Floret sterility and outcrossing in two spring wheat cultivars

A tendency for higher outcrossing potential in Canadian semidwarf wheat (Triticum aestivum L.) cultivars compared with tall Canadian cultivars has been postulated by breeders and seed growers. In the present study, the outcrossing potential of a semidwarf Canada Prairie Spring wheat (Triticum aestivum L.) cv. Cutler and a conventional height Canada Western Red Spring wheat, cv. Roblin was determined under controlled greenhouse conditions. Outcrossing of each cultivar was induced by applying moisture stress followed by exposure to pollen from a phenotypic marker stock, cv. P8901. In the controlled absence of external pollen, moisture stress significantly reduced seed set in both cultivars. Application of external pollen following moisture stress increased seed set significantly in Cutler and nonsignificantly in Roblin, and was associated with a higher level bf floret opening in Cutler. Outcrossing frequency was also assessed by analysing progeny seed (selfed or outcrossed) using acidic polyacrylamide gel electrophoresis of seed protein; RAPD markers and morphological phenotype, including height, awnedness, black chaff and time to maturity. All three assay techniques demonstrated a higher outcrossing frequency in Cutler than in Roblin under this protocol. The frequency of outcrossing in different parts of the spike wits also determined for both cultivars. In both cultivars the highest proportion of outcrossing was found in the mid-upper region of the spike, followed by the mid-lower region.