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Developing Hybrid Wheat for the Great Plains: Addressing Hybridization, Heterosis, and Heterotic Pool Development
The rate of yield gains in wheat needs to double to meet the needs of a growing global population. One means to meet this demand is by developing high-yielding wheat hybrids for the wheat-growing region of the Great Plains. The objectives of this study were to produce and evaluate ~650 hybrids developed using a chemical hybridizing agent (CHA) as a full diallel of 26 parents. The first aspect of the project was to evaluate the efficacy of a CHA in producing hybrids. Using data collected on the CHA-treated plots, we can identify if and to what extent the hybrids are pure. Isolated heads from CHA-treated wheat plants were used to obtain counts of self-pollinated seed after CHA application. The data was modeled first with threshold models then additionally evaluated using Gaussian, transformation, Poisson, and Negative Binomial linear mixed models, as well as zero-modified mixed models. The fits and estimates from these models were compared and revealed that zero-modified models can separate the proportion of completely sterile heads from the seed count if not completely sterile, as originally determined using threshold models. Biologically, these data allow breeders to make selections on female parents early in the breeding cycle and help to build heterotic pools for hybrid wheat. Hybrids were planted in an augmented design at three locations in Nebraska (Alliance, Lincoln, and North Platte) in 2016 and 2017 with replicated checks and parents. The grain yields of these trials were spatially corrected using the experimental design and adding complex covariance structures where needed. Using these corrected means, there was not a carryover effect of CHA treatment on the hybrids. Reciprocal crosses were compared and shown to have an effect only about 15% of the time. Mid- and high-parent heterosis was measured to evaluate hybrid performance against that of the parents and was as high as 24% for some hybrids. The ranges were wide and indicated potential for breeding for heterosis. Finally, combining abilities of the parents and crosses showed that general combining ability is most helpful for evaluating hybrids. The general combining abilities can be leveraged in future research and in developing heterotic pools.
Easterly, Amanda Christine, "Developing Hybrid Wheat for the Great Plains: Addressing Hybridization, Heterosis, and Heterotic Pool Development" (2017). ETD collection for University of Nebraska - Lincoln. AAI10682750.