is regulated predominantly by Ph1, a gene mapped on long arm of chromosome 5B. We report direct evidence that a mutant of the gene (ph1b) arose from a submicroscopic deletion. A probe (XksuS1-5) detects the same missing fragment in two independent mutants ph1b and ph1c and a higher intensity fragment in a duplication of the Ph1 gene. It is likely that XksuS1-5 lies adjacent to Ph1 on the same chromosome fragment that is deleted in ph1b and ph1c. XksuS1-5 can be used to tag Ph1 gene to facilitate incorporation of genetic material from homoeologous genomes of the Triticeae. It may also be a useful marker in cloning Ph1 gene by chromosome walking.