Rosemarie Wahnbaeck Hammond was born July 13, 1953, in Houston, TX. She received a B.S. degree in botany from Miami University, Oxford, OH, in 1975. She then earned M.S. (1977) and Ph.D. (1981) degrees in botany from the University of Tennessee, Knoxville. After postdoctoral positions at Purdue University and USDA Agricultural Research Service, Hammond joined the Molecular Plant Pathology Laboratory, ARS, USDA, Beltsville, MD, as a research plant pathologist in 1988.
Hammond’s research career began by studying regulation of the biosynthetic pathways leading to synthesis of lysine, threonine, and methionine in corn and spinach. In 1979, Hammond found that the enzyme that catalyzes the first, and the rate-limiting step in the pathway, is localized in the chloroplast, thus providing new insight into biological constraints on storage protein synthesis and quality.
As a postdoctoral research associate in the Department of Botany and Plant Pathology at Purdue University, Hammond studied the Bowman-Birk trypsin inhibitor protein of soybean seed. She successfully obtained and sequenced the first cDNAs corresponding to the gene for this inhibitor. This protein functions in protecting plants from microbial invasion and may serve as a site of sulfur storage in the seed.
Hammond then changed research emphasis and began her career in plant pathology at the University of Maryland and USDA. Hammond worked with Ted Diener and Robert Owens and became recognized as a national and international authority on the structure and function of viroids, unique phytopathogenic RNA molecules that encode no proteins. Hammond’s creative application in 1987 of site-directed mutagenesis to study structure/function relationships in Potato spindle tuber viroid resulted in the discoveries that certain single-site mutations can render an infectious viroid nonviable and that other mutations may change symptoms elicited in hosts or may alter movement or cell-specific replication of the viroid. Her discovery in 1989 of a naturally occurring chimeric viroid and of alternate cleavage sites that exist within the viroid molecule proved conclusively that intragenomic RNA recombination is involved in viroid evolution. In 2000, Hammond discovered that viroid infection induces the synthesis of a host protein kinase, opening the way for studies of the kinase’s involvement in signaling pathways leading to symptom induction in diseased plants. These landmark discoveries contributed fundamental new understanding of the complex genomic and structural determinants of viroid replication and disease induction, and they opened avenues for novel strategies to engineer useful viroid disease resistance in plants, a critically important step since no conventional genetic resistance to viroids is known.
While making pioneering advances in fundamental understanding of viroids and the diseases they induce, Hammond has also addressed a series of practical problems. For example, she molecularly characterized numerous viroids associated with diseases of international importance, including citrus B viroid in Italy and Indian bunchy top disease of tomato, and with collaborators, discovered citrus viroids and Potato spindle tuber viroid in the principal citrus and potato production regions of Costa Rica, pointing out the need to develop certification programs for these crops.
Hammond also demonstrated strength and versatility by applying her expertise and originality, nationally and internationally, to molecular characterization, detection, strain differentiation, and understanding of the evolution of two agronomically important plant viruses, Prunus necrotic ringspot virus (PNRSV) and Maize rayado fino virus (MRFV). She developed the earliest nucleic acid probes for diagnostic use, and she identified and characterized the coat protein genes of these viruses for use in engineering disease-resistant plants. Her design of a polymerase chain reaction-based assay for pathotype differentiation of PNRSV strains advanced disease control. With colleagues, her molecular analysis of MRFV, which causes significant yield losses in maize throughout Central and South America, demonstrated distinct evolutionary lineages in Latin America. In 2001, she determined the complete nucleotide sequence of the MRFV genome, providing fundamental new knowledge of the virus as well as molecular tools to engineer resistance to MRFV in maize. In conjunction with these contributions, Hammond and collaborators at the University of Costa Rica identified two Zea mays accessions with resistance to MRFV, providing critical germplasm for maize breeding programs in the Americas.
Recently, Hammond led the design of novel plant virus-basedgene vectors, which she and colleagues R. A. Owens and Y. Zhao have utilized to demonstrate nuclear targeting of PSTVd RNA molecules. This advance provides unique insights into cellular pathways that viroids harness for movement in plants, opening the way to understanding RNA trafficking in healthy plants.
In recent achievements beyond plant pathology, Hammond also led research that developed virus-based vectors as novel epitope display systems for vaccine production, for creating a complementation system to express and evaluate disease resistance genes, and for producing a biologically functional bovine protein for treatment of mastitis. This pioneering technology provides safe and affordable pharmaceutical products and alternative value-added agricultural products.
Hammond’s achievements demonstrate a career-long dedication to advancing knowledge in plant physiology and plant pathology through personal and team research. During the past decade, she initiated national and international collaborations and trained numerous U.S. and foreign visiting scientists, who were attracted to share her creative insights. In recognition of her accomplishments, Hammond has been invited as a U.S. and international consultant for IAEA and US AID, served as principal plant pathologist at USDA CSREES, and delivered many invitational seminars at national and international meetings. She has authored or coauthored 99 papers in referred journals, reports, reviews, and book chapters and has coauthored three invention disclosures and a patent application. Hammond served as member and vice chair and is currently chair of the APS Virology Committee and has organized and chaired special sessions at APS annual meetings. She served as associate editor for Plant Disease, is adjunct professor at the Center for Biosystems Research of the University of Maryland Biotechnology Institute, and is frequently sought to review grant proposals and manuscripts for APS and other professional scientific journals.
