|LIPKA, ALEXANDER - Benedictine University Of Illinois|
|QIAN, WEI - Southwest University For Nationalities|
|GORE, MICHAEL - Cornell University|
|JENKS, MATTHEW - West Virginia University|
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2015
Publication Date: 11/6/2015
Citation: Tassone, E.E., Lipka, A.E., Tomasi, P., Lohrey, G.T., Qian, W., Dyer, J.M., Gore, M.A., Jenks, M.A. 2015. Chemical variation for leaf cuticular waxes and their levels revealed in a diverse panel of Brassica napus L. Industrial Crops and Products. 79:77-83.
Interpretive Summary: 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. The geographic regions in which the crop may be planted, however, are limited to cooler, temperate climates, since crop performance is negatively impacted by environmental stresses such as heat and drought. One of the biological factors that influences the tolerance of plants to heat and drought is the plant cuticle, which forms a waxy, protective barrier on the surface of leaves and stems. Plants that contain higher amounts of surface wax are generally more resistance to heat and drought, while plants with lower amounts of wax are more susceptible to these stresses. To determine whether the waxy, protective layer of B. napus might be a target for improving tolerance of the crop to heat and drought, scientists at the ARS lab in Maricopa, AZ, in collaboration with scientists at the University of Illinois, West Virginia University, Cornell University, and the Southwest University in Chongqing, China, measured the content and composition of waxes in a large, diverse population of B. napus varieties. The results revealed that there were substantial differences in content and composition of waxes among the plant varieties, and statistical analyses revealed that this variation was likely due to differences in the genetic makeup of the plants. In addition, specific plant lines were identified that had elevated amounts of surface waxes, and these lines represent important genetic diversity that can be used in breeding programs to transfer these traits into commercially important B. napus cultivars. Taken together, these results will be especially important to plant breeders who are interested in improving the heat and drought tolerance of B. napus, which could significantly expand the geographic regions in which this valuable oilcrop is planted.
Technical Abstract: 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.