Analyse und Integration wirksamer Mehltauresistenzen in Triticale

Increasing triticale acreages in Middle Europe stimulated the adaptation of powdery mildew populations to the race-specific resistances of most recommended varieties. As a consequence only a few varieties remained resistant after the first epidemics emerged in 2004 in Germany. Our findings indicate that powdery mildew of triticale most probably developed from wheat mildew. The triticale mildew population in Germany is highly diverse as shown by an analysis of 366 isolates from the main growing areas. In seedling tests with these 366 isolates only ‘Grenado’ was completely resistant among the currently registered triticale varieties. A screening of 826 preselected triticale breeding strains showed that 8% of this material has been completely resistant to four highly virulent isolates. In the field, 86% of these triticale strains were highly resistant after mildew inoculation indicating a combination of effective seedling and adult-plant resistance. Our aim is to characterise some of these resistances and to make them available for the breeders in future. The effects of known resistance genes from wheat could not be predicted when incorporated in primary triticale, i.e. resyntheses from wheat x rye. Obviously, the rye genome had a high impact on the resistance level of triticale. Indeed, a resistance gene from the triticale strain JKI.5015 could already been localized on rye chromosome 6RL by SSR markers. The high diversity of powdery mildew populations is a clue that newly detected race-specific resistances might be effective only for shorter periods. On the long run, breeders should combine them with effective adult-plant resistances to select for triticale varieties with durable resistance.