Submitted to: Proceedings Assoc for Advancement of Industrial Crops (AAIC) Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/14/2006
Publication Date: 10/14/2006
Citation: Coffelt, T.A., Ray, D.T. 2006. Utilizing Natural Crosses in a Guayule Breeding Program.. Proceedings Assoc for Advancement of Industrial Crops (AAIC) Annual Meeting, p. 97. Interpretive Summary:
Technical Abstract: Guayule (Parthenium argentatum Gray) is a perennial shrub native to the Chihuahuan Desert. Apomictic reproduction in guayule makes breeding progress difficult. Breeding methods to take advantage of the facultative apomixis and occasional sexual reproduction that occurs in guayule are needed for faster breeding progress. The objective of this study was to evaluate the possibility of utilizing the pedigreed natural crossing method as a breeding method in guayule. In the first experiment, three guayule lines (AZ 101, P10-4, and CAL-6) were interplanted with P. tomentosum plants in a natural crossing block. Plants were allowed to flower and set seed. Seed were germinated and the resulting plants compared to parents to identify potential interspecific hybrids. In the second experiment, hybrid plants from crosses between diploid lines of guayule were interplanted and allowed to cross. Seed were collected randomly and the resulting plants evaluated to identify potential hybrids. We isolated several natural hybrids from both breeding nurseries that are the result of hybridization between Parthenium species and between guayule germplasm lines. These interspecific and intraspecific hybrids have been identified by characteristics such as leaf shape, leaf color, and leaf size. Current work is underway to verifiy the parents by chromosomal analyses. Plants that reproduce by apomixis and those that are highly self-pollinated both have highly uniform progenies, except for the occasional off-type. This off-type is frequently the result of out-crossing in self-pollinated species as well as in facultative apomictic species. Inter-planting of parents, allowing crossing to occur naturally, harvesting seed from the parents, and then examining the progeny for off-types can be used to develop populations for further selection and development of desirable lines. In self-pollinated species the development of uniform lines may take several generations of selection and self pollination, while in an apomictic species uniform lines may be able to be developed within one generation of apomictic reproduction. The added advantage is that any hybrid vigor associated with the original cross would also be fixed. Preliminary studies indicate that utilizing the pedigreed natural crossing method or modifications of this method in guayule is feasible. Using this method in guayule breeding programs could lead to faster development of germplasm lines and cultivars for industry.