Effect of Sm1 Gene Conferring Resistance to the Wheat Orange Blossom Midge On Durum Quality and Its Fine Mapping.

The orange wheat blossom midge (Sitodiplosis mosellana Gèhin) (OWBM) causes significant damage to wheat crops in western Canada. The OWBM larvae feed on developing wheat kernels causing shrivelled, cracked or deformed seed, resulting in reduction in grain yield, quality and crop grade. Sm1 confers resistance to OWBM by antibiotic properties against the OBWM larvae. Currently, no midge tolerant durum (Triticum turgidum L. var. durum) cultivars are available in Canada. The objective was to study the effect of the midge resistance gene on end-use quality in durum wheat using sister lines with and without the Sm1 gene. Six sister-line pairs and checks were grown at five locations as an RCBD with three replications in western Canada representing low, medium and high OWBM incidence. OWBM incidence and damage in each plot was assessed. Grain yield, grain protein, grain yellow pigment, test weight, kernel weight, falling number and gluten index were determined from each plot. Statistical analysis was done in SAS v 9 using PROC MIXED with genotypes and locations as fixed variables. Significant genotype x location interaction was observed for all traits and subsequent analyses were done on individual locations. Genotypes were a significant source of variation for grain yield and resistant genotypes had significantly higher grain yield in high OWBM level locations, while they were not significantly different at other locations. Resistant genotypes were not significantly different from susceptible genotypes for test weight, kernel weight, and grain protein.  The susceptible genotype group had significantly stronger gluten strength than the resistant group. No difference between groups was observed for falling number except at a low OWBM location, where the resistant group had significantly higher falling number than susceptible group. At all locations, genotypes that possessed the Sm1 gene had higher grain pigment.  Results suggest that presence of the Sm1 gene increased the grain pigment and reduced gluten strength. Efforts are on-going to fine map the Sm1 locus and study epistatic effects.