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DETERMINING THE BREEDING VALUE OF PRIMARY SYNTHETIC BREAD WHEATS FOR INCREASED GRAIN YIELD
Long term domestication and breeding of bread wheat increased grain yield, but this increase has slowed down, in part, due to the reduction of genetic variation. To introduce new genetic diversity from wheat progenitors, Aegilops tauschii (Coss.) Schmalh and durum wheat (Triticum. turgidum L. subsp. durum) into the bread wheat gene pool, 20 spring bread wheat parents (BWPs) were crossed to 33 synthetic hexaploid wheat parents (SYNPs) at the International Wheat and Maize Improvement Center. Single spike descent was used to develop 97 synthetic derived populations (SDLs). Yield trials were conducted under irrigated (IRRI), drought (DRO) and heat (HEAT) stress environments from 2011 to 2014 in Ciudad Obregon, Mexico. Genomic estimated breeding values (GEBVs) of genotypes were estimated using a genomic best linear unbiased prediction model with markers. The result of this study addressed that First, SYN lines and SDLs were more diverse than BWPs for A, B and D genomes confirming that the SYN lines are promising genetic resources of novel diversity. Second, grain yield (YLD) increases in SDLs were more frequent under DRO and HEAT stresses and were predominantly in SDLs from first back-cross derived lines. The SYNPs GEBVs for YLD were less negative under DRO and HEAT stresses than those under IRRI indicating SYN lines could increase YLD under stresses. Under DRO and HEAT, the SYNPs increased plant height (PLH) and days to maturity (DMA). Higher PLH increased YLD but longer DMA decreased YLD. Under IRRI, 29% of SDLs had higher thousand kernel weight (TKW) than BWPs (P < 0.05) indicating SYNPs were valuable genetic resources for TKW. Third, a genome-wide association study using SDLs identified associated QTL with TKW, PLH, YLD and DMA and SYNP alleles of these QTL retained in SDLs and increased trait values. Our finding confirmed that SYN lines had positive alleles that can be easily introgressed into cultivated wheat to improve agronomic and phenological traits especially in stress conditions. Therefore, SYN lines should be used in breeding programs to expand the genetic diversity for agronomic traits but selection against undesirable phenology is required to realize the benefit of the novel genetic variation.
Drought stress; Genetic diversity; Genomic estimated breeding value; Genomic prediction; Grain yield; Synthetic hexaploid wheat; Agriculture; Plant sciences
Sorrells, Mark Earl
Bonnett, David; Jannink, Jean-Luc; Yu, Haiyuan
Ph. D., Plant Breeding
Doctor of Philosophy
dissertation or thesis