The Roots of Robusta: Cultivating Growth for a Species Once Overlooked | 25, Issue 22
World Coffee Research’s MAEVE HOLLER and Dr. ROBERT KAWUKI write about how the organization is fast-tracking innovation for robusta to forge the future of coffee.
When I first began drinking coffee—as an eager and over-caffeinated student riding the emerging “third wave” in Wellington, New Zealand—I was taught that a specialty coffee’s defining characteristics were high acidity (with a firm [but apocryphal] insistence that “coffee is a fruit”) and that it was certainly, absolutely, 100 percent arabica. I’m profoundly glad that, in the subsequent years, discussions about robusta’s role in specialty coffee’s present and future have become far more nuanced, more open-minded, and frankly, more interesting. Today, I see roasteries adding robusta to their offer lists, accompanied by complex flavor descriptors and recommended recipes. In 2023, Maya Crowley used a robusta coffee from Vietnam in the US Barista Championship.
Certainly, robusta “has entered the chat” amid the context of concern about arabica’s future, particularly in the face of climate change. The specialty coffee industry’s acknowledgement and acceptance of robusta has often been centered around its resistance to certain diseases and ability to grow at comparatively low altitudes. That said, there is so much more to robusta than its “robustness,” and—as this article written by Maeve Holler and Robert Kawuki of World Coffee Research (WCR) illustrated to me—it is important to critically interrogate many of our presumptions about robusta’s best qualities.
Reading this article I learned, for example, that robusta is more susceptible to environmental changes and diseases than many people assume. I was reminded that robusta’s high pyrazine (an aromatic compound known for its earthiness) content helps to create a particularly full-bodied cup profile, something that I always personally prize in espresso. I also learned that robusta’s modern history and much of its genetic development—like that of so many commodities—is rooted deeply in colonial trade and extractivism.
Today, WCR is building the foundations of a world-leading robusta breeding program, one that will focus on creating robusta varieties that fulfill the needs of robusta growers and processors, as well as on characteristics that are valued in coffee markets. Coffea robusta should not be relegated to the role of Coffea arabica’s inferior sibling (in fact, it could also be described as a parent species of C. arabica), but we should also not presume that it is coffee’s hardy savior.
LAUREL CARMICHAEL
Publications Manager, SCA
The roots of robusta—a species of coffee plant visually recognizable by its especially large blossoms and wide, spreading canopy, and scientifically known as Coffea canephora—trace back hundreds of thousands of years to the humid, understory evergreen forests in tropical areas of central and western sub-Saharan Africa, an expansive region that extends from Guinea to Uganda to Angola.[1]
Figure 1. Robusta flowers. Photo credit: Genthophoto, stock.adobe.com.
Throughout history, people have grown robusta in numerous forms and ecotypes and in regions beyond its birthplace. Today, the species robusta is grown in about 20 countries across the globe that are characterized by warm climate and/or high humidity. Robusta’s genetic diversity is vast, and while scientists have been researching the extent of this since the 1980s, there is still much to be uncovered about arabica’s sister species. But one thing about robusta is certain: it has dramatically evolved into a major market force and has become an integral agricultural tool as we forge the future of coffee.
In recent decades, robusta cultivation has steadily grown, rising from 25 percent to 40 percent of total global coffee production since the early 1990s.[2] Many factors, including the increasing demand for coffee, have led to expansions in robusta production. In the last year alone, 177 million 60-kilogram bags of coffee were consumed worldwide—a 2.2 percent increase from the 2022–23 production year and a striking 4.5 percent jump from 2019 to 2020[3]—and demand is not expected to slow down. As the demand for coffee soars, the effects of climate change and limited historical investment in coffee research and development are placing significant pressure on farmers and producing countries, which are increasingly struggling to keep up. In this ecosystem, an investment in innovation to realize robusta’s full potential is practical and necessary.
The Story of a Species
The cultivation of C. canephora was first recorded around 1870, using genetic material from the Lomami River region (which is today part of the Democratic Republic of Congo), though it is likely that small-scale production in diverse geographic areas had been ongoing for decades prior. French botanists observed subtypes of C. canephora in the wild thereafter, and by 1897, the species was officially named and published. In the years following, Belgian researchers sought to exploit the economic potential of these crops, which were rich in genetic diversity, collecting thousands of seeds from an early robusta plantation in the region.[4] From the early 20th century onwards, Brussels sent seeds from Congo to Indonesia, where the species was valued due to its resistance to coffee leaf rust (a fungal disease that had devastated arabica crops in the late 1800s). Pioneering, systematic robusta breeding was first conducted there. The genetic material was then enriched with material from robusta populations in Gabon, Uganda, Guinea, and Ivory Coast. The robusta bred in Indonesia was reintroduced to Congo and central Africa, and to Latin America for the first time—notably to the state of Espírito Santo in Brazil in 1912.
It was only after the 1960s that more targeted, globally coordinated robusta collection and exchange was conducted from centers of domestication, with the establishment of gene banks in Cameroon, Ivory Coast, Madagascar, and India.[5] Throughout robusta’s modern history, its germ plasm (seeds, plants, or parts that are used for breeding or conservation) has faced— and continues to face—significant challenges around management and genetic erosion.
Today, just six countries—Vietnam, Brazil, Indonesia, Uganda, India, and Ivory Coast—produce 95 percent of the world’s robusta.[6] Laos, Tanzania, Madagascar, and Thailand are the next largest producers. Countries that lie within Asia and Oceania are collectively the largest producers of robusta, generating 60 percent of the world’s output, at 41.5 million 60-kilogram bags annually. South America produces 28 percent of the world’s share of robusta, generating 19.8 million bags of coffee in the 2020–21 year.
Realising Robusta’s Potential
Figure 2. Robusta seedlings. Photo credit: World Coffee Research.
Much of the movement of robusta beyond its centers of origin and domestication and its increase in popularity in the early 1900s can be attributed to its resistance to coffee leaf rust. One of the greatest benefits of robusta production is that some varieties possess an exceptionally high natural resistance to some of the major pests and diseases that impede successful and profitable production of arabica. Robusta plants can often thrive under harsh conditions.[7] This is one of the reasons why colloquially, C. canephora is often simply referred to as “robusta,” as described and commercialized by L. Linden in 1900.[8]
Robusta possesses innately desirable attributes: its tremendous genetic diversity explains its different observable phenotypes and, in part, its sensory characteristics (including bitterness, low acidity, high mouthfeel, and pyrazine content), which are highly valued in some markets. Nonetheless, robusta also faces considerable challenges across the geographies in which it is cultivated. For example, one of the primary threats to long-term, sustainable robusta production is lack of profitability, which is a result of numerous factors including heightened labor costs, increased competition from other crops, and lower productivity per planted area in some regions.[9] In addition, despite its oft-cited “robustness,” robusta is still sensitive to environmental disturbances. Further, many robusta varieties are somewhat susceptible to key diseases and pests, such as coffee leaf rust, coffee wilt disease, red blister disease, stem borer, coffee berry disease, coffee berry borer, and nematodes, among others.[10]
Nonetheless, the fact that robusta can be grown in a wider range of climates and elevations compared to currently available arabica varieties is the primary motivation for increased robusta production today. For example, robusta plants can produce high crop yields at elevations between 200 and 800 meters above sea level, while arabica is typically grown at higher altitudes. Robusta plants maintain a reasonable stress resilience, requiring less maintenance via herbicide and pesticide.[11]
“Both arabica and robusta have their place in our industry—both species being options for farmers to choose from according to their unique locations. Oftentimes, robusta can grow in places not suited for arabica, and vice versa,” says Emilia Umaña, Senior Manager of the Nursery Program for World Coffee Research (WCR). “However, one of the main benefits of robusta is that its vegetative propagation is faster and more cost-effective than arabica. For example, grafting and top-working techniques are more successful in this species.”
Ongoing climate predictions of rising temperatures and altered precipitation patterns by 2050 indicate that cultivation of today’s coffee varieties in current growing areas may no longer be sustainable in the coming years, and the world is facing supply shortages of millions of bags as soon as 2030. To address this shortfall, WCR is breeding new arabica varieties through the Innovea Global Coffee Breeding Network[12] to ensure the species is more climate resilient, investing in innovation to improve populations and adapt them to the environments of the future. To enable the industry to meet growing demand, these realities are likely to in turn increase the production of robusta by a significant margin,[13] underscoring the need for further research to enhance the positive and market-desired traits inherent to the species.
One repeated topic in the conversation about robusta is that its beans generate different sensory characteristics and impressions of quality than arabica.[14] For instance, coffee brewed from robusta beans is often lower in acidity, higher in bitterness, and more “full- bodied” due to its pyrazine content,[15] an aromatic known for its earthiness. But, as many in the industry already know, when handled and processed well, robusta can serve as a product for specialty markets.[16] “The new trends in processing robusta are using fermentation as a crucial step to improve quality,” says Dr. Veronica Belchior, WCR Research Scientist for Coffee Quality Evaluation. “Fermented robustas are often cited as cleaner and show a wider spectrum of descriptors— mostly winey, whiskey, and some positive herbal notes.”
Agronomic and post-harvest processing efforts can make an immediate and crucial difference on robusta production and quality. As the coffee industry considers an increase in robusta production as a solution to impending supply shortages and climate-related challenges, it will inevitably seek to unlock the species’ untapped potential to optimize its performance in the field and its cup quality on a commercial scale—and that’s where science enters the scene.
Discovering Diversity
C. canephora has a wide scope of genetic diversity. Wild populations are the primary genetic relative of robusta coffee, and cultivated coffee has changed relatively little from its wild progenitors. It is also a secondary genetic relative of C. arabica, conferring potential disease and pest resistance to arabica.[17] Even so, there are many unknown variations largely yet to be explored by scientists.
“Previous genetic studies show that C. canephora has high diversity and various distinct subpopulations,” says Dr. Jorge Berny, WCR Research Scientist in Breeding and Genomics. “Nevertheless, use of the beneficial variation across groups has been lacking, as the populations and breeding efforts remain relatively isolated. Deepening the understanding of the species’ diversity, and its integration [of genetic diversity into breeding populations], is a crucial part of continuous and long-term genetic gains.”
There are several reasons for the lack of knowledge of robusta’s genetic diversity. First, many different common terms are used to describe robusta in the areas where it is grown, such as “robusta,” “conilon,” “nganda,” “koillou/quillou,” and others. These terms are generally regional, colloquial, and do not necessarily correspond to specific genetically distinct varieties/clones that have been developed and released by breeders over the years. Second, robusta must cross-pollinate—a single robusta tree cannot successfully pollinate its own flowers as arabica trees can do (scientists call this “allogamous”). This means that subtypes grown in the same field typically interbreed.[18]
What scientists do know is that C. canephora has two sets of chromosomes in each cell (compared to arabica’s four), and that as a species, it is divided into two broad genetic groups, Guinean and Congolese. The Guinean group, which is generally characterized by narrow internodes, high caffeine content, low bean weight, drought resistance, secondary branching, and early harvest, originated primarily in west Africa, while the Congolese group, which is typically characterized by higher rust resistance, medium caffeine content, high bean weight, drought susceptibility, big internodes, tall growth, and late harvest, originated in central Africa.[19] Of these two groups, the Congolese is the more widespread. In addition, within each group, there are different populations, or subgroups.
Research into the genetic relationships within the species show that, in general, these populations are well differentiated and genetically isolated.[20] In the shadow of the unforgiving climate crisis and its increasing spillover effects, WCR scientists recognize that uncovering robusta’s genetic diversity will unlock great potential for the industry to harness the species’ positive attributes for the benefit of all.
Cultivating Growth
The world may soon face challenges in keeping up with rising demand for robusta just as it currently does for arabica. Robusta plants generally have high precipitation needs, and recent research suggests that robusta’s ability to thrive in hotter climates may have been previously overstated—temperatures over 20.5 degrees Celsius can have a significant negative impact on yields. For instance, in March 2024, Vietnam’s agriculture department projected that its national coffee production (across both robusta and arabica) this year could drop by nearly 20 percent due to drought.[21] WCR and AbacusBio’s 2023 study of opportunities for robusta variety development predicts that the industry may face robusta shortages, estimated to reach up to 35 million bags by 2040.[22]
In the face of this prediction, and given the pace and intensity of climate change, the lack of global collaboration and global breeding efforts in place for robusta is alarming. While some strong breeding initiatives have taken shape at national coffee institutes across Asia, Africa, and Latin America, and some bilateral partnerships have formed, there is still a clear opportunity for scientists to better understand robusta’s genetic diversity and tap into it via modernized breeding initiatives to strengthen the species’ long-term viability for farmers and to selectively improve cup quality.
In parallel with its arabica breeding efforts, WCR has recognized the need for genetic improvement in robusta on a global scale, and the organization is starting to build the foundation for a robusta breeding program that is slated to launch in partnership with key producing countries in 2025. While the program is in its early stages, WCR’s breeding team has already initiated crosses at the organization’s research farm in preparation for the official rollout, with a keen focus on traits prioritized by growers, processors, and roasters to ensure that desirable attributes are accessed and cultivated by farmers and are seamlessly accepted by processors, roasters, and consumers.
WCR’s robusta breeding strategy, which was generated through technical consultation with scientists from prospective network partners, has undergone rigorous peer review and approval by a group of diverse and world-renowned breeding experts. These reviewers’ expertise spans a wide variety of crops, and they represent a mix of public and private-sector organizations from both high- and low-income countries. In other words, the robusta breeding program’s design is demand-led—it includes the perspectives of those already involved in the species’ value chain, from the production and processing level to the marketing and consumption ends of the stream. Ultimately, this approach facilitates co-creation and co-ownership, which are key to ensuring that robusta breeding outcomes and impacts are both relevant to farmers and durable against the production challenges of the future.
Figure 3. Ashim Abdalla operates a robusta coffee nursery at Kasenda coffee estate (which is owned by his father, farmer Abdallah Mangalji) in Kabarole district, Rwenzori region, Uganda. Photo credit: Arnold Mugasha for World Coffee Research.
In addition, as WCR continues these efforts, the technical team will make breeding decisions that work towards achieving specific quality targets to improve the taste of robusta and meet the demands of farmers, buyers, traders, and consumers alike. “We are planning to do sensory evaluations for C. canephora varieties that are already known, using the Coffee Quality Institute form to evaluate robusta with a particular definition of the roasting profile,” says Dr. Belchior. “It’s important that robusta and arabica are evaluated in different ways, using specific protocols. We hope to map the quality for robusta and arabica together, though, and this may allow us to introduce new quality targets in the breeding program.”
WCR’s efforts to support robusta nursery infrastructure aim to ensure immediate availability of officially released varieties and that genetic improvements are maintained over time through good agricultural practices. For example, in 2023, WCR initiated work alongside local partners to understand the challenges and opportunities for robusta propagation via a project in Uganda that aims to increase the ability of local nurseries to supply improved varieties in the country. The project’s goal is to move 100,000 healthy, coffee wilt disease–resistant NARO-Kituza Robusta plants into farmers’ hands, while also increasing the future supply of good-quality plants by teaching farmers how to propagate healthy, disease-resistant seedlings. These interventions reinforce lessons that can be applied in other nations and help pave the way for later variety releases to occur more quickly.
In addition, over the last two years, WCR has created numerous resources to advance knowledge of the robusta landscape and support enhanced production, including a focus report[23] on the future of robusta quality, an updated coffee varieties catalogue[24] now featuring robusta varieties, a nursery training manual and best practices guide[25] for grafting robusta, and a video series[26] on robusta clonal coffee nursery management.
“Robusta coffee is a very important asset to Ugandan coffee farmers,” says Maureen Namugalu, Uganda Country Project Manager for WCR. “The distribution of Uganda’s exports are 80 percent robusta and 20 percent arabica, and the country’s coffee road map highlights—among its other initiatives—the relevance of planting material in increasing production and productivity. This increase will be possible through the implementation of strategies that ensure quality planting material gets into the hands of farmers, and by supporting those farmers with training on the right techniques on how to best propagate these materials.”
Clearing a Path
As scientists race to ensure the continued sustainability and climate resilience of arabica, and as robusta takes its seat as a major market force, it is clear that the coffee industry is at a precipice. We are grappling with the historical lack of investment in coffee’s innovation and the resulting myriad of challenges impeding successful production. Not only is the supply and quality of coffee at stake, but the millions of livelihoods of those who primarily depend on coffee’s longevity are as well. Clearing a path for transformative innovation for robusta, as we are doing for arabica, can help safeguard the well-being of our communities.
MAEVE HOLLER is the Communications Manager and Dr. ROBERT KAWUKI is a Research Scientist and Scientific Partnership Manager for Asia & Africa at World Coffee Research.
References
[1] Stéphane Dussert et al., “Le caféier, Coffea canephora,” in Diversité Génétique des Plantes Tropicales Cultivées, eds. Perla Hamon et al. (Boca Raton, Fla.: CRC Press, 1999), 175–94.
[2] See Table 5 in AbacusBio, “Opportunities for Robusta Variety Innovation” (white paper, World Coffee Research, 2023), https://worldcoffeeresearch.org/resources/opportunities-for- robusta-variety-innovation..
[3] International Coffee Organization, Coffee Market Report (April 2024), https://www.icocoffee.org/documents/cy2023-24/cmr-0424-e.pdf.
[4] Editor’s note: In 1885 Belgian King Leopold II claimed ownership of what he, called the Congo Free State. Leopold’s forces perpetrated horrific atrocities against the local people. In 1908, the Belgian Federal Parliament annexed the area as a formal Belgian colony, known as Belgian Congo. Both regimes violently extracted rubber, ivory, and minerals from the Congo Basin.
[5] Paula Bramel et al., Global Conservation Strategy for Coffee Genetic Resources (Global Crop Diversity Trust, 2017), https://cdn.croptrust.org/wp/wp-content/uploads/2017/07/Coffee- Strategy_Mid_Res.pdf.
[6] AbacusBio, “Opportunities for Robusta Variety Innovation.”
[7] Luis Fernando Campuzano-Duque and Matthew Wohlgemuth Blair, “Strategies for Robusta Coffee (Coffea canephora) Improvement as a New Crop in Colombia,” Agriculture 12, no. 10 (2022), https://doi.org/10.3390/agriculture12101576.
[8] Jesse D. Dagoon, Agriculture and Fishery Technology III (Manila: Rex Book Store, 2005).
[9] Compare 1.9 bags/ha in Ivory Coast to 10.4 bags/ha in Uganda and 47.7 bags/ha in Vietnam.
[10] Fernando E. Vega et al., “Penicillium Species Endophytic in Coffee Plants and Ochratoxin A Production,” Mycologia 98, no. 1 (2006): 31–42, https://doi.org/10.1080/15572536.2006.11832 710.
[11] Daniel Cohen Goldemberg et al., “Coffea canephora: A Promising Natural Anticariogenic Product,” in Coffee in Health and Disease Prevention (Academic Press, 2015), 615–25; Benoit Daviron and Stefano Ponte, The Coffee Paradox: Global Markets, Commodity Trade and the Elusive Promise of Development (London: Zed Books, 2005).
[12] “Innovea Global Arabica Breeding Network,” World Coffee Research, https://worldcoffeeresearch.org/programs/global-breeding-network, accessed July 25, 2024.
[13] Christian Bunn et al., “A Bitter Cup: Climate Change Profile of Global Production of Arabica and Robusta Coffee,” Climate Change 129, no. 1 (2015): 89–101, https://doi.org/10.1007/s10584-014-1306-x; Sinara Oliveira de Aquino, et al., “Adaptive Potential of Coffea canephora from Uganda in Response to Climate Change,” Molecular Ecology, 31, no. 6 (2022), 1800–1819, https://doi.org/10.1111/mec.16360.
[14] Thierry Leroy et al., “Genetics of Coffee Quality,” Brazilian Journal of Plant Physiology, 18, no. 1 (2006), 229–42, https://doi.org/10.1590/S1677-04202006000100016.
[15] Walter Miyanari, Aloha From Coffee Island (Honolulu: Savant Books and Publishing, 2008).
[16] Robusta Coffee Handbook: A Sustainable Coffee Industry with High Stakeholder Value for Social Economic Transformation (Kampala: Uganda Coffee Development Authority, 2019), https://greeninguganda.com/images/product/coffee/robusta.pdf.
[17] Aaron P. Davis et al., “High Extinction Risk for Wild Coffee Species and Implications for Coffee Sector Sustainability,” Science Advances 5, no. 1 (2017), https://www.science.org/doi/10.1126/sciadv.aav3473.
[18] A. S. Thomas, “Types of Robusta Coffee and Their Selection in Uganda,” The East African Agricultural Journal 1, no. 3 (1935), 193, 7, https://doi.org/10.1080/03670074.1935.11663646.
[19] Juan Carlos Herrera and Charles Lambot, “The Coffee Tree—Genetic Diversity and Origin,” in The Craft and Science of Coffee, ed. Britta Folmer (Academic Press, 2017), 1–16, https://doi.org/10.1016/B978-0-12-803520-7.00001-3; Catherine Kiwuka et al., “Genetic Diversity of Native and Cultivated Ugandan Robusta Coffee (Coffea canephora Pierre ex A. Froehner): Climate Influences, Breeding Potential and Diversity Conservation,” PLOS One 16, no. 2 (2021), https://doi.org/10.1371/journal.pone.0245965.
[20] Herrera and Lambat, “The Coffee Tree”; Kiwuka et al., “Genetic Diversity of Native and Cultivated Ugandan Robusta Coffee.”
[21] “Vietnam's Coffee Exports Surge to $2.9 Billion in Five Months,” International Trade Council, https://tradecouncil.org/vietnams-coffee-exports-surge/, accessed July 2, 2024.
[22] AbacusBio, “Opportunities for Robusta Variety Innovation.”
[23] AbacusBio, “Opportunities for Robusta Variety Innovation.”
[24] World Coffee Research, “Coffee Varieties Catalog,” https://varieties.worldcoffeeresearch.org/.
[25] World Coffee Research, Grafting Robusta: Nursery Training Manual and Best Practices Guide (2023), https://worldcoffeeresearch.org/resources/grafting-robusta.
[26] World Coffee Research, “Robusta Clonal Coffee Nursery Management: Supporting Videos,” https://worldcoffeeresearch.org/resources/robusta-nursery-videos.
We hope you are as excited as we are about the release of 25, Issue 22. This issue of 25 is made possible with the contributions of specialty coffee businesses who support the activities of the Specialty Coffee Association through its underwriting and sponsorship programs. Learn more about our underwriters here.