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

14.05.2008
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:
http://www.cirad.fr/en/actualite/communique.php?id=929

More articles from Agricultural and Forestry Science:

nachricht Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University

nachricht New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien

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: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>