F2 hybrid HEAR agronomic and seed quality studies

Canada is the world's largest producer of spring habit HEAR cultivars (McVetty et al., 1991). The currently grown HEAR cultivars, MillenniUM 03, Red River 1826 and Red River 1852 are open pollinated population cultivars. Even though there is no wholly adequate explanation to describe the phenomenon of hybrid vigor or heterosis, the seed yields of HEAR hybrids far exceed those of open pollinated population HEAR cultivars/strains. They also demonstrate greater vigor and better disease resistance. Hybrid cultivars/strains have many other advantages over open pollinated cultivars/strains such as larger seeds, enhanced oil and protein contents and superior agronomic performance. They produce bigger plants with more extensive root systems able to scavenge nutrients and moisture better. Recent studies have shown that crosses between different HEAR cultivars/strains can result in 40 to 100% high-parent heterosis for seed yield. For this study two different types of HEAR hybrids were used including Conventional F2 HEAR hybrids and F2 Roundup Ready HEAR hybrids. These hybrids originated from crosses of genetically and geographically distinct HEAR cultivars/lines (parents). Seven of the twelve parental lines used in this study were HEAR strains developed by the University of the Manitoba (UM) and the rest were European (EU) strains. Adequate F2 HEAR hybrid seed was produced to assess the hybrids and parents in six environments in Manitoba during 2006 and 2007. All entries in all trials had agronomic parameters assessed during the growing season including vigor, days to flower, days to maturity, lodging, plant height and seed yield. After harvest, six seed quality characteristics including oil concentration, protein concentration, sum of oil and protein concentration, meal protein concentration, erucic acid concentration and glucosinolate concentration were assessed in this study. Agronomic and seed quality studies in F2 HEAR hybrids will help characterize a novel approach to using HEAR hybrid seed efficiently. Three estimates of heterosis, mid-parent, high-parent and commercial heterosis for each F2 HEAR hybrid combination were calculated. As all F2 HEAR hybrids showed higher vigor than their parents, differences between hybrids and parental strains/cultivars were easily visually distinguishable in the F2 HEAR hybrid field trials. Conventional F2 HEAR hybrids displayed high-parent heterosis estimates for seed yield of up to 75%, mid-parent heterosis for seed yield of up to 91% and commercial heterosis for seed yield of up to 56%. Furthermore, F2 Roundup HEAR hybrids displayed high-parent heterosis estimates for seed yield of up to 76%, mid-parent heterosis for seed yield of up to 97% and commercial heterosis for seed yield of up to 53%. The levels of heterosis for seed yield observed in this study were half or more of the heterosis levels observed for the corresponding F1 HEAR hybrids. The levels of heterosis observed were sufficient to warrant further study of the use of F2 HEAR hybrids. In this study, F2 HEAR hybrids were much taller and had significantly better lodging resistance than their parents in all field trials. Conventional F2 HEAR hybrids displayed lower protein concentration and higher oil concentration than their parents. In contrast, F2 Roundup Ready HEAR hybrids displayed higher protein concentration and lower oil concentration. These two hybrid types were cross progeny from genetically distinct pools, so these differences were most likely genetics related.