QTL Analysis for High Yield Protein Content Genes in a Triticum aestivum RIL Mapping Population.

Increasing grain protein content (GPC) is an important objective of wheat (Triticum aestivum) breeding programs. However, direct selection for grain protein is limited by the negative correlation between yield and GPC. With the objective of finding genes for high GPC we developed a mapping population of 96 recombinant inbred lines that was obtained by crossing Klein Proteo and Klein Chajá, both Argentinean varieties; the first with high GPC and the second with low GPC. Using an iSelect Illumina platform for 9000 wheat SNPs, we mapped 2,698 SNP and combined them with 108 SSR markers. The population was evaluated in field experiments in Davis, CA in 2011 (three replications) and 2012. Two QTL on chromosome arms 1BL and 4DS were consistent both years. The high protein allele for the 4DS QTL was contributed by K. Proteo, but co-segregated with a QTL for lower yield. Both QTL are likely the effect of the Rht-D1 gene that segregates for plant height in this population and is at the peak of both QTL.  As expected, semi-dwarf lines have higher yield and lower GPC. The high protein allele for the 1BL QTL was contributed by K. Chaja but it co-segregated with a consistent QTL for stripe rust resistance (both for severity and infection type). High levels of stripe rust infection are known to reduce GPC. Other QTL for GPC were detected but they were not consistent between years. In summary, the two consistent QTL for GPC seem to be pleiotropic effects of major genes and therefore, might not be useful for improving GPC. Fortunately, the consistent 1BL QTL for stripe rust resistance might provide a useful tool for wheat breeding programs to control this devastating disease. This population was highly polymorphic and also provided a valuable high-density genetic map integrating SNP and SSR markers.