Location: Plant Physiology and Genetics ResearchTitle: A Set of Descriptions for Evaluating Guayule Germplasm Author
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2010
Publication Date: 5/14/2010
Citation: Coffelt, T.A. and Johnson, L. 2010. A set of descriptions for evaluating guayule germplasm. Industrial Crops and Products. 34:1252-1255. Interpretive Summary: As guayule becomes commercialized and more scientists become involved in germplasm evaluation and development, a standardized set of descriptors is needed to compare evaluation results across experiments and provide information needed for plant variety protection certificates. A set of 31 descriptors was developed with a subset of 14 minimum descriptors and evaluated on breeding populations developed both by traditional breeding and transgenic breeding procedures. Results showed that the descriptors were adequate to evaluate differences among germplasm and could be used with a minimum amount of time to evaluate large numbers of lines. The descriptors will provide uniformity in comparing germplasm performance across environments, and will also be valuable to regulatory agencies in granting various plant protection certificates.
Technical Abstract: Commercialization of guayule (Parthenium argentatum Gray) as a source of rubber is receiving world-wide attention as an alternative to Hevea in order to meet increasing demand for natural rubber. As more breeders, agronomists, botanists, and other scientists become involved in evaluating and developing guayule germplasm, it is imperative that a uniform set of germplasm descriptors is available. These descriptors are also necessary for use in obtaining plant variety protection certificates. The objective of the current study was to develop a set of descriptors for evaluating guayule germplasm in breeding and agronomic studies as well as identify a minimum set of descriptors to use when time or labor make using all of the descriptors not feasible. Based on the experience of the authors and previous research, a set of descriptors was developed and used to evaluate breeding nurseries of both traditionally developed and transgenically developed guayule plants. The descriptors were easy to use and required a minimum amount of time per plant, so that a large number of lines could easily be evaluated. The descriptors adequately covered the range of diversity observed in the nurseries evaluated. A set of 14 minimum descriptors is proposed – plant height, plant width, biomass, number of main branches, bark thickness, leaf shape, leaf serration number, dormancy break, flower bud score, 1,000 seed weight, rubber content and yield, and resin content and yield. For germplasm protection uses, the full set of descriptors should be used. The descriptors will provide uniformity in comparing germplasm performance across environments. The descriptors will also be valuable to regulatory agencies in granting various plant protection certificates.