Gideon Marais, Bradley Bisek and David Cookman, North Dakota State University, Fargo, ND
A recurrent mass selection (RMS) pre-breeding program is being implemented to facilitate development of improved breeding parents with high levels of winter-hardiness coupled with effective resistance against major diseases such as Fusarium head blight, leaf and stem rust, tan spot and the septoria complex. The breeding method is ideally suited to this purpose as it does not impose a yield ceiling or limit genetic background diversity as is typical of backcrossing. It furthermore maximizes opportunities for genetic recombination and gene pyramiding. Execution and effectiveness of a RMS program can be greatly enhanced with the use of genetic male sterility; incorporation of marker-aided selection and the use of generation acceleration methodologies. A highly diverse pre-breeding base population is being established through a complex cross that involves ± 110 diverse genotypes contained within five populations. These include a range of native and exotic resistance and adaptation genes, most of which derive from either spring wheat or less cold-hardy winter wheat from the southern United States. While making the cross, the Ms3 (dominant male sterility) gene has been incorporated within the hybrid population such that the final F1 will segregate 1:1 for male sterility/ fertility. The final F1 will be randomly intercrossed twice to ensure full dispersal of the genes before the onset of selection. Male fertile plants will be inbred and F4-derived F5rows will be selected in the field to obtain male parents (F6) for the next crossing cycle. An accelerated single seed descent (SSD) inbreeding strategy is being developed with the ultimate aim to achieve three generations of winter wheat per year. To do this, plants are being stressed (small soil volume, extended daylight hours, elevated temperature); prematurely harvested and the seed dried and stored at higher temperatures to prematurely break seed dormancy.