LSU AgCenter Unlocks Secrets Beneath the Soil for Sweet Potato Yields, Lower Fertilizer Use
LSU AgCenter
BATON ROUGE, La. — A dedicated group of researchers are behind the sweet potato casserole that will grace many Louisiana tables on Thanksgiving. At the LSU AgCenter Sweet Potato Research Station, scientists have developed sweet potato varieties that have ample sweetness for consumers, ideal shape for processors and high yields for farmers.
One project at the station is aimed at helping growers produce their crop with just the right amount of fertilizer. LSU AgCenter researcher Arthur Villordon is leading the study that uses gene expression to predict the fertilizer requirements of sweet potatoes by variety.
Researchers can’t see what is happening with the storage root of the sweet potato plant — the part we eat — while it develops underground. Villordon said this study can give them new insights into what is happening beneath the soil.
“What if we can hear what the plant says? What if we can communicate with the plant?” Villordon said. “That’s where gene expression profiling comes in.”
Villordon, relying on prior research in other plant systems, was able to identify candidate genes that express nitrogen and phosphorus needs, calling it a game changer.
Lisa Arce, a doctoral student working with Villordon, helped carry out the research. Her work focused on characterizing gene expression patterns. Gene expression is how plants communicate with the environment and interpret its signals. She did this by subjecting the genes to low nitrogen and phosphorus conditions and using quantitative polymerase chain reaction to better understand the plants’ responses at the molecular level.
“We will know if those genes are upregulated or the expression is higher if they are under low nutrient conditions,” Arce said.
She said fertilizer recommendations in Louisiana are typically 45 pounds of nitrogen per acre, 80 pounds of phosphate per acre and 120 pounds of potash per acre. The researchers questioned whether this was best for all cultivars.
“Based on our research that we have conducted, it’s not best all the time, and certainly more is not always better. So that’s why we wanted to investigate what’s the molecular basis behind cultivar-specific fertilizer requirement,” Arce said.
The research led them to nutrient transporters. Arce described them as delivery trucks that bring nitrogen and phosphorus from the soil to the root and help the plant absorb the nutrients. They determined that cultivars with what they called active transporters need less fertilizer while those with lazy transporters need more.
Through two years of greenhouse trials and third year with a field trial, the researchers discovered the accurate fertilizer requirements for popular sweet potato varieties. The variety Beauregard needs more nitrogen than Orleans, and Evangeline needs more phosphorus than Bayou Belle. These outcomes affect the shape and size of the storage root.
“If we grow Bayou Belle under low phosphorus condition, it will form storage roots that are blockier-shaped,” Arce said. “This is important because processors like blockier shaped roots for more efficient and uniform slicing.”
With this information, the researchers can tailor cultivar-specific recommendations.
Villordon said it is possible that growers have been applying too much phosphorus to their fields all this time. He said they will get more precise with growers.
“We will be able to tell the growers that you’re in this field, and this field has too much phosphorus. And if you’re growing this cultivar — maybe Bayou Belle — maybe you don’t need to be putting in phosphorus anymore.”
This can lead to savings for growers.
“That means no more spending money for those fertilizers or nutrients that your specific cultivars don’t really need,” Arce said. “We are one step closer to achieving our main goal, which is to help our growers earn more by spending less.”