Humans have used Brassicas for thousands of years as a source of food, energy and medical cures. Plant architecture, leaf form, and flower and fruit structure have evolved independently and multiple times in wild and domesticated Brassicas. Little is known about how these important and diverse groups of plants are related to each other. Integrating the knowledge about genetic relationships with morphological data will help to decipher the dynamics of evolution and plant domestication. The research goals for this study are to: (1) Understand the evolutionary relationships among Brassica crops and wild relatives (2) Examine the evolution of morphology (3) Relate morphological evolution with gene molecular variation
The proposed methods offer new and inexpensive ways to sequence multiple genes at once while simultaneously providing an innovative way to understand plant development. Graduate and undergraduates students will be trained on the methods developed here, including an online resource for the scientific community. An ?evo-devo? lab that takes advantage of college freshman?s familiarity with the grocery store Brassica oleracea (cabbage, broccoli, cauliflower, kale, etc.) will be implemented. Outreach to the public through the Columbia Center of Urban Agriculture (CCAU) is planned.
The crop Brassicas are some of the most spectacular examples of human domestication of plants and have often been referred to as the "dogs of the plant world." Common species and their grocery store varieties include: Brassica oleracea (broccoli, cauliflower, kale, kohlrabi, Brussel sprouts), Brassica rapa (vegetable turnip, Chinese cabbage), and Brassica napus (canola, rutabaga). Understanding the evolutionary relationships among these species and their wild relatives has been challenging given frequent hybridization among species, and genome doubling (polyploidy) events. We used DNA to understand the history of domestication (molecular phylogenies) and to elucidate the biogeographical origins and diversification times for the Brassica crops and their wild relatives in the tribe Brassiceae (in the mustard family, Brassicaceae). Our data suggest that the maternal genomes of the three diploid species are not closely related but separated by a 20 million years ago, much older than the previous estimate of 7.9 million years ago. Their lineages originated around the forming intersection between the Arabian Peninsula and Saharan Africa shortly after a whole genome triplication event (about 24 million years ago) shared by all members of the tribe. These results not only challenge previous hypothesis about their genetic proximity but also about their biogeographical origins. Our results also suggest that members of the lineage that gave rise to Brassica oleracea and Brassica rapa originated around 3 million years ago in the North Eastern Mediterranean, from where ancestors of Brassica oleracea spread through Europe and Brassica rapa to Asia. During the course of our research, we trained graduate and undergraduate students at the University of Missouri, as well as scientists visiting from other universities. For public outreach, we developed an "evo-devo" lab that takes advantage of college freshmanâ€™s familiarity with the grocery store Brassica oleracea (cabbage, broccoli, cauliflower, kale). This lab has been implemented in the general botany class that is taught at the University of Missouri. The goals of this lab are to understand the evolutionary process and the relationship between phenotype and genotype using the extraordinary morphological diversity of the cole crops (Brassica oleracea) that was artificially selected by humans during the domestication process. The results of our research were presented at research findings at several international conferences and local meetings at the University of Missouri.