Bruce McDonald was born in Newport Beach, California, in July 1960. He received his B.Sc. in plant science at UC-Riverside in 1982, and his Ph.D. in genetics at UC-Davis in 1987. He joined the Plant Pathology Department at Texas A&M University in 1988 and moved to his current position of professor and chair of plant pathology at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland in 1998.
Throughout his career, Dr. McDonald has taken an interdisciplinary approach combining plant pathology, genetics, and evolutionary biology to elucidate the population genetics of plant pathogens. As part of his Ph.D. training under the supervision of Professors Robert Allard and Robert Webster, he looked for evidence of coevolution between barley composite crosses and the scald pathogen Rhynchosporium secalis. He determined how different resistance genes and resistance gene combinations grown in mixtures and pure stands affected epidemic development. In collaboration with his Ph.D. student colleagues Joseph McDermott and Stephen Goodwin, he used isozyme and RFLP markers to characterize the genetic structure of R. secalis populations on composite cross populations that had different evolutionary histories. The latter work led him into a very productive line of research on the genetic structure of pathogen populations that he continues to this day.
During his 10 years at Texas A&M, Dr. McDonald worked on seven different fungal pathosystems, including pathogens of wheat (Mycosphaerella graminicola, Phaeosphaeria nodorum), barley (Rhynchosporium secalis), sorghum (Colletotrichum graminicola, Sporisorium reilianum), rice (Rhizoctonia solani), and oak trees (Ceratocystis fagacearum). During this period, he popularized the use of hierarchical sampling strategies and neutral DNA-based genetic markers to characterize the genetic structure of pathogen populations. The techniques and strategies he developed during this time have been widely adopted and have driven forward our knowledge of pathogen genetic structure.
After arriving at the ETH in Zurich, Dr. McDonald moved rapidly into the new fields of phylogeography and experimental evolution to elucidate the roles of sexual recombination and immigration as drivers of pathogen evolution and to trace historical pathways of pathogen movement and speciation. He and his colleagues recently began applying tools of evolutionary ecology, in particular using QST analysis, to better understand the connection between variation at neutral loci and variation for selected quantitative characters. This work promises to open important new areas for investigation within plant pathology. Dr. McDonald’s work on the population genetics of plant pathogens remains at the forefront of this field.
As a result of his work, the population genetics of the wheat leaf blotch pathogen M. graminicola is now better understood than any other plant pathogen. This line of inquiry recently culminated in the first complete set of parameter estimates for all five evolutionary forces in any plant pathogen, allowing modeling of the relative contributions of different forces in the evolution of this important pathogen and demonstrating the importance of gene flow as a driver of evolution. Dr. McDonald and his colleagues were the first to conduct a hierarchical analysis of gene diversity in a pathogen using molecular markers. They also were the first to make quantitative estimates of gene flow between pathogen populations; to differentiate and quantify the relative contributions of recombination, immigration, and asexual reproduction to the development of an epidemic in a replicated field experiment; and to conduct microtransect sampling through lesions to illustrate the relative positioning of clones within a lesion on a millimeter scale. His group also made the first quantitative measurements of selection coefficients during a growing season in replicated field experiments, based on mark and recapture strategies. His group recently published the first paper on the population genetics of a fungal avirulence gene (the NIP1 gene in R. secalis).
The work of Dr. McDonald and his colleagues has illustrated the utility of pathogen population genetics to better understand pathogen biology and to implement more sustainable disease management strategies. Their work has contributed fundamentally to our understanding of the nature of pathogen diversity and how it affects disease management. He and his colleagues recently developed and published a simple model for predicting pathogen evolutionary potential. This model shows considerable promise, as it appears to work well for viruses, fungi, and nematodes. It is particularly exciting that this model predicts the development of fungicide resistance much better than existing risk assessment models developed and promoted by the Fungicide Resistance Action Committee (FRAC) over the last decade.
Dr. McDonald made significant contributions to plant pathology education at several levels. He traveled extensively to raise awareness of the importance of population genetics in the plant pathology community, giving 81 invited lectures over the past 15 years, including at 32 universities in 18 countries. He developed and taught intensive multi-day short courses on pathogen population genetics for Ph.D. students in Nordic countries and Switzerland. Since joining the ETH and assuming his responsibilities as a professor of plant pathology in Switzerland, he began to teach the entire discipline of plant pathology in the only College of Agriculture at a Swiss university. His courses are taught at all university levels, including B.Sc., M.Sc., and Ph.D. students. Through 5 years of steady effort, Dr. McDonald and his co-workers restructured the plant pathology curriculum at the ETH, which now attracts students from other Colleges of the ETH, including the College of Biology and the College of Environmental Sciences. Students also are now attracted from other Swiss universities and other European countries. With assistance from APS, he recently converted a portion of his teaching materials into a web-based platform and donated them to the APS Education Center, where they currently form the largest online course in the Center. Dr. McDonald’s teaching will likely influence the next generation of plant pathologists and increase the role of population biology in the plant pathology curriculum.
