Early in his career, Hartman worked on red leaf blotch of soybean, a disease only known to occur in Africa. He elucidated the life cycle of the fungus, named a new genus, Dactuliochaeta glycines Hartman & Sinclair, and published Latin descriptions of the life stages based on voucher herbarium and sampled specimens from Africa. Hartman pioneered research to extract and enumerate sclerotia from soil, tested the survival of fungal propagules, and determined the host range of the pathogen. Hartman documented disease progress curves, yield loss models, and the relationship of disease to yield. Hartman published four refereed journal articles on red leaf blotch which led to an APHIS invitation to write the Recovery Plan for Red Leaf Blotch. In 2012, Hartman completed a book chapter published in the Manual of Security Sensitive Microbes and Toxins about the disease and its causal agent.
Hartman’s research at AVRDC in Taiwan included studies on pathogen biology, epidemiology, and management of bacterial and fungal diseases of vegetables and soybean. His research on black leaf mold of tomato showed the importance of humidity and temperature conditions on conidial germination and production and the cross-infectivity of fungal isolates from tomato and Solanum nigrum. He developed disease progress curves and yield loss models and reported on new sources of resistance and host range of the fungus. While at AVRDC, Hartman published 21 refereed journal articles on diseases of vegetables and soybean. He convened the International Bacterial Wilt Symposium that culminated in a published proceeding and an edited book on the subject, both co-authored with Dr. Chris A. Hayward. Hartman also became an expert on soybean rust research and was senior editor for the Annotated Bibliography of Soybean Rust.
Dr. Hartman’s current research with the USDA ARS focuses on pathogen biology, disease epidemiology, and management of a wide array of soybean diseases and pests. He has published on anthracnose, bacterial pustule, brown spot, brown stem rot, charcoal rot, green stem syndrome, Phytophthora root and stem rot, Pythium root rot, Sclerotinia stem rot, soybean aphid, soybean mosaic, sudden death syndrome, and tobacco streak and ringspot. Hartman has a long history of research on anthracnose that includes five refereed journal articles during his graduate years, four on pepper anthracnose while at AVRDC, and four more recent articles that report in the discovery of a new species (Colletotrichum incanum), the first occurrence of C. chorophyta in the U.S., the development of a multiplex real-time polymerase chain reaction to differentiate Colletotrichum species, and the evaluation of soybean lines for new sources of resistance to C. truncatum.
Another major area of work that he has devoted time to include investigations on sudden death syndrome of soybean. Hartman and his colleagues published 25 refereed journal articles documenting its distribution and yield losses in Illinois, identified multiple phytotoxins including a phytotoxic effector (FvNIS1), completed a fungal genomic characterization of plant cell wall degrading enzymes and in silico analysis of xylanases and polygalacturonases, and evaluated over 18,000 soybean plant introductions in the USDA Soybean Germplasm collection for resistance.
In 2001, Hartman and his colleagues reported the first occurrence of the soybean aphid in North America. Since then, 24 refereed journal articles were published resulting in the discovery of the first aphid resistance gene, map locations for this and other genes, and two patents to identify Rag1 and Rag2 in soybean plants. Even before the introduction of soybean rust in the continental United States in 2004, Hartman devoted time to soybean rust research. Currently, he has published 59 refereed journal articles on various aspects about the fungus (aggressiveness, archaeophytopathology, dispersal, fungicide sensitivity, hosts, molecular quantification, penetration, and survival), soybean resistance (cellular interactions, mapping genes, and nine releases of resistant germplasm) and rust management (cultural effects, fungicides, and fungicide application timing).
Hartman held the role of the lead editor for the 4th and 5th edition of the Compendium of Soybean Diseases and Pests and has served on more than 50 committees including those with APS, the University of Illinois, and the Departments of Plant Pathology and Crop Sciences. Hartman has advised 25 graduate students and supervised 38 professionals including academic professionals, post-docs, and visiting scientists. Before rust was reported in the continental U.S., Hartman co-organized a Soybean Rust Workshop in 1995. He was an active member of the APHIS emergency response team, participated in mock exercises, and was part of the team of first responders in Louisiana in November 2004. He contributed to the USDA Soybean Rust Working Group, the USDA national sentinel plot network, and the national commentary. Hartman has traveled widely during his overseas employment visiting over 30 countries professionally. As a USDA scientist, Hartman was invited to present his research in Australia, Argentina, Brazil, Canada, China, Korea, India, and Paraguay, and Taiwan. He currently serves on three scientific advisory boards, two international and one national, and holds a 0%-time professorship at the University of Illinois.