Radwan emphasized that it's not just soybean crops at risk. The fungus causes charcoal rot in about 500 other host plants, including corn, sorghum, sunflower, and other important crops. This fungus also grows in high concentrations of salt, which isn't much of a problem to growers in the United States, but it is for farmers in developing countries where salinity is considered an issue. Consequently, the plant must be able to tolerate drought, salt, and resist this fungus at the same time.
One intriguing direction Radwan described that shows promise is that there may be interactions between M. phaseolina and other soil pathogens such as soybean cyst nematode (SCN) and sudden death syndrome (SDS).
"We have some assumptions about whether SCN can increase or decrease the incidence of charcoal rot as resistance to both pathogens might be controlled by two different pathways," Radwan said. He explained that biotrophic pathogens such as SCN need plant tissue to survive, but the fungus that causes charcoal rot is necrotrophic, meaning that it kills the plant tissue, then lives on the dead plant cells.
"We need to understand at the molecular level how these two pathogens interact when they are present in soybean fields. Understanding the mechanisms of molecular interactions between SCN and M. phaseolina will help molecular biologists and breeders to design an effective method to control both diseases and to breed soybean for resistance to both pathogens," he said.
Although no plants have complete immunity from the fungus, some soybean lines have been shown to have partial resistance to it. Hartman's group has already begun screening many lines in soybean for resistance to charcoal rot.
In controlled greenhouse conditions, Radwan grows a variety of soybean cultivars in sandy soil and then stops watering the plants
|Contact: Debra Levey Larson|
University of Illinois College of Agricultural, Consumer and Environmental Sciences