There’s nothing like this in nature, Jonathan Wendel said as he showed a visitor in his Bessey Hall office the long white puffs billowing from a cotton boll – the protective flower capsule of the plant cultivated by humans for thousands of years. In the wild, cotton bolls are far smaller and hold darker, coarser and shorter fibers.
How did we get from there to here? Wendel, a distinguished professor of ecology, evolution and organismal biology at Iowa State University, has been asking that question for decades.
“This is my 40th year on faculty, and I came here with this project in mind. And it took 40 years to develop the resources, tools and technologies to solve the problem,” he said.
Wendel and a team of 19 co-authors outlined an answer in a paper published last month in the Proceedings of the National Academy of Sciences, showing that newly collected wild plant samples and advanced analysis of genomic sequencing data confirm modern cotton was domesticated from a diverse population native to Mexico’s Yucatan Peninsula.
Tracing the lineage of cotton gives scientists a better understanding of how plants evolve. But given the plant’s significance as a crop – cotton remains the most common source of natural textiles, by far – there are also direct practical benefits. Knowing where cotton came from is a genetic treasure map, pointing where to look for valuable traits such as disease resistance or salt tolerance that were lost along the way as farmers bred for other qualities.
“When humans domesticate a plant, you pick from a big population and everything else is left behind. Do that for 1,000 generations, and you have a very narrow genetic base,” Wendel said. “So we’re very interested in that wild genetic diversity. We want to know what’s still out there.”
Collections years in the making
Pinpointing modern cotton’s home in the Yucatan was not a surprise. Earlier studies by Wendel, a prominent expert in cotton genetics, used less precise methods to suggest the peninsula curling to the north in southeastern Mexico was a likely origin of the plant’s domestication – a process that began about 5,000 years ago.
The advent of quick, affordable genome sequencing put a more definitive determination within reach, if Wendel and his colleagues could gather a wide enough sampling of wild specimens. He’s been collecting wild cotton his whole career, scouring herbarium shelves and Caribbean coastlines for variants.
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