Characterizing the genetic architecture of fitness related traits in an annual grass, Avena barbata.

摘要

I conducted a series of experiments designed to characterize the phenotypic differences between two genetically distinct ecotypes of Avena barbata, that inhabit mesic and xeric habitats, and their F6 inbred line progeny in both common garden greenhouse and natural environments. In the greenhouse environment, the two ecotypes differed for a suite of quantitative traits including fitness. These differences translated into a substantial release of variation among the F6 lines, with broadsense hertitabilities for most traits exceeding 50% and the range of phenotypes exceeding both parental ecotypes. There were constraints to the release of trait variation manifest as strong genetic correlations among traits, including flowering time and spikelet production. A genetic linkage map of the wild oat genome was constructed by genotyping 180 F6 inbred lines with 133 Amplified Fragment Length Polymorphism (AFLP) markers. The map spanned 640 cM, or approximately 40%, of the genome and consisted of 21 linkage groups. Quantitative Trait Loci (QTL) were identified for all traits in the greenhouse except one. Each trait had at least one QTL with additive effects in the opposite direction than expected, thus providing a mechanism for transgressive segregation. Clusters of QTL were found on several linkage groups indicating pleiotropic loci underlie the genetic correlations among traits. The QTL could account for approximately 50--60% of the genetic variation indicating a relatively few loci account for a substantial amount of the variation among traits. In the native environments, the effects of epistasis overshadowed the additive effects for fitness and plant height. Growth and fitness were poorly genetically correlated across field environments, and the greenhouse, indicating the presence of loci with environment specific effects. Few QTL were identified for fitness in the field, and they mapped to locations devoid of QTL for fitness in the greenhouse.