Genetic Analysis of Natural Variation in the Control of Flowering Timing and Inflorescence Architecture in Brassica rapa

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PI: C. Robertson McClung (Dartmouth College)Co-PIs: Richard M. Amasino (University of Wisconsin), Cynthia Weinig (University of Minnesota)The geographic range of species can be broad, and this is particularly true among domesticated species that are widely cultivated. Crop species encounter widely differing environments, including variable daylength and temperature, across their latitudinal ranges. In many plant species, including Brassica rapa, daylength modulated by the circadian clock strongly affects flowering time. In addition, both flowering time and clock function are influenced by ambient temperature. There is considerable natural variation to the daylength response, the circadian clock, and temperature responsiveness, and this genetic variation undoubtedly contributes to the ability of these species to thrive in diverse environments. It is important to extend the study of these complex genetic interactions to the environments experienced by crop plants, because the genetic mechanisms that underlie flowering time likely interact with the environment and determine the latitude over which a crop can be cultivated. The Brassica crops offer an especially attractive system. First, Brassica is closely related to Arabidopsis, which means that this model system offers a powerful information base to support such studies. Second, the Brassica species offer enormous diversity in morphology: B. rapa is cultivated for seeds, vegetables, and storage organs, and the cultivated types represent only a fraction of the diversity in the genus. This project will evaluate B. rapa natural variation in circadian clock function, flowering time, and flower size and shape in response to daylength and temperature. In addition, the contributions of this variation to the ability of B. rapa to thrive across a broad environmental range will be studied. Finally, this project will develop a mutagenized B. rapa population and laboratory exercises to use this population for the teaching of genetics for K-12 and undergraduate education.Broader Impacts: This project will shed new light on fundamental questions and has the potential to add value to Brassica crops (representing over $1 billion/yr in value) in terms of manipulation of flowering time and daylength responses. This project also offers educational opportunities at the undergraduate, predoctoral and postdoctoral levels in quantitative molecular and classical genetic analysis. In addition, this project will develop rapid-cycling B. rapa mutants as an educational resource to teach classical, molecular, and biochemical genetics at the K-12 and undergraduate levels. This will expand the Wisconsin 'FastPlants' program which is a resource that has already gained widespread acceptance in the classroom. Thus, the outreach aspects of this project should be manifest on a national level. Access to data generated in this project will be accessible through a project website. Germplasm generated will be available on request as well as through the Arabidopsis Biological Resource Center.