PIRE: U.S.-East Africa Research and Education Partnership: Cassava mosaic disease - A paradigm for the evolution of insect-transmitted plant virus pathosystems

North Carolina State University, Raleigh NC

Investigators

Abstract

This PIRE project establishes a research and training partnership between scientists and students in the United States and East Africa to study how plant DNA viruses change over time. Plant DNA viruses have emerged as leading pathogens that threaten crops worldwide. These studies will focus on Cassava mosaic disease, which is endemic to Africa and severely limits the production of cassava, a major food crop across the continent. Because Africa is one of the fastest growing regions in the world, with a population projected to double to 2.4 billion people by 2050, producing sufficient quantities of high quality, nutritious food is a challenge there. Agriculture is increasingly a global enterprise and finding solutions to food security problems will depend on research partnerships such as this one that explores the basic science of how plant DNA viruses evolve and what limits their ability to adapt over time. Such fundamental knowledge can then be used by others to develop rational, durable strategies to control these important plant pathogens. The project, which relies on the combined expertise and resources of U.S. and African participants, provides an excellent framework for training U.S. students to develop their scientific skills and to work in a global community to help ensure the future security of the developing and developed world. Molecular evolution of plant viruses occurs through mutation, recombination and reassortment of viral genome components, resulting in a high degree of variation. In complex pathogen-host systems, the evolutionary outcomes are influenced by many ecological factors including agricultural practices, insect vector populations, interactions between crops and reservoir plants, and climate. Most of our knowledge of viral evolution is based on field-collected samples, which only provide snapshots of viral diversity at specific times and locations. To examine the full evolutionary potential of plant DNA viruses and the bottlenecks that constrain their evolution, we propose a comprehensive analysis of the drivers of viral genetic diversity, emergence, persistence and spread under tightly controlled experimental conditions. We will focus on the DNA viruses that cause Cassava mosaic disease using NexGen sequencing to compare their diversity during vegetative and whitefly transmission, in mixed infections, and in wild plants that serve as reservoir hosts. We will ask if movement through the host plant and/or transmission by insect vectors serve as bottlenecks that limit viral diversity. Our study of the evolutionary potential and factors that contribute to Cassava mosaic disease is transformative in that it will provide a comprehensive framework for examining viral evolution in relationship to the host, the insect vector and the environment using a crop and inoculation methods that accurately reflect real world conditions. Our integrated approach will also serve as a model for examining viral evolution and will inform the development of control strategies for other insect-transmitted viruses that negatively impact plant, animal and human health. Postdoctoral researchers, graduate students and undergraduates will be mentored by a strong international research team, which includes experts on viral population genetics, insect vector transmission and population dynamics, virus/vector/plant interactions, and STEM education. The multidisciplinary nature of the research will provide trainees experience in laboratory and field-based research as well as bioinformatics. This will prepare them to become globally engaged, independent scientists with a solid foundation in a range of research methodologies and environments and first-hand experience in international and multidisciplinary collaborations.