Isolation distances for minimizing out-crossing in spring wheat

Currently recommended isolation distances of 3 or 10 m for pedigreed seed production of spring wheat (Triticum aestivum L.) may not be sufficient for cultivars with high out-crossing (OC) rates. The detection of higher than expected OC rates in wheat has directed this research to reassess currently recommended minimum isolation distances. The objective of this study was to determine if increased isolation distances are needed for cultivars that exhibit higher than normal levels of out-crossing. In each of 2 yr, OC rates were determined for four Canadian spring wheat cultivars at each of 15 distances (0-33 m) from a blue aleurone pollen source. Cultivars were grown in rows perpendicular to the pollinator block to the north, south, west, and east. Target rows were replicated four times within each direction. Out-crossing in 'Katepwa' and 'Biggar' was not detected beyond 3 m. Cultivars 'Roblin' and 'Oslo' exhibited higher than normal OC at distances of up to 27 m. For Roblin and Oslo, an isolation distance of 30 m is recommended to mitigate OC-derived off-types in the subsequent generation of pedigreed seed.