|WEAVER, JOSHUA - University Of Arizona
|JENKS, MATTHEW - West Virginia University
|FELDMANN, KENNETH - University Of Arizona
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2018
Publication Date: 3/22/2018
Citation: Weaver, J.M., Lohrey, G.T., Tomasi, P., Dyer, J.M., Jenks, M.A., Feldmann, K.A. 2018. Cuticular wax variants in a population of switchgrass (Panicum virgatum L.). Industrial Crops and Products. 117:310-316.
Interpretive Summary: Switchgrass is a perennial warm-season grass that is being studied extensively for development as a biofuel and biomass crop in the US. Like most other plants, switchgrass is susceptible to environmental abiotic stresses, including heat and drought. Efforts to improve and stabilize crop yields through breeding will be dependent in part on determining the phenotypic variation present in important stress-related traits within a diverse switchgrass population. Scientists at the University of Arizona, West Virginia University, and ARS lab in Maricopa, Arizona collaborated to evaluate the phenotypic diversity of cuticle wax content and composition present in a diverse panel of switchgrass varieties. The cuticle forms a hydrophobic protective barrier on the surface of plants and is known to be important for tolerance to abiotic stresses, particularly for drought. The scientists demonstrated that there was significant phenotypic variation in wax content and composition, suggesting that there are important genetic differences in the population that might contribute to this variation. Identification of certain plant lines with distinct and variable wax loads will provide useful tools to breeders for future efforts to improve switchgrass tolerance to abiotic stresses through directed modification of the plant cuticle.
Technical Abstract: Leaf cuticular waxes are known to influence both biotic and abiotic stress tolerances of plants. The objective of this work was to characterize the wax phenotypic diversity present in a population of 1849 switchgrass plants. We identified 92 visually distinct variant plants that possessed altered leaf glaucousness relative to the common standard type (ST), which exhibited a bluish-white (glaucous) leaf color. The variants could be grouped into three classes: 1) non-glaucous types (NG) that possessed a shiny green leaf surface, 2) reduced glaucous types (RG) that appeared less glaucous than ST, and 3) highly glaucous types (HG) that exhibited more intense bluishwhite color than ST. Analyses of total cuticular wax content averaged over each of three NG (mean 304.79 ± 15.16 µg/dm2), RG (mean 533.33 ± 21.62 µg/dm2) and HG types (mean 1228.23 ± 45.74 µg/dm2) showed significant differences (P < 0.001) from three selected STs (mean 810.92 ± 30.57 µg/dm2). Analysis of wax composition among these selected types revealed that the C33 ß-diketones were the most abundant wax compounds in all but NG types. Field emission scanning electron microscopy showed that abaxial leaf surfaces exhibited predominantly rod-shaped crystals, and adaxial surfaces exhibited predominantly plate-shaped wax crystals on all lines, except for NG that lacked wax crystals on the abaxial leaf surface. As a target for crop improvement, this study reveals that a large amount of variation for cuticle waxes exists within this switchgrass germplasm.