Wild relatives good for something after all

We all know that plants produce flowers so those flowers can, in turn, produce seeds for the next generation. That’s the way it’s always been and shall remain, we assume.

But what about plants that produce flowers that do not, in turn, produce seeds? Do they produce flowers just to look pretty?

You or I may not have pondered this mystery, but Elizabeth Kellogg thinks about it a lot. Kellogg is a plant scientist at the Donald Danforth Plant Science Center in St. Louis, Missouri, where she delves into this mystery in commercial crops. Her current studies are focused on the wild relatives of sorghum. These wild plants produce two sorts of flowers. Some flowers produce seeds and some flowers don’t.

“We’re particularly perplexed as to why a plant would invest energy if that structure (flower) isn’t making a seed,” says Kellogg. “It seems as though it would be a waste of energy.”

Wild relatives of our commercial crops are the original plants prior to human cultivation. Over thousands of years of plant breeding, humans selected seeds from the plants with the best traits to pass on to the next generation. Eventually, these became the crops we grow today. The wild relatives were left to grow and adapt on their own, often unnoticed.

But what if, during those years, we missed a beneficial wild trait? How do we go back and check? This is the importance of studying wild relatives, explains Kellogg. Her curiosity about the purpose of the non-seed-bearing flowers took her back to studying the importance of wild grasses that are the ancestors of sorghum.

“The plant structure, genomes, and makeup of the wild species are similar to that of the cultivated ones. But wild species often have solved the problem of adapting to drought or heat in a way that could benefit work for commercial crops. It may sometimes be effective to work entirely in the wild species first, determine how they solve an environmental problem, and then transfer that information to the crop.”

The grasses she studied produce flowers in tiny clusters called spikelets. They come in sets of two, but only one makes a seed. At first, this would seem like a strange thing for the plant to do. It’s wasting resources on a flower that won’t produce anything. Kellogg investigated the seedless spikelets to see if they benefit the spikelet with seeds in some way.

Her research team performed multiple experiments using carbon they could trace as it moved through the plant. In one test she could see carbon being moved from the non-seed-bearing spikelet to the one producing seeds. She determined that indeed the spikelets function as “nurse tissue” that provide carbon to help the seeds develop. The research showed the extra spikelets make a significant contribution to yield.

Cultivated sorghum also makes non-seed-bearing spikelets. However, Kellogg says there hasn’t been much work put into breeding plants with larger non-seed-bearing spikelets to see if they could help increase yield. Her new research showing their benefits could be of interest to plant breeders.

“I am interested in the forces that make different species of plants look different from each other. All plants start out from a single cell and look pretty much the same. At the stage of a fertilized egg, corn, rice, and soybeans look similar. By the time they are mature, however, they are easy to distinguish. You could tell them apart blindfolded. Those differences must be caused by genetic differences that cause development to proceed in different ways. I’m interested in what those genetic differences are.”

Kellogg’s recorded presentation findings to the annual meeting of the American Society of Agronomy and the Crop Science Society of America is available online. For more on crop wild relatives at https://www.crops.org/crop-wild-relative.

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