The green berries of the robusta coffee bush

© IRD - Valérie Poncet

Uganda may hold the key to the future of robusta coffee!

Hit by climate change, coffee production is seriously under threat. To combat this risk, international teams, including the IRD team led by Valérie Poncet, went in search of wild coffee plants such as robusta in the forests of Uganda. They thus identified previously unknown and drought-resistant genetic profiles, which could save the livelihoods of thousands of coffee producers.

Robusta coffee (Coffea canephora) grown in Uganda represents 7% of world production and provides a living for around 8 million Ugandans, i.e., 19% of the population. According to Valérie Poncet, IRD researcher at the Plant Diversity - Adaptation -Development Unit in Montpellier and specialist in environmental impacts on tropical plants, in particular coffee, “studies in climate change show that the world production of arabica and robusta could drop by 50%”. This grim prospect is tinged with hope, however, with the discovery by Catherine Kiwuka, a researcher for the Ugandan National Agricultural Research Organization (NARO), of wild coffee bushes that are potentially resistant to climate change.

The ex-situ collection in Kituza, with coffee bushes in the foreground

© IRD - Valérie Poncet

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In the framework of her thesis, the researcher analysed the genomes of both wild coffee samples taken from seven Ugandan forests and cultivated varieties from the NARO collection. “Five distinct genetic groups were identified. Four are to be found in North-West Uganda, in the Zoka, Budongo, Itwara and Kibale forests. The fifth genetic profile is common to wild coffee varieties from the Mabira, Malabigambo and Kalangala forests and cultivated varieties conserved at the Kawanda and Kituza centres, all located in the centre and south of the country.” 

Unique genetic material

In addition, the vast majority of north-west coffee varieties are unique to Uganda. On the other hand, the  central and southern varieties are a “mixture” of wild and cultivated species, of which a certain number share similar genetics to those found in the Democratic Republic of Congo (DRC). “This may be explained by the importation of cultivated coffee bushes from neighbouring DRC and by the high level of plantations adjacent to forests”, Valérie Poncet says.

Catherine Kiwuka in the Kalangala forest

© Jan Vos

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Catherine Kiwuka then studied the climatic and geographical conditions in which these various coffee bushes grow. “Our results show that the Zoka forest is the most arid. Its unique genetic material may help in the reproduction and development of drought-resistant coffee varieties”, she says. “But this isn’t the only interesting aspect of the newly-discovered genetic material, because it may contain other significant characteristics for the coffee sector, such as the quality of the cup (i.e., its taste) and resistance to pests and diseases. For example, robusta from the Itwara forest grows at the highest altitude known to date, at about 1,500 metres.”  This world record is potentially significant as the higher robusta is grown, the better its quality. In fact, “even if robusta is considered to have be of lesser quality than arabica, Ugandan robusta grown at around 1000 metres would have a virtually similar quality” Valérie Poncet points out.

Forests for protection

Following the discovery of these high-potential coffee varieties, the teams involved in the project carried out a series of experiments to examine more closely their resistance to drought.

At the Kawanda centre, cuttings from the plants collected in the forest were planted in pots. Valérie Poncet and student N. Dorcus take leaf samples to study their genetic material.

© IRD /Alexandre de Kochko

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The results are expected in the near future. This does not mean the task is complete, however. “We will also have to check the quality and yield of initial experimentations and then carry out appropriate selections. In other words, at least two more years of research”, Catherine Kiwuka emphasizes. There are considerable stakes at play. “In order to face climate change, coffee producers will have to replace their current plants by varieties which are better adapted”, Valérie Poncet adds. “Lastly, a second challenge is to be met: the protection of forests that are home to wild coffee bushes, because, as this study reveals, they a hold potential for natural adaptation to highly-contrasted environments.” These forests may represent a source of new coffee varieties for a long time to come.