WOOSTER, Ohio - Ohio State University and U.S. Department of Agriculture researchers are screening a variety of soybean lines in the hope at least one will show resistance to a soybean virus relatively new to Ohio.
The bean pod mottle virus, transmitted by the bean leaf beetle, was reported in Ohio the past two years and researchers and growers are monitoring this year's soybean crop for its presence. "Before 1999, this virus had never been found in Ohio," said Anne Dorrance, an OSU plant pathologist. "We found it again in 2000 and that prompted us to begin studying this virus." Researchers inoculated 15 soybean lines -- including food-grade, insect-resistant, grain, and low-fat varieties -- with the virus to determine if any of them show resistance and how much the virus may impact yields. "We know very little about this virus, how the bean leaf beetle transmits it, where the virus comes from, or if yield is really affected," said Dorrance. "It could be that the virus does little to yields, but if it does, then hopefully we'll have resistant lines that can be incorporated into existing commercial varieties." Bean pod mottle virus has been associated with the occurrence of green-stem syndrome, a condition where the stems of the soybean plant remain green up to harvest. "The beans are really dry. They only have seven or eight percent moisture, which is way too low to harvest, and the stems are tough and green," said Dorrance. "In severe cases, the pods become malformed and stand upright on the stem." By inoculating various soybean lines, researchers hope to confirm that the virus is the cause of the symptoms.
Researchers are also studying the bean leaf beetle to determine which generation carries the virus and at what point during the season the insect transmits the virus to the plant. "We are collecting beetles all over the state at various stages of their life cycle and studying which generation is carrying the virus and seeing how that correlates with the appearance of the disease at the end of the year," said Peg Redinbaugh, a USDA plant molecular biologist.
The insect has three generations: an over-wintering generation, a first generation that emerges in mid to late July and a second generation that emerges in mid to late August. "We are trying to find out if the virus is present in the over-winter generation," said Redinbaugh. "Previous data suggests that if the virus is present in this generation, it is not transmitted to soybeans. So, where does the virus come from?" Researchers believe the virus enters the plant at the beginning of the season, in April or May.
The study, which began in June, is expected to be completed by December or January of next year. "We are not sure what the impact of this virus is going to be on growers. I think we are taking a very proactive approach," said Dorrance. "It's important to find the answers before growers have serious problems. I hate standing in a grower's field and saying to him or her that I don't know."