A century of guayule: Comprehensive genetic characterization of the US national guayule (Parthenium argentatum A. Gray) germplasm collection

Authors: ILUT, DANIEL - Cornell University; SANCHEZ, PAUL - Rice Experiment Station - California; Coffelt, Terry; Dyer, John; JENKS, MATTHEW - West Virginia University; GORE, MICHAEL - Cornell University

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2017
Publication Date: 12/15/2017
Publication URL: https://handle.nal.usda.gov/10113/5828875
Citation: Ilut, D.C., Sanchez, P.L., Coffelt, T.A., Dyer, J.M., Jenks, M.A., Gore, M.A. 2017. A century of guayule: Comprehensive genetic characterization of the US national guayule (Parthenium argentatum A. Gray) germplasm collection. Industrial Crops and Products. 109:300-309.

Interpretive Summary: Natural rubber is a critical raw material of modern society, essential to a diverse range of industries such as automotive, electronics, clothing, and health care. However, 99.9% of natural rubber is derived from a single source, the rubber tree (Hevea brasiliensis), and 75% of it is produced in South Eastern Asia. Guayule (Parthenium argentatum) is a woody perennial shrub native to the desert regions of northern Mexico and southwestern United States that produces rubber in its bark tissues, but attempts to increase rubber yields through crop breeding have been hampered by a lack of well-characterized germplasm. To help address this issue, scientists at Cornell University, West Virginia University, and the ARS lab in Maricopa, Arizona, performed a detailed assessment of all publically available guayule germplasm, including closely related species and interspecific hybrids. By using a combination of next generation sequencing technologies and phylogenetic approaches, the scientists could clearly determine the genetic identity and relationships for each accession. Overall, these data help to identify specific lines that can be used for crop breeding, identify geographical regions that should be explored to obtain additional genetic diversity, and provide robust molecular tools to enable genomics-assisted crop improvements. This paper will be of great value to the guayule research community and represents a substantial step forward in the development of guayule as an alternative, commercial source of natural rubber.

Technical Abstract: The fragility of a single-source, geographically concentrated supply of natural rubber, a critical material of the modern economy, has brought guayule (Parthenium argentatum A. Gray) to the forefront as an alternative source of natural rubber. The improvement of guayule for commercial-scale production has been limited by the lack of genomic tools and well-characterized genetic resources, as for example, would be required for genomics-assisted breeding. To address this issue, we developed nearly 50,000 single nucleotide polymorphism (SNP) genetic markers and genotyped 69 accessions of guayule and its sister taxa mariola (Parthenium incanum Kunth), representing the entire available NALPGRU germplasm collection. We identified multiple interspecific hybrid accessions previously considered guayule, including six guayule-mariola hybrids and non-mariola interspecific hybrid accessions AZ-2 and AZ-3, two commonly used high-yielding cultivars. We dissected genetic diversity within the collection to identify a highly diverse subset of guayule accessions, and showed that wild guayule stands in Big Bend National Park, Texas, USA have the potential to provide hitherto untapped guayule genetic diversity. Together, these results provide the most thorough genetic characterization of guayule germplasm to date and lay the foundation for the rapid genetic improvement of commercial guayule germplasm.