December 16, 2020

“Crash Testing” Coffee Hybrids’ Resistance To Adverse Growing Conditions


According to research conducted in 2016, within the next 30 years, climate change could remove more than 50% of the world’s suitable coffee-growing land. A change like this would have a huge impact on millions of smallholder farmers across the world by reducing the amount of land suitable for growing a key cash crop. 

Assuming that the effects of global warming do not slow, the only solution is to develop arabica varieties that will thrive in a broader range of conditions. However, for the moment, the number of contenders is very limited.

As a result, under the Breeding Coffee for Agroforestry Systems project (BREEDCAFS), coffee researchers are working together with a consortium of 17 partners all over the world. They are digging in fields in Nicaragua, Mexican, Cameroon, and Vietnam, nurturing plants in environment-controlled labs in Denmark, France and Portugal, and consulting existing scientific research to find out more about suitable varieties.

To learn more, I spoke to stakeholders involved with these trials. Read on to find out how they are “crash testing” different varieties’ resistance to climate change.

You might also like Combating Climate’s Change Impact With Hybrid Coffee Varieties

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Coffee plants grown in barrels under artificial shade in Nicaragua

Mitigating The Impact Of Climate Change

Sophie Léran is a young molecular physiologist who specialises in coffee and works at CIRAD. She says: “Our efforts are combining fine-tuned lab-controlled experiments and rigorous fieldwork to assess how certain varieties, and especially new arabica hybrids, respond to climate change.”

To cope with the impact of climate change, future varieties must be able to survive in more exacting environmental conditions, including severe droughts, increased temperature extremes, and higher levels of CO2.

However, with existing varieties, producers can start by growing coffee plants under the shade of taller trees using agroforestry techniques.

The ecological advantages of shade-grown coffee have been discussed in the sector for some time already. Jean-Christophe Breitler is an arabica coffee researcher who works with CIRAD. “[Coffee plants] look better under trees,” he explains. “This is because water is more available, and the temperatures are lower.”

While growing coffees in shade generally provides the producer with a more favourable climate, yields can fall by as much as 40%. This can be explained by the fact that coffee plants generally grown today have been bred from ancestors adapted for full sun conditions, rather than shade.

Sophie tells me that one of the BREEDCAFS project’s main aims is to select and test varieties that are suited for agroforestry systems in terms of both quality and productivity.

To find suitable coffees, Jean-Christophe tells me that researchers are evaluating different varieties across field trials in Nicaragua, Mexico, Cameroon and Vietnam. Plants grown on-farm are evaluated and their agronomic performance is assessed through a number of factors, including growth, yield, biochemical composition and cup quality. 

In Mexico, Nicaragua, and Cameroon, he says that researchers are testing arabica hybrid varieties and local cultivars under both light and heavy shade cover at a range of altitudes. The results are subsequently being used to pilot breeding programs and select high-yield hybrid varieties for agroforestry systems. 

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A shade net covering coffee plants at Finca La Cumplida, Matagalpa, Nicaragua

In Nicaragua, Jean-Christophe says researchers are specifically looking into the effects of increased temperature on fruit maturation, bean density, and cup quality.

In these trials, he specifies that coffee plants are grown in 200L barrels at different altitudes and temperatures; plants grown at 1,500 m.a.s.l., for instance, are generally exposed to temperatures around 5°C below those at 750 m.a.s.l.

Jean-Christophe tells me that the team in Nicaragua is collecting a huge amount of information during these trials. He says this includes features that are visible on the plant itself (such as plant height, cherry size, fruit yield, and so on). However, this information also includes plant genetics, the biochemical composition of the beans, and cup quality, all of which allow researchers to better understand the molecular mechanisms behind coffee quality.

In Vietnam, Pierre Marraccini, a researcher at CIRAD, and CIRAD-ECOM PhD student Thuan Sarzynski are studying how plants adapt to drought conditions in agroforestry systems.

Pierre and Thuan have exposed the same arabica varieties to a range of water regimens (such as irrigation, normal rainfall, and 30% water exclusion) and are subsequently recording the same information points during dry and wet periods.

Pierre says that while his team does evaluate how the different hybrid varieties perform when subjected to water stresses, it also focuses on the varieties’ ability to recover once the drought stress is over. In agricultural research, this is the meaning of “resilience”. 

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Water exclusion trial in Son La, Vietnam 

Crash Testing Coffee Plants In Laboratories

Field trials are the closest we can get to “real world” conditions. However, Sophie explains that it is difficult to study and understand the effect of one specific parameter in the field, given the interaction with many other fluctuating environmental factors. This makes it difficult to pinpoint which part of the plant’s response is associated with a given change in the climate.

Sophie tells me that the CoffeeAdapt team at CIRAD in Montpellier is studying the effect of climate change on coffee plants, with a focus on the damage caused by rises in temperature. While climate change is often mainly associated with average temperature elevation, it will also lead to more frequent and severe heat waves. 

Sophie says: “By using growth chambers set up with optimal growth conditions (light, temperature, humidity, CO2, and so on), and varying only one parameter, we can break down specific effects, highlight tolerant or resistant varieties, and identify molecular mechanisms involved in the adaptive response to the stress. 

“These chambers are powerful tools that allow us to mimic field conditions while avoiding variations in the climate (such as wind, rainfall, clouds), and also pests and diseases,” she explains. “In this example, we used these growth chambers to mimic a heatwave. The arabica hybrids were exposed to temperatures of 42°C for ten consecutive days. During that period, we collected samples and data every day.

“We noticed the first burn symptoms on leaves after three days. We are now planning to test other varieties to find some resilient plants in the future, and to pinpoint some that are more resilient to thermal stresses.

“This experiment was actually conducted just a few months before the real heatwave damaged other crops in June 2019 in Europe. Our worst predicted scenario was not too far from reality!”

A growth chamber in Portugal to test CO2 levels

As well as Sophie and her team in Montpellier, in Portugal, José C. Ramalho, a PhD researcher at the University of Lisbon’s School of Agriculture, is testing the resilience of coffee plants in projected future environmental conditions.

 “[In these chambers], you can see what happens, which changes occur in the cell, in the plant under high CO2 levels, under drought, heat, cold… anything you want,” he says. “We believe that CO2 levels will still increase a lot in the coming years.” 

Accordingly, he says he is organising experiments to stress-test plants at “high CO2 levels, different temperatures, and different levels of water availability”.

He says it is unclear how the plants will respond, but notes that in some conditions, projections expect certain varieties to even perform better than they normally would. José says: “If we can achieve higher CO2 without warming, [some] plants would produce more.”

Generally, Lisbon University and CIRAD researchers expect that the new coffee hybrids they’re testing will tolerate and adapt to increasingly aggressive environmental conditions including higher CO2 levels, less water, and more heat. However, José says they’re particularly interested in an “inflection point” where “acclimation and adaptation is no longer possible”.

At Copenhagen University, researchers are also using their facilities to grow coffee in controlled conditions. Anders Raebild and Athina Koutouleas are two ecophysiologists interested in light intensity adaptation.

In these trials, Anders and Athina are mimicking the varying densities of shade trees that coffee producers naturally find when growing plants in an agroforestry system. They grow arabica hybrids alongside their parents under five different light levels, and subsequently measure their capacity for photosynthesis, growth rates, and cherry development as well as the genetic expression underlining each of these characteristics.

“Despite the low light conditions we have here in the global north, we have managed to rear cherry-bearing coffee plants at a similar point in time to their natural development in tropical environments, albeit only enough beans for a couple of cups of coffee,” Athina says. “We may very well be the only people seriously growing coffee in Denmark right now.” 

Coffee plants with varying stages of leaf damage after heat stress in growth chambers

Analysing Data From Fields and Growth Chamber Trials

Data from both the field and growth chamber trials eventually finds its way to Marcus McHale, a Postdoctoral Researcher at the University of Ireland in Galway. All recorded data is stored in the BREEDCAFS database that Marcus has developed. So far, more than 16,000 trees have been listed and individually marked with a unique code. 

Firstly, for Jean-Christophe and Pierre’s work in the outdoor field trials, Marcus records all of the measurable traits of the coffee plants (such as stem diameters, leaf sizes, and so on). He then correspondingly predicts which physical traits may be associated with a positive outcome. 

Marcus says: “For example, right now we’re predicting traits that are associated with yield, such as height or trunk diameter.”

This is valuable for a farmer. “If you give me data on 10,000 individual [plants], I can sequence it and tell you immediately which ones are of the highest value,” Marcus says. After analysis, this information is passed back to researchers, who breed these selected coffees for the next generation of trial plants. 

As the plants grow, produce fruit, and offer more data, this information is looped back into the model to make it more accurate. However, Marcus adds that often it’s not clear specifically why a certain physical attribute in a plant may be correlated with higher yield – we just know that it is.

However, he adds that with the information from the growth chamber trials, it is possible to understand which specific gene leads to which desirable property (e.g. higher yield) using transcriptomic analysis, a method that analyses a plant’s genetic makeup. This effectively provides a “screenshot” of all the relevant genes at a certain point in time. 

At the end of the experiments conducted in growth chambers, the plants are cut up, quickly frozen in liquid nitrogen, and sent to specialist labs for genome sequencing and biochemical analysis.

Marcus then analyses this data in a similar fashion. He says that, for instance, there is data that suggests a genetic link to the size of the microscopic openings on a coffee plant’s leaves that allow it to “breathe”. 

In theory, coffee breeders could then pinpoint this specific gene and supply it to producers in more testing climates, such as those where CO2 levels are much higher, for example. These plants will then hypothetically be better able to cope with the impact of climate change.

Harvesting coffee beans in Vietnam for an altitudinal trial

By combining field experiments and controlled-condition trials, researchers have been able to study coffee plants and how certain varieties are likely to react to the impact of climate change. This spans from the behaviour of coffee trees in agroforestry systems to the genetic expression of certain desirable or undesirable traits.  

BREEDCAFS researchers have considered farmers’ needs throughout the course of this project. They have sought their feedback on specific varieties through surveys in all involved countries, as well leveraging the expectations of coffee consumers. In all of the field trials, samples have been subsequently sent to local or European roasters (including Illycafè) to evaluate cup quality.

Despite the challenges that the coffee sector faces with regards to climate change, this broad and comprehensive project is working towards a solution. Stakeholders involved are hopeful that varieties will emerge from this project and offer consumers high-quality cup profiles alongside improved yield and resilience for the producer. If this is the case, coffee farmers will be able to increase their financial security in the long term, and hopefully be able to mitigate the impact of climate change on their livelihoods. 

Enjoyed this? Then read Combating Climate Change’s Impact With Hybrid Coffee Varieties

Please note: CIRAD is a sponsor of Perfect Daily Grind.

Photo credits: Benoît Bertrand, Jean-Christophe Breitler, Sophie Léran, Pierre Marraccini, Thuan Sarzynski

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