About

Christine Durbahn Smart is the Goichman Family Director at Cornell AgriTech and a Professor in the School of Integrative Plant Science, specializing in Plant Pathology and Plant-Microbe Biology. Her program aims to develop improved management strategies for vegetable diseases by increasing understanding of pathogen biology and diversity under field conditions. Her research utilizes genomic tools to understand the diversity of plant pathogen populations, identify and track pathogen movement, and inform disease management options. She focuses on bacterial and oomycete pathogens of vegetables, with an emphasis on population genomics, genotypic diversity, and effector complement of plant pathogens. Her extension work is dedicated to working with conventional, transitional, and organic growers, seed companies, chemical companies, and private consultants to improve vegetable disease management while promoting sustainable agricultural practices. She also develops partnerships between Cornell University and elementary school educators and students to increase awareness of agriculture, vegetables, and nutrition. Her efforts aim to educate the broader population about food production and the value of agriculture, especially as the percentage of the population that farms decreases. Her contributions include significant research, outreach, and extension activities focused on vegetable disease management, pathogen diversity, and agricultural education.

Research topics

• Biology
• Genetics
• Botany
• Horticulture
• Agronomy
• Biotechnology
• Medicine
• Microbiology

Selected publications

• A new species of <i>Didymella</i> from the eastern United States is a pathogen of invasive <i>Reynoutria japonica</i>

  Plant Disease · 2026-01-11

  articleSenior author

  Reynoutria japonica (Polygonaceae) is widely considered one of the most persistent and problematic non-native invasive weeds introduced to North America. Conventional methods to manage infestations are labor-intensive and often require annual monitoring and re-treatment. Biological control agents (BCAs) present an alternative management strategy. Currently, few organisms are effective for managing Re. japonica, presenting a need to discover additional candidate BCAs. Recently, leaf spots were observed on Re. japonica in two locations in the eastern United States, and the causal agent was investigated as a potential BCA. In this study, fungi isolated from symptomatic Re. japonica were identified as belonging to a previously undescribed species of Didymella based on DNA sequence homology, phylogenetic analysis, and morphological characteristics. The host range of related Didymella spp. includes other polygonaceous plants, notably cultivated Rheum rhabarbarum. Therefore, the pathogenicity of isolates representing this new fungal species was tested on seedlings of Re. japonica and Rh. rhabarbarum ‘Victoria’. The novel species was capable of infecting both Re. japonica and Rh. rhabarbarum under artificial conditions. An isolate of D. rhei (Ellis &amp; Everh.) Qian Chen &amp; L. Cai, a close relative and known pathogen of Rh. rhabarbarum, was included in pathogenicity tests but failed to cause disease on Re. japonica. The pathogen from Re. japonica was described as D. polygonacearum sp. nov. This study suggests D. polygonacaeum is a poor candidate for biological control use and that Re. japonica may harbor crop pathogenic microbes.

  PublisherDOI

• The USDA-SCRI CucCAP Projects: Building Genomic, Breeding and Disease Management Tools for Cucurbit Crops

  Journal of the American Society for Horticultural Science · 2026-02-18

  articleOpen access

  Cucurbit crops including watermelon ( Citrullus lanatus ), melon ( Cucumis melo ), cucumber ( Cucumis sativus ), squash, and pumpkin ( Cucurbita spp.) make important nutritional and flavorful contributions to the human diet. The primary challenge for US cucurbit production is disease caused by numerous fungal, oomycete, bacterial, and viral pathogens that reduce crop yield and quality and engender costly control measures. The USDA National Institute of Food and Agriculture–Specialty Crop Research Initiative funded CucCAP (Cucurbit Coordinated Agricultural Project) projects “CucCAP: Leveraging applied genomics to improve disease resistance in cucurbit crops” and “CucCAP2: Harnessing genomic resources for disease resistance and management in cucurbit crops–Bringing the tools to the field” brought together members of the cucurbit community across the country with expertise in genomics, bioinformatics, breeding, genetics, plant pathology, integrated disease management, and economics to address these disease challenges. Collectively, the projects produced extensive genomic resources and bioinformatic tools including genome assemblies and pan-genomes for cucurbit species; genetically characterized the full US National Plant Germplasm System (NPGS) collections for watermelon, melon, cucumber, and squash; developed deeply resequenced core populations for these crops; identified single nucleotide polymorphism and structural variants; and developed the Cucurbit Genomics database (CuGenDB, http://cucurbitgenomics.org/v2/ ). New sources of resistance were identified for 17 cucurbit crop/disease combinations; quantitative trait loci were mapped and molecular markers developed for 24 combinations; and 15 breeding lines with resistances to various diseases were released. New detection methodology was developed for several pathogens; extensive disease monitoring and multilocation disease management trials and resistance tests were performed; a centralized web portal ( https://cuccap.org ) was developed to provide cucurbit disease information in English and Spanish; and disease management information was shared with growers, commodity groups and industry organizations through publications and presentations at conferences, field days, and extension schools delivered at more than 100 venues in 24 states. The CucCAP projects were carried out through joint efforts among 26 university and USDA coinvestigators and their research groups along with valued input and assistance from NPGS cucurbit crop curators, seed industry collaborators, cucurbit growers, external evaluators, and international collaborators. In addition to the specific genomic, breeding, and disease management outputs, the CucCAP projects have had broader impacts including use of the new genomic tools to provide insights into cucurbit biology, synergistic effects resulting from a more cohesive cucurbit community, and scientific training of a cadre of students and postdoctoral researchers.

  PublisherDOI

• Evaluation of downy mildew resistance in the USDA Hemp Germplasm Repository using high-throughput and traditional phenotyping methods

  Plant Disease · 2026-03-29

  articleSenior author

  Pseudoperonospora cannabina, the causal agent of downy mildew in Cannabis sativa, was first identified in New York in 2020. The pathogen causes angular brown lesions on foliar tissue and dark sporulation on the leaf underside, often leading to leaf curling, defoliation, and yield loss. To date, no sources of genetic resistance or effective chemical controls have been reported. In this study, 108 hemp entries were evaluated for resistance to downy mildew using three phenotyping methods: 1) high-throughput Blackbird robotic imaging coupled with convolutional neural network-based leaf disc analysis, 2) visual rating of the same leaf discs, and 3) detached leaf assays. Susceptibility ranged from 0 to 100%, with two entries, G 33532 and 'Santhica 27', exhibiting 0% severity across all three phenotyping methods. Detached leaf assays produced the lowest disease severity estimates, whereas Blackbird convolutional neural network ratings exhibited the lowest residual variance but consistently underestimated disease severity relative to visual assessments. Visual leaf disc ratings produced the highest severity estimates and had the greatest variability. These results suggest that while Blackbird convolutional neural network analysis holds promise for high-throughput phenotyping of the hemp downy mildew interaction, additional refinement is required to improve accuracy.

  PublisherDOI

• Spatial and temporal localization of <i>Serratia ureilytica</i> causing cucurbit yellow vine disease in cucurbits indicates phloem-associated colonization and systemic movement

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-20

  articleOpen accessSenior authorCorresponding

  Abstract Cucurbit yellow vine disease (CYVD), caused by the bacterium Serratia ureilytica , is a phloem-associated disease of cucurbits. This study characterized the spatial and temporal distribution of S. ureilytica in Cucurbita pepo cultivar ‘Delicata’ plants under greenhouse conditions using a GFP-tagged isolate (P01). Seedlings were sampled weekly for four weeks. Transverse sections from the stem, petiole, leaf, shoot apex, and root were imaged by laser scanning confocal and fluorescent dissecting microscopy. In parallel, bacterial abundance in each plant tissue was assessed by quantifying colony-forming units (CFU) via droplet plating over a 4-week time course. Across plant tissues and time points, S. ureilytica fluorescent signal was primarily concentrated in the inner and outer periphery of the bicollateral vascular bundles, with higher magnification images revealing mainly symplastic localization within phloem-associated cells. Consistent with the imaging results, bacterial quantification data showed a high abundance of CFUs in the main stem across weeks, with an irregular pattern of presence in the distal tissues at later time points. These results suggest that S. ureilytica is predominantly localized within phloem-associated cells and spreads both acropetally and basipetally during infection.

  PublisherOA PDFDOI

• Diseases of Rhubarb

  Handbook of plant disease management · 2025-01-01 · 1 citations

  book-chapterSenior author
  PublisherDOI

• First Report of <i>Agroathelia rolfsii</i> Causing Southern Blight on Eggplant in New York

  Plant Disease · 2025-08-25

  articleOpen accessSenior author

  Eggplant (Solanum spp.) is a widely grown fresh market crop in New York, with a total of 262 acres grown on 564 farms in 2022 (USDA-NASS 2024). In July 2024, one eggplant (Solanum melongena cv. Snowy) was found wilted in a research field trial at the Hudson Valley Research Laboratory in Highland, NY. The field site was previously planted with apple trees, which were removed in 2023. The diseased eggplant had a necrotic lesion at the crown covered with white mycelial mats spreading over the stem. Diseased tissue was surface sterilized with 5% bleach for 60 s, plated on potato dextrose agar (PDA) and incubated at 25 °C under natural lighting. Morphological characteristics of the resulting fungal growth resembled those of Agroathelia rolfsii. Cottony mycelia grew rapidly in a radial pattern and was white to off-white in color. Spherical, ellipsoid, and irregular-shaped sclerotia formed near Petri plate edges, initially whitish, then turning tan and eventually dark red-brown, often reaching 2-5 mm in diameter. The isolate (EP24-1) was grown in potato dextrose broth for 1 week before harvesting mycelial tissue through vacuum filtration. Genomic DNA was extracted using a DNeasy Plant Mini Kit (Qiagen) following the manufacturer’s instructions. PCR assays using species-specific primers SCR-F/SCR-R (Jeeva et al. 2010) and primers EF595F/EF1160R (Mascarenhas and Quesada-Ocampo 2024) were used to amplify products in the internal transcribed spacer (ITS) and the translation elongation factor 1 alpha (EF-1α) regions. Products were Sanger sequenced and deposited in GenBank. The ITS sequence (PV606914) shared 100% (544/544 bp) identity with Agroathelia (Athelia) rolfsii accession MH858139.1, and the EF-1α sequence (PV833089) shared 97% (521/539 bp) identity with A. rolfsii accession MN262527.1. To fulfill Koch’s postulates, healthy 6-week old eggplants (cvs. Snowy, Black Beauty, and Nadia) were inoculated in a greenhouse. There were 6 replicates per variety for each of the 3 treatments. EP24-1 was grown on PDA and 7 mm plugs were placed mycelia-side down against the base of the plant stems. Sterile PDA plugs were used for mock-inoculations and plants were left uninoculated as controls. Plants were covered with a plastic bag overnight. The following day, plants were moved to a growth chamber at 19°C with a 12-h photoperiod, misted to maintain >80% relative humidity. Symptoms of infection were visible 4-5 days post inoculation (dpi) and included water-soaked lesions, mycelial growth, and sclerotia formation. At 14 dpi, 2 of the 6 inoculated Snowy plants, 5 of the 6 inoculated Black Beauty plants, and 1 of the 6 inoculated Nadia plants had developed symptoms, while mock and uninoculated control plants remained asymptomatic. Symptomatic stem tissue at lesion margins was surface sterilized for 60 s in 10% bleach and plated onto 25% acidified PDA. The isolated fungus was identified as A. rolfsii through morphological and molecular characterization. To our knowledge, this is the first report of A. rolfsii infecting eggplant in NY State. This pathogen causes Southern blight disease in tropical and subtropical regions and is capable of infecting over 500 plant species (Xie et al. 2014). A. rolfsii has previously been reported in NY on other hosts including table beet (Pethybridge et al. 2019) and pale swallow-wort (Gibson et al. 2012). The detection of A. rolfsii on eggplant in NY signals the need for continued monitoring of this pathogen in higher latitudes.

  PublisherOA PDFDOI

• Evaluation of Organic Fungicides for Control of Hemp Powdery Mildew, Geneva, NY, 2025

  Plant Health Progress · 2025-11-07

  articleSenior author

  Powdery mildew, caused by the fungus Golovinomyces ambrosiae, is a common disease of greenhouse-grown hemp ( Cannabis sativa L.). Symptoms include white, powdery patches on the adaxial leaf surface that spread to other plant tissues including stems and inflorescences, impacting the plant's photosynthetic capacity and marketability. The purpose of this study was to evaluate the efficacy of organic fungicides commonly used to manage hemp powdery mildew in New York. The field trial was conducted in 2025 in Geneva, NY, on ‘White CBG’, a hemp cultivar with known susceptibility to G. ambrosiae. This report provides useful information for hemp growers who aim to reduce losses from powdery mildew infections and to develop disease management programs.

  PublisherDOI

• Determining the Causal Agents of Alternaria Leaf Blight and Head Rot Affecting Broccoli in the Eastern United States

  Plant Disease · 2025-05-22 · 1 citations

  article

  Alternaria brassicicola is the causal agent typically associated with Alternaria leaf blight and head rot (ABHR) disease in broccoli and related crops in the Eastern United States. In 2020, a new species, A. japonica, was reported as causing disease in broccoli and other vegetables in this region. We conducted a multistate pathogen survey during the growing seasons of 2022 and 2023 to assess the distribution and occurrence of A. japonica in relation to A. brassicicola in five broccoli-producing states. Our approach specifically targeted collection of broccoli leaves with lesions typical of ABHR within commercially grown fields that were managed using either organic or conventional approaches in Connecticut, Massachusetts, New York, Virginia, and Georgia. Only typical ABHR leaf lesions were selected for pathogen isolation, and subsequently, sequencing of the Alternaria major allergen a1 gene was used to identify Alternaria species. The predominant species isolated was A. brassicicola (88% in 2022 and 94% in 2023), and the second most common was A. alternata (12% in 2022 and 6% in 2023), which was obtained from fields in Connecticut and Massachusetts in 2022 and in Virginia in both years. Alternaria japonica was not found in either year. Symptoms of A. alternata were indistinguishable from A. brassicicola, as were colony morphologies. Although A. alternata is considered a generalist and of little consequence for broccoli, it is considered a pathogen of significance on multiple crops (blueberry, citrus, pistachios), but there remains scant information on the disease etiology on broccoli. Therefore, we inoculated broccoli with A. alternata in controlled conditions to shed light on possible differences in infectivity of these species on broccoli. Results of our study showed that A. alternata is pathogenic on broccoli, capable of initiating infection and causing lesions typical of ABHR. This indicates that future disease surveys of ABHR should conclusively identify the species of Alternaria that are causing disease. Additional research is needed to determine the significance of this finding in relation to yield impacts, epidemiology, fungicide resistance, and management recommendations.

  PublisherDOI

• Screening diverse <i>Cannabis sativa</i> germplasm for resistance to <i>Golovinomyces ambrosiae</i>

  Plant Disease · 2025-11-29

  article

  Powdery mildew is one of the most common diseases affecting indoor hemp (Cannabis sativa L. &lt;0.3% tetrahydrocannabinol) cultivation. The primary causal organism is the biotrophic fungus Golovinomyces ambrosiae, whose polycyclic nature and short latent phase allow it to rapidly produce asexual conidia that spread to other plants. Control strategies that rely on the use of fungicides are limited by the efficacy of products that are registered for use on hemp, thus the breeding of resistant cultivars is critical. Two resistance genes and one susceptibility gene involved in powdery mildew resistance have been described for C. sativa. In the present work, we evaluated the susceptibility to G. ambrosiae of 70 C. sativa entries in one year and 98 in a second year, including accessions from the United States Department of Agriculture – Agricultural Research Service germplasm repository, breeding lines, and commercial cultivars. Entries represented different geographic origins, levels of improvement, and market classes. The trials were inoculated with G. ambrosiae, and disease severity was rated on a weekly basis. A wide range of disease severity was observed among and within entries. Several entries displayed no or very low levels of disease across years, suggesting that they have genetic resistance to G. ambrosiae. This screening provides a foundation for further characterization of the mechanisms of powdery mildew resistance in hemp and contributes to broaden the publicly available phenotypic data that will better serve stakeholders who rely on germplasm collections.

  PublisherDOI

• Evaluation of an Integrated Management Program in Partially Resistant Processing Pumpkin Breeding Lines to Manage Powdery Mildew, 2023

  Plant Health Progress · 2025-01-01

  articleSenior author

  Cucurbit powdery mildew, caused by the fungus Podosphaera xanthii, is a common disease of pumpkin in North America. This report evaluates the efficacy of integrating biorational fungicides with partially resistant processing pumpkin germplasm for the management of powdery mildew. The trial was conducted in 2023 in Geneva, NY, on Cucurbita moschata breeding lines. Results from this trial are expected to help in managing powdery mildew of cucurbits.

  PublisherDOI

Frequent coauthors

• Natalie Ives

  Cancer Research UK Clinical Trials Unit

  324 shared

• Samir Mehta

  324 shared

• Kelly Handley

  324 shared

• James Glasbey

  243 shared

• Aneel Bhangu

  National Institute for Health Research

  243 shared

• Dion Morton

  243 shared

• Thomas Pinkney

  243 shared

• Dmitri Nepogodiev

  243 shared

Education

• Ph.D., Plant Pathology

  Michigan State University

  1992

Awards & honors

• Awardee (2018) New York Farmers Club
• Fellow (2017) American Association for the Advancement of Sc…
• Outstanding accomplishments in applied research (2013) Corne…
• Excellence in the teaching, advising and mentoring of gradua…
• Fellow (2016) American Phytopathological Society