Thomas R. Gordon graduated from California State University, Northridge, with a B.S. degree in biology in 1974 and an M.S. degree in botany in 1976. In 1981, he received his Ph.D. degree in plant pathology from the University of California (UC), Davis, where he thereafter served as a post-doctoral scholar through 1984. He joined the faculty in the Department of Plant Pathology at UC Berkeley in 1985 and moved to UC Davis in 1996, where he achieved the rank of professor in 1998. He served as department chair from 2005 to 2013.
Gordon’s research has been devoted to the study of plant-pathogenic fungi, with the objectives of advancing the science of plant pathology and developing information that can help guide management of plant diseases. One major focus of his work has been Fusarium oxysporum, a cause of vascular wilts in many economically important crops. Research in his laboratory provided insights into the genetic structure of formae speciales, which included evidence for the independent origins of pathogenic races. His work also showed that pathogenic and nonpathogenic strains of F. oxysporum could be somatically compatible owing to a coincidental sharing of het alleles rather than clonal derivation from a common ancestor. Investigations into relationships within a forma specialis revealed that different sequences in the intergenic spacer of the rDNA could reside within the same isolate of F. oxysporum. This discovery was counter to predictions of concerted evolution and indicated that phylogenetic inferences based on the IGS may be confounded by intra-isolate divergence in this region. Gordon’s lab also used molecular markers to characterize the structure of F. oxysporum populations in soil. Hierarchical gene diversity analysis showed no significant subdivision between native and cultivated soils, supporting the conclusion that populations of F. oxysporum found in an agricultural soil are resident in that soil prior to its cultivation. Findings germane to management of Fusarium wilt diseases include documentation of the capacity for wilt pathogens to colonize nonsusceptible crops without inducing symptoms, allowing for production of survival structures that will add to the soil population of the pathogen. Similarly, cultivars that are resistant to Fusarium wilt may support extensive growth in the taproot. These findings help to explain the persistence of Fusarium wilt pathogens in soil and why crop rotation often fails to prevent recurrence of Fusarium wilt. Other studies have demonstrated significant effects of temperature on disease development, knowledge of which can reduce the risk of disease through adjustments in planting date. Lastly, Gordon has worked with plant breeders to enhance genetic resistance to Fusarium wilt in muskmelon, lettuce, and strawberries.
Another focus of research in Gordon’s program has been on pitch canker, a disease of pines caused by Fusarium circinatum, which causes significant losses in plantations, seed orchards, and nurseries throughout the world. In California, pitch canker is a cause of dieback and mortality in planted pines and in native forests of Pinus radiata, P. muricata, and P. attenuata. Gordon’s studies have characterized intraspecific differences in susceptibility in P. radiata, and he has worked with local and international groups to exploit this resource for disease management. His research has also documented the occurrence of systemic induced resistance (SIR) to pitch canker in P. radiata, the first record of this phenomenon in a woody perennial. Furthermore, SIR was shown to be operative in natural populations of P. radiata, something that has not previously been reported for any plant species. Although pitch canker is found in many locations throughout the world, it is by no means uniformly distributed. Research in Gordon’s lab established the biological basis for the current distribution by characterizing the environmental conditions required for infection. This information has made it possible to identify regions where the disease does not yet occur but would likely become established if the pathogen was to be introduced. In collaboration with entomologists at UC Berkeley, Gordon’s group demonstrated a previously unrecognized role for native insects as wounding agents and vectors of the pitch canker fungus, which has since been confirmed to occur in other parts of the world. Working with USDA scientists, he studied the breeding biology of F. circinatum, showing it to be interfertile with F. subglutinans and characterizing the inheritance of virulence in interspecific crosses. The close relationship to F. subglutinans, which is both a pathogen and symptomless endophyte of corn, motivated studies that showed F. circinatum, previously known only as a pathogen of coniferous trees, to be capable of infecting corn seed, growing within a corn plant asymptomatically and causing ear rot when introduced into silk channels. Subsequent surveys revealed natural infections of understory grasses in native pine forests in California and in plantations in South Africa. This expanded host range for F. circinatum suggests that grasses may serve as a host bridge, allowing movement of the pathogen between disjunct stands of susceptible pines. In addition, grasses serving as cryptic reservoirs of inoculum may help to explain why aggressive sanitation measures have failed to eradicate the disease in seedling nurseries.
Gordon’s contributions to plant pathology include his leadership of the Department of Plant Pathology at UC Davis for a period of eight years, during which time five new faculty members were hired, with a sixth under recruitment. He has served APS as an associate editor of Plant Disease, an associate and senior editor for Phytopathology, and a senior editor for APS PRESS. As a professor of plant pathology, he is engaged in instruction at both graduate and undergraduate levels and as a mentor of graduate students. His teaching responsibilities include a general education course that uses fungal biology to illustrate how science allows us to gain new knowledge and promote human welfare. Through this course, more than 500 students each year learn about the importance of fungi as pathogens of plants. In 2013, he received the Academic Senate Distinguished Teaching Award at UC Davis. In summary, Thomas Gordon has made consistent and outstanding contributions to the science of plant pathology, provided effective academic leadership, and introduced thousands of college students to the importance of plant diseases.
