US wheat breeders face increasing demands for improvements of grain quality and yield, and resistance to diseases, insects, and abiotic stresses to remain US wheat competitive in domestic and international markets. Marker-assisted breeding makes it possible to select for complicated traits and for several traits simultaneously. To facilitate implementation of marker-assisted selection (MAS) in wheat breeding, US Department of Agriculture (USDA) has established four Regional Small Grain Genotyping Centers across the country. The Genotyping Center in Kansas was the first center set up in 2002, and is responsible for marker analysis of hard winter wheat from six states that represent half of the wheat acreages grown in the USA. In the Genotyping Center, high-throughput DNA isolation and PCR amplification protocols have been established with capacity to isolate at least 1 000 samples of DNA and analyze 5 000 PCR daily. Quantitative trait loci (QTL) for resistance to leaf rust (Xu et al., 2005a; 2005b), Fusarium head blight (FHB) (Bai et al., 1999; Guo et al., 2003; Bai and Shaner, 2004; Zhou et al., 2002; 2004; Yang et al., 2005), pre-harvest sprouting (Chen et al., 2006), aluminum toxicity from various sources (Ma et al., 2005; Zhou et al., 2007) have been mapped and some of linked makers have been validated and used in MAS. Currently, about 50 SSR and STS markers linked to more than 20 genes/ traits are screened routinely on parents, segregating breeding materials of various generations, and elite lines from different regional nurseries for the breeders in this region. Marker-assisted backcross has been used to successfully transfer Chinese FHB-resistance QTL into US wheat backgrounds (Bai et al., 2006) and generated valuable near-isogenic lines for genetic research and new, adapted, FHB-resistant lines for breeding. Since last year, the genotyping Center has been actively involved in the Wheat Coordinated Agricultural Project (Wheat-CAP, http://maswheat.ucdavis.edu/). This is a national-wide applied genomics project involving public wheat breeders and geneticists from 25 states and four USDA Regional Genotyping Centers to develop molecular markers for important wheat traits, and implement molecular markers in wheat breeding. This project has developed 17 mapping populations from parents representing all US wheat classes, and is mapping new QTL for pest resistance, agronomic and quality traits using microsatellite and SNP markers (Soria et al., 2007). In the first year, Kansas genotyping Center alone analyzed more than 40 000 marker data points of breeding materials from participating HWW breeding programs. After 4-years Wheat-CAP is completed, all HWW cultivars released from the Great Plains will involve molecular marker work provided by the Genotyping Center.
Genotyping center Wheat Molecular marker Marker-assisted selection
USDA-ARS, Plant Science and Entomology Research Unit, Manhattan KS, USA Dept of Plant and Soil Science, Oklahoma State University, Stillwater,OK, USA Dep. of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, USA Dept of Soil and Crop Sciences, Colorado State University,Fort Collins, CO, USA Dept, of South Dakota State University, Brooklyn, SD, USA Dept. of Agronomy, Kansas State University, Manhattan, KS, USA Texas A & M Agricultural Research Station, Amarillo, TX, USA