Traditional Plant Breeding Approach Used by Bridgestone Americas, Inc. to Develop Guayule as a Domestic Natural Rubber Source

Currently Hevea brasiliensis, the rubber tree, is the sole source of the world’s natural rubber and is grown in southeast Asia.  Because of the volatile costs of natural rubber, changes in demand of natural rubber and the threat of leaf blight (M. ulei) infecting Hevea, Bridgestone Americas Tire Operations (BATO) in collaboration with Bridgestone Japan started investigating the use of Parthenium argentatum, guayule, as a sustainable, domestic and alternative natural rubber source.

A Guayule Research Farm in Eloy, AZ and a Processing Research Center in Mesa, AZ are being developed to fully understand the potential of guayule from the agronomic and industrial perspectives.  Bridgestone’s agricultural research is focused on: 1) supplying guayule shrub to the Process Research Center, 2) determining best growing practices for guayule to optimize yield and rubber production and 3) increasing rubber content and improving agricultural characteristics through a traditional plant breeding approach.

Mass selection will be the primary breeding strategy used to develop guayule varieties to be grown as a commercial crop in the southwestern United States because it is a cross pollinating species, but also exhibits self incompatibility, polyploidy and apomixis.  Germplasm for the breeding program originated from the National Genetic Resource Program, where approximately 69 accessions of guayule or related species are publically available, and Bridgestone Americas, Inc. Texas Proving Grounds in Fort Stockton, TX, where Partheniumwas planted in the 1980s and has since been open pollinating.  Because guayule is still considered a “wild” species, many traits are needed to be improved, such as rubber content as well as cold, heat, water logging, drought and salt tolerance.  The main focus of the breeding program consists of 1) collecting germplasm, 2) evaluating and selecting germplasm for traits of interest, 3) evaluating individuals for ploidy level, 4) making cross pollinations in the greenhouse, 5) collecting open pollinated seed between two selected lines in pollination cages and 6) planting field trials at different locations from seed collected in the greenhouse and pollination cages.

In conclusion, a traditional breeding approach has been implemented to develop guayule as a commercial crop to be used as a domestic source of natural rubber.  The long term goal of the guayule breeding program is to produce varieties that can be grown in the southwestern United States by commercial growers.