Genetic diversity of the DREB1 gene in Hordeum vulgare and Hordeum spontaneum

Abstract

Environmental stresses often disrupt and alter the growth of plants and their life cycles. This causes molecular responses to upregulate gene expression, inducing important stress responsive genes. Dispersal and continuous domestication of crop plants may cause a loss of genetic diversity that may be detrimental to these stress responsive genes. A population-based resequencing and phylogenetic analysis of the dehydration responsive element binding 1 (DREB1) stress responsive gene was used to determine its genetic diversity in three populations of wild and cultivated barley. Variation between China wild, China cultivated, and Middle Eastern wild populations were examined to understand gene-pool exchanges with the spread and development of barley cultivation. My results showed genetic differentiation among and within the three populations of barley by examination of nucleotide diversity (π), theta (per site) (θ), and number of haplotypes. Middle East wild-type and China wild-type were statistically significant with Fu and Li’s D and F tests however, China cultivated-type was not. It was found that the highest diversity occurred in Middle Eastern wild-type, with the second highest diversity value as China wild-type, and lowest diversity in China cultivated type. These results provide important observations about the domestication processes of crop plants like barley where selection processes may be detrimental to the survival of stress responsive genes. After this thesis was completed, some questions arose about sequence clarity and reliability, and how they affected alignment and phylogenetic analysis. These questions were analysed at the end of this thesis in an addendum (page 40).