Genetic analysis of self-fertilization traits in Nicotiana plumbaginifolia, a derivate of N. longiflora [abstract]

Abstract

N. plumbaginifolia evolved from N. longiflora and is characterized by a short corolla and the tendency to prior self-fertilize. N. longiflora is a dedicated out-crosser characterized by long, protandrous (male-first) flowers that exhibit little or no self-fertilization. In some native populations where these two species coexist, three morphs can be found (short, intermediate and long). Plants of intermediate characteristics were the subject of study because they showed traits of both N. plumbaginifolia (ability to prior self-pollinate) and of N. longiflora (flowers of mixed length). We are taking two separate approaches in order to observe the genetics behind the morphological differences. First, we selfed three different lines of intermediates (two from N. longiflora and one from N. plumbaginifolia) to determine if the intermediates were F1 hybrids and if morphology was determined by a single gene. If morphology was caused by a single gene, then we expected a 1:2:1 ratio in our selfed progeny. The maternal parent was known for each intermediate plant; however, the paternal source was unknown. If the ratio of the selfed progeny was not 1:2:1 then we know that there are most likely multiple genes determining morphology. After analysis of the morphological distribution in the selfed progeny, I believe that if these plants were hybrids, then they are so after many generations, which would explain the discrepancy in the morphological spectrum. Using family structured data we can identify by linkage analysis the quantitative trait loci involved in the changes to self-fertilization. We can also determine if the intermediates are actual hybrids, or if they evolved separately from one of the two species. The second approach that we took was that we chose ten parents representing all lineages in the population and crossed them to create F1 and F2 generations. We will then use the F2 generation for QTL analysis and create multiple CAPS markers to try to determine genetic differences between the morphs. We are currently working on CAPS markers and searching for genetic polymorphisms. In the future, we would like to be able to classify whether the intermediate morph is an actual hybrid of N. plumbaginifolia and N. longiflora, or if it evolved separately.