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Interview with a Plant Scientist: Shuwen Wang, Perennial Wheat

Shuwen Wang, Lead Scientist, Perennial Wheat

Shuwen Wang, lead scientist for perennial wheat, makes heavy use of The Land Institute’s lab, where he charts DNA to identify chromosome structures that might indicate whether a plant is perennial or annual. That information helps inform his decisions of which plants to include in crossbreeding.

Why did you come to The Land Institute (TLI)?

Back in 2010, Lee (DeHaan) was overseeing both perennial wheat and Kernza® intermediate wheatgrass, but spending increasing time on Kernza breeding. So, TLI decided to hire a new person to focus on perennial wheat. My advisor at Oklahoma State University got the news from Stan (Cox) and encouraged me to apply. I graduated from Oklahoma State University back in 2009, then was at South Dakota State University for just 10 months doing post doctorate research before I came here.

Have you always done research on wheat?

I have worked on wheat since I graduated from college. My first job was annual wheat breeding in China. First, hybrid wheat breeding, then winter wheat breeding and genetics, and now, I work on perennial wheat breeding and genetics!

Do you feel you’ve grown the perennial wheat program substantially since taking it over?

Yes. I think Lee started with the perennial wheat breeding in 2001, together with Stan. In a paper written by Stan and Lee in 2008, 1,500 crosses had been made between 2001 and 2008. At the beginning, Lee tested some perennial lines from Washington State University and several other institutions, and none survived in our field. So, he decided to make new crosses trying to breed lines more adapted for heat and to Kansas’ environment: the weather changes, the moisture, soil…  He left me many seeds, and, more importantly, about 843 plants in the field. He told me it was the first time he had that many plants which survived both the summer and the winter in the field. I started with those plants and some seeds and plants in the greenhouse. Now we have tens of thousands of plants that have survived two or more years.

I know the greenhouse isn’t always representative of the field, but what’s the longest that you’ve had plants survive there?

Six years in the greenhouse, because there all the conditions are favorable, so plants have a better chance of long-term survival.

Are there any specific pests or pathogens that cause problems with perennial wheat?

Some of the old perennial wheat lines have lost resistance to rust disease. Another common problem is a disease called bacterial leaf streak, but it doesn’t occur every year. And it’s not a very big problem because wheatgrass is very resistant to all the prevailing diseases, so the hybrids of perennial wheat tend to be resistant. Disease is not a big concern for me.

Is your primary focus trying to increase grain production?

Not the grain production. Improving perenniality is more important in this stage. In addition to the perennial lines that Lee introduced, I introduced many more. We tested them in our field. All of them, except for a type called MT-2, are weak perennials. They regrow immediately after the grain harvest but could not survive the summer. MT-2 was developed by Montana State University and released around 1987 for forage production. The seed size is not big, and the fertility is low. I tested it in our field and found that it could survive the summer. It inspired me to think we should make new crosses like it. So, I introduced durum wheat cultivars and then made crosses with different wheatgrass species, including Kernza. I used colchicine to treat the hybrid F1 to restore the fertility and got many seeds from the treatment. I grew those seeds out in the greenhouse and the field, and they showed excellent field survival. So, I did more and more crosses or selections. Now we have many plants in the field that survive at least two years.

Another very important finding is that I realized that flowering time genes have a close relationship with perenniality.

That sounds like an important discovery – what does that mean?

Perennial plants flower more than once a year. We are trying to understand the flowering time gene to get them to only flower once a year at a specific time, so the plant survives all seasons.

Around 2012 or 2013, I tested many perennial wheat lines. After grain harvest, most of the plants died. But some of them dropped seeds during harvest, which germinated after rain. These plants, called “volunteer,” survived the summer. So, I started to wonder why the second-year plant is different from the first-year plant. Also, I did a mulch experiment. After the grain harvest I put about four-inch thick mulch on the ground to decrease the soil temperature and improve the moisture of the soil. In that experiment, some of the plants survived the summer but didn’t survive the winter. However, some volunteer plants around the experiments in the border strips (around the mulched area) survived the winter. This was a second example that a second-year plant is different from the first-year in terms of tolerance to some heat. I thought something weird must have happened in the transition from first-year to second-year. In genetics, this phenomenon is called memory effect, or a more technical term: epigenetic modification. Some genes are modified with time to maintain the memory of some environmental factors.

At that point, I found that even when the second-year plants were still very small, their growing point (the part of a plant where it keeps growing and finally forms a head), had been well developed, ready for flowering quickly. So, I realized flowering time genes might be the critical factors that underlie the difference between the second-year and the first-year plant.

Do you now use material from the second-year plant instead of the first-year plant for breeding?

I compare first and second-year plants. The growing point in the second-year plants is ready for flowering very soon. The outside looks more static before that point, but the inside may have changed significantly.  I do not know yet when that transition happens inside of a perennial wheat plant. In the first-year plant, the growing point stays dormant.

Once the wheat survives the first year, then it will produce every year?

It will produce many times in the same year. This is not good for summer and winter survival because when the plant is in the reproductive phase, it becomes vulnerable to adverse environments. It’s using more resources. In winter wheat, the winter allele (or variant form of a given gene) of the flowering time gene can suppress the plants in the winter and keep them from growing too quickly. It gives them protection, conserves their energy. Because of this finding, I am trying to find if there is a way to manipulate these genes in perennial wheat in order that the plants could stay vegetative. I want suppression to come back in the second year. Flowering more times is not good for the plant.

It looks like we have quite a few international partners (Turkey, Italy, Canada, Sweden, Germany, Australia, China) who are working on perennial wheat – are any of those programs that you collaborate with extensively?

This international collaboration started in 2011 when Lee DeHaan, Richard Hayes, Kevin Murphy, and I took part in the perennial wheat meeting at Michigan State University. At that time, a group of Australian researchers had just finished the evaluation of 155 perennial lines in Australia. They found that perennialized wheat from TLI and Washington State University had the best chance of surviving there. We discussed this and wondered if some environmental factors are more important for the survival of perennial wheat.

So, we came up with a collaboration called the genotype by environment (GxE) trial. We contacted many researchers and formed a group of 24 scientists in eight countries. Both Richard and I sent our own perennial wheat seeds to this group of researchers and tested a common panel of perennial lines following the same design across different environments to see how performance varied. We found a winter durum wheat by wheatgrass hybrid that showed greater longevity in test plots from Australia to Sweden. The five-year international trial ended in 2017. We have just finished a paper about the work, which was published in early 2018.

Are you planning any polyculture experiments or are you more focused on just further refining perennial wheat?

I am just focused on the wheat itself at this point. When I have a large quantity of seeds for the new perennialized wheat, I would like to try a bi-culture or intercropping with different species.

What are your current 5 to 10-year goals for perennial wheat and the program at TLI?

Because of the international collaboration, we know that no current model could guarantee the perennial wheat we have could survive for many years. So, we still need a lot of breeding. We tested our new perennial lines derived from durum by wheatgrass hybridization in the international GxE trial. The plants could survive at least two years in areas ranging from Australia to Canada – a wide range of environments. So, we will continue working on winter durum by wheatgrass hybridization, trying to get stable lines as quickly as possible.

This year in the field I have found several of these rows that survived from the year before. We will increase seeds on a larger scale the next year, then send the seeds to more researchers to test the potential. We have field-tested many generations of plants of this kind of hybridization since 2014. Most of them have little problem surviving at least two years, so that perenniality is much stronger than our older perennial lines. Next, we will keep improving this type of perennial wheat and try to increase the grain yield. The seed size of this new perennial wheat is pretty good, but the grain yield needs to be improved.

A second thing is to do more genetic studies on flowering time genes to get a better understanding of which genes control perenniality, then use the knowledge to get even stronger perenniality and improve the breeding efficiency. In this stage, it is difficult to select for perenniality. We need more molecular markers to assist in selection or use them to find more useful wheat cultivars or wheatgrass plants for the breeding. We are sequencing 26 important genes to search for useful variations in the breeding population.

In the past, we didn’t have perennial wheat that could live in our field for more than a year. As we now have developed this new wheat that has greater perenniality, we can start to try many other different things.

 

Check out the other interviews in the series!

Interview with a Plant Scientist: Stan Cox, Perennial Sorghum

Interview with a Plant Scientist: David Van Tassel, Perennial Oilseeds

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