Microsatellite mapping of complementary genes for purple grain colour in bread wheat (Triticum aestivum) L.

Complementary genes for purple grain colour Pp1, Pp2, Pp3 (now designated Pp1, Pp3b, Pp3a, respectively) were mapped using crosses between purple-grained hexaploid wheats ‘Purple Feed’ – Pp1Pp1/Pp2Pp2 (Pp1Pp1/Pp3bPp3b), ‘Purple’ – Pp1Pp1/Pp3Pp3 (Pp1Pp1/Pp3aPp3a) with non-purple-grained cultivars ‘Novosibirskaya 67’ (‘N67’) and ‘Saratovskaya 29’ (‘S29’). The genes Pp2 (Pp3b) and Pp3 (Pp3a) were inherited as monofactorial dominant when purple-grained wheats were crossed to ‘N67’. Both were mapped in the centromeric region of the chromosome 2A. Therefore, they were suggested being different alleles at the same locus and designated Pp3a and Pp3b. In the crosses between purple-grained wheats and ‘S29’ a segregation ratio of 9 (purple) to 7 (non purple) was obtained suggesting a complementary interaction of two dominant genes, Pp1 and Pp3. To map Pp1 as a single gene, the influence of the other Pp gene was taken into consideration by determining the Pp3 genotype of the F₂ plants. The gene was mapped on chromosome 7BL, about 24 cM distal to the centromere. The Pp1gene was shown to be non allelic to the Rc-1 (red coleoptile) and Pc (purple culm) genes, contrary to what was previously suggested. The colouration caused by the Pp genes has no effect on pre-harvest sprouting.