Every summer, potato diversity overwhelms a greenhouse in Dundee, Scotland. At the James Hutton Institute, the curator of the Commonwealth Potato Collection (CPC) is tasked with maintaining about 1,500 accessions (distinct samples registered in the collection) representing more than 80 potato species. These accessions include both genetically diverse exemplars of the few cultivated potato species—of which most readers will likely be familiar with just one, Solanum tuberosum—and many related wild tuber-bearing Solanum species.

The CPC first materialized as the Empire Potato Collection through the work of the British Imperial Bureau of Plant Breeding and Genetics. In 1939, the Bureau dispatched three collectors on a nine-month journey across Andean South America to collect wild and cultivated potatoes. Those samples, shipped mostly as tubers to be reproduced vegetatively, arrived first to Cambridge, England. Although the initial plan imagined materials moving quickly from Cambridge to breeders across the Empire to sustain production of a critical subsistence crop, the project morphed into a centralized operation. Over several decades, researchers in Cambridgeshire and beyond conducted taxonomic analyses and probed samples for their latent qualities. Accessions accrued and new research questions emerged. This operation later moved to what is today the John Innes Horticultural Center (Norwich), then to the Scottish Plant Breeding Station (Edinburgh), and finally to its current home in Dundee.

Since its inception, the CPC has provided living materials to breeders and researchers in Britain and beyond who wish to work with potato diversity that is otherwise difficult to access quickly. Over time, it has acquired a preservation function: like other genebanks, it is today prized as a storehouse of exemplars that may be increasingly rare in the field. Yet the most consistent justification for the expense of maintaining the collection has been the promise that its samples contain genetic material that will enable breeders to make potato varieties better, chiefly by providing resistance to diseases and pests (e.g., Hawkes 1951; Bradshaw and Ramsay 2005).

This function of crop genebanks—that is, keeping modern cultivars ahead of pathogens and other trouble-making organisms—is well known. However, it is not the full story of genebanks’ relationships to disease and pest management. Seeds and other plant materials coming into the bank may themselves harbor diseases and pests. Because of the service functions of genebanks, they risk spreading these not only in the bank but also far beyond (Hernández Fernández 2023). In other words, genebanks pose a threat of spreading pesky organisms even as they are imagined as a bulwark against their presence.

Keeping genebanks on the right side of this equation demands regimes of phytosanitary observation and care. Depending on the plant materials being maintained, the entire operation of a crop genebank might be understood best as a continuing effort in pest and disease risk mitigation. As a CPC curator writing about the history of the collection in the 1980s summarized, “Phytosanitary considerations have dominated the history of the CPC” (Glenndinning, n.d.).

Consider that, on arrival in Cambridge, accessions to the Empire Potato Collection were first subject to quarantine and phytosanitary inspection to ensure that unwanted pest and pathogen diversity did not accompany incoming potato diversity. Although a crucial first step, this assessment was not a once-and-done activity. On the contrary, diseases were a constant companion and threat. As early as 1945, some 75 percent of the samples were assessed as harboring one or more viruses (Glendinning, n.d.). Increased plant health measures were put in place, such as new glasshouses to keep virus-harboring plants separate and measures to limit disease-transmitting insects.

The most important disease-management strategy eventually adopted by CPC caretakers was shifting from keeping samples as tubers to storing them as seeds. Viruses were known to be transmitted easily from generation to generation in the fleshy, nutrient rich tuber. By comparison, seeds did not seem ever to transmit viruses. It therefore appeared possible to create entirely virus-free stocks by keeping accessions as seeds rather than tubers. This lofty objective ultimately proved illusory when Scottish plant health authorities detected a seed-transmissible viroid not known yet to exist in Europe in the collection in 1971. A prohibition on moving materials in or out of the collection and a tumultuous search for contaminated accessions ensued.

The eventual impact on the collection was catastrophic. In 1968, the CPC numbered about 6,000 accessions and included 65 species of wild and primitive cultivated potatoes; in 1989, the collection contained just 1,067 accessions and only 43 species, with most of those losses occurring through inability to adequately manage the collection through the viroid eradication efforts (Germplasm Collections at SCRI, n.d.). In other words, the potential sources of novel disease resistance were decimated through the manifestation of a novel seed-borne disease. Agricultural biodiversity routinely touted as an invaluable resource evidently presented too much of a risk to the more highly prized potato monocrops on its doorstep.

STS scholar Xan Chacko has demonstrated that disease outbreaks within genebank collections provoke complications for carefully honed regimes of seed care, raising questions about the precarious security they offer (Chacko 2018). The history of disease management in the CPC similarly prompts reflection on the relationship between technical regimes of care and the worlds that researchers and institutions seek to sustain beyond the genebank. In the potato genebank, giving attention to these regimes reveals the banking of agricultural biodiversity as not only working in service of the extension of monoculture—an observation routinely made by scholars who study these operations—but also working very much in the same mode as monoculture. That is: seeking control, regularity, predictability, and even prioritizing these aspirations over the perpetuation of diversity.

Contextualized within this series on plant responsability, this history also highlights how plants and their distinctive ecologies shape genebanking practices. The lively materials of the CPC—tubers and seeds but also viruses and viroids—often frustrated attempts at idealized purity and cleanliness, insisting that caretakers diverge from carefully laid plans and adapt their technical regimes to potatoes’ unpredictable vitalities.