James H. Graham, Jr.
James H. Graham, Jr. grew up near Philadelphia, PA, and received his B.S. degree in biology from the University of California, Irvine. Subsequently, he received his Ph.D. degree from Oregon State University in 1980, working on ectomycorrhizal symbiosis and soilborne diseases. Later, he spent 2 years as a postdoctoral fellow with John Menge, investigating arbuscular mycorrhizal fungi at the University of California, Riverside. In 1981, he was appointed assistant professor of soil microbiology at the University of Florida, Citrus Research and Education Center (CREC), and he was promoted to full professor in 1991.
His initial assignment was to investigate the etiology of citrus blight. He contributed to the evaluation of soil organisms in relationto that disease, to the development of diagnostic tests for thedisease, and to the eventual demonstration of graft transmissibilityof blight.
Graham developed an extensive program on Phytophthora diseases of citrus early in his career. One of his major contributions, along with L. W. Timmer, was the development of a quantitative assay for soil populations of P. nicotianae that allowed determination of the effect of root rot on yields of citrus. He discovered that P. palmivora was a major pathogen in Florida and elucidated its role in brown rot of fruit and in a serious decline disease associated with the root weevil, Diaprepes abbreviatus. Graham investigated that decline and showed that it resulted from a complex ofinsect larval feeding, causing severe structural root damage with rapid tree loss in the presence of P. palmivora. The discovery that trifoliate orange and hybrids, such as Swingle citrumelo, were susceptible completely redirected the efforts of rootstock development programs. Graham currently is working with the plant improvement teams of the University of Florida and USDA to discover and evaluate new sources of resistance.
Throughout his career, Graham has maintained a program on mycorrhizal fungi, emphasizing the costs and benefits to the host. In collaboration with D. M. Eissenstat, he developed methods to study the interactions of phosphorus supply and mycorrhizal fungi on the carbon economy of citrus. Genotypic control of root colonization in relation to carbohydrate supply to the fungus was defined and the basis for growth depression of citrus at high phosphorus supply was assessed. They defined “aggressiveness” of mycorrhizal fungi as the rate of root colonization and found that higher colonization rates predicted increased phosphorus uptake and greater carbon cost of fungal genotypes. They were the first to demonstrate the carbon cost of mycorrhizae in the field. They were also the first to study mycorrhizal effects on the ecophysiology of roots of mature trees and reveal that mycorrhizae increase root longevity in dry soils. With several collaborators, Graham explored the broader implications from cost/benefit analyses in relation to the functioning of mycorrhizae at high nutrient supply in wheat, vegetables, and sugarcane.
When citrus canker was discovered in the mid-1980s, Graham redirected his program and made major contributions to research on Xanthomonas axonopodis and served in an advisory role to regulatory agencies and the citrus industry. In the early years, he was instrumental in characterizing citrus bacterial spot, a nursery disease that was confused with canker and resulted in the eradication of many nurseries. His work led to the discontinuation of eradication for that disease. He cooperated with the Citrus Canker Eradication Program (CCEP) and conducted research and provided information aimed at improving control and eradication of canker. Graham collaborated with T. R. Gottwald and CCEP to demonstrate that the 125-ft eradication radius was inadequate to suppress the spread of citrus canker. As a result, a new regulation, the “1900-ft rule”, was put into practice in late 1999. Eventually, the eradication program proved to be unsuccessful after several hurricanes in 2004–2005, and Graham now has developed programs to manage canker by regulatory means and by the use of windbreaks and copper bactericides. He was a leader of the Citrus Health Response Plan and worked with nurserymen and growers to revamp the citrus nursery industry in Florida from the field to indoor production to produce trees free of canker and greening disease.
In addition, Graham has made contributions to the characterization of the canker pathogen and to molecular diagnostic techniques. Existing sets of polymerase chain reaction (PCR) primers were inadequate for the detection and identification of certain canker strains. Graham and J. Cubero, a postdoctoral associate from Spain, designed and applied new primers that detect all canker strains. A novel protocol utilizing rep-PCR elements was applied to identify the genotypes present in outbreaks of canker in Florida and worldwide. Genotype identification of Florida strains has been used for tracking and risk assessment in existing and new outbreaks of canker. Three genotypes were discovered, indicating that separate introductions of the disease have occurred over the last 20 years and that most of the new outbreaks of canker were due to spread of the Miami strain introduced in 1995.
His research program has been well funded and he has received about $7.5 million in grants from USDA CSREES and more than a million dollars from the citrus industry and commercial sources. Graham has contributed to the profession in many other ways as well. He served as an associate editor of Phytopathology, held editorial posts with Plant & Soil and New Phytologist, and is currently an editor for APS PRESS. Graham received the Lee Hutchins Award several years ago for his contributions to the understanding of canker and bacterial spot. Graham contributes greatly to CREC, the University of Florida, and to the citrus industry of Florida and worldwide. He has trained several Ph.D. and master’s students and frequently receives visiting scientists, students, and citrus growers from other countries seeking training and information. He travels extensively to present talks at meetings and to provide advice to citrus growers nationally and internationally. Graham is an exceptional research scientist who has distinguished himself by his research in diverse areas in plant pathology and soil microbiology. He is a renowned expert on citrus canker who is looked to by colleagues, regulatory agencies, and citrus growers in Florida and elsewhere for advice on the establishment of regulations and practices for disease management.
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