The enigmatic narrow-leaved coffee (Coffea stenophylla), a rare and little-known species of wild coffee from West Africa, has a similar flavor profile to high-quality Arabica coffee (Coffea arabica), but grows and crops under the same range of key climatic conditions as robusta (Coffea canephora) and Liberica (Coffea liberica) coffee, according to new research led by the Royal Botanic Gardens, Kew.
Coffea stenophylla, cultivated in Trinidad Botanical Garden, with Demerara sugarcanes, photograph taken around 1900. The man in the photograph is 1.72 m tall. Image credit: Royal Botanic Gardens, Kew / Davis et al., doi: 10.3389/fpls.2020.00616.
Coffee is a ubiquitous beverage that drives a multibillion dollar global industry, supports the economy of several tropical countries and provides livelihoods for over 100 million coffee farmers.
Despite its global success, the coffee supply chain is beset with challenges, including cyclic price volatility, extreme weather events, increases in the prevalence, severity of pests and diseases, and even modern-day slavery.
In addition to these issues, and compounding them, are the negative influences of accelerated climate change.
Progress on breeding climate-resilient coffee crop plants is at an early stage, with attention focused on the two main coffee crop species: Arabica and robusta.
In 2019-2020, Arabica coffee contributed about 56% of global production, robusta 43% and Liberica coffee less than 1%.
Arabica is a cool-tropical plant, originating from the highlands (1,000-2,200 m) of Ethiopia and South Sudan. In the wild and in cultivation, it has an optimum mean temperature range of 18-22 degrees Celsius.
Robusta coffee is a predominately low-elevation species (50-1,500 m), occurring naturally across much of wet-tropical Africa and is adapted to higher mean temperatures of 24-26 degrees Celsius or perhaps even higher to 30 degrees Celsius.
There is a well-defined price difference between the two species, with Arabica achieving higher prices 10 due to its superior taste.
Robusta and Liberica are excluded from the higher value specialty coffee sector, which is currently the sole preserve of Arabica.
Coffea eugenioides, a very minor crop species, has an excellent flavor and has started to gain attention as a niche-market, high-end coffee but its seeds are small and yields are low.
Amongst the other 120 coffee species, there are numerous species able to grow in warmer and drier environments relative to Arabica, robusta and Liberica and some markedly so.
So far, however, none of them has demonstrated the required flavor and agronomic attributes for wide-scale commercial success.
In this respect, Coffea stenophylla, a species endemic to Guinea, Sierra Leone and Ivory Coast, is of considerable interest.
In the wild, this species grows in hot-tropical conditions at low elevations, and is reported to be drought tolerant and partially resistant to coffee leaf rust.
Several historical references suggest that Coffea stenophylla has an excellent flavor, but no sensory information about the species has been published since the 1920s.
Coffea stenophylla in fruit at Centre National de Recherche Agronomique in Ivory Coast. Image credit: Charles Denison / Davis et al., doi: 10.3389/fpls.2020.00616.
Following the rediscovery of wild Coffea stenophylla in Sierra Leone in 2019, and the production of a limited crop on the Mascarene island of Reunion (originally from Ivory Coast) in 2020, Dr. Aaron Davis from the Royal Botanic Gardens, Kew, obtained samples of Coffea stenophylla beans.
The researchers conducted standardized sensory evaluations to compare the taste of the rare wild coffee to two Arabica samples and one robusta sample.
They found that Coffea stenophylla had a similar flavor profile to high-quality Arabica coffee.
The scientists also modeled climate data for Coffea stenophylla, which suggest that it grows under similar climatic — or slightly warmer — conditions to robusta and Liberica coffee.
The species also can potentially tolerate a much higher mean annual temperature (24.9 degrees Celsius), which is at least 6 degrees Celsius higher than Arabica.
“Coffea stenophylla substantially broadens the climate envelope for high-quality coffee and could provide an important resource for the development of climate-resilient coffee crop plants,” the authors said.
“Efforts must be taken to safeguard it in the wild and to further study its potential as a climate-resilient, high-quality crop species and breeding resource.”
The findings appear in the journal Nature Plants.
A.P. Davis et al. 2021. Arabica-like flavour in a heat-tolerant wild coffee species. Nat. Plants 7: 413-418; doi: 10.1038/s41477-021-00891-4