Uncovering Disease Resistance in Soybean
A major effort to identify the genes essential for the soybean plant's defense against three diseases will be supported by a new $2.1 million grant by the National Science Foundation under its Plant Genome Research Project. This project holds great promise for Missouri, where soybeans reign as the number one cash crop.
The project, which is being led by Iowa State University, will focus on genetic resistance against three important soybean pathogens: soybean mosaic virus, Asian soybean rust and soybean cyst nematode. Melissa Mitchum, assistant professor of plant sciences at the University of Missouri and member of the Interdisciplinary Plant Group, will help lead the research on the soybean cyst nematode.
According to the National Agricultural Statistics Service, 4.6 million acres of land in Missouri were planted with soybean in 2007, yielding approximately 1.8 tons of soybean and $1.7 billion in production. Although no statistics exist on the impact of the cyst nematode on soybean yield in Missouri, yield losses linked to the cyst nematode have been estimated to cost U.S. soybean producers $750 million annually.
Despite the heavy reliance on host plant resistance to manage this nematode, scientists know little about the specific genes responsible for defending the soybean plant against the cyst nematode or against any diseases for that matter. Mitchum, along with her colleagues at Iowa State University, hope to close this knowledge gap by identifying the defense signaling pathways in soybean.
"Currently, more than 95 percent of soybean cultivars in the field derive their resistance from a single source of resistance, a plant introduction called 88788," explains Mitchum, who is also an investigator in MU's Christopher S. Bond Life Sciences Center. "The problem with having a single source of resistance is that we end up selecting for populations of the nematode that can grow on that type of resistance. We can deploy new types of resistance using natural resistant cultivars, but the same thing is going to happen: the nematode is going to adapt."
To overcome this cyclical problem, Mitchum and her colleagues will use a new approach in soybean, called virus-induced gene silencing, to identify the genes that provide the underlying basis of resistance in the soybean plant.
"Once we understand the genetic mechanism for resistance in the plant, we can then use that information to assist breeders in developing soybean cyst nematode resistant cultivars as well as design novel transgenic resistance," said Mitchum.
Additional benefits of the project include training of MU undergraduates and K-12 teachers, which may encourage students to consider careers in the plant and biological sciences.
Mitchum said the success of the NSF grant application was rooted in results of earlier studies supported by the Missouri Soybean Merchandising Council.