100 years of breeding guayule

Guayule has been known for 100 years as a potential source of natural rubber. Breeding efforts have been sporadic limiting progress in guayule breeding compared to other crops. Even though the genetic base appears to be rather narrow, it has not hindered guayule breeding programs. The most extensively employed breeding approach has been single-plant selections. The primary objective for guayule breeding programs has been increased rubber yield. Limited studies utilizing biotechnology, chemical, molecular, or other new methods of improvement have been conducted in guayule. Most have involved trying to understand the rubber synthesis pathway or to modify the rubber biosynthesis pathway through genetic engineering. While these previous attempts to increase rubber yields have met with little or limited success, the studies have shown that guayule can be successfully transformed. It might be more effective in the short term to use biotechnology to insert genes for other potentially useful traits such as herbicide tolerance and insect resistance. For future progress in guayule breeding to be made, much work remains to be done.