CYTOGENETICALLY MONITORED TRANSFER OF POWDERY MILDEW RESISTANCE FROM RYE INTO WHEAT

Powdery mildew, caused by the fungus Erysiphe graminis DC. ex Merat f. sp. tritici Fm. Marchal, is a serious disease of cultivated bread wheat, Triticum aestivum L. em Thell. About 20 powdery mildew resistance genes are known in wheat and most of them are used in cultivar improvement. However, many of these genes were overcome by the fungus and are no longer effective and therefore, new sources of resistance are continuously being sought. Recently, we reported a new source of powdery mildew resistance, preliminarily designated MIP6L, that was derived from the long arm of chromosome 6R of Secale cereale L. cv. Prolific. The aim of this study was to transfer MIP6L to a cytologically stable wheat-rye chromosome translocation. Here we report the transfer of MIP6L from a monosomic 6RL (6D) chromosome substitution Line by homologous recombination to a cytologically stable T6BS.6RL wheat-rye chromosome translocation. The powdery mildew resistance gene was designated Pm20. C-banding analysis was used to physically map Pm20 in the distal third of the recombined translocation chromosome T6BS.6RL(rec). The successful transfer of the resistance gene was verified by artificial inoculation with the powdery mildew fungus. Furthermore, a strategy for transferring additional useful genes from alien species to wheat is discussed.