| The domestication of cultivated plant species from their wild ancestors represents one of the most important events of human history, allowing early humans access to greater food resources than were previously available. Cultivated Asian rice, Oryza sativa, represents the world's most important agricultural species and has fed more people since the time of its domestication than any other crop. Using an analysis of nuclear DNA sequences from the p-VATPase region, the phylogeography of the wild ancestor of rice, Oryza rufipogon, was examined in order to test the hypotheses of single or multiple domestication of O. sativa. Results show that the two major subspecies of cultivated rice, O. sativa indica and O. sativa japonica, as well as a third rice type, O. sativa indica var. Aus, arose from independent domestication events from different geographic regions of South and Southeast Asia.; Oryza sativa hybridizes with its wild ancestor, O. rufipogon, and these events have been hypothesized to result in the major weed of rice cultivation, weedy red rice. Hypotheses for the origins and occurrence of weedy rice in US rice cultivation were tested using a combination haplotype network and genetic distance analysis. Results suggest that US weedy rice formed via hybridization between cultivated and wild rice in Asia with subsequent transfer to the US. However, hybridization between US rice cultivars and weedy rice is ongoing as well as hybridization between weedy rice.; An important phenotypic trait that shows variation in cultivated rice is aluminum toxicity. Aluminum toxicity is a leading abiotic stress affecting crop yields worldwide. Cultivated and wild rice grow in acid-aluminum soils of Southeast Asia and are an excellent system for evaluating the phenotypes and mechanisms of aluminum resistance. Three traits associated with aluminum tolerance were examined for their roles in the aluminum tolerance response of rice. Results indicate that O. sativa japonica is inherently more tolerant that O. sativa indica, reflecting their independent domestications. Furthermore, the mechanisms responsible for aluminum tolerance are likely different in rice than those utilized in other crops. |
