Spectral Reflectance for Indirect Selection and Genome-Wide Association Analyses of Grain Yield and Drought Tolerance in North American Spring Wheat

The goals of this study were to evaluate the use of spectral reflectance indices (SRIs) in indirect selection of genotypes with superior agronomic performance and to identify chromosome regions that contribute to drought tolerance and yield potential in North American spring wheat (Triticum aestivum L.). A diversity panel with 250 elite lines was evaluated for various SR1s, grain yield, heading date, plant height, and grain volume weight under irrigated and drought-stressed field conditions for 2 yr (2012 and 2013) in Othello, WA. Analysis of variance across environments revealed that normalized chlorophyll-pigment ratio index (NCPI), normalized difference vegetation index (NDVI), and normalized water index-1 (NWI1) showed high genetic correlation (0.37-0.64) with grain yield, heritability, and efficiency of indirect selection. Population structure had lower effects on SRIs (<= 14%) compared with the agronomic traits (8-57% on whole grain protein). Association mapping using 19,967 single nucleotide polymorphism markers revealed 42 loci on 15 chromosomes that were associated with the SRIs in two or more field trials, 10 of which colocalized with phenology measurements and plant height. Grain yield shared quantitative trait locus regions with NDVI, NCPI, and NWI1. Lines with a greater number of SRI-favorable alleles showed higher grain yield (9-16%). Overall, this study highlights the utility of spectral reflectance technology to identify chromosome regions that contribute to yield and drought tolerance in North American spring wheat.