Guayule (Parthenium argentatum Gray) has the potential of becoming an important domestic source of natural rubber. Although some progress has been achieved in increasing yields, for guayule to become an economically feasible crop of the southwest desert, further increases in rubber yield, either by increasing biomass or the plant's rubber content, are necessary. Providing the variability for these desired traits is present in available germplasm, the plant breeder must find a means of selecting for these two traits. It is obvious that biomass can be visually estimated, and it is therefore easier to select for this trait in comparison to the plant's rubber content. Due to practical consideration such as harvesting and processing, high rubber content becomes more desirable than extremely large plants. However, it is hoped that measured characters can be found to predict both traits in order to aid the plant breeder. The variables measured in this study were percent rubber and resin, rubber and resin yield(g/plt.), plant height (cm), width (cm) and volume m³, fresh and dry weight (kg/plt.), mean steam diameter (cm), total and mean steam area (cm²), total and mean stem circumference (cm), total circumference/total area (cm⁻¹), stem number, percent dry weight, and regeneration. This study examined a field with 234 guayule breeding lines. A high amount of variability existed both within and among these lines. It was found that dry weight (kg/plt.) had the best correlation to rubber yields (r = 0.92) and plant volume best predicts dry weight (r = 0.84), but none of these variables correlated well with rubber content. The best statistical regression model for percent rubber included four variables, fresh and dry weight (kg/plt.), dry weight (%) and plant volume (m³). This model accounted for 51% of the variability. In comparison, the best regression on rubber yield had an R² = 0.85 for our variables including plant height (cm), width (cm), volume (m³) and dry weight (kg/plt.). It is obvious that rubber yields may be more easily increased by selecting for biomass. However, it appears that in the long term, increases in rubber content will be of critical importance for maximum efficiency. Therefore, a measurable indication of rubber content is needed to aid in selecting for this trait.

No description available.

Thesis (M. Agr. St.)--University of Queensland, Gatton, 2002. / Includes bibliographical references.

Thesis (M. Agr. St.)--University of Queensland, Gatton, 2003. / Includes bibliographical references.

No description available.

Thesis (Ph. D. - Plant Sciences)--University of Arizona, 1984. / Includes bibliographical references (leaves 75-77).

Item lacks publication date - publication date of 1980-1985 indicated by UA Library Catalog and WorldCat.

Conducted under USDA Agreement No. 58-3159-7-11 Guayule Natural Rubber Program / Introduction: The United States imports 100 percent of its natural rubber. Ninety-two percent of our natural rubber production is concentrated in Southeast Asia, which is subject to interruptions through political action or direct military intervention. Natural rubber, a critical and strategic material, is necessary in such articles as aircraft and ground vehicle tires, medical supplies, resilient mounts, and certain acoustical applications. Synthetic elastomers cannot meet performance requirements in these areas. A domestic source of natural rubber will assist in assuring a supply of this critical material for industry and defense. The U.S. Department of Defense (DoD) and the U.S. Department of Agriculture (USDA) signed a Master Memorandum of Understanding in 1982 that calls for cooperation with respect to food, agriculture, forestry, nutrition, and other research of mutual interest. With this MOU both agencies adopted a supplemental agreement in 1986 that initiated the Joint Guayule Domestic Rubber Program, whose ultimate goal is to promote an economically viable domestic guayule rubber industry. To accomplish this goal, both agencies have provided funding to plant and cultivate guayule shrubs, construct a 150 -long- ton -per -year prototype plant to extract rubber from the shrubs, and conduct evaluations to establish the performance capability of military products fabricated with domestic guayule rubber. A critical component of the supplemental agreement calls for the USDA to assess the feasibility of a commercial guayule rubber processing facility of 50,000-long-ton-per-year nameplace capacity. This report, based on the best available data (1990) and on assumptions of future advancements in technology (for 1996), is designed to address the commercial prospects for the establishment of a domestic guayule rubber industry. It also examines the feasibility and factors involved in meeting either 20 percent or 100 percent of the natural rubber needs of the U.S. Department of Defense in both peacetime and national emergency conditions.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.