Author: Dr. Punya Nachappa Assistant Professor, Department of Biology Indiana University - Purdue University Fort Wayne
Soybean is an important crop throughout the world due to its versatility as a food source along with applications in various industries such as textiles and biofuels. Soybean growth and productivity is adversely affected by multiple environmental stresses including extreme weather events, insect pests and diseases. One of the biggest threats to soybean production in the U.S is caused by an insect pest, the soybean aphid and a plant virus, Soybean mosaic virus that the insect transmits. Insect pests and diseases are likely to be affected by climate change but there is little empirical evidence related to insect responses with respect to pathogen transmission. Our goal was to determine whether drought and flooding altered soybean aphid population and virus levels (Nachappa et al. 2016). We found that aphid population was reduced on drought-stressed and saturated plants compared to well-watered plants (Figure 1).
Interestingly, virus levels was lowest under drought stress and highest under saturated conditions (Figure 2). We were able to show that aphid population was correlated with aphid feeding on the corresponding plants (Nachappa et al. 2016). For example, aphids spent less time feeding on saturated and drought-stressed plants compared to well-watered plants, which presumably resulted in lower populations on these plants. Analysis of the nutrient content revealed that drought-stressed plants had highest amount of amino acids but it did not benefit aphids (Nachappa et al. 2016).
We believe that quality rather than quantity of specific amino acids is important for aphid populations. Gene expression analysis indicated that multiple plant defense genes are involved in the interaction between water stress, soybean plant, aphid and virus. Taken together, these data suggest that the mechanism(s) underlying the impact of water stress on aphid feeding and virus infection is complex and likely involves several plant functions including, nutrient content and defense responses.
Nachappa, P., C. T. Culkin, P. M. Saya, J. Han, and V. J. Nalam. 2016. Water stress modulates soybean aphid performance, feeding behavior and virus transmission in soybean. Frontiers in Plant Science 7.