Rubber is one of those unusual substances that isn’t thought about much, but is used in practically everything. From the simple and direct usage in tires for vehicles to any kind of hose or machinery belt or insulation in tiled flooring. There is also the rubber that is used to create latex, which is so ubiquitous in medical settings.

The Boom And Bust

All of this and more makes up the universal need for some source of rubber. Originally, the two kinds of rubber trees, Hevea brasiliensis and Castilla elastica, were used as the primary sources of rubber during the rubber boom in the 1830-40’s after the discovery of the vulcanization process. This allowed the soft natural rubber to be transformed into a harder, yet still elastic polymer that enabled its usage in so many products.

But demand quickly grew and other sources of rubber were soon sought after. This led to the creation of synthetic rubber as an alternative that could be mass-produced to suit the worldwide need for it. Unfortunately, since that introduction, the world has begun to see how the process of making it isn’t as environmentally friendly as would have been hoped and, with issues like climate change becoming more and more relevant every day, the production of such a widely used material from petroleum products was no longer desired.

So, back to the old alternatives, I assume you’d expect. And, yes, that is what is being done, but there is still the question of appropriate supply. In addition to the Asian and Panama rubber trees, even more sources of natural rubber are required.

Making New, Better Rubber

That’s where Parthenium argentatum, the guayule plant, comes into play. It was already a secondary source for latex back in the Aztec and Mayan civilization days, with Native Americans also using the plant as it grew across what is now Texas, Mexico, and parts of Central American countries.

One of the main benefits of the guayule’s latex, especially today, is that it is hypoallergenic, meaning that it is unlikely to trigger latex allergic responses for those with that allergy. But even with this alternative source, increasing production is the focus to meet global demand.

That’s where the scientists at the USDA’s Agricultural Research Service have stepped in. Specifically, the organization’s Bioproducts Research Unit set up an arrangement with the tire company Bridgestone Americas back in 2013 to work on producing a genetically modified guayule plant with increased amounts of rubber formed per plant. They, obviously, accomplished this task.

Finding Use In Negative History

Another plan for the future is to mix the guayule germplasms, the seeds and tissues saved for future breeding, with genes that allow drought tolerance and disease resistance, allowing it to be grown in an even more widespread area. Though it would have been easier just to find a cultivar of guayule with those traits than to have to go through the long effort of modifying in such complicated processes as drought tolerance. So they began the hunt for other cultivars instead with some help from Cornell University, sequencing all the guayule plants they could find from private collections.

While the hunt is still ongoing, it did result in them finding some interesting specimens.

They soon ran across a guayule breeding project that had been started in a not very positive part of American history. As i’m sure many of you are aware, during the course of World War II, the American government set up internment camps to keep all Japanese Americans as a precaution against some supposed threat they posed that the government never really explained. In one such camp in Manzanar, California, they forced the prisoners to breed guayule plants for them in order to assist in the war’s rubber needs.

After the war, the site was turned into a National Historic Site of regretful remembrance. The caretakers of the site, however, kept the guayule plants and kept growing some amount of them ever since. The seeds donated to the scientific effort grew guayule plants that looked very different from the norm. Rather than large dark green leaves, they grew small silver-green leaves that would have otherwise looked like a completely different plant.

More Rubber For All

It is unknown at this point whether these seeds will yield any useful genetic information, but it’s a special part of history nonetheless.

The research is ongoing to obtain those extra traits, but thus far the scientists have succeeded in producing guayule plants with significantly increased rubber content and they appear to be able to grow in field conditions just as well as in a lab. With some more work, they hope to eventually be able to release the plants to growers to serve as a new source for rubber that has the added benefit of being hypoallergenic.

Only time will tell whether this small shrub-like plant will serve as the basis for a new boom in worldwide rubber production.

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Photo CCs: PSM V81 D325 A fine source of guayule near las caopas zacatecas from Wikimedia Commons

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