Cross-breeding to boost crop yields

Converting crops like wheat from annuals to perennials could significantly reduce environmental impacts...
07 February 2023

Interview with 

Tessa Peters, The Land Institute


Ears of wheat


One striking aspect about the foods we tend to farm most often is that these plants are all annuals: they grow, fruit and die all within a single season. This means farmers need to re-prepare the soil and re-sow each year, which costs time, fuel and wear on machinery. This in turn adds to the production costs and makes income harder for farmers to predict: fuel and fertiliser prices, for instance, have skyrocketed this year. So wouldn’t it be nice if we could plant these crops once and then harvest from the same plants over a series of years? That’s what an organisation called The Land Institute are working on: by breeding high yield modern crops with perennial wild relatives to produces cereals that keep growing year after year. Tessa Peters…

Tessa - At the Land Institute, our goal is that you would have a crop that gets planted and then you would harvest that summer and then the following year you wouldn't have to go back and plant. You would simply harvest the grain that was produced the next summer. And for us, we want to see crops that are producing grain for at least three years.

Chris - Our farming ancestors though, have spent literally thousands of years choosing, evolving, selecting and breeding plants that are the cream of the crop that we grow at the moment. And they are annuals; they come up, they produce their seed and then they die. So you are saying you want to reverse all that and come up with plants that doesn't happen to? How?

Tessa - Yeah, very much that. We are trying to go back 10,000 years and say, okay, with new technologies, can we choose different crops or can we choose to cross different crops to make the grains that we've currently chosen (like wheat) into a perennial? The reason that we think this is possible is that we can go back and we can look at crops that have been grown by communities for thousands of years and we can say these have been grown primarily as forages, but they have good qualities. We know they can be cultivated, so let's look and see if we can develop those into a grain crop. Can we make selections for things like bigger seed size and free threshing abilities so that we can make sure we can use them for different things like flour? And we believe that this is possible because we have folks who have selected perennial rice in Yunnan China. They've been really successful at producing perennial rice.

Chris - What's the starting point? Do you start with the perennial and then try and breed the characteristics of what we've got the best of the annuals into it? And what are those perennials? Are there cereals that you are basing this on that do come up year after year after year?

Tessa - We approach this from two different ways. We have a perennial program where we're looking at annual crops, sorghum, wheat, and rice. And then we cross them with a perennial relative, for example, for perennial wheat, we cross it with intermediate wheat grass and we try and keep everything that we like about the wheat. We like the big seed size, we like that it's easily harvested, that it doesn't shatter, it doesn't fall off the stem before harvest, those kinds of things. But then we want to bring in all of the perennial characteristics that we really like: the ability to overwinter and produce grain that next year.

Chris - When one grows perennials in the garden, you generally find that they're good for a few years and then they clap out and most gardeners tell you that's the time to chew them up and you replace them. So how long do you think you can extend the life cycle of some of these wheat plans? In other words, how many times do I end up not plowing a field and therefore saving on the fuel, saving on the tyre wear and everything else that goes into tilling a field so that I get the same sort of yield without all those other costs and the cost of the soil?

Tessa - Our goal is at least three years. We know that these are herbaceous perennials and they probably will have to be replanted. But for wheat, that's a third as many passes across the field with your tractor. Perennial rice has been in the ground now in China for eight harvests. It's two harvests a year. So that's four years.

Chris - And what are the yields looking like?

Tessa - For perennial rice? The yields are equal to annual rice. For some of the other crops that we work on, the yields are substantially lower, so about a third to a half of the wheat yields. And so the goal for us is of course to increase the yield through plant breeding and hopefully at some point rival the yields of wheat.

Chris - Are there any problems with something being in the ground for longer? That's more opportunity for pests to attack it, it's more opportunities for the plant to weaken for other reasons and dent yields further. So how are you building in safeguards against those?

Tessa - One of the things that we're finding is that perennial crops also have defenses that make them more resilient to disease in some cases. And that's how they've evolved so far. We haven't really run into any really big disease issues.

Chris - And the main sort of bonuses here, apart from the fact that you are breaking the link between a farmer having to buy seed every year to plant. But that means as well as your fuel savings of not having to run a tractor across that land, the soil is also a beneficiary because you are not getting soil erosion because you are not turning it over, you're not exposing the interior of the ground to the air and getting various erosion events and loss of nutrients and so on.

Tessa - Yeah, that's definitely one of the big advantages with a living root in the soil. The soil is being held by that living root and also by all of like the microbial and fungal interactions that are happening in the soil. Those microorganisms also secrete a lot of chemicals that help hold the soil in place and hold it together. So they also increase infiltration because the roots are penetrating the soil. And so when it rains, a lot more of that water is actually making it into the soil versus just running off and carrying the top soil with it. Another really important aspect of this is that these perennials tend to have much larger root structures than annual crops. This big root structure increases the amount of carbon that's stored in the soil. It can also scavenge nitrogen that's available in the soils and getting it out of the system and out of the water supply that humans are then using to drink. These crops tend to also be fairly resilient to drought because they have these long root structures that can source water from deeper in the soil profile. So there are a lot of benefits to having a perennial in the ground from reducing the number of passes that your tractor has to make to improving the soil and water quality.


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