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James E. Adaskaveg

James E. Adaskaveg was born in Waterbury, CT, in 1960. He received his B.S. degree in agronomy in 1982 at the University of Connecticut, Storrs, and his M.S. and Ph.D. degrees in plant pathology in 1984 and 1986, respectively, at the University of Arizona, Tucson. He was post-doctoral researcher and subsequently research plant pathologist/lecturer in the Department of Plant Pathology at the University of California, Davis, from 1986 to 1990 and 1990 to 1995, respectively. In 1995, Adaskaveg joined the faculty of the Department of Plant Pathology, University of California, Riverside, where he is currently professor of plant pathology with statewide responsibilities in tree fruit and nut pathology. Adaskaveg is recognized nationally and internationally for his outstanding contributions on the biology, epidemiology, and management of tree pathogens, including postharvest fruit decays. He received the Almond Research Appreciation Award in 1997 for his investigation of almond anthracnose, the Cherry Man of the Year Award in 2003 for his pre- and postharvest research on brown rot of sweet cherry, and the Albert G. Salter Memorial Award in 2006 for his research on Septoria spot and postharvest decays of citrus. For the last 3 years, he has been the scientific advisor for USDA-APHIS in negotiations with the Korean government on the exportation of California oranges to Korea.

Adaskaveg was associate editor of Phytopathology from 2005 to 2007, and he is serving on the APS Mycology, Pathogen Resistance, and Postharvest Pathology Committees. He has served the Pacific Division of APS as president (2002–2003) and was on committees within the division for 18 years. He also has organized two well-attended field trips on tree fruit diseases during the 2005 and 2007 APS Annual Meetings.

Adaskaveg is recognized specifically for his contributions to our understanding of anthracnose diseases. In the early 1990s, when the California almond industry suffered devastating losses from an unknown disease, he was fundamentally involved in identifying and characterizing the causal pathogen, Colletotrichum acutatum, studying the epidemiology of the disease, designing effective management strategies, and investigating the infection process of the pathogen. He reported this work in six publications in Phytopathology and Plant Disease, in several abstracts at APS and other meetings, and in a book chapter (published by APS PRESS).

Adaskaveg and his research team demonstrated that two distinct subpopulations of C. acutatum were involved in anthracnose outbreaks that differ in colony morphology and spore characteristics, molecular fingerprints, and temperature-growth responses. These studies helped to correctly identify the cause of almond anthracnose as C. acutatum and not C. gloeosporioides in California and other almond-growing regions. In laboratory, growth chamber, and field studies, Adaskaveg and his associates found that the pathogen not only overwinters in mummified fruit that remain on the tree, but also in fruit spurs. Furthermore, leaf symptoms and terminal dieback of twigs were found to be caused primarily by the production of phytotoxic, water-soluble compounds. Temperature and wetness duration requirements for almond anthracnose development were studied on leaves and flowers, which served as the basis for a disease model to improve timing of fungicide applications.

Subsequently, Adaskaveg and his colleagues focused their research on the infection process of C. acutatum in almond tissues, resulting in three publications in Phytopathology. Using novel methods in digital image analysis of light micrographs together with scanning electron microscopy and histological sectioning of tissues, they provided direct evidence that the internal light spots of fungal appressoria correspond to the penetration pore and the infection peg. Digital image analysis was used to evaluate infection and colonization strategies in this host-pathogen system. A unique combination of two infection strategies was found within almond petals and leaves. Based on the presence of subcuticular infection vesicles, subcuticular, intra- and intercellular hyphae of different types, and an extended biotrophic phase, almond tissue colonization by C. acutatum was described as subcuticular-intracellular hemibiotrophy and intercellular necrotrophy. During the first 24–48 h after penetration, fungal colonization was biotrophic and host cells adjacent to fungal hyphae were healthy, but later, the host-pathogen interaction became necrotrophic with collapsed host cells. The relative importance of the different stages of subcuticular-intracellular hemibiotrophy and intercellular necrotrophy during colonization of the almond host depended on the tissue infected. Thus, on leaves, subcuticular growth usually extended farther than on petals before penetration of epidermal cells. In a feature article in Plant Disease coauthored by Adaskaveg, infection strategies and life styles of different C. acutatum-host systems on fruit crops were compared that demonstrated the wide spectrum of host-pathogen interactions. Depending on the host and tissue infected, C. acutatum can exist as a necrotroph, biotroph, endophyte, or epiphyte. Thus, the pathogen develops a highly specialized relationship at the cellular level that is reflected in the disease cycle for each host-pathogen system.

Recently, Adaskaveg pioneered the visualization of pH modulation in C. acutatum-almond host-pathogen interactions. Others have described the pH modulation of host tissue based on biochemical, physiological, and molecular studies. Adaskaveg and coworkers were among the first to use pH-sensitive probes and fluorescence confocal microscopy to study host-pathogen interactions, which allowed visualization of the spatial distribution of localized pathogen-induced alkalinization in proximity to fungal infection structures at the cellular level. Ratiometric measurement of fluorescence at two wavelengths and in situ calibration allowed the quantification of pH ranges. A sequence of events in the C. acutatum-almond interaction was established that includes penetration, production of ammonia by C. acutatum, and subsequent pH modulation within almond leaf epidermal tissue to an alkaline environment that leads to colonization of the host.

Adaskaveg’s accomplishments on anthracnose diseases represent significant contributions to plant pathology. Additionally, he is an outstanding scientist in other areas of the discipline. His broad-spectrum tree fruit and nut pathology program encompasses research on fungal and bacterial diseases of many tree crops grown in California. His program elegantly merges basic and applied aspects of plant pathology. He is a frequent speaker at a range of meetings, where he enthusiastically communicates his knowledge to help solve disease problems in production agriculture.