Virus diseases seriously affect potato and pea crops in the Pacific Northwest. The most serious of these are vectored by aphids and management focuses on aphid control. Better understanding of aphid behavior and patterns of infection could improve effectiveness of these control methods. This proposal aims to understand better the effects of virus infection on the behavior of the aphids that are the required vectors for these viruses. The project focuses on Potato leaf roll virus in potato and Bean leaf roll virus and Pea enation mosaic virus in pea. We know that virus infection influences aphid development and behavior. The project will better describe and understand the basis of these responses and use the information to model their effects on virus spread. In pea, we will conduct a parallel project assessing spatial and temporal patterns of infection of pea by Pea enation mosaic virus and Bean leaf roll virus as a basis for forecasting risks of virus infection that producers can use to make treatment decisions.
Part 1. Chemical Ecology of Virus-Plant-Vector Interactions a. Determine the role of nonvolatile cues (gustatory, visual) from virus-infected plants on aphid behavior. b. Determine the mechanisms of volatile release from infected potato plants. c. Measure behavioral responses of green peach aphid to other Solanum tuberosum genotypes and to S. nigum. d. Assess pea aphid responses to Bean leaf roll virus-infected pea plants. e. Examine the effects of aphid behavioral responses to virus-induced changes in plants we are studying on virus spread using computer-based simulation modeling.
Part 2. Risk Assessment for viruses Affecting Legumes a. Pursue development of virus risk detection in legumes based on monitoring immigrating pea aphids. b. Assess the spatial patterns of virus infection in the crops in the region over several years to determine the location of infectionb hot spots. c. Publish results of regular monitoring of immigrant pea aphids to a web site for use by producers. d. Search for the source of PEMV inoculum in the region or to the west where aphid colonists evidently originate.
This project has two conceptually linked sections. The first concerns the interactions between aphid vectors and virus-infected plants mediated by volatiles and other cues. The second concerns monitoring viruses and deciphering patterns of infection to assist with vector based management of viruses affecting legumes in the inland Pacific Northwestern USA. The approach for the first part involves laboratory based studies of aphid responses to plants infected with viruses they vector. Bioassays will assess aphid preference for infected plants as it changes during the disease cycle in potato infected with Potato leaf roll virus and in peas infected with Bean leaf roll virus. Aphid responses will be used to parameterize models of aphid movement and subsequent secondary spread of these viruses in potato and pea crops. The approach for the second part involves field based monitoring of the occurrence of Pea enation mosaic virus and Bean leaf roll virus throughout the Palouse region where dry peas are grown over several seasons. Virus will be monitored in fields and in trapped incoming aphids using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) methods. The patterns discerned will be used to accumulate sufficient information to develop a risk assessment model for use by growers.