YIA-PGR: Molecular Evolutionary Genetics of Crop and Weed Responses to Crowding

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PI: Cynthia Weinig (University of Wyoming)CoPI: Julin Maloof (University of California-Davis)Domestication of wild species is characterized by changes in diverse traits, including plant architecture, fruit and seed morphology, fruit dispersal, and the timing of developmental events. These changes result from human selection to increase yield. Changes in environmental responses are also important in this regard. For instance, higher planting densities could increase yield in many crop species, but densities are limited by developmental responses to crowding, in which time to flowering decreases and relative allocation to structural organs increases at the cost of agronomically desirable traits such as leaf, root, and fruit production. Regardless of the trait selected in a crop species, agricultural weeds exhibit dramatic compensatory evolution that increases weed fitness at the cost of crop productivity. Comparative genetic approaches and genomic tools provide a means to investigate the genetic basis of phenotypic responses to crowding. The research program focuses on crowding responses in Brassica rapa. In addition to domesticated varieties, naturalized populations occur in both agricultural fields and disturbed, weedy sites. Thus, this system is appropriate for investigating both the loci targeted during domestication and those underlying adaptation of weed species to agricultural settings. The research takes advantage of available genomic tools to investigate the genetic basis of competitive responses in agricultural and natural settings. Specific goals include 1) identifying the genetic determinants (known as quantitative trait loci or QTL) for fitness and traits affecting competitive ability in field settings, 2) using controlled light environments to identify QTL important for response to specific environmental cues, 3) quantifying evolutionary responses (measured as allele frequency changes) at QTL determining fitness and phenotypic responses to competition in agricultural and disturbed sites, and 4) cloning QTL for traits important to competitive ability with the aim of determining both genetic targets for crop improvement and loci underlying evolutionary change in agricultural weeds. The experimental research will not only apply current genomic tools to evolutionary studies but also develop and distribute additional genetic resources for dissemination to other researchers. The results will contribute significantly to both crop improvement and an understanding of weed evolution that may aid in management. Finally, the collaborative nature of this work will provide unique, cross-disciplinary training for undergraduates, graduate students, and postdoctoral researchers in the application of genomic tools to evolutionary genetics and the study of both crop species and agricultural weeds.