Wheat functional genomics and engineering crop improvement

Abstract

Genetic mapping and determination of the organization of the wheat genome are changing the wheat-breeding process. New initiatives to analyze the expressed portion of the wheat genome and structural analysis of the genomes of Arabidopsis and rice are increasing our knowledge of the genes that are linked to key agronomically important traits.

Figure 1

Diagram of the PCR primers used to distinguish the Rht-B1b and Rht-D1b genes [30]. The primers on the right differentiated the wild-type (WR1 and WR2) from the mutant (MR1 and MR2) genes by a single nucleotide change in the coding region. The primers cannot, however, distinguish between the genes on homeologous chromosomes 4B and 4D. The primers on the left-hand side differentiated between the 4B and 4D genomes because the upstream promoter regions have undergone sufficient evolutionary change to be distinguishable from each other. The figure is based on Ellis et al. [30] emphasizing the challenges faced when studying multiple gene copies in the wheat genome.

Figure 2

The effect on the genetic gain in elite lines of conventional and marker-assisted breeding. The effect of increasing the number of parental allele combinations, with selection at F2, F4 and F6 generations, highlights the value of a strategic use of molecular markers in breeding [32,33]. The larger base of the inverted triangle implies that more genetic variation is sampled for inclusion into the smaller numbers of lines examined in the F6 generation.