RELATIONSHIP BETWEEN THE Lr67 LEAF RUST RESISTANCE GENE AND THE Rht-D1 DWARFING GENE OF WHEAT

Abstract

Gene Lr67, located on chromosome 4D, confers resistance to leaf rust caused by Puccinia triticina E. This gene was common in tall wheat (Triticum spp.) varieties released in Mexico before 1960, but not in semi-dwarf varieties released from that date to the present. Semi-dwarf wheat varieties released in Mexico carry either the Rht-B1 dwarfing gene located on chromosome 4B or the Rht-D1 gene located on chromosome 4D. To test whether there is a genetic impediment to combine the Lr67 and Rht-D1 genes in the same wheat variety, the F₃ of the cross between the Nasma variety, Rht-D1 gene carrier, and the Marroqui 588, Lr67 gene carrier, was genotypically characterized. By using chi-square tests and diagnostic molecular markers, it was found that genetic distance between both genes is 23.6 cM with linkage analysis and 27.6 cM with molecular analysis. These distances are large enough for genetic recombination to exist; thus, there is no genetic impediment to obtain recombinant genotypes that combine the leaf rust resistance gene (Lr67) with the dwarfing gene (Rht-D1), that in the parents are in repulsion phase.