The cotton historical lines project—Part I: History and field evaluation

Common garden experiments have provided great insights into crop adaptation across many systems. Cotton ( Gossypium spp.) cultivars have changed in the 20th and 21st centuries, but breeders have not quantified the degree of these changes. We synthesized a panel of 164 non‐genetically modified genotypes, from the private and public sectors, which we refer to as the “US Historical Lines Panel.” We collected historical documentation, including parentage and time of release, to group each genotype into one of four eras. We grew all genotypes in a common garden experiment, collected data, and then used univariate and bivariate statistical methods to analyze the changes in cotton trait genetic architecture over time. Through this comprehensive analysis we found that cotton breeders have improved average cotton fiber quality and yield. The variance for traits and their pairwise correlations have also undergone significant changes. We estimated that the net genetic gain accounts for 46% of the increase in historical fiber yield increase. Our results lay the groundwork for future analysis on the cotton historical lines, providing a long‐term historical and phenotypic resource for follow‐up experiments.