Sensitivity to Photoperiod Is a Complex Trait in Camelina sativa

Day neutrality, or insensitivity to photoperiod (day length), is an important domestication trait in many crop species. Although the oilseed crop C. sativa has been cultivated since the Neolithic era, day-neutral accessions have yet to be described. We sought to leverage genetic diversity in existing germplasms to identify C. sativa accessions with low photoperiod sensitivity for future engineering of this trait. To do so, we quantified variation in hypocotyl length across 161 C. sativa accessions of 4-day-old seedlings grown in long-day and short-day conditions as a high-throughput approximation of variation in the photoperiod response. Soil-grown adult plants from selected accessions also showed variation in the response to day length in several traits; however, the responses in seedling and adult traits were not correlated, suggesting complex mechanistic underpinnings. Although RNA-seq experiments of the reference accession Licalla identified several differentially regulated Arabidopsis syntelogs involved in photoperiod response and development, including COL2, FT, LHY, and WOX4, expression of these genes in the accessions did not correlate with differences in their photoperiod sensitivity. Taken together, we show that all tested accessions show some degree of photoperiod response and that this trait is likely complex, involving several and separable seedling and adult traits.