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Plant virus threatening African staple food

Cassava breeders meet plant virologist at Brunswick (Germany) (© Johannes Kaufmann/JKI)

The disease attacks the roots of the cassava plant, also known as manioc. African cassava growers as well as the coordinator of the international "NextGen Cassava" breeding project meet with the DSMZ’s plant virus researchers at the Federal Research Centre for Cultivated Plants (JKI) in Brunswick. Their goal: to swiftly cultivate cassava varieties resistant to the new disease and thereby to safeguard the alimentation of millions of Africans.

For approximately half a billion people in Africa – mainly south of the Sahel – the most important foodstuff is neither wheat nor rice, but the starchy roots of the cassava plant, also known as manioc. However, the supply with this otherwise robust crop is currently under threat: In recent years, a virus has spread (and is still spreading) rapidly across many African nations, infecting cassava plants and causing their roots to die off. As the infection leaves hardly any visible trace on the above ground part of the plants, the farmers usually only notice an infection when they try to harvest the at this point inedible roots.

On the initiative of the international cultivation project ‘NextGen-Cassava’, growers from across the globe are currently spending several days on an intensive exchange visit at the Julius Kühn Institute (JKI) in Brunswick, in the German state of Lower Saxony. The farmers are discussing the most effective strategies to prevent a further spread of the disease in the most important producing nations of Nigeria and Congo, with a focus on how to speed up the cultivation of virus-resistant cassava plants. Dr. Stephan Winter of the Department for Bioinformatics at the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures is acting as host.

Dr. Winter has been collaborating with the JKI’s plant virologists for more than 20 years, investigating new, unknown viruses. He is one of the world’s leading experts on the aggressive ‘cassava brown streak virus’ or CBSV. Since 2014, the Bill-and-Melinda-Gates foundation has been partially sponsoring Stephan Winter’s successful cassava research. “These accomplishments would not be possible without the close, door-to-door cooperation with the internationally renowned virologists at the JKI”, says Dr. Winter. “For instance, in my cassava research I was able to use the JKI’s research greenhouses for my practical experiments with plant viruses.” Professor Dr. Johannes Hallmann of the JKI, at whose institute Dr. Winter performs most of his research, could not agree more. “It is a clear win-win situation: The DSMZ’s professional expertise and content assignments complement our own tasks perfectly. The close cooperation of the plant virologists at the DSMZ and the JKI creates an added value, culminating in highly successful joint projects.”

One important step in the fight against the brown streak virus has already been taken: Stephan Winter managed to track down virus-resistant cassava plants in Columbian gene banks, vigorously tested these plants in JKI greenhouses and had them successfully planted in open fields on the African continent. The next task on the list is to cross this resistant material as quickly as possible into varieties adapted to African farming conditions.

Cassava

The cassava plant originally stems from South America, from where the Portuguese brought it to Africa about 400 years ago. Whilst the plant is as good as unknown in Germany, cassava plays an even more important role in the diet of people south of the Sahara – especially in Nigeria, the Congo and partially in South America – than wheat or potatoes do in European countries. The roots of the plant are boiled, baked or fried; in addition, they can be stored over longer periods of time or processed to starch (tapioca). In many African countries, it is the rural poor in particular who depend on cassava as their main supply of calories. Cassava plants are famed for being extraordinarily robust, as they are not overly demanding as far as the soil is concerned and are able to withstand droughts. However, viral diseases have threatened their growth time and again, and due to the vegetative reproduction cycle of the plant, its genetic variety on the farmlands is extremely restricted. Luckily, scientists have been able to breed varieties that are resistant to the fatal cassava mosaic virus (CMV), and these varies were then comprehensively introduced. But these plants now seem vulnerable to the cassava brown streak disease (CBSD), a virus that first appeared several years ago.

The meeting in Brunswick took place at the request of Prof. Dr. Chiedozie Egesi, project coordinator of the international “NextGen Cassava” breeding project.

About the Leibniz Institute DSMZ

The Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures is the world's most diverse collection of biological resources (bacteria, archaea, protists, yeasts, fungi, bacteriophages, plant viruses, genomic bacterial DNA as well as human and animal cell lines). Microorganisms and cell cultures are collected, investigated and archived at the DSMZ. As an institution of the Leibniz Association, the DSMZ with its extensive scientific services and biological resources has been a global partner for research, science and industry since 1969. The DSMZ is the first registered collection in Europe (Regulation (EU) No. 511/2014) and certified according to the quality standard ISO 9001:2015. As a patent depository, it offers the only possibility in Germany to deposit biological material in accordance with the requirements of the Budapest Treaty. In addition to scientific services, research is the second pillar of the DSMZ. The institute, located on the Science Campus Braunschweig-Süd, accommodates more than 71000 cultures and biomaterials and has 200 employees. www.dsmz.de

About the Julius Kühn-Institute, Federal Research Centre for Cultivated Plants

Research at the Julius Kühn Institute (JKI) is dedicated to plant health and to maintaining and improving high performance in cultivated plants. The 17 specialized institutes with more than 1,200 employees under the roof of the JKI encompass in their research a wide range of crops from agricultural and horticultural crops, fruit crops, grapevines, forest plants and urban greenery. Our major fields of research are plant genetics, plant diseases and plant protection. The specially targeted breeding research carried out by the JKI is fundamental for enhancing the genetically conditioned resistance of our crops against pathogens and pests as well as enhancing their tolerance towards abiotic stress. Also high on the agenda are efforts to achieve a better adaptation of the cultivated plants and cropping systems in general to climate change. The JKI headquarter is located in Quedlinburg. More JKI branches are to be found at nine different locations all over Germany. www.julius-kuehn.de/en