A Curators’ Distinguished Professor in the Division of Plant Sciences, Henry Nguyen’s longstanding research focus is related to abiotic stress tolerance and disease resistance in plants, primarily soybeans. Two United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) grants, totaling almost $900,000, will allow Nguyen to build on those focus areas.

The grants will help Nguyen and his team tackle important issues related to soybeans, including waterlogging tolerance and soybean cyst nematodes (SCN). Flooding and SCN cause billions of dollars worth of damages every year.

“These are incredibly important projects, as yield loss from flooding and soybean cyst nematodes truly affect a farmer’s bottom line,” Nguyen said. “We want our soybean lines to be as effective as possible, so diving into their genetic makeup is a vital part of the process. We need to understand these genetics, and the sooner the better, as these flooding events and nematode issues continue to be a major issue facing our farmers and producers.”

Waterlogging Tolerance and Yield Stability

As flooding events ramped up in 2019, affecting numerous Midwest states, crop losses were widespread as water sat in fields for days and weeks at a time. With a research program in molecular genetics, genomics and biotechnology, Nguyen and his team are looking at how to make the soybean plant more tolerant to extreme flooding events.

“Studies have found that when there is a heavy rain and waterlogging occurs for just two to three days, yield is reduced by around 20 percent,” Nguyen said. “If that waterlogging takes place for seven to 10 days, yield is reduced by around 80 percent.

“Waterlogging is also much more difficult for producers to see, as pests and drought, for example, leave behind definite signs of stress. Flooding stress oftentimes isn’t caught until it’s too late to act.”

Nguyen’s team has map-based, cloned and validated a candidate gene that features a major waterlogging tolerance trait (qWT_Gm03). That candidate gene encodes a Small-Auxin-Up-Regulated (SAUR) protein that helps root development under waterlogging stress. Waterlogging events force the roots of the soybean plant to be under constant stress.

“The candidate gene, qWT_Gm03, is involved in altering the soybean root system,” Nguyen said. “When the soybean plant is under flooding stress, there is a lack of oxygen that causes the plant to not grow. Ideally, the candidate gene allows for nutrient uptake and helps the plant overcome flooding stress, which allows it to not struggle as much under flooding conditions.”

Within this grant, Nguyen and his team are looking to characterize the naturally occurring SAUR-FT (flooding tolerant) protein variation in the soybean germplasm, as well as develop a waterlogging tolerant and high-yielding germplasm. They are also evaluating the agronomic importance of SAUR-FT in sustainable soybean production.

“We’re working to understand the candidate gene,” Nguyen said. “We’re in the final stretch of studying the function and its molecular mechanism.”

Nguyen is collaborating with Julia Bailey-Serres, director, Center for Plant Cell Biology at the University of California, Riverside, on the project.

Soybean Cyst Nematodes

Soybean cyst nematodes are one of the biggest pathogen pest problems in the soybean industry in the United States, causing more than $1 billion in damages. It’s a massive problem that causes serious and prolonged yield loss. Nguyen said that soybean breeding programs have depended on a couple of different sources of genetic resistance for the past 20 years.

“Genetic resistance is still the best strategy for management of soybean cyst nematodes,” Nguyen said. “Pesticides can be used for immediate problems, but they aren’t the best long-term strategy. Nematodes can become resistant to those pesticides over time, plus there is the cost factor – not to mention the possible environmental concerns.”

Resistance genes at rhg1 and Rhg4 have been utilized for the past 20 years in those breeding programs; however, the continuous use of these two sources have led soybean cyst nematodes to develop resistance. Nguyen is looking at how to combat that resistance and find new ways to handle the pests.

“Soybeans have started to break that resistance,” Nguyen said. “Soybean cyst nematode populations are shifting and evolving. We have to find other sources of resistance.”

Nguyen is looking at an exotic soybean line, PI 567516C, that carries two novel genes for SCN resistance that, according to Nguyen, seem to display different mechanism of action than the previous resistance genes.

“This is definitely a unique source of resistance,” Nguyen said. “We’re in the process of figuring out what those two novel genes do; the molecular mechanisms of those genes. We’re wanting to come up with new genetic solutions.”

Nguyen said the Fisher Delta Research Center, located in Portageville, Mo., has a long history of SCN genetic research. The Research Center has been at the forefront of SCN genetics, and Nguyen is looking forward to building on SCN research that is already taking place there.

Nguyen is collaborating with Khalid Meksem, professor, Plant Soil and Agricultural Systems, Southern Illinois University, Carbondale, on the project.

“It’s a process, one that can take three to five years to develop commercially competitive varieties,” Nguyen said. “Once we get the gene nailed down, we start doing gene editing and then it will enter a breeding program. We’ll plant it and test its yield. There are several steps in the process, but it’s an exciting process resulting in new solutions for durable SCN resistance.”