Quiet heroes of coffee science gather in China to share latest research

Researchers share the latest on genetic diversity, climate change and more.

At the biannual International Conference on Coffee Science (ASIC), held this year in China's Yunnan province, the world's top coffee researchers gathered to share their recent findings on everything from genetics to agroforestry to espresso chemistry. World Coffee Research-affiliated researchers contributed three presentations, including a keynote on coffee and climate change from Christian Bunn. The other presentations were on coffee's genetic diversity and the relationship between coffee leaf rust and quality (abstracts below).

Bunn coffee climate original

Christian Bunn delivered a keynote on coffee and climate change

ASIC brings together researchers from all disciplines that work on coffee for four days of lecture and discussion. World Coffee Research extends its congratulations to all of the presenters, as well as to our chief coffee breeder, Benoit Bertrand, who organized the scientific sessions.

This year's conference was held in China, where coffee production is growing rapidly. The land planted in coffee has grown from 10,000 hectares just 15 years ago to nearly 200,000 hectares today, with more investments planned, especially in Yunnan province, known for its tea.

WCR-Affiliated Presentation Abstracts

An extensive study of the genetic diversity of Arabica coffee reveals two subpopulations in Ethiopia and a cultivated subpopulation in Yemen

Patricia K.1, Murray S. 1, Solano W. 2, Montagnon C.3, Schilling T.3, Bertrand B3.

1Texas A&M University (TAMU), 2CATIE, Turrialba, Costa Rica, 3World Coffee Research, info@worldcoffeeresearch.org


Arabica coffee production in America or Asia is based to a large extent on cultivars developed long ago by line selection on a very narrow genetic base. The ‘wild’ accessions surveyed in Ethiopia in the middle 20th century have not really been exploited in breeding programs. Analysis of molecular genetic diversity is useful to better understand origins and relatedness of cultivars as well as to identify novel accessions of use in breeding. To date, there has not been a genome-wide study of Arabica genetic diversity. Here we report a genotyping by sequencing (GBS) approach for polymorphism detection on Arabica accessions to determine their relatedness and structure. We have developed a general description of Arabica species structure and its relation to geographic and historical data. We address two basic questions: can we corroborate the historical data by genetic diversity identified within the species and can we find traces of domestication and gene flow between the different genetic groups.


A collection of 699 C. arabica accessions collected in Ethiopia by FAO and ORSTOM surveys and 95 C. arabica accessions collected in Yemen, were analyzed using a genotyping by sequencing (GBS) approach for polymorphism detection to determine the relatedness and structure of these accessions. The full Arabica marker set contained 23,519 bi-allelic markers using a cutoff that at least two individuals of the 794 share the minor allele (i.e. no singletons, which could be due to genotyping error). The final marker set contained 1035 bi-allelic markers using a minor allele frequency cutoff of 97.5%. All summary statistics of genetic diversity were conducted within PowerMarker v2.35 or ADZE v1.0.


A factorial analysis followed by a model-based clustering procedure revealed three subpopulations. The first subpopulation contained mainly cultivated accessions, Yemeni and Harar genotypes and the Bourbon/Typica derived cultivars. The second subpopulation corresponded mainly to Ethiopian accessions originating from the geographic regions of Jimma and Bonga in the Southwestern region of Ethiopia. The third subpopulation included Ethiopian origin cultivars from Tippi and ‘Sheko forest’. We provide evidence that gene flow between the three subpopulations has occurred and especially between the cultivated ‘Yemen-Harar’ subpopulation and the ‘Jimma-Bonga’ subpopulation. We didn’t identify an impact of domestication on the Yemen subpopulation. Contrary to historical reports we cannot discard the idea that Yemen is a primary dispersal center.


Our genetic diversity results suggest structuring the Arabica species based on three subpopulations. This genetic diversity structure appears strongly supported by geographic and historic background. The two western subpopulations could represent an important and valuable source of genetic diversity for coffee improvement and will probably be heterotic subpopulations when crossed with accessions from the ‘Yemen-Harar’ subpopulation as suggested by previous work.

Effectively guiding forward looking climate change adaptation of global coffee supply chains

BUNN, Christian (1), LÄDERACH, Peter (1), LUNDY, Mark (1), MONTAGNON, Christophe (2), MOSNIER, Aline (3), OBERSTEINER, Michael (3)

(1) International Center for Tropical Agriculture, Cali, Colombia; (2) World Coffee Research, College Station, TX, USA; (3) International Institute for Applied Systems Analysis, Laxenburg, Austria


Across coffee growing regions stakeholders along the coffee supply chain demand guidance to effectively adapt to projected climatic changes. Coffee famers report unusual climatic events that negatively impact their production systems. A growing body of literature shows that these perceived changes such as novel pest and disease patterns or precipitation excess and deficiency are not anecdotal but part of a global change process.

Future projections show that over the coming decades challenges to production are likely to increase to an extent that significant shares of currently suitable area for coffee production will become unsuitable with current production techniques. Remaining suitable area is often located in higher elevations with uncertain agronomic quality but high biodiversity value. At the same time global demand for coffee is growing, driven by growing population and economic growth. The predicament that global coffee production faces is thus that production needs to be increased in a sustainable way while its most productive areas have come under pressure from adverse climatic changes.

Effective adaptation is therefore a vital challenge that the sector faces. A strategy to make coffee production climate smart will need to address the specific climatic changes, the structure of the value chain and the needs of the coffee producers to be viable. Because of the multi-decadal life span of coffee plantations adaptation planning requires a forward looking component. Locations that will remain suitable will be able to adapt by transferring adequate existing technological solutions. With increasing severity of climate impacts novel solutions will have to be developed in joint public-private efforts that expand the climatic niche in which coffee can be produced. Finally, at locations where adaptation appears unfeasible because of the projected climate change impact alternative crops have to be promoted by public actors for an orderly change process.

View presentation here (PowerPoint)

Read a blog post about the presentation here

Thinning Effect On Rust Incidence and Quality For Two Varieties of Coffea Arabica in Costa Rica Revealed by the WCR Sensory Lexicon, GC-MS and SPME

Echeverria, F.*; Murray, S.; Klein, T.; Miller, R.; Kerth, C.; Lombardini, L; Bertrand, B.²

¹ Texas A&M University (TAMU), College Station, TX, USA; ² CIRAD, Montpellier, France. *Corresponding author: fabianebtec@gmail.com

Beverage quality is a complex attribute of coffee (Coffea arabica L.). The environment (E), genetics (G) and management (M) are involved in addition to post-harvest processing. However, little is known about how G, E, and M and their interactions affect beverage quality. For that reason, we have investigated the yield and leaf rust disease (Hemileia vastatrix) in two coffee varieties: a susceptible inbred and a tolerant hybrid. These varieties were conditioned to thinning (50% or 0%) and chemical rust control (with or w/o spraying) treatments under a randomized complete block design with 4 replications. The number of leaves, rust incidence and severity were measured monthly. The yield was measured by weighing the mature fruits during all the harvest season. Beverage quality was evaluated using the new WCR Sensory Lexicon and chemical volatile compounds by Solid Phase Microextraction (SPME) followed by Gas Chromatography Mass Spectrophotometry (GC-MS). Statistical linear models and multivariate analyses were made in JMP® Pro 12.0.1.

The difference in rust incidence between chemical treatment groups was 10.7% and 9.8% for the inbred and hybrid varieties respectively. Thinning correlated to a reduction in rust incidence of 2-3% on both varieties. Beverage sensory analysis revealed that 5 of 60 attributes were significantly different between the thinning and rust control treatments and between varieties. From the 154 chemical volatile compounds detected, 13 were significantly differentially expressed in the inbred and 9 in the hybrid; 5 of the compounds were significant for both varieties.

These results were used to generate a model that explains between 78-86% of the variation obtained from the interaction of disease, yield and variety. This model will be used to understand the complexity of the physiological, metabolic and molecular changes correlated to thinning and leaf rust control to improve new coffee variety breeding.

Key words: coffee, quality, rust, volatiles, GC-MS, SPME, thinning, WCR Sensory Lexicon.