Seed systems are key to the availability of good crop varieties, especially after system shocks such as drought or civil unrest (Garrett et al. 2017).

Our work with seed systems addresses both availability of varieties and crop health considerations.  Without good management, seed systems can spread pathogens.

We work on strategies for detecting and mitigating pathogen spread in seed and postharvest systems, while maintaining variety dissemination (Andersen et al. 2018, Buddenhagen et al. 2017, Hernandez Nopsa et al. 2015).

We propose an integrated seed health strategy to combine benefits from formal seed systems and on-farm management approaches (Thomas-Sharma et al. 2016, Thomas-Sharma et al. 2017).  Phytosanitary thresholds in formal seed systems may be adjusted to offer greater benefits (Choudhury et al. 2017).

We also work to understand how stakeholders in seed systems can be better served, including using exponential random graph models (ERGMs) to evaluate demographic effects on people’s roles in seed systems (Buddenhagen et al. 2017).

Recently developed tools, including impact network analysis (Garrett 2021), are part of the new Seed Systems Toolbox (  Related user guides are listed at the bottom of the references below (Andrade Piedra et al. 2020, Garrett 2021, Garrett and Xing 2021).

Our work includes analyses of seed and postharvest systems in Australia, Burundi, Cambodia, Ecuador, Haiti, Kenya, Nigeria, the Republic of Georgia, Tanzania, Thailand, Uganda, Vietnam, the US, and globally.


Bold = Member of Garrett Lab / Underline = Other scientist mentored by Garrett / Asterisk = *Equivalent contributions

Published Journal Articles

Andersen Onofre, K. F., G. A. Forbes, J. Andrade-Piedra, C. E. Buddenhagen, J. C. Fulton, M. Gatto, Z. Khidesheli, R. Mdivani, Y. XingK. A. Garrett. 2021. An integrated seed health strategy and phytosanitary risk assessment: potato in the Republic of Georgia. Agricultural Systems 191:103144. [open access link]

Buddenhagen*, C. E.Y. Xing*, J. Andrade Piedra, G. A. Forbes, P. Kromann, I. Navarrete, S. Thomas-Sharma, R. A. ChoudhuryK. F. Andersen, E. Schulte-Geldermann, B. A. EthertonA. I. Plex Sulá, and K. A. Garrett. 2021. Management performance mapping and the value of information for regional prioritization of management interventions. Phytopathology. [link, soon to be open access]

Garrett, K. A. 2021. Impact network analysis and the INA R package: Decision support for regional management interventions. Methods in Ecology and Evolution, in press. (Preprint version available at bioRxiv 2020.11.08.373621 [open access link])

Klein-Gordon, J., Y. XingK. A. Garrett, P. Abrahamian, M. L. Paret, G. V. Minsavage, A. L. Strayer-Scherer, J. Fulton, S. Timilsina, J. B. Jones, E. M. Goss, and G. E. Vallad. 2021. Assessing changes and associations in the Xanthomonas perforans population across Florida commercial tomato fields via a state-wide survey. Phytopathology [open access link]

McEwan, M. A., C. J. M. Almekinders, J.L. Andrade-Piedra, E. Delaquis, K. A. Garrett, L. Kumar, S. Mayanja, B. A. Omondi, S. Rajendran, and G. Thiele. 2021. “Breaking through the 40% adoption ceiling: Mind the seed system gaps.” A perspective on seed systems research for development in One CGIAR. Outlook on Agriculture 50:5-12. [open access link]

Xing*, Y.J. Hernandez Nopsa*, K. F. Andersen, J. Andrade-Piedra, F. Beed, G. Blomme, M. Carvajal Yepes, D. Coyne, W. Cuellar, G. Forbes, J. Kreuze, J. Kroschel, L. Kumar, J. Legg, M. Parker, E. Schulte-Geldermann, K. Sharma, and K. A. Garrett. 2020. Global cropland connectivity: A risk factor for invasion and saturation by emerging pathogens and pests. BioScience 70:744-758. [open access link]

Andersen, K. F.C. E. Buddenhagen, P. Rachkara, R. Gibson, S. Kalule, D. Phillips, and K. A. Garrett. 2019. Modeling epidemics in seed systems and landscapes to guide management strategies: The case of sweetpotato in Northern Uganda. Phytopathology 109:1519-1532.  [open access link]

Ogero, K., J. Kreuze, M. McEwan, N. Luambano, H. Bachwenkizi, K. A. GarrettK. F. Andersen, S. Thomas-Sharma, and R. A. A. van der Vlugt.  2019.  Efficiency of insect-proof net tunnels in reducing virus-related seed degeneration in sweetpotato. Plant Pathology 68:1472-1480. [open access link]

Poudel, R., A. Jumpponen, M. M. Kennelly, C. Rivard, L. Gomez-Montano and K. A. Garrett. 2019. Rootstocks shape the rhizobiome: Rhizosphere and endosphere bacterial communities in the grafted tomato system. Applied and Environmental Microbiology 85:e01765-18. [link]

Delaquis, E., K. F. Andersen, N. Minato, C. T. L. Thuy, M. E. Karssenberg, S. Sophearith, K. A. G. Wyckhuys, J. Newby, D. D. Burra, P. Srean, I. Phirun, L. D. Niem, P. T. Nhan, K. A. Garrett, C. J. M. Almekinders, P. C. Struik, S. de Haan. 2018. Raising the stakes: cassava seed networks at multiple scales in Cambodia and Vietnam.  Frontiers in Sustainable Food Systems 2:73. [open access link]

Garrett, K. A., R. I. Alcalá-Briseño, K. F. Andersen, C. E. Buddenhagen, R. A. Choudhury, J. C. Fulton, J. F. Hernandez Nopsa, R. Poudel, and Y. Xing. 2018. Network analysis: A systems framework to address grand challenges in plant pathology.  Annual Review of Phytopathology 56: 559-580. [open access link]

Buddenhagen*C. E.,  J. F. Hernandez Nopsa*K. F. Andersen, J. Andrade-Piedra, G. A. Forbes, P. Kromann, S. Thomas-Sharma, P. Useche, and K. A. Garrett. 2017. Epidemic network analysis for mitigation of invasive pathogens in seed systems: Potato in Ecuador.  Phytopathology 107:1209-1218. [open access link]

Choudhury, R. A.K. A. Garrett, S. J. Klosterman, K. V. Subbarao, and N. McRoberts.  2017.  A framework for optimizing phytosanitary thresholds in seed systems. Phytopathology 107:1219-1228. [link]

Garrett, K. A.K. F. Andersen, F. Asche, R. L. Bowden, G. A. Forbes, P. A. Kulakow, and B. Zhou. 2017. Resistance genes in global crop breeding networks. Phytopathology 107:1268-1278. [open access link] [interactive interface for exploring model behavior]

Hilker, F. M., L. J. S. Allen, V. A. Bokil, C. J. Briggs, Z. Feng, K. A. Garrett, L. J. Gross, F. M. Hamelin, M. J. Jeger, C. A. Manore, A. G. Power, M. G. Redinbaugh, M. A. Rúa and N. J. Cunniffe.  2017. Modelling virus coinfection to inform management of maize lethal necrosis in Kenya.  Phytopathology 107:1095-1108. [open access link] [in the news]

Thomas-Sharma, S., J. Andrade-Piedra, M. Carvajal Yepes, J. Hernandez Nopsa, M. Jeger, R. Jones, P. Kromann, J. Legg, J. Yuen, G. A. Forbes, and K. A. Garrett. 2017. A risk assessment framework for seed degeneration: Informing an integrated seed health strategy for vegetatively-propagated crops. Phytopathology 107:1123-1135. [open access link]  [Interactive interface for exploring model behavior]

Thomas-Sharma, S., A. Abdurahman, S. Ali, J. L. Andrade-Piedra, S. Bao, A. O. Charkowski, D. Crook, M. Kadian, P. Kromann, P. C. Struik, L. Torrance, K. A. Garrett, and G. A. Forbes. 2016. Seed degeneration in potato: the need for an integrated research and development strategy to mitigate the problem in developing countries.  Plant Pathology 65:3-16. [link] [CGIAR press release]

Hernandez Nopsa, J. F., G. J. Daglish, D. W. Hagstrum, J. F. Leslie, T. W. Phillips, C. Scoglio, S. Thomas-Sharma, G. H. Walter, and K. A. Garrett. 2015. Ecological networks in stored grain: identifying key nodes for emerging pests and mycotoxins in postharvest networks.  BioScience 65:985-1002. [open access link] [UF press release] [UF/IFAS FAES High Impact Award winner]

User guides

Garrett, K. A. 2021. User guide to impact network analysis (INA). CGIAR Research Program on Roots, Tubers and Bananas (RTB). RTB User Guide. No. 2021-4. Lima, Peru. [open access link]

Garrett, K. A., and Y. Xing. 2021. User guide to the seedHealth model as part of the integrated seed health approach. CGIAR Research Program on Roots, Tubers and Bananas (RTB). RTB User Guide. No. 2021-5. Lima, Peru. [open access link]

Andrade-Piedra, J. L., C. J. M. Almekinders, M. A. McEwan, F. B. M. Kilwinger, S. Mayanja, L. Mulugo, E. Delaquis, K.A. Garrett, A. B. Omondi, S. Rajendran, P. L. Kumar and G. Thiele. 2020. User guide to the toolbox for working with root, tuber and banana seed systems. CGIAR Research Program on Roots, Tubers and Bananas (RTB), Lima, Peru. [open access link]