The society grants this honor to a current APS member in recognition of distinguished contributions to plant pathology or to The American Phytopathological Society. Fellow recognition is based on significant contributions in one or more of the following areas: original research, teaching, administration, professional and public service, and/or extension and outreach.
Dr. Melissa Mitchum earned a B.S. in biology in 1993 from the University of Puget Sound, a M.S. in plant pathology in 1995 from the University of Nebraska, and her doctorate in plant pathology from North Carolina State University in 2001. After two years as a Postdoctoral Fellow at Duke University, she accepted an Assistant Professor position in the Division of Plant Sciences at the University of Missouri and progressed through the faculty ranks to Professor in 2017. In 2016 Mitchum became the Founder and Director of SCN Diagnostics that provided timely, high-quality plant and nematode screening services to farmers, crop advisors, and industry. In 2018 Mitchum was awarded the Missouri Soybean Merchandising Council Endowed Professorship. In 2019 Mitchum and her outstanding research program were recruited by the University of Georgia where she is currently a Professor in the Department of Plant Pathology and the Institute of Plant Breeding, Genetics, and Genomics.
Mitchum is highly respected as a scientist and scholar who leads a productive and creative nationally and internationally recognized research program that primarily focuses on the molecular basis of the interaction of the destructive soybean cyst nematode (SCN) with its soybean host. Her pioneering research is producing important and timely scholarly contributions that uniquely address both the nematode side and the host side of SCN-plant interactions. The results of her innovative research are published in high-impact top-tier journals and have practical significance for the breeding of conventional soybean resistance and for bioengineering novel forms of resistance to nematodes.
Mitchum is a recognized leader in discovery of the function of effector proteins secreted by SCN that direct the pathogen’s interaction with its soybean host. Her research is pioneering our understanding of the molecular basis of nematode parasitism of plants. Mitchum’s team studied the remarkable role of an effector mimic of CLAVATA3/ESR (CLE), a class of plant signaling peptides, secreted by SCN to direct the pathogen’s interaction with its host. This novel SCN effector was the first CLE signaling peptide identified outside of the plant kingdom. Her team’s comprehensive analysis of cyst CLE function identified two distinct forms that determine its function in different host plant species revealing a potential role in host range specificity of cyst nematodes. Antibodies recognizing CLEs provided the first molecular confirmation of secretion of phytonematode effectors directly into host plant cell cytoplasm. Mitchum’s lab subsequently demonstrated that a cryptic signal peptide in the nematode CLE variable domain trafficked the effector, via a formerly undiscovered mechanism of post-translational uptake into the endoplasmic reticulum-Golgi secretory pathway, to external CLE receptors on the host cell plasmalemma to trigger a cascade of signaling events leading to host susceptibility and demonstrated that silencing of these receptors enhanced plant resistance. Mitchum and collaborators also have characterized multiple other novel nematode effector proteins and their host cell targets that reveal how the effectors hijack recipient host cell processes for the benefit of the nematode opening the door to potentially engineer novel types of plant resistance to nematodes.
SCN is managed in grower fields primarily through deployment of resistant cultivars. The monoculture of the same genetic resistance has led to widespread shifts in virulent SCN field populations that now reproduce on available resistant cultivars. Mitchum has collected and maintains the largest active inventory of SCN populations that have been experimentally adapted (inbred) to reproduce on many of the current sources of resistance. Now that the SCN genome has been sequenced, she is leading a group to identify the virulence genes SCN uses to evade soybean resistance. Mitchum’s lab and colleagues have used these SCN inbred virulent and avirulent populations for comparative transcriptomics and mapping studies to identify a set of candidate genes involved in virulence. Knowledge of SCN virulence genes will enable the development of molecular tests to diagnose a grower's field for virulent populations to facilitate selection of the most effective type of resistance for prescriptive management of SCN.
Mitchum’s research on the host side of plant-nematode interactions is equally as impressive. Until recently, nothing was known about the molecular basis of SCN resistance in soybean. Mitchum’s team and collaborators pioneering studies led to the seminal discovery of an SCN resistance gene in soybean at the Rhg4 locus that encodes a unique type of R-protein, a serine hydroxymethyltransferase (SHMT8). Her collaboration with structural biochemists demonstrated that impaired binding of folate by the soybean SHMT8 underlies the gain of function in resistance to SCN. Mitchum’s lab and collaborators also identified a novel soybean SNAP02 gene that confers a unique mode of resistance to SCN through loss-of-function mutations that implicate SNAP02 as a nematode virulence target. This new knowledge not only enables soybean breeders to develop new SCN resistant cultivars with greater efficiency and precision using markers developed from the resistance genes, but opens the door to genome editing approaches for enhancing plant resistance to nematodes.
Mitchum is committed to training the next generation of scientists as demonstrated through her outstanding teaching activities (received Outstanding Senior Teaching Award), mentoring graduate students (15) and postdoctoral research associates (13) and being a strong advocate of training undergraduates (35) in her research program. As PI or co- PI, Mitchum has garnered over $29 million of funding from a variety of national grant agencies, commodity groups, and industry. She has authored 75 peer-reviewed publications, 22 invited reviews and book chapters, made 30 invited presentations at scientific congresses, and presented 35 invited seminars throughout the US. Mitchum has received numerous awards including the University of Missouri College of Agriculture, Food, and Natural Resources Distinguished Researcher Award, the MSMC Endowed Professorship, and the APS Syngenta Award. She excels in service to the scientific community through assignments in our scientific societies and on federal grant panels, as an editor and reviewer, and in many university service functions.
In summary, Mitchum’s scholarship and service to our profession are clearly exemplary and demonstrated by excellence in all her professional responsibilities. She is a pioneer and leader in molecular plant nematology who is recognized and highly respected throughout the world. Her outstanding accomplishments to science and plant pathology richly merit her being recognized as an APS Fellow.
