History of Robusta

Intro­duc­tion

Cof­fee is one of the most impor­tant cash crops in the world, gen­er­at­ing sig­nif­i­cant for­eign exchange and sup­port­ing the liveli­hoods of mil­lions of peo­ple glob­al­ly. Over the last 30 years, demand for cof­fee has grown steadi­ly, lead­ing to an expan­sion in pro­duc­tion and exports. 

There are 131 species in the Cof­fea genus known to sci­ence (Davis, et al., 2021), with two that are cul­ti­vat­ed wide­ly and on a glob­al scale —Cof­fea ara­bi­ca (com­mer­cial­ly known as ara­bi­ca) and Cof­fea canepho­ra (com­mer­cial­ly known as robus­ta). Through­out this essay and the cat­a­log gen­er­al­ly, we use this term ​“robus­ta” to refer to the entire C. canepho­ra species and all its subtypes.

Until recent­ly, ara­bi­ca held reign over most of the cof­fee mar­ket due to pref­er­ences for its cup qual­i­ty, but var­i­ous fac­tors, includ­ing the increas­ing demand for cof­fee, have led to expan­sions in the pro­duc­tion of robus­ta, as the species requires less strin­gent grow­ing con­di­tions and pos­sess­es a cer­tain lev­el of resis­tance to pests and dis­eases that often plague farm pro­duc­tiv­i­ty. Robus­ta pro­duc­tion expand­ed rapid­ly after the emer­gence of sol­u­ble cof­fee in the 1950s. 

Present­ly, approx­i­mate­ly 60% of the cof­fee pro­duced and mar­ket­ed in the world comes from ara­bi­ca plants and 40% comes from robus­ta plants (ICO, 2021).

The top glob­al pro­duc­ers of robus­ta are cur­rent­ly Viet­nam, Brazil, Indone­sia, Ugan­da, and India, which togeth­er pro­duce over 90% of the world’s robus­ta (Slipchenko, 2021). Of these pro­duc­ers, Viet­nam and Ugan­da are the fore­most exporters of robus­ta (Brazil, for exam­ple, retains a sub­stan­tial por­tion of its pro­duc­tion for inter­nal con­sump­tion). How­ev­er, an increas­ing num­ber of coun­tries that cur­rent­ly restrict or have pre­vi­ous­ly restrict­ed cof­fee pro­duc­tion to ara­bi­ca are begin­ning to explore robus­ta; these include Mex­i­co, Nicaragua, Guatemala, and Colom­bia, among oth­ers. Addi­tion­al­ly, there is grow­ing inter­est in explor­ing the poten­tial of increas­ing the cup qual­i­ty of robusta.

About Robus­ta

Cof­fea canepho­ra Pierre ex A. Froehn­er is a species of cof­fee that orig­i­nat­ed in cen­tral and west­ern sub-Saha­ran Africa. In the wild, it is found main­ly in the under­sto­ry of humid, ever­green forests (but some­times in sea­son­al­ly dry humid forests or gallery forests) with ele­va­tions rang­ing from 50 to 1500 m above sea lev­el (Davis, et al., 2006).

The inter­est in pro­duc­ing Robus­ta at a glob­al lev­el resides in the fact that it can be grown in a wider range of cli­mates and alti­tudes com­pared to ara­bi­ca, which requires pre­cise con­di­tions in order to thrive, like heavy shade and high alti­tudes. In con­trast to ara­bi­ca, robus­ta plants typ­i­cal­ly have a greater crop yield, con­tain high­er lev­els of caf­feine, low­er lev­els of sug­ar, high­er lev­els of sol­u­ble solids, and are less sus­cep­ti­ble to dam­ag­ing pests and dis­eases (Goldem­berg et al., 2015). Fur­ther, robus­ta can be grown in hot­ter, more humid tem­per­a­ture ranges, found in low­er alti­tudes between 200 – 800 meters (Slipchenko, 2021), and often requires less main­te­nance via her­bi­cide and pes­ti­cide (Dav­i­ron & Ponte, 2005). Despite these attrib­ut­es, robus­ta is still sen­si­tive to envi­ron­men­tal dis­tur­bances. Research sug­gests that robusta’s abil­i­ty to thrive in hot­ter cli­mates may be over­stat­ed and that tem­per­a­tures over 20.5 degrees centi­grade can have a sig­nif­i­cant neg­a­tive impact on yields Kath et al., 2020). Addi­tion­al­ly, many robus­ta vari­eties are still sus­cep­ti­ble to key dis­eases and pests, such as cof­fee leaf rust, stem bor­er, cof­fee berry dis­ease, cof­fee berry bor­er, and nema­todes, among oth­ers (Vega et al., 2006)

Due to the afore­men­tioned ben­e­fits, though, robus­ta is often eas­i­er to farm, allows for greater pro­duc­tiv­i­ty, and is more cost-effec­tive to pro­duce than Ara­bi­ca. Ongo­ing cli­mate pre­dic­tions of ris­ing tem­per­a­tures and altered pre­cip­i­ta­tion pat­terns by 2050 indi­cate that ara­bi­ca cul­ti­va­tion may no longer be sus­tain­able in the com­ing years, which may, in turn, increase the pro­duc­tion of robus­ta by a sig­nif­i­cant mar­gin (Bunn, et al., 2015, Kath, et al., 2023, Dinh, et al., 2022, Kath et. al, 2022, de Aquino, et al., 2022). Even so, robus­ta faces its own lim­i­ta­tions and cli­mate vul­ner­a­bil­i­ty (Tournebize, et al., 2022). 

How­ev­er, the beans that come from robus­ta pro­duc­tion gen­er­ate dif­fer­ences in terms of taste and cup qual­i­ty (Leroy, et al., 2006). For instance, cof­fee brewed from robus­ta beans is often low­er in acid­i­ty, high­er in bit­ter­ness, and more ​“full-bod­ied” due to its pyrazine con­tent (Miya­nari, 2008), an aro­mat­ic known for its earth­i­ness. But when han­dled and processed prop­er­ly, Robus­ta can serve as a prod­uct for spe­cial­ty mar­kets (Ugan­da Cof­fee Devel­op­ment Author­i­ty, 2019). 

Robus­ta Diversity 

Many dif­fer­ent com­mon terms are used to describe robus­ta in the areas where it is grown. These include ​“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. Because robus­ta cross-pol­li­nates — a sin­gle robus­ta tree can­not suc­cess­ful­ly pol­li­nate its own flow­ers, as Ara­bi­ca trees can do; sci­en­tists call this ​“allog­a­mous” (Nowak, et al., 2011) — ­sub­types grown in the same field typ­i­cal­ly inter­breed (Thomas, 1935). A con­se­quence of this mat­ing sys­tem is that the major­i­ty of cul­ti­vat­ed robus­ta is still made up of uns­e­lect­ed pop­u­la­tions obtained from open-pol­li­nat­ed seeds (Labouisse et al, 2020). For more back­ground on Robus­ta breed­ing, see Mon­tagnon, Thier­ry, and Eskes, 1998a & b.

Put sim­ply, robus­ta plan­ta­tions are not genet­i­cal­ly uni­form; con­se­quent­ly, many robus­ta farm­ers have lit­tle aware­ness of which vari­ety or sub­types they are grow­ing. This is one rea­son why col­lo­qui­al­ly, C. canepho­ra is often referred to as sim­ply ​“robus­ta,” as described and com­mer­cial­ized by Lin­den in 1900 (Dagoon, 2005). 

Because robus­ta is a cross-pol­li­nat­ing species (i.e., it requires pollen from two dif­fer­ent types of plants in order to pro­duce new cher­ries), it is nec­es­sary for farm­ers to grow more than one type of robus­ta in their fields in order to have suc­cess­ful pol­li­na­tion and fruit pro­duc­tion. Some breed­ing pro­grams have devel­oped and released ​“poly­clon­al” or ​“mul­ti­line” vari­eties to address this chal­lenge where the ​“vari­ety” is an inten­tion­al mix of genet­i­cal­ly dis­tinct clones (Cam­puzano, et al., 2022, Mon­tagnon, et al., 2003, Berthaud & Char­ri­er, 1998). 

How­ev­er, not all Robus­ta types can suc­cess­ful­ly grow togeth­er in a field — the cross-com­pat­i­bil­i­ty of types is genet­i­cal­ly con­trolled. Some vari­eties are unable to fer­til­ize one anoth­er (Lash­er­mes et al., 1996, Prakash, 2018). So far, research on opti­mal com­bi­na­tions of sub­types in pro­duc­tion has been scarce, but one key con­sid­er­a­tion is simul­ta­ne­ous flowering. 

In dif­fer­ent pro­duc­tion regions, how such mix­es are released and dis­trib­uted for farm­ers is han­dled dif­fer­ent­ly. It is com­mon in West Africa, for exam­ple, for breed­ers to cre­ate poly­clon­al seed vari­eties (i.e., mul­ti­ple dif­fer­ent types of robus­ta are dis­trib­uted togeth­er in the same seed pack­ets to farm­ers). In Brazil, it is more com­mon for breed­ers to cre­ate mul­ti­ple unique clones that are then test­ed for com­pat­i­bil­i­ty; the high­est-per­form­ing com­pli­men­ta­ry clones are then prop­a­gat­ed and released to farm­ers (Depo­lo, et al., 2022, Surya, 2018). 

The scope of genet­ic diver­si­ty in robus­ta cof­fee is much larg­er than that of ara­bi­ca. There are many unknown vari­a­tions (includ­ing traits relat­ed to cup qual­i­ty) in the robus­ta gene pool. By and large, these hid­den vari­a­tions are yet to be explored by breeders. 

His­to­ry of cul­ti­va­tion & dispersal

Robus­ta orig­i­nates from humid low­land forests in trop­i­cal areas of Africa, an area with a wide nat­ur­al geo­graph­ic dis­tri­b­u­tion from Guinea to Ugan­da and Ango­la, grow­ing in numer­ous forms and eco­types. It has been sur­veyed and prospect­ed by ORSTOM and FAO mis­sions (Dussert et al., 1999). The exact nat­ur­al ori­gins of the cul­ti­vat­ed types are difficult to know for cer­tain giv­en the wide­spread intro­duc­tion and nat­u­ral­iza­tion of dif­fer­ent sub­types around the region and the gene­flow between wild and near­by plan­ta­tions (Davis, 2006, Kiwu­ka et al., 2021).

Cul­ti­va­tion of the species began around 1870 in Con­go, using mate­r­i­al com­ing from Zaïre’s Loma­mi Riv­er region, now known as the Demo­c­ra­t­ic Repub­lic of Con­go (Berthaud & Char­ri­er, 1988). A sub­type of robus­ta called ​“kouil­lou” (lat­er renamed ​“conilon” via lin­guis­tic dis­tor­tion when it was intro­duced to Brazil) was observed in the wild by the French in 1880 between Gabon and the mouth of the Con­go Riv­er, main­ly along the Kouilou-Nari Riv­er region. The species was named C. canepho­ra by the botanist Louis Pierre in 1895. Pierre, who worked in France at the Muséum Nation­al d’Histoire Naturelle, received a sam­ple of the plant col­lect­ed in Gabon by the Rev­erend Théophile Klaine. The name was first pub­lished along with a descrip­tion of the species by Froehn­er in 1897. In 1898, Edouard Luja, in prepa­ra­tion for the 1900 Paris Expo­si­tion, was sent to col­lect 10 species with eco­nom­ic poten­tial in the Con­go. Dur­ing this mis­sion, Luja col­lect­ed sev­er­al thou­sand seeds in the sur­round­ings of Lusam­bo of a ​‘new’ cof­fee species (Benoit, 1968). These seeds were prob­a­bly col­lect­ed on an ear­ly robus­ta plan­ta­tion in the region. Bel­gian Con­go became one of the prin­ci­pal breed­ing cen­ters, from which breed­ing lines were dis­trib­uted through­out the tropics. 

At the turn of the cen­tu­ry, the species began to spread to oth­er parts of the world. Robus­ta seeds from Con­go were sent to Brus­sels, and from there it was sent under the name ​“robus­ta” to Java, Indone­sia, where it was quick­ly accept­ed by farm­ers due to its pro­duc­tiv­i­ty and appar­ent resis­tance to cof­fee leaf rust (Cramer, 1957), as a major out­break occurred in South­east Asia in the late 1800s. These mate­ri­als were lat­er enriched with those from Gabon and Ugan­da. Around the same time, oth­er Robus­ta mate­r­i­al select­ed from wild pop­u­la­tions was brought to areas of Ivory Coast, Guinea, and Ugan­da (Char­ri­er and Eskes, 1997). 

From here, robus­ta con­tin­ued to move around the world, enter­ing India by way of Java (with lat­er intro­duc­tions from west Africa). Mate­r­i­al select­ed in Java was rein­tro­duced to cen­tral Africa from 1910 onward, and to the Bel­gian Con­go in 1916 at the Insti­tut Nation­al pour Étude Agronomique du Con­go (INEAC), which served as the home to the major­i­ty of selec­tion from 1930 to 1960. With­in Africa, robus­ta pro­duc­tion grew in Mada­gas­car, Ugan­da, Ghana, and the Ivory Coast, often inter­min­gling endem­ic vari­ants with those intro­duced from com­mer­cial pro­duc­tion in oth­er parts of the continent.

As not­ed pre­vi­ous­ly, much of the move­ment of robus­ta and the increase in the pop­u­lar­i­ty of its pro­duc­tion dur­ing this peri­od may be attrib­uted to the spread of cof­fee leaf rust (CLR), a fun­gal dis­ease that rav­ages cof­fee plants. One of the great­est ben­e­fits of robus­ta pro­duc­tion is that the species pos­sess­es a nat­ur­al resis­tance to some of the major pests and dis­eases that impact cof­fee pro­duc­tion; they can thrive under harsh con­di­tions (Cam­puzano, et al., 2022).

Robus­ta was lat­er intro­duced to Latin Amer­i­ca, and in par­tic­u­lar Brazil, with some addi­tion­al com­mer­cial intro­duc­tions in Cen­tral Amer­i­ca via Guatemala between 1930 – 1935. Fur­ther, CATIE in Cos­ta Rica intro­duced robus­ta plants called ​“French lines” between 1981 – 1983. 

In present day, coun­tries that lie with­in Asia and Ocea­nia are col­lec­tive­ly the largest pro­duc­ers of robus­ta, gen­er­at­ing 60% of the world’s out­put at 41.5 mil­lion 60 kg bags annu­al­ly. This region is fol­lowed by South Amer­i­ca, which pro­duces 28% of the world’s share of robus­ta, gen­er­at­ing 19.8 mil­lion bags of cof­fee in the 2020 – 2021 year.

Genet­ic diver­si­ty and conservation

C. canepho­ra is is a diploid (2n=2x=22) species divid­ed into two broad genet­ic groups, Guinean and Con­golese. The Guinean group orig­i­nat­ed in cen­tral-west Africa, while the Con­golese group orig­i­nat­ed in cen­tral Africa. Among these two groups, the Guinean is the most wide­spread. In addi­tion, with­in each group, there are dif­fer­ent pop­u­la­tions, or sub­groups. With­in the Guinean group, there are at least two sub­groups, named ​“kouilou” or ​“conilon,” and ​“robus­ta.” How­ev­er, more recent stud­ies using advanced genet­ics tech­niques, have fur­ther refined the robus­ta species into eight sub­cat­e­gories. Stud­ies of the genet­ic rela­tion­ships with­in C. canepho­ra have shown that, in gen­er­al, these pop­u­la­tions are well dif­fer­en­ti­at­ed and genet­i­cal­ly iso­lat­ed (Berthaud, 1986, Mon­tagnon, 1992, Cubry, et al., 2008, Musoli, et al., 2009, Dussert et al., 1999, Gomez et al. 2009, Mérot‑L’Anthoëne et al., 2019). Mon­tagnon (1992) pro­posed a sub­struc­ture with­in the Con­golese group with two sub­di­vi­sions, SG1 and SG2. Dussert (1999) added two extra groups (includ­ing B and C, as ref­er­enced below) to the Con­golese group. How­ev­er, these sub­groups are not nec­es­sar­i­ly visu­al­ly dis­tinct from one anoth­er (Chad­burn & Davis, 2017, Charr et al., 2020).

Using RFLP and SSR mark­ers, Gomez et al. (2005) pooled C. canepho­ra genet­ic diver­si­ty into five genet­ic groups (A, B, C, D, and E). Geo­graph­i­cal­ly, genet­ic group A com­prised wild pop­u­la­tions from Con­go and Cameroon, group B from east­ern-cen­tral Africa, group C from west­ern-cen­tral Africa, Cameroon and north­east­ern Con­go, group E from Con­go and south­ern Cameroon, while group D con­sist­ed of wild pop­u­la­tions from Côte d’Ivoire and Guinea, sep­a­rat­ed geo­graph­i­cal­ly by the Dahomey Gap from the oth­er diver­si­ty groups. Musoli et al. (2009) fur­ther deter­mined that some Ugan­dan wild pop­u­la­tions clus­tered into anoth­er dis­tinct group (group O). Final­ly, Mérot‑L’Anthoëne et al. (2019), using a genome-wide Cof­fee 8.5K SNP array, described C. canepho­ra genet­ic diver­si­ty with eight dis­tinct genet­ic groups, includ­ing the Ugan­dan one (group O), thus iden­ti­fy­ing two new genet­ic groups, (com­pris­ing sam­ples from south­ern Demo­c­ra­t­ic Repub­lic of the Con­go) and G (com­pris­ing sam­ples from Ango­la), where­as the dif­fer­en­ti­a­tion between groups E and R was weaker.

Wild pop­u­la­tions are the pri­ma­ry genet­ic rel­a­tive of robus­ta cof­fee, and cul­ti­vat­ed cof­fee has changed lit­tle from its wild prog­en­i­tors. It is also a sec­ondary genet­ic rel­a­tive of ara­bi­ca, con­fer­ring poten­tial dis­ease and pest resis­tance (Chad­burn & Davis, 2017). 

As a part of the genet­ic con­ser­va­tion of the species, gene banks of robus­ta were estab­lished in sev­er­al pro­duc­ing coun­tries in Africa and Asia. There are cur­rent­ly 40 known col­lec­tions of this species held in ex-situ col­lec­tions (Tram, et al., 2022, Botan­ic Gar­dens Inter­na­tion­al, PlantSearch). The species was set into col­lec­tion in Côte d’Ivoire, with 700 wild geno­types by ORSTROM in col­lab­o­ra­tion with the Cen­ter de Coopéra­tion Inter­na­tionale en Recherch Agronomique Pour Development. 

In addi­tion, the species was col­lect­ed in Guinea, Cameroon, the Con­go, and Cen­tral African Repub­lic and lat­er intro­duced into field gene banks. The species is found in pro­tect­ed areas such as Man­gala For­est Reserve in Tan­za­nia, Bia Nation­al Park in Ghana, Isa­lowe For­est Reserve in the Demo­c­ra­t­ic Repub­lic of Con­go, and Reserve du Dja in Cameroon. 

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