Chemical variation for leaf cuticular waxes and their levels revealed in a diverse panel of Brassica napus L.

• Heritable variation for 24 leaf cuticular wax chemical constituents in B. napus.
• Strong positive correlation between two major branches of the cuticular wax pathway.
• C29 alkanes are potential breeding targets to improve stress tolerance in B. napus.
• Most extensive analysis of wax chemical diversity within any plant taxon to date.

Brassica napus L. is one of the most important oilseed crops in the world, providing oil and protein used for food, fuel, and industrial purposes. Despite high oil yields and desirable agronomic traits, its geographical range is mainly limited to temperate climates, and oil yields and quality are negatively impacted by drought and heat stress. Leaf cuticular waxes are known to protect plants from many forms of environmental stress, including those caused by drought and heat. To shed light on the wax phenotypic diversity in B. napus, we quantified the levels of 24 leaf cuticular wax chemical constituents, and seven of their sums, in a diverse panel of 517 accessions representing B. napus seed stock center collections worldwide. Most of the 31 traits had moderately high heritability (H2 = 0.19–0.81), suggesting that the observed phenotypic variation was influenced primarily by genetic effects. Further, we obtained a strong positive correlation between the two major branches of the metabolic pathway responsible for cuticular waxes. Although this metabolic linkage has been suggested by previous studies, it has not yet been statistically supported. We observed high correlations among individual alkane, secondary alcohol, and ketone constituents, and low correlations among individual primary alcohol and ester constituents. This study is the most extensive analysis of wax chemical diversity within any plant taxon to date, and lays a foundation for future studies of wax metabolism and function, and the application of new breeding strategies to modify leaf waxes and improve stress tolerance in B. napus.