Development and Preliminary Evaluation of a Hard Red Winter Wheat Recurrent Selection Base Population.

Recurrent selection is a population improvement strategy that is ideally suited to pre-breeding as it maximizes opportunities for genetic recombination and gene pyramiding; allows for shorter generation cycles and more rapid progress while avoiding yield or genetic diversity ceilings typical of backcrossing. Its effectiveness can be enhanced by using genetic male sterility and by supplementing phenotypic with marker-aided selection.  In order to facilitate pre-breeding efforts in the hard red winter wheat breeding program at NDSU, a highly diverse base population was established. Parents were assembled with emphasis on resistance to the major diseases, e.g. Fusarium head blight, leaf and stem rust, tan spot and the septoria disease complex. These sources contribute a wide range of native and exotic resistance and adaptation genes, most of which derive from either spring wheat or less cold-hardy winter wheat. A complex cross was developed, combining genes from approximately 100 diverse genotypes contained within four parental populations.  The Ms3 gene was simultaneously established within the hybrid population such that the final F₁ will segregate 1:1 for male sterility/ fertility. The intermediate and final hybrid populations were evaluated in an attempt to quantify the genetic diversity that it contains by employing phenotypic and/or marker-based evaluations of disease resistance. Leaf and stem rust, tan spot, and S. nodorum seedling evaluations were performed using the intermediate populations from the complex cross. In addition, marker analysis was done across ninety-six hybrid F₂ plants to detect existing disease resistance genes within the final pre-breeding population. Finally, a cluster analysis was done using 228 selected SNP markers that were applied to the winter and spring wheat parents and a sample of F₂ plants from the hybrid base population. The population constitutes a valuable resource that will be subjected to a first cycle of field planting and bulk selection in the fall of 2015.