100 Years of Breeding Guayule - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 347

Hevea latex and in much lower quantities [ 11 - 13 ]. The need for an alternative
source of natural rubber latex led to the fourth and current commercialization effort.
Commercialization of non-allergenic guayule latex came closer to reality when
Yulex Corporation ( www.Yulex.com ) was granted the exclusive license to US
Patent No. 558094 [ 11 ] and to US Patent No. 5717050 [ 12 ] on guayule latex
processing and products, respectively. Yulex has established a business organiza-
tion, developed a financial base, increased seed of promising lines, built a latex
extraction processing plant, and is in the process of planting large acreages to
support the industry. Additionally, another new US company, PanAridus
( www.PanAridus.com ), has begun a guayule breeding effort to develop improved
germplasm and production practices with the hiring of a full-time plant breeder.
More recently in 2012, Bridgestone Americas ( www.bridgestone.com ) has hired a
plant breeder and an agronomist to develop new germplasm and production prac-
tices for using guayule as a source of natural rubber for tire manufacture and has
plans to build a processing facility. All three of the commercial groups described
above are putting together plant breeding programs, showing a long-term commit-
ment to guayule. This most recent commercialization effort differs from the
previous two in that it is largely being driven by interest in guayule by commercial
companies and not by government support. The interest by commercial companies
is not only because of the hypoallergenic properties of guayule latex compared to
Hevea latex but also a predicted increase in demand for natural rubber and an
expected decrease in supply of Hevea natural rubber, due to plant diseases and
political, economic, and social factors in rubber-producing countries [ 14 ].
Germplasm Resources
Guayule ( Parthenium argentatum Gray, Compositae) is a perennial shrub native to
the Chihuahuan Desert of North-Central Mexico and the Trans Pecos of Southwest
Texas (Stockton Plateau and Big Bend Region) [ 3 ]. Native populations are found on
semiarid plateaus scattered throughout approximately 300,000 km 2 of rangeland
and over a range of climatic conditions [ 8 ]. Currently available germplasm can be
traced back to the first efforts on guayule breeding.
Parthenium argentatum Resources
The first collection of guayule germplasm was made during the first commercial-
ization effort when civil strife and revolution began in northern Mexico. W. B.
McCallum employed by the Intercontinental Rubber Company gathered seeds in
1912 from wild stands in order to move his cultural operations into the United
States. The germplasm was initially planted at Valley Center, California, and
evaluation was subsequently conducted at Continental, Arizona, and Salinas,