Genetic analysis of powdery‐mildew resistance of a winter‐wheat line, RE714, and identification of a new specific‐resistance gene

The winter‐wheat line RE714, resulting from an intergeneric cross between Aegilops squarrosa and Triticum dicoccum , and implying a sister line of ‘Roazon’ (VM4) in its genealogy, was obtained in order to increase the genetic diversity for disease resistance. The aim of this study was to identify and characterize the powdery‐mildew‐resistance gene(s) present in this line at the seedling stage on detached leaves. The comparison of the reaction of the RE714 line and of differential hosts to 24 Erysiphe graminis. f.sp. tritici isolates indicated that only Pm4a, Pm4b and/or Mlar genes could be present and that a new resistance factor, different from all known mildew‐resistance genes, was present in this line. The powdery‐mildew reactions of segregating F 2 populations produced evidence that RE714 carries the Pm4b allelic form and a recessive new resistance gene, tentatively designated mlre. While Ae. squarrosa was resistant to most isolates, T. dicoccum was specifically attacked by REV 14‐virulent isolates and was therefore assumed to be the donor of mire. The VM4 parent was confirmed as the Pm4b donor.