Out-crossing rates for 10 Canadian spring wheat cultivars

The genetic purity of pedigreed wheat seed can be compromised by inter-cultivar cross-pollination. Common wheat (triticum aestivum L.) is assumed to be highly self-pollinated, an assumption that has not been verified for more recent western Canadian spring wheat cultivars. This field study was designed to estimate the outcrossing (OC) rate in three market classes of spring wheat in each of 2 yr and to determine whether OC rates were associated with specific spike characteristics. Highest OC rates were detected for the cultivar Oslo (6.05%) followed by Rongotea (2.30%), Roblin (1.43%), Wildcat (1.35%), Biggar (1.05%) and Glenlea (0.95%). In contrast, Katepwa and CDC Makwa had OC rates of 0.38 and 0.30%, respectively. The cultivars Oslo, Columbus, Roblin and Glenlea tended to have lower iodine pollen viabilities. Of those four cultivars, three had higher-than-average OC rates. No single spike characteristic was correlated with OC rate. However, the cultivars Oslo, Wildcat and Glenlea had high OC rates, low pollen staining and spikes which tapered at the extremeties. Furthermore, cultivars with higher OC rates tended to have a greater degree of spikelet opening at anthesis. The high levels of OC observed in this study could result in obvious off-types if morphologically diverse cultivars were grown in adjacent pedigreed seed fields. The current 3 to 10 m isolation distance for pedigreed wheat seed production may not be enough to ensure that OC is minimized.