Expression of resistance against powdery mildew (Blumeria graminis f.sp. tritici) in bread wheat (Triticum aestivum)

Abstract

Blumeria graminis f.sp. tritici (Bgt) causes an important disease of wheat, the powdery mildew to which accessions TA1055 and TA1150 of Triticum turgidum L. ssp dicoccoides (T. dicoccoides) were resistant. These carry MlTd1055 gene for resistance to Bgt. The Fâ‚ hybrid plants obtained from crosses between ‘Chinese Spring (CS) ’ and T. dicoccoides were sterile or partially sterile. Overall, the mean number of BCâ‚ seed set was 1.43 seed/spike. Selfed seeds were harvested from 78 BCâ‚ plants grown to maturity. The levels of fertility were, 33.6% with TA1055 and 26.4% with TA1150. The chromosome numbers of the selfed seed from BCâ‚ plants ranged from 27 - 44. Fifty eight per cent of their BCâ‚ progeny had chromosome numbers between 40 and 42. The segregating of BCâ‚ plants fit a 1:1 ratio and BCâ‚Fâ‚‚ fit a 3:1 ratio for resistance to susceptibility supporting further the hypothesis of one dominant gene for resistance. Based on screening of two BCâ‚Fâ‚‚ lines carrying powdery mildew resistance derived from TA1055 and TA1150, it appeared that a new gene (MlTd1055) for powdery mildew resistance has been transferred to bread wheat Triticum aestivum. Bread wheat carrying this gene gave intermediate reaction types when inoculated with the tested mixed population of Bgt, while the T. dicoccoides parents were highly resistant to the mixed population of isolates.