I am going to date myself but, when working at the University of Illinois Plant Clinic during graduate school, I can remember finding these strange brown/yellow blotches or symptoms near veins on soybean leaves submitted to the Clinic. After further investigation, we knew these symptoms were not caused by bacteria or fungus. Nancy Pataky, former U of I Plant Clinic diagnostician, would collect the leaves and take them to various specialists (virologists and weed scientists) on campus hoping to get more answers. Now that I am in the industry a plant breeder said he had seen symptoms even earlier, so we now know that soybean vein necrosis virus (SVNV) has been around for quite some time in Illinois, but no one had fully identified the issue.
In 2008 SVNV was first confirmed in Arkansas and Tennessee (Tzanetakis et al. 2009; Zhou et al. 2011) and after its detection, it was found throughout soybean-producing regions of the United States. SVNV is one of two tospoviruses that can infect soybeans. Tospoviruses or SVNV are transmitted by several different kinds of thrips to soybeans. I normally see SVNV symptoms show up later in the season, but the timing of infection could be related to thrip arrival and feeding. There are also hints that some soybean varieties could be more susceptible to SVNV, but there needs to be more research done on soybean cultivar response as well as on the impact of disease severity. Recent work (Groves et al. 2016) showed that SVNV is seed transmitted, which means it can move systemically through the plant.
Since SVNV is a newly discovered disease, no one truly knew its effect on soybean production until recently. On August 9, 2017, the Effect of soybean vein necrosis on yield and seed quality of soybean was published. The objectives of this study were to evaluate the impact of SVNV on yield (seeds per pod, pods per plant and seed weight), as well as determine the effect of SVNV on soybean seed quality (protein, oil and fatty acid). Data for this study was collected in 2013, 2014 and 2015 from six states. Protocols differed across states because of variations in disease levels. Ultimately, the research concluded that SVNV influenced the quality and chemical composition of harvested soybean seed, but had little negative effect on overall yield of the plants. Again, more soybean cultivar and SVNV infection timing research is needed to fully investigate the effects of SVNV on seed size and yield.
SVNV, like other viruses, can cause changes to oil content and fatty acid composition of soybean seed. When the plant is under stress from viral infections, there may be less photosynthate activity or energy to produce protein or oil. In addition, like other viruses, SVNV causes soybean seeds to have decreased palmitic, linolenic and stearic fatty acids. Thanks to this study’s findings, we will have a foundation for further studies on the impact of SVNV on seed quality. This research is appreciated because of soybean’s importance as an oilseed and its economic significance in specialty markets.
Stephanie Porter is a sales agronomist with Burrus® Hybrids. She educates growers and Burrus staff on all types of pests, weeds, diseases and other agronomic issues that affect corn, soybean and alfalfa production. She is a 2017 Illinois Soybean Association CCA Soy Envoy.