Orange Wheat Blossom Midge

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Varietal variation for resistance to orange wheat blossom midge (owbm) has been observed in material from different countries. However, there have been very few studies of the genetics of these resistance sources. The most significant study demonstrated that resistance in Canadian material was conditioned by a single major gene, termed Sm1, on wheat chromosome arm 2BS. Additionally, a PCR based molecular marker was developed (Wm1) which was linked to the resistance gene and could be used for marker assisted selection in crosses involving the resistance source. However, there is little information on whether European sources of resistance carry Sm1, if the Wm1 marker is diagnostic in European germplasm or whether there are other, independent, resistance genes.

We have recently shown that three resistant UK varieties carry Sm1 as a major source of owbm resistance (Ellis et al. 2009). We also showed that marker Wm1 is associated with Sm1 resistance in these related pedigrees, but that it is not diagnostic across a more extensive set of UK germplasm (i.e. some susceptible varieties carry the Wm1 diagnostic band; Oakley et al. 2005). As part of a parallel project (Simmonds et al. 2008), we established colinearity between wheat, rice, and Brachypodium across the complete Sm1 interval (Wm1-Xgwm210; Thomas et al. 2005). This allowed us to recently develop over 20 additional markers across this 2BS region.

We now propose to use this knowledge to identify and molecularly characterize the sources of owbm resistance in French wheat varieties. The objectives of the work were to:
a) Identify better markers for Sm1 by genotyping markers across the 2BS region for 96 varieties and phenotyping 96 varieties across France and UK (2011 and 2012)
b) Identify additional OWBM resistances different from Sm1 by using the information from above and mapping additional resistances using available DH populations.

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