Keynote Speakers

Citrus tristeza virus (CTV) is considered one of the most important viral pathogens of tree fruits, and Pappu was the first to decipher its genome structure and organization and structure–function relationships. His work laid the foundation for subsequent research on the molecular biology and host–CTV interactions.

Pappu is especially noted for his research on thrips-transmitted tospoviruses. Globally, these viruses cause more than $1 billion in crop losses annually to field and horticultural crops. Pappu developed an internationally recognized research and extension program on Tomato spotted wilt virus (TSWV), the most common and economically important tospovirus in the United States. He has published more than 50 refereed articles on TSWV and contributed to diagnostics and IPM for this pest complex. He was part of a team that field-tested transgenic peanut for TSWV resistance and developed a risk index for TSWV in peanut that was adopted by more than 80% of peanut growers in Georgia. He was the first to characterize a new tospovirus from watermelon that was a significant constraint to cucurbit production in parts of Asia. His findings provided clarity for tospovirus identification and paved the way for improved virus diagnostics and management.

In 2003, Pappu reported Iris yellow spot virus (IYSV) on onion in Washington State and, by 2005, it became the number one constraint on onion production in the Pacific Northwest. Pappu developed descriptors for virus strains, new experimental hosts for studying virus biology, improved screening protocols, and new detection tools and applied them to understand the epidemiology of the virus. Further, he evaluated and identified onion varieties with tolerance and developed a national network for IYSV surveillance and response. Pappu used IYSV and TSWV to investigate intervirus interactions at the molecular level in dually infected plants. He was the first to show genetic complementation between two viruses that resulted in the expansion of the host range, and his findings identified a new role for the viral gene-silencing suppressor in potentially modulating the biology and host range of tospoviruses. Using next generation sequencing technologies, Pappu was the first to obtain information on the origin, distribution, and abundance of TSWV-specific small RNAs. The findings could advance our understanding of the differential processing of vsiRNAs in antiviral defense and viral pathogenicity. His research on the genomics and proteomics of tospovirus infections has contributed to an increased understanding of virus–host interactions at the molecular level. His group prepared the first-ever protein interaction maps for tospoviruses in mixed infections. His recent research on using artificial microRNA-based approaches to trigger virus resistance in plants has opened up new possibilities for introducing broad-spectrum virus resistance.

Nursery and ornamental industry in the United States is valued at more than $5 billion and viruses are of quarantine concern affecting interstate and international commerce. Pappu identified and characterized new viruses infecting dahlia and developed molecular methods for their detection. His fundamental research has shown the existence of endogenous caulimoviral sequences and showed that these integrated viral sequences are present in cultivated ornamentals and in wild relatives at their center of origin.

Potato is Washington’s third largest crop, contributing more than $3.5 billion annually to the state’s economy. Pappu was the first to show that infection by Potato virus S (PVS) could result in the breakdown of late blight resistance. His research into genetics of this interaction identified a potential source of linkage between late blight resistance and virus susceptibility. His findings have important implications for potato breeding programs worldwide since PVS is a common potato virus and could compromise late blight resistance.

Pappu teaches two undergraduate courses (General Plant Pathology; Agricultural Food Systems) and a graduate course (Plant Virology). He was recognized by WSU as Mentor of the Year and Advisor of the Year. His contributions to the success of the department as one of the most productive units in the college were recognized with the Dean’s Meritorious Service Award. Pappu’s mark on the Plant Pathology Department cannot be overstated. As chair, he built the graduate program into the largest in the nation. In recognition of his international standing, Pappu was elected secretary of the International Working Group on Viruses of Legumes and Vegetables. He was invited to serve on the organizing committees of the International Symposium on Plant Virus Epidemiology and the International Symposium on Thysanoptera and Tospoviruses, and he was an invited participant in workshops organized by the Gates Foundation and FAO in Africa. He served as a reviewer of grant proposals from several countries and served on grant review panels of USDA, NSF, and the U.S. National Academies. Pappu’s outstanding and sustained record of research, teaching, extension, outreach, service, and administration make him highly deserving of the APS Fellow Award.