Using Canopy Spectral Reflectance for Mapping Drought Resistance from a Rye Chromosome Arm Introgression in Common Wheat.

The translocation of the short arm of rye (Secale cereale L.) chromosome one (1RS) onto wheat (Triticum aestivum L.) chromosome 1B (1RS·1BL) is used in wheat breeding programs worldwide due to its positive effect on yield, particularly under abiotic stress. Unfortunately, the translocation is also associated with several quality defects. To mitigate the negative effects of this translocation a derived 1RS line carrying proximal (^P) and a distal (^D) interstitial wheat segments (henceforth, 1RS^WPD) was previously developed, which we introgressed into two genetic backgrounds. Canopy spectral reflectance (CSR) was used in conjunction with yield and physiological traits and showed that lines with the 1RS translocation had significantly higher yield and better canopy water status than the 1RS^WPD NILs under both well watered and reduced irrigation conditions, indicating one or both of the regions are responsible for the difference in performance. We intercrossed the NILs and generated two additional NILs, carrying either the distal (1RS^WD) or the proximal (1RS^WP) wheat segment. Using CSR, we showed that the lines which contained rye chromatin in the distal region (1RS and 1RS^WP) had better field performance than lines containing wheat chromatin in the distal segment (1RS^WPD and 1RS^WD). This result was confirmed in following field trials where yield and physiological traits were also measured. Results from physiological measurements suggest that the 1RS lines have increased access to stored soil moisture. We conclude that the distal region of the 1RS arm replaced in the 1RS^WD genotype carries the beneficial allele(s) in both well watered and water stressed environments.