Crop biodiversity can be used to counter climate change

Call to action 28 September 2022
Droughts, heatwaves, storms, flooding... the list goes on. Climate change is a threat to agricultural production across the planet, and to food supplies for the world's most vulnerable people. To counter its effects, farmers will have to dig into the riches offered by crop biodiversity. CIRAD's researchers and their partners are supporting those farmers with their unique expertise in the diversity and adaptability of tropical plants.
Different sorghum varieties © S. Champion
Different sorghum varieties © S. Champion

Different sorghum varieties © S. Champion

In the light of climate change, it is now vital that we develop more drought-resistant, heat-tolerant crop varieties, and fast. CIRAD's history and vocation have given it unique expertise in tropical crop diversity. Nevertheless, the challenge remains huge.

Varietal improvement lies at the crossroads between a range of issues: food and nutrition, obviously, but also scientific, cultural or socioeconomic concerns. The characters governing adaptability to climate change (tolerance to water and heat stress, ability to take advantage of higher atmospheric CO2 levels, etc) are both numerous and interlinked. They depend on genetic and physiological factors, and on interactions with the environment.

Building an interdisciplinary approach to varietal improvement

In response to that complexity, CIRAD and its partners have been working for a decade or so to test a multidisciplinary approach to support varietal breeding programmes. The approach associates geneticists, breeders, ecophysiologists, modelling specialists and social scientists, working together to determine target characters for breeding operations, in line with societal expectations and agroclimatic constraints, understand the physiological and genetic factors behind those characters, and use crop biodiversity to breed and improve varieties suitable for local use.

These approaches are central to the innovation and plant breeding in West Africa platform in partnership for research and training (dP IAVAO). This regional network implements breeding programmes that combine an exploration of the diversity of dry cereals and pulses with an analysis of societal expectations in terms of practices and usage, and modelling and experimental programmes under controlled conditions and on farms.

Participatory sorghum breeding in Burkina Faso © J. Chantereau

Participatory sorghum breeding in Burkina Faso © J. Chantereau

From plot to high-tech experiments

Adaptability to drought depends on a large number of characters and genes. Identifying and understanding those characters and genes means combining trials covering a broad range of agroclimatic conditions representative of a target region with high-tech research infrastructures.

To back up its field approaches, CIRAD also has experimental facilities that include climate chambers: the Abiophen greenhouse. This serves to simulate current and future climate scenarios and study in detail how plants respond to climate change factors (temperature, hygrometry, atmospheric CO2 levels).

Prior to varietal improvement programmes, genome analysis facilities such as the regional genotyping technology platform and the functional analysis and genome editing platform serve to identify worthwhile genes and alleles.

CIRAD has positioned itself as an indispensable global expert in the genetic diversity and breeding of sorghum, a cereal that shows promise by virtue of its ability to adapt to constraints linked to climate change.

The same type of integrated approach has also been rolled out within operations to breed tree crops better armed to cope with climate change, such as coffee, notably as part of the Breedcafs project.

Plants from the global South are already being grown in the North

In some regions, the genetic diversity of a given species is no longer sufficient to overcome the growing impact of droughts. In such cases, it is worth switching to another crop with similar uses. For instance, some European farmers have switched from maize to a related species: sorghum. "CIRAD is working to strengthen a North-South partnership working on this species (Sorgnet)", says Delphine Luquet, an ecophysiologist at CIRAD specializing in sorghum. "CIRAD is federating research around value chains, such as sorghum, that offer good prospects for adapting farming systems in both North and South to climate change. We are convinced this is now a matter of urgency."

CIRAD's renowned expertise in this cereal is being used in several projects centring on the resilience of farming systems in the global South (ABEE, Sorghum Genomics Toolbox, AFAFI-sud) or on growing the crop in the global North (Biomass For the Future). CIRAD will also be co-organizing a global conference on sorghum in Montpellier in June 2023.

Reintroducing traditional varieties and species

In regions with severe climate risks, using the diversity of crop species and varieties is generally a winning strategy. Those species and varieties include traditional, indigenous species, which play a major role that should be exploited further. Many of them have been abandoned in favour of imported products or crops, and are classed as "forgotten" or "orphan" species. They include fonio, Polish millet (Digitaria sanguinalis), pearl millet or tuber crops such as taro. However, these crops have significant nutritional and cultural value, and are suited to local tastes and different agro-ecosystems.

By virtue of their origin and their history of adaptation, they have often been bred to tolerate drought and extreme temperatures. It is a fair bet that their diversity offers many opportunities for flexible varietal breeding operations tailored to a range of social and environmental situations. Building more resilient agro-socio-ecosystems undoubtedly means investing more in researching and developing these crops, backed by various initiatives such as the Forgotten Crops Society chaired by CIRAD's Michel Ghanem, or the regional varietal breeding network led by dP IAVAO, which is working steadily to integrate these "forgotten" species.

Can crop biodiversity mitigate global warming?
Work on crop diversity currently focuses on adapting to climate change rather than mitigating it. However, research is starting to look into varietal solutions that improve carbon capture within cropping systems, while assessing the potential compromises and synergies with adaptation solutions. The recent EU BOLERO project, for instance, set out to improve coffee and cocoa rootstocks to ensure deep, vigorous root systems, which boost drought tolerance and carbon capture.