A Recombinant 1RS.1BL Chromosome with Interstitial Wheat Segments in the Sec1 and Glu-B3 Regions Is More Susceptible to Drought Than the Intact 1RS.1BL Chromosome.

The 1RS.1BL translocation from rye increases drought tolerance in wheat but also reduces breadmaking quality. In an effort to eliminate the quality defects associated with the 1RS arm, a recombinant 1RS arm, hereafter designated 1RS-MA, was engineered to carry interstitial wheat segments in the Sec1 (dough stickiness) and Glu-B3 regions (gluten strength). The objective of this study was to test if the beneficial effects of the 1RS chromosome on drought tolerance were retained in the 1RS-MA chromosome.  Two pairs of near isogenic lines (NILs) were developed for the 1RS.1BL and 1RS-MA.1BL chromosomes in the drought susceptible varieties Hahn and Attila. Isogenicity of the lines was confirmed using an iSelect Illumina platform for 9000 wheat SNPs (>99.5% similar). Replicated field trials were performed between 2009 and 2011, in which the NILs were characterized for yield and water status, using both Canopy Spectral Reflectance (CSR) and carbon isotope discrimination (CID). In all experiments, the lines carrying the complete 1RS chromosome showed higher yield and higher plant water content than those carrying the 1RS-MA chromosome. In 2011, trials were performed with and without irrigation and a significant interaction (P < 0.0001) was detected between genotype and irrigation treatments. These results indicate that the yield and plant water content differences between the NILs were affected by the irrigation treatments. These studies also showed that the differences in all traits were more significant in the Hahn background than in the Attila background, suggesting that the effect of the 1RS chromosome on drought tolerance is influenced by the genetic background. Our results indicate that rye gene(s) in the vicinity of Sec1 and/or Glu-B3 confer drought tolerance, a trait of critical importance in the face of increasing climate variability. We have developed recombinant lines carrying each of these segments separately to determine more precisely the location of the gene(s) conferring drought resistance.