Squashes, the hounds of the plant world, can weigh a pound or 1,000. Geneticists think they know why

Squashes, the hounds of the plant world, can weigh a pound or 1,000. Geneticists think they know why

They can weigh two pounds or 200, small and spherical or deformed and oblong, and feature a range of colors, coats, and patterns. No, we’re not talking about dogs, we’re talking about gourds – another genetically malleable life form that comes in a bizarre wide range of sizes and shapes, most of which can (again, like dogs) cross paths with each other. with each other although they are so radically different. This genetic malleability is unique in the plant world: apples, tomatoes and oranges show many genetic variations, but not three orders of magnitude of mass differences as squash do.

These genetic oddities have a concomitant range of uses in humans – culinary, decorative and musical. Pumpkins have spicy seeds that can turn into a snack or oil; yellow squash can be cooked in a savory pasta sauce; and gourds with fashionable warts are a traditional home decoration, especially at this time of year.

Genetically speaking, it is a remarkable plant. So what’s going on with gourds to allow for such incredible natural variation? And what makes them so biologically strange compared to other plants?

The evolutionary history of gourds intersects with human history, with our beloved plants changing as civilization changed. You could even say that, in a sense, the squash variety is a testament to both human ingenuity and the wonders of the natural world.

“The origin of these crops – which plays a huge role in terms of diversity of forms and genetics.”

Taxonomically, gourds belong to a family known as Cucurbits — and, as Dr. Ajay Nair, chair of Iowa State University’s sustainable agriculture graduate program, told Salon, there are three main reasons gourds are so genetically diverse that they’ve been raised in subspecies as diverse as giant pumpkins and watermelons.

“If you look at where crops come from, where those crops come from, it plays a huge role in terms of diversity of forms and genetics,” Nair pointed out, like pumpkins from South America or squash from snake originating from India. He also noted that squashes have great diversity in their gene pool: cucumbers have only 7 haploid chromosomes, while watermelons have 11 different chromosomes.

Finally, there is human intervention: “These cultures have been around for a very long time, and humans have interacted with them. There have been a lot of very direct ways to breed those crops, domesticate those crops, and improve those crops,” Nair says.

Sometimes these factors complement each other, such as when humans take advantage of gourd infertility to breed specialized designer gourds. Still, human domestication sometimes limits the genetic diversity of squash, as explained by Heather R. Kates of the University of Florida’s Institute of Genetics.

“When we compared one of the species of squash that exhibits a very wide diversity of shapes, sizes, colors and textures (The biggest pumpkin) to a species that does not (Cucurbita argyrosperm), species that have different shapes, sizes, colors and textures do not appear to have experienced the “bottleneck of domestication” or the reduction in genetic diversity that characterizes many cultures,” Kates pointed out. . In other words, cultivated squash species that have many varieties have not had their genetic variety cut off by domestication in the same way as other commonly used crops like corn and bananas. While archaeologists can’t determine with certainty the extent to which past human civilizations unwittingly altered squash genetics for their own ends, it’s plausible to suspect that it happened somewhat.

“We can’t know for sure what is responsible for the genetic or even archaeological patterns we see in gourds, but we do have evidence that thousands of years ago humans continued to interbreed or leave the first domesticated types of squash to interbreed with wild species,” Kates explained. This, she says, allowed the development of many types of gourds.

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Human intervention in squash farming is still strong. Last year, South African researchers published an article in the journal Frontiers in Sustainable Food Systems about the latent potential of bottle gourds. They noted that bottle gourds could be an essential crop for food security, but there has not been enough research on them.

“There is great genetic variation among the germplasm of gourds in Africa” ​​that can be used for everything from creating better products to improving marketing, the authors wrote. “However, the crop is underexplored and underutilized, and improved varieties have yet to be developed and marketed in the region.”

“Plant pathogens are expected to spread and infect plants more easily under current climate change scenarios.”

In addition to being understudied, gourds may also be threatened by mankind’s ecological irresponsibility. As with so many other things, climate change could end up affecting humanity’s appetite for squash. From supercharging hurricanes, intensifying supply chain disruptions, or even fueling pandemics, the continued warming of Earth’s climate is altering our planet in countless ways. In that vein, as Kates pointed out, climate change will “intensify” the challenges facing gourd farmers and gardeners.

“Some plant pathogens are expected to spread and infect plants more readily under current climate change scenarios, and environmentally stressed pumpkins and squash are more susceptible to initial infection and subsequent disease development,” Kates, who is also a postdoctoral researcher at the Florida Museum of Natural History, pointed out. “Changes in precipitation also pose a threat to Pumpkinespecially for winter squash and pumpkin cultivars that require high water supply and bear fruit susceptible to rot as they ripen. At the same time, “there are characteristics of Cucurbita cultivation that can make it resistant to climate change”, such as the fact that they are pollinated by several types of bees, the fact that there is such a varied range of types grown and the fact that they are versatile enough to be grown over a wide range of temperatures and altitudes.

That’s good news for pumpkin, squash and melon lovers, especially since holidays like Thanksgiving make gourds all the more important. As Nair explained when asked about his own favorite water bottles, tastes and trends change over time.

“I think there’s been a move towards smaller, more decorative pumpkins or gourds that people can put on a plate or in front of their house,” Nair said. “I like that. I like these gourds just because they bring a different hue, a different palette, a different texture. Not just these big pumpkins, but different shapes, different sizes, maybe even sometimes different colors on the same squash. I like these squashes.”

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