Relative performance of four midge-resistant wheat varietal blends in western Canada
Orange wheat blossom midge, Sitodiplosis mosellana (Géhin), causes significant yield losses to spring wheat in western Canada in severe infestations. To mitigate losses, midge-resistant wheat varietal blends, consisting of cultivars carrying the Sm1 midge resistance gene and 10% interspersed midge susceptible refuge, have been made available to farmers. To test their performance relative to conventional midge-susceptible cultivars, four varietal blends were grown during four consecutive years, at eight locations in the provinces of Manitoba Saskatchewan and Alberta, in comparison to four conventional, midge-susceptible cultivars. Midge damage was higher in 2007 and 2010 than in 2008 and 2009. In general, the varietal blends, as a group, yielded more grain than the susceptible cultivars, especially when grown in environments with high midge pressure (5.5 - 35% seed damage). In environments with low midge pressure (0 – 2.6% seed damage), the varietal blend average yield advantage was smaller but still significant, indicating that some of the varietal blends had additional superior attributes, in addition to midge resistance.
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