Development of Genetic and Genomic Resources for Hybrid Wheat (Triticum Aestivum L.) Development in the US Great Plains

Hybrid wheat offers promises to break the yield stagnation in global wheat productivity. Studies were conducted in Texas, Nebraska and the International Maize and Wheat Improvement Center (CIMMYT) in Mexico to develop genetic and genomic resources needed for development of hybrid wheat. Hybrids developed from elite winter wheat lines of the University of Nebraska Lincoln and Texas A&M University wheat breeding programs were evaluated across Texas in 2016 and 2017. The grain yield data was used to estimate heterosis and combining ability of parents. The heterosis estimates were promising with commercial heterosis ranging from -78.3 to 20.4% in 2016 and -32.9% to 6.2% in 2017. General combining ability (GCA) variance was significantly higher than zero whereas specific combining ability (SCA) variance was not. A set of hybrids with high to low yield potential were advanced to F2 stage evaluation. They were planted in six locations across Texas and Nebraska in 2017 and 2018 to test the possibility of using F2 yield and heterosis in supplementing selection decisions of F1 hybrids. The hybrids exhibited positive heterosis at F2 stage as well. A comparison of heterosis estimates between F2 and F1 stage revealed that F2 heterosis was highly indicative of superior F1 performance. A population of 299 recombinant inbred lines (RILs) were developed at CIMMYT to map fertility restoration and develop molecular markers for marker assisted selection (MAS) of Rf genes. The RILs were characterized for their fertility restoration capacity in a series of field trials across three locations in Mexico. The results indicated the presence of known fertility restorer genes Rf3 and Rf4 and a minor effect quantitative trait locus (QTL) in the restorer line. Kompetitive allele specific PCR (KASP) assays were developed using markers tightly linked to major gene Rf3 and validated in an independent population. The parents with GCA estimates and hybrid yield can be used to develop heterotic pools whereas F2 testing provide a cost effective way of evaluating hybrids in replicated trials. The KASP assays developed can be used for MAS of Rf genes. The genetic and genomic resources developed in these studies can serve as valuable assets in developing wheat hybrids for US Great Plains