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 Camelina 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. We quantified variation in the photoperiod response across 161 accessions of C. sativa by measuring hypocotyl length of four-day-old seedlings grown in long-day and short-day conditions, finding wide variation in photoperiod response. Similarly, soil-grown adult plants from selected accessions showed variation in photoperiod response in several traits; however, photoperiod 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, 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. Significance StatementDay neutrality (photoperiod insensitivity) is a common trait in domesticated crops; however, the ancient oilseed crop Camelina sativa has remained photoperiod-sensitive, which likely limits seed yields. Here, we show that photoperiod sensitivity is conserved across many C. sativa cultivars, albeit to different degrees, and we establish that photoperiod sensitivity is a complex trait, which will require genetic engineering to achieve day neutrality.