Interactions between genetics and environment shape Camelina seed oil composition

Abstract

Background: Camelina sativa (gold-of-pleasure) is a traditional European oilseed crop and emerging biofuel source with high levels of desirable fatty acids. A twentieth century germplasm bottleneck depleted genetic diversity in the crop, leading to recent interest in using wild relatives for crop improvement. However, little is known about seed oil content and genetic diversity in wild Camelina species.

Results: We used gas chromatography, environmental niche assessment, and genotyping-by-sequencing to assess seed fatty acid composition, environmental distributions, and population structure in C. sativa and four congeners, with a primary focus on the crop's wild progenitor, C. microcarpa. Fatty acid composition differed significantly between Camelina species, which occur in largely non-overlapping environments. The crop progenitor comprises three genetic subpopulations with discrete fatty acid compositions. Environment, subpopulation, and population-by-environment interactions were all important predictors for seed oil in these wild populations. A complementary growth chamber experiment using C. sativa confirmed that growing conditions can dramatically affect both oil quantity and fatty acid composition in Camelina.

Conclusions: Genetics, environmental conditions, and genotype-by-environment interactions all contribute to fatty acid variation in Camelina species. These insights suggest careful breeding may overcome the unfavorable FA compositions in oilseed crops that are predicted with warming climates.

Keywords: Camelina; Environmental association; Fatty acid; Oil content; Phenotypic plasticity; Population structure; Wild crop relatives.

Fig. 1

Box and whisker plot of fatty acid abundances detected in Camelina spp. determined via gas chromatography. Numbers of accessions measured: Camelina hispida (blue) n = 6, C. laxa (yellow) n = 3, C. microcarpa (red) n = 57, C2019. rumelica (green) n = 17, C. sativa (purple) n = 6.Values for S/U are represented as the proportion of saturated to unsaturated fatty acids. Total seed oil is represented as the percent oil relative to seed weight

Fig. 2

Accessions of C. microcarpa for which seed oil composition was analyzed are mapped as a collections along the Eastern Rocky Mountain range of the U.S. and b collections from the Caucasus and Ukraine. Colored circles represent the population structure for individuals, blue = Caucasus population, pink = northern Ukraine population, brown = southern Ukraine population, black = not genotyped/insufficient data. c Population structure results from ADMIXTURE analysis at K = 3 subdivided into country of origin, including 27 additional samples for which oil was not measured. Map was created under liscense using ArcGIS® software by Esri. Basemap is a source of the National Geographic Society and Esri (2019)

Fig. 3

Linear Mixed Effects Model results for saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), poly-unsaturated fatty acids (PUFA), and total oil content in C. microcarpa. The northern Ukraine population was used a reference population in the models, based on its difference in FA composition relative to the other genetic subpopulations (see Fig. S6). Only informative predictors are included in the figure. Colored predictors shown had confidence intervals in which the lower bound (7.5%) and upper bound (92.5%) did not overlap zero in the linear mixed effect models, and their 85% confidence intervals did not overlap zero when robust regression was performed. The 85% confidence intervals were consistent with the model selection method (see Methods)

Fig. 4

Box and whisker plot of proportions of mono-unsaturated FAs (MUFA), poly-unsaturated FAs (PUFA), saturated FAs (SFA), and total oil by seed weight in three replicates each of three C. sativa accessions grown at 12 °C (blue) and 30 °C (orange). P-values < 0.001 denoted with ***