OBJECTIVES: 1. Breed dwarf corn for hybrid performance. 2. Determine the genetic gains, variability, and performance of old and current corn germplasm for sucrose content. 3. Identify molecular markers associated with sucrose concentration in the corn stalk. 4. Determine the added genetic gain, compared with pedigree breeding, from marker-assisted recurrent selection and double haploids in corn. 5. Design and evaluate marker-driven selection schemes for corn.

APPROACH: COPOP1, a strain of dwarf corn developed in Canada, will be subjected to recurrent selection for testcross performance to develop two different, improved strains of COPOP1 that will be useful in hybrid breeding. Specifically, COPOP1 will be selected for performance when crossed to an Iowa Stiff Stalk Synthetic (BSSS) inbred. In a parallel recurrent selection program, COPOP1 will be selected for testcross performance when crossed to a non-BSSS inbred. Genetic gains, variability, and performance for sucrose content of old and current corn germplasm will be evaluated. Sucrose concentration will be measured from Brix readings based on calibrations available in the literature. Old and new corn hybrids will be compared, and combining ability for sucrose content will be estimated for old and new corn inbreds. The intermated B73 ? Mo17 population, a publicly available mapping population, will be used to identify molecular markers associated with sucrose concentration and sucrose content. The added genetic gain, compared with pedigree breeding, from marker-assisted recurrent selection (MARS) and double haploidy in corn will be examined. By computer simulation, selection schemes that combine MARS and double haploids will be designed and evaluated. From the results of simulation research, empirical evaluation of MARS and double haploid schemes will be conducted in conjunction with a seed company. Furthermore, evaluations of selection schemes will focus in gain per unit time and gain per unit cost, rather than gain per cycle. Simulations will be conducted towards the design and evaluation of full-sib selection schemes involving molecular markers, to achieve concurrent improvement in both sides (instead of only one side) of the heterotic pattern.

KEYWORDS: corn; plant breeding; dwarfism; sucrose; genetic markers; selection systems; poly haploids; hybrids; plant genetics; performance evaluation; sugar content; molecular biology; recurrent selection; brix; combining ability (genetics); population genetics; genetic mapping; heterosis; ethanol; biomass crops

PROGRESS: 2006/01 TO 2006/12
Colleagues and I finished one study and initiated three studies in 2006. First, Craig Sheaffer and I conducted the second (and last) year of our dwarf corn trials. Results from 2005 indicated that, compared with conventional corn, dwarf corn is 10 percentage points drier at harvest but is about 50% lower in grain yield. Dwarf corn has 10% higher predicted dairy-cattle milk yield per ton of stover, but 40% lower milk yield per hectare. Second, I initiated a study on the potential of corn as a sugar crop for ethanol production. Initial results indicated new and old maize hybrids vary in their sugar content in stalk juice. Third, Jianming Yu (Kansas State University) and I investigated the prospects for genome-wide selection for quantitative traits in maize. Unlike traditional approaches in marker-assisted selection, genome-wide selection does not require the identification of markers with significant effects on the trait. In simulation studies, we found that the response to genome-wide selection was 18 to 43% larger than the response to marker-assisted selection. We consider this a most important finding, and we are exploring ways to empirically compare genome-wide selection and marker-assisted selection. Fourth, Patricio Mayor (Ph.D. student) and I initiated a study on the use of double haploids in marker-assisted recurrent selection in maize. Selection gains from marker-assisted recurrent selection, based on F2 or double haploid progenies, will be compared with selection gains from conventional pedigree selection without markers.

IMPACT: 2006/01 TO 2006/12
Corn yields in the U.S. have increased at a rate of about 2% per year. This project focuses on finding new uses for corn and exploiting modern tools from the biosciences to breed corn more quickly and more efficiently. This research may therefore lead to expanded uses for the major crop in the U.S. and larger annual gains in corn productivity.

PUBLICATIONS (not previously reported): 2006/01 TO 2006/12
No publications reported this period

PROJECT CONTACT:
Name: Bernardo, R.
Phone: 612-625-6282
Fax: 612-625-1268
Email: bernardo@umn.edu