Map-Based Cloning Of SKr, a Major QTL Involved In Crossability Of Wheat With Rye

Although wheat can be crossed with a wide range of related species, most adapted bread wheat varieties are non-crossable because of the failure of pollen to fertilize the ovary, thereby reducing the possibilities to reintroduce genetic diversity in the elite wheat gene pool through intra- and interspecific crosses. Only ancient wheat and landraces are crossable, in particular those originating from the Asian gene pool. Inhibition to crossability between wheat (Triticum aestivum L.) and related species such as rye (Secale cereale L.) is genetically controlled and dominant. A number of QTL have been identified to date, including Kr1 on chromosome 5BL and SKr, a strong QTL mapped at the distal end of chromosome 5BS. Fine mapping of SKr was initiated using a HIF population of 223 individuals derived from a cross between the French variety Courtot (non crossable with rye) and the variety Chinese Spring (crossable). Using shotgun sequences from Chinese Spring BAC clones identified by chromosome walking as well as the homologous relationships with rice and barley, 9 markers and 5 candidate genes were identified in a genetic interval of 0.6 cM spanning SKr. SSR markers cosegregating with Skr were developed to support primary triticale breeding programs. Finally, more than 200 lines from various gene pools (European, Asian) have been phenotyped and genotyped to perform association studies with the candidate genes and for analyzing the spatio-temporal origin of crossability. An update of the project will be presented.