By John Lovett, University of Arkansas System Division of Agriculture, Arkansas Agricultural Experiment Station
Arkansas Soybean Breeding Team
With an increasing frequency and intensity of flooding events and an eye to capitalize on a common rice production technique, soybean breeders are on a quest to develop varieties with flood tolerance at any stage in the plant’s development.
Caio Vieira, assistant professor of soybean breeding and a researcher for the Arkansas Agricultural Experiment Station, the University of Arkansas System Division of Agriculture’s research arm, is the lead author of a study offering more insight into how soybean plants respond to flooding in the critical early reproductive stage. The study, “Impact of flooding at the early reproductive growth stage on soybean yield and seed composition,” was published in the journal Crop Science.
“Flooding research has focused on the early reproductive stage simply because it is when the stress is most pronounced and causes the greatest yield loss,” Vieira said. “Across the mid-South, soybeans are most susceptible to flooding at the R1 stage.”
Vieira said that temperature changes in the United States have allowed earlier soybean planting dates so that shifting rain patterns are also resulting in additional stress on the soybean plants.
“The intensity and frequency of rain has been shifting to earlier in the season,” he added. “We’re pretty much getting the potential for flooding throughout the season.”
Typically, soybeans in Arkansas are planted from early April to mid-May, which puts the R1 stage in late June to early July. As growers see the benefits of earlier planting, Vieira said, naturally, the early reproductive stage would also shift.
While grain yield losses from flooding stress have been well documented, Vieira said there has been a gap in literature on the impact of flooding on soybean seed composition. The study compared 31 soybean genotypes over the 2019 and 2020 growing seasons. The plants were exposed to non-flooded and flooded conditions to look at yield and seed composition. A surprising discovery, Vieira said, was that four-day flooding in the early reproductive stage did not significantly alter the soybean seed composition of any of the varieties tested compared to the non-flooded control group.
Visual inspection of flood-damaged soybeans has been useful, Vieira noted, but it doesn’t tell the whole story. The study found that some genotypes visually classified as “moderately tolerant” to flooding had higher yields than those classified as “tolerant.” On average, for each unit increase in flood damage score, the study showed that grain yield decreased by 17.4%. Tolerant genotypes experienced roughly 33% yield losses between flooding and non-flooding treatments, while “moderately” tolerant and “susceptible” genotypes experienced 44% and 51% yield losses, respectively.
Vieira said the study will help his team identify and incorporate flood-tolerant characteristics into future soybean genetics.
In a recent update to the study, Vieira said they have developed a model using molecular markers that can accurately identify tolerant/susceptible genotypes before reaching the field. This work has been accepted at The Plant Genome.
Co-authors of the study included Arkansas Agricultural Experiment Station program associates Chengjun Wu, Liliana Florez-Palacios, Andrea Acuna, and Derrick Harrison; program technician Daniel Rogers; former experiment station faculty member Leandro Mozzoni; and John Carlin, director of the Arkansas Crop Variety Improvement Program. Henry Nguyen and Grover Shannon of the University of Missouri Plant Science and Technology department were also co-authors.
The study was supported by funding from the United Soybean Board and the Mid-South Soybean Board.
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