Predicted Genetic Gains from Targeted Recombination in Elite Biparental Maize Populations.

Targeted recombination is the ability to induce or select for specific recombination points on chromosomes. A first study with the intermated B73 × Mo17 maize ( L.) population showed that targeted recombination doubles the predicted gains for yield and other agronomic traits. Our objective was to assess the predicted gains from targeted recombination for quantitative traits in multiple, elite maize populations. A total of 969 biparental maize populations were phenotyped at four to 12 environments in the United States from 2000 to 2008. Positions of one and two targeted recombinations per chromosome were determined from genomewide marker effects for 2911 single nucleotide polymorphism (SNP) loci. Relative efficiency (RE) was calculated as the predicted response to targeted recombination divided by the predicted response to nontargeted recombination. On average, targeted recombination doubled the predicted genetic gains for yield, moisture, and test weight. For each trait, RE ranged from around 60 to 400% among the populations, and targeted recombination did not increase gains in around 4% of the populations. The RE tended to decrease as the similarity between the parents increased. Having targeted recombination on three chromosomes (for yield and test weight) to seven chromosomes (for moisture) led to the same or greater predicted gain than nontargeted recombination. Marker intervals for targeted recombination varied across populations and traits. Overall, our results for multiple, elite maize populations indicated that targeted recombination is a most promising breeding approach.