Floret sterility and outcrossing in two spring wheat cultivars

A tendency for higher outcrossing potential in Canadian semidwarf wheat (Tr iticum aestivum L.) cultivars compared with tall Canadian cultivars has bee n postulated by breeders and seed growers. In the present study, the outcro ssing potential of a semidwarf Canada Prairie Spring wheat (Triticum aestiv um L.) cv. Cutler and a conventional height Canada Western Red Spring wheat , cv. Roblin was determined under controlled greenhouse conditions. Outcros sing of each cultivar was induced by applying moisture stress followed by e xposure to pollen from a phenotypic marker stock, cv. P8901. In the control led absence of external pollen, moisture stress significantly reduced seed set in both cultivars. Application of external pollen following moisture st ress increased seed set significantly in Cutler and nonsignificantly in Rob lin, and was associated with a higher level bf floret opening in Cutler. Ou tcrossing 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, bl ack chaff and time to maturity. All three assay techniques demonstrated a h igher outcrossing frequency in Cutler than in Roblin under this protocol. T he frequency of outcrossing in different parts of the spike wits also deter mined for both cultivars. In both cultivars the highest proportion of outcr ossing was found in the mid-upper region of the spike, followed by the mid- lower region.