02357nas a2200205   4500008004100000245011700041210006900158260004300227300001000270490001400280520164800294653004301942653002401985653002202009653002402031653001502055653003002070100001602100856003502116       2007                        eng d00aDiversity of a disease resistance gene homolog in Andropogon gerardii (Poaceae) is correlated with precipitation0 aDiversity of a disease resistance gene homolog in Andropogon ger  aManhattan, KSbKansas State University  a1 -530 vMS Thesis3 a<p>Ecological clines often result in gradients of disease pressure in natural plant communities, imposing a gradient of selection on disease resistance genes. We describe the diversity of a resistance gene homolog in natural populations of the dominant tallgrass prairie grass, Andropogon gerardii, across a precipitation gradient ranging from 47.63 cm/year in western Kansas to 104.7 cm/year in central Missouri. Since moisture facilitates infection by foliar bacterial pathogens, plants along this precipitation gradient will tend to experience heavier bacterial disease pressure to the east. In maize, the gene Rxo1 confers resistance to the pathogenic bacterium Burkholderia andropogonis. Rxo1 homologs have been identified in A. gerardii and B. andropogonis is known to infect natural populations of A. gerardii. The spatial genetic structure of A. gerardii was assessed from central Missouri to western Kansas by genotyping with AFLP markers. Samples were also genotyped for Rxo1 homologs by amplifying an 810 base pair region of the leucine-rich repeat and digesting with restriction enzymes. We compared Rxo1 homolog diversity to AFLP diversity across different spatial scales. Genetic dissimilarity based on AFLP markers was lower than would have occurred by chance at distances up to 30 m, and different prairies were more dissimilar than would have occurred by chance, but there was not a longitudinal trend in within-prairie dissimilarity as measured by AFLP markers. Dissimilarity of the Rxo1 homologs was higher in the east suggesting the presence of diversifying selection in the more disease-conducive eastern environments.</p>10aAmplified fragment length polymorphism10aAndropogon gerardii10agenetic diversity10aLeucine-rich repeat10aPolyploidy10aSpatial genetic structure1 aRouse, M.N.  uhttp://hdl.handle.net/2097/517