Exploration of Genes Controlling Grain Yield Heterosis in Hybrid Wheat (\u3ci\u3eTriticum aestivum\u3c/i\u3e L.) Utilizing 3ʹ RNA Sequencing

The implementation and future success of hybrid wheat (Triticum aestivum L.) is impacted by breeders’ inability to create consistent high yielding, high heterosis hybrids. This research addresses this problem by conducting an exploration of transcriptomes from hybrids and parent lines to determine what genes are active in heterotic or non-heterotic hybrids and how their level of expression can explain the phenotype of grain yield heterosis. Using hybrids that showed positive mid-parent heterosis (MPH), classified as heterotic in our study, and negative or no difference MPH hybrids, classified as non-heterotic, differentially expressed genes (DEGs) potentially related to heterosis and hybrid yield response can be identified. Differential gene expression analysis found that more genes are differentially expressed in the non-heterotic hybrid to parent comparisons than in the heterotic hybrid to parent comparisons. Another important aspect of conducting a transcriptome study is adequately preserving the RNA for extraction and sequencing. Previous work has used liquid nitrogen to preserve samples taken out in the field, but this is dangerous and cumbersome. RNAlater® has been used as an alternative to liquid nitrogen but is not as consistent at preservation compared to liquid nitrogen. Another study to investigate this problem was conducted by sampling leaf and immature kernels from wheat, storing the samples at two temperatures for up to six months, extracting the RNA, and testing the quality parameters associated with using RNA for sequencing. The results showed that the lower storage temperature had a negative impact on the parameters while storage time only negatively affected the purity. Both studies can be applied to research conducted on the transcriptome of wheat and allow for differences to be detected to explain heterosis. Advisor: P. Stephen Baenzige