185V Poster Online - Virtual Posters
Tuesday June 07, 11:00 AM - 3:00 PM

Authors:
Jill Marzolino ¹; Jacob Landis ^1,2; Astrid Junker ³; Juliane Streit ³; Henning Tschiersch ³; Thomas Altmann ³; Claude Becker ⁴; Daniel Koenig ¹

Affiliations:
1) University of California, Riverside, CA; 2) Cornell University, Ithica, NY; 3) The Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gaterslaben, Germany; 4) Gregor Mendel Institute of Molecular Plant Biology, Vienna, Austria

Keywords:
Experimental evolution

The opportunity to directly observe the process of adaptation is exceptionally rare in multicellular organisms. Here, we examine the tempo and mode of genetic and phenotypic change in a barley evolution experiment, the Composite Cross II (CCII), begun in 1928 and continued throughout the last century. The CCII experiment began with over 10,000 unique recombinant progeny derived from 329 intercrosses between diverse barley varieties. For each cycle, plants were grown with minimal human intervention in Davis, CA, allowed to compete over the growing season, and harvested in bulk to propagate the experiment in the following year. Previous studies of a small number of fitness-correlated traits in early and late generations of the CCII showed significant increases in flowering time, height, and yield. Here, we dramatically increase our understanding of phenotypic evolution in the CCII by describing the evolutionary trajectories of 401 traits throughout the lifecycle of 192 genotypes spanning 58 generations of the experiment. The final dataset includes daily measurements of many traits expected to contribute to plant fitness — including descriptors of plant biomass, architecture, pigmentation, and photosynthetic capacity. Natural selection has played a major role in shaping phenotypic change in the experiment, with dozens of traits showing strong directional shifts. Selection was particularly strong in traits related to plant architecture and pigmentation. Genome wide association studies for 80 traits identified 273,947 loci that controlled variation in the early stages of the experiment. Phenotypic shifts were driven by simultaneous selection across 94,497 loci controlling adaptive phenotypes. Alleles targeted by selection were enriched for color-related traits. Our experiments provide a framework for understanding phenomic shifts in response to selection over the decades of adaptation in a real world environment.