College of Agriculture & Natural Resources Department of Plant, Soil and Microbial Sciences

• Tree Fruit Pathology YouTube Channel

Research: 

My current research centers on the Erwinia amylovora fire blight pathosystem with projects ranging from basic studies of pathogen-host interactions to developing improved chemical and biological approaches for fire blight management.  We are currently working on the regulation of the major pathogenicity determinants type III secretion and amylovoran exopolysaccharide by regulatory small RNAs and cyclic di-GMP.  We have recently shown the importance of biofilm formation to E. amylovora pathogenesis, invasion of xylem, and systemic spread of the pathogen within trees.  We also study E. amylovora plasmids, streptomycin resistance, and are developing and evaluating strategies to increase the potential for biological control of fire blight in the midwest and eastern United States.

My work with fungal tree fruit pathogens in Michigan focuses on detecting, tracking, and understanding the evolution of fungicide resistance in organisms such as Venturia inaequalis (apple scab), Blumeriella jaapii (cherry leaf spot), and Monilinia fructicola (American brown rot).  We have worked on resistance to sterol demethylation inhibitors, strobilurins, and succinate dehydrogenase inhibitor classes of fungicides.

Extension:  

I have Extension responsibilities in tree fruit disease control.  My research includes field and lab studies covering management of fire blight and apple scab of apple, cherry leaf spot, American and European brown rot, and bacterial canker of sweet and tart cherry, and bacterial spot of peach, nectarine, and plum.  We also actively work on fungicide resistance in apple and cherry pathogens, and the evaluation of new bactericides and fungicides for disease management in apple, cherry (sweet and tart cherry), and peach.  The goals of my Extension program are to provide timely information and recommendations on management of tree fruit diseases to growers in Michigan and in other fruit-growing regions.  Extension updates on disease issues are published on the MSUE News website and through presentations at various grower meetings.  Disease control recommendations are updated yearly in the MSU Fruit Management Guide.  Fruit tree disease management video resources are also available from the Sundin lab.

Courses Taught:

• PLP 884: Plant bacteriology.

Publications:

Erwinia amylovora and fire blight

Kharadi, R.R., J.K. Schachterle, X. Yuan, L.F. Castiblanco, J.Peng, S.M. Slack, Q.Zeng, and G.W. Sundin.  2021.  Genetic dissection of the Erwinia amylovora disease cycle.  Annual Review of Phytopathology (in press).

Yuan, X., G.C. McGhee, S.M. Slack, and G.W. Sundin.  2021.  Functional exploration of the ubiquitous plasmid pEA29 reveals a novel signaling pathway that connects thiamine biosynthesis, bacterial respiration, and production of the exopolysaccharide amylovoran in Erwinia amylovora.  Molecular Plant-Microbe Interactions (in press).

Slack, S.M., K.J. Walters, C.A. Outwater, and G.W. Sundin.  2021.  Effect of kasugamycin, oxytetracycline, and streptomycin on in-orchard population dynamics of Erwinia amylovora on apple flower stigmas.  Plant Disease (in press).

Kharadi, R.R., and G.W. Sundin.  2021.  Dissecting the process of xylem colonization through biofilm formation in Erwinia amylovora.  Journal of Plant Pathology (in press).

Yuan, X., M.T. Hulin, and G.W. Sundin.  2021.  Effectors, chaperones, and harpins of the type III secretion system in the fire blight pathogen Erwinia amylovora: a review.  Journal of Plant Pathology (in press).

Peng, J., L.R. Triplett, and G.W. Sundin.  2021.  Activation of metabolic and stress responses during subtoxic expression of the type I toxin hok in Erwinia amylovora.  BMC Genomics 22:74.

Peng, J., J.K. Schachterle, and G.W. Sundin.  2021.  Orchestration of virulence factor expression and modulation of biofilm dispersal in Erwinia amylovora through activation of the Hfq-dependent small RNA RprA.  Molecular Plant Pathology 22:255-270.

Kharadi, R.R., and G.W. Sundin.  2020.  Cyclic di-GMP regulates autoaggregation through the putative peptidoglycan hydrolase EagA, and regulates transcription of the znuABC zinc uptake gene cluster in Erwinia amylovora.  Frontiers in Microbiology 11:605265.

Yu, M., J. Singh, A. Khan, G.W. Sundin, and Y. Zhao.  2020.  Complete genome sequence of the fire blight pathogen Erwinia amylovora strain Ea1189.  Molecular Plant-Microbe Interactions 33:1277-1279.

Schachterle, J.K., and G.W. Sundin.  2019.  The leucine-responsive regulatory protein Lrp participates in virulence regulation downstream of small RNA ArcZ in Erwinia amylovora.  mBio 10:e00757-19.

Schachterle, J.K., Q. Zeng, and G.W. Sundin.  2019.  Three Hfq-dependent small RNAs regulate flagellar motility in the fire blight pathogen Erwinia amylovora.  Molecular Microbiology 111:1476-1492.

Slack, S.M., C.A. Outwater, M.J. Grieshop, and G.W. Sundin.  2019.  Evaluation of a contact sterilant as a niche-clearing method to enhance the colonization of apple flowers and efficacy of Aureobasidium pullulans in the biological control of fire blight.  Biological Control 139:104073.

Schachterle, J.K., D.M. Onsay, and G.W. Sundin.  2019.  Small RNA ArcZ regulates oxidative stress response genes and regulons in Erwinia amylovora.  Frontiers in Microbiology 10:2775.

Kharadi, R.R., L.F. Castiblanco, C.M. Waters, and G.W. Sundin.  2019.  Phosphodiesterase genes regulate amylovoran production, biofilm formation, and virulence in Erwinia amylovora.  Applied and Environmental Microbiology 85:e02233-18.

Fungicide resistance

Peng, J., H. Sang, T.J. Proffer, J. Gleason, C.A. Outwater, G. Jung, and G.W. Sundin.  2021.  A method for the examination of SDHI fungicide resistance mechanisms in phytopathogenic fungi using a heterologous expression system in Sclerotinia sclerotiorum.  Phytopathology (in press).

Lesniak, K.E., J.Peng, T.J. Proffer, C.A. Outwater, L.I. Eldred, N.L. Rothwell, and G.W. Sundin.  2021.  Survey and genetic analysis of demethylation inhibitor fungicide resistance in Monilinia fructicola from Michigan orchards.  Plant Disease 105:958-964.

Outwater, C.A., T.J. Proffer, N.L. Rothwell, J. Peng, and G.W. Sundin.  2019.  Boscalid resistance in Blumeriella jaapii: distribution, effect on field efficacy, and molecular characterization.  Plant Disease 103:1112-1118.