Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Fighting pod pests and diseases by exploiting the merits of wild cocoa trees from French Guiana

Fighting pod pests and diseases by exploiting the merits of wild cocoa trees from French Guiana

In every production zone worldwide, cocoa trees are faced with pests and diseases that can wipe out entire harvests. To protect their crops, farmers often use costly, polluting chemicals or labour-intensive manual techniques. However, there are now clean, ecological methods, for instance using sources of natural resistance.

In this respect, a highly specific group of cocoa trees, the wild trees found in French Guiana, looks very promising. A new project, called "Dicacao", coordinated by CIRAD, has been set up to conduct more in-depth research on these trees over the next three years.

Cocoa was domesticated in central America by the Mayas, discovered by Europeans at the very start of the 16th century, and introduced by them in tropical zones on every continent. Cocoa improvement is still largely dependent on wild genetic resources, particularly in terms of disease control. CIRAD has thus been studying the wild cocoa trees of French Guiana since the mid-1980s. At Sinnamary, in French Guiana, it has a reference collection of local wild material with more than 350 accessions, including almost 200 clones.

This genetic material has many assets. In addition to their agronomic and processing performance, which is often better than that of cultivated varieties, wild cocoa trees have high natural resistance to diseases. They are particularly resistant to black pod disease, which is primarily caused by the fungus Phytophthora palmivora, and to witches' broom disease, caused by Moniliophthora perniciosa.

Detecting clones that are resistant to the main three cocoa diseases

The Dicacao project, which has just been launched with EU funding attributed by the French Guiana Regional Council–ERDF Convergence Programme–will enable further studies and surveys of this exceptional wild material. CIRAD has already carried out three surveys, in 1987, 1990 and 1995. The worthwhile material found was cloned, after being studied individually for several years, to make up a core collection of 185 wild cocoa tree clones. Tests in several countries of some of those clones, for their resistance to diseases or to bugs of the family Miridae, gave very promising results: many clones proved to be resistant to Phytophthora palmivora and Phytophthora megakarya. The latter fungus, which is only found in Africa, is the more dangerous. Under the Dicacao project, researchers intend to test all the clones in the French Guiana core collection in relation to local strains of the main three cocoa diseases.

In particular, the results obtained with regard to Phytophthora palmivora will have to be confirmed, and the aim is also to identify clones that are resistant to Ceratocystis wilt, a disease caused by Ceratocystis fimbriata, and to witches' broom, if not to all three diseases at the same time. This is the first planned line of research under the project, centring on genetic control, and should make it possible to offer Guianan farmers interested in organic farming resistant clones tested for local disease strains.

Cocoa endophytes: hope for biological control

Another line of research will be looking into biological control of the main cocoa diseases, using beneficials. Researchers will be studying the existence and properties of microscopic fungi that live on cocoa trees: endophytes. Endophytes live in symbiosis with cocoa trees, but are generally lost during the domestication process. In some cases, after being introduced into plantings, they have been known to boost protection against diseases. This phenomenon has been seen in Ecuador and Panama in particular. Preliminary data from the upper Amazon Basin show that the endophyte groups found in the region are radically different from those found in Panama. Moreover, they include species from groups not usually known as endophytes.

However, the available knowledge of the endophyte groups found on wild cocoa trees is still sketchy. During the second part of the project, the aim will be to identify the endophytes associated with cocoa trees in French Guiana, and to compare them with those from other parts of the Americas. It is the United States Department of Agriculture (USDA) that will be in charge of laboratory operations (taxonomy and biological tests). The aims include the discovery and identification of endophytes found on leaves (for instance of the genera Colletotrichum and Botryosphaeria), trunks and branches (notably of the genera Trichoderma and Clonostachys) that could be used for biological control. There are high hopes: in Brazil, a Trichoderma is already the active ingredient in a patented product sold to control witches' broom. If the results obtained in Petri dishes are positive, they could then be confirmed in full-scale field trials in French Guiana, by CIRAD and any interested local partners.

The main two cocoa diseases worldwide

Black pod disease, which is pantropical, is caused by several fungi of the genus Phytophthora (for instance P. palmivora, P. megakarya, P. capsici). The fungi attack various organs of cocoa trees, particularly the pods, causing brown patches that gradually cover the surface, before spreading to the inside of the fruit. New, more resistant cocoa varieties are gradually being distributed to growers. However, the most common way of controlling the disease is still to use chemicals (which pollute), which very few cocoa growers have the means to purchase.

Witches' broom is a disease of American origin, also caused by a fungus: Moniliophthora perniciosa (formerly Crinipellis perniciosa). The fungus attacks not only the pods, but also the floral cushions and buds. Affected trees no longer produce real pods, but "chirimoyas", and shoots grow anarchically, leading to the characteristic "witches' brooms". The only ways of controlling the disease are to cut out any contaminated tissue or to practise genetic control via resistant varieties.

Helen Burford | alfa
Further information:

More articles from Agricultural and Forestry Science:

nachricht Unique communication strategy discovered in stem cell pathway controlling plant growth
23.03.2018 | Cold Spring Harbor Laboratory

nachricht “How trees coexist” – new findings from biodiversity research published in Nature Communications
22.03.2018 | Technische Universität Dresden

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>