Wheat Research Goes Undergound

An informal but extensive network based in Turkey conducts research that could raise farmers’ wheat yields by a third or more in dry environments.

Microscopic worm-like animals called nematodes eat their way into the roots of plants and quietly destroy 10% of world crop production every year. Root diseases cause the same unperceived damage. Many farmers on the Central Anatolian Plateau in Turkey can lose up-to half of their winter wheat crop to cereal cyst nematodes.

Nematodes and root diseases are so aggressive in the dry environments where winter and spring wheat are produced that they have become a significant priority for CIMMYT’s global research in these environments. Through the International Winter Wheat Improvement Program (IWWIP) and with support from a large, informal network of collaborating institutions (see box), researchers are working to restore lost yields to farmers. Their efforts are concentrated in the Central Anatolian Plateau of Turkey, where 5 million hectares are sown to wheat, yet yields often do not surpass 2 tons per hectare. The benefits should be particularly significant in West and Central Asia and North Africa.

Breaking New Ground

In 2000, researchers from Turkey, CIMMYT, ICARDA, and France’s Institut National de la Recherche Agronomique (INRA) collected 53 soil and root samples from Syria and Turkey to get a firm idea of the problem. They used traditional as well as molecular techniques to identify pathogens. The molecular techniques enabled researchers to cross-check results from traditional methods and identify pathogens more precisely. They found that 72% of the root samples and 83% of the soil samples from Turkey had cysts of one or more species of cereal cyst nematode (Heterodera spp.). Root rotting fungi such as crown rot (Fusarium spp.) and common root rot (Bipolaris spp.) affected 60% of the samples. To complicate matters, 57% of the soil samples lacked zinc and 40% lacked iron. Zinc is particularly important in building and protecting root systems.

Researchers also discovered they were contending with Heterodera filipjevi, a nematode species little known or studied. “This work is a whole new ball game—we don’t have 20 years of experience to build on as with the more common H. avenae,” explains CIMMYT pathologist Julie Nicol. “We have to understand the nematode’s population dynamics and do other basic work.” For example, masters’ student Elif Sahin from Osman Gazi University in Eski¸sehir determined that the major hatch occurs after snow melt in winter wheat areas, just when wheat starts to grow (see figure). She also identified fungi and bacteria that could offer a biological control strategy.

Nationwide and
Worldwide Research

Turkey’s General Directorate of Agricultural Research (GDAR) and CIMMYT initiated two jointly coordinated nationwide research programs on cereal nematodes and root rots in 2001. The cereal nematode program is coordinated by Necmetin Bolat of ANADOLU Research Institute, Eskisehir. Work on cereal root rots is coordinated by Ahmet Bagci of Selcuk University, Konya. Nicol is the CIMMYT counterpart for both programs. Each program includes pathogen surveys, yield loss studies, work to identify sources of resistance, and the examination of alternative control methods, including crop rotations and other management practices. “This nationwide approach with CIMMYT is one of the best mechanisms to work collectively on this difficult problem,” says Mesut Keser, Deputy Director General of GDAR. It also complements international efforts to develop winter and spring wheat varieties that resist these pathogens, says Hans Braun, who directs CIMMYT’s Rainfed Wheat Systems Program. “CIMMYT can cross new sources of resistance into wheat lines,” he explains, “but the most important step is the validation of resistance through the two nationwide programs.”

Work on Root
Rotting Fungal
Diseases

Researchers are also coming to grips with root rotting fungi. Turkish and CIMMYT scientists conducted the first study to demonstrate the impact of root disease pathogens on winter cereals grown in the dry, marginal conditions of Central Anatolia. Based on an extensive plant survey, mycologist Berna Tunali of the Plant Protection Institute in Ankara concluded that F. culmorum is the main causal agent of dryland root rot on the Central Anatolian Plateau. “Based on a three-year study we conducted, we think that farmers probably lose 26% of their cereal harvest on average to several root diseases,” says Hakan Hekimhan, pathologist at Bahri Dagdas International Agricultural Research Center.

The Roots of Resistance

The scientists are using every tool at their disposal to identify resistant wheat lines and provide them to breeding programs in Turkey and internationally. For example, wild relatives of wheat have resistance to some nematodes. Breeders have used conventional approaches to put that resistance into bread wheats from Australia, France, Spain, and CIMMYT. The resistance of these wheats is being studied throughout the world. Researchers are using molecular markers, obtained through collaboration with research institutes in Australia, to identify and select resistant wheat early in the breeding cycle, reducing the need for expensive field trials.

More markers are being identified through collaboration between CIMMYT, the Plant Protection Institute in Adana, Çukorova University, and Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). Doctoral student Halil Toktay showed that yield losses in southeastern Turkey are caused by the root lesion nematode. His studies, conducted at the Plant Protection Institute under the supervision of Halil Elekcioglu of Çukurova University and Nicol, are partly sponsored by Australia’s Grains Research and Development Corporation (GRDC) to find molecular markers to known sources of resistance. The root rot program in Turkey has tested more than 7,000 wheats for their reaction to F. culmorum. Over 200 proved to have some resistance. Through an extensive crossing program, researchers hope to move closer to their ultimate goal: varieties that withstand several root diseases at once. First results are available from CIMMYT, where wheat breeder Richard Trethowan has developed new spring wheat lines that yield up to 20% more than their parent lines. These are now being validated by CIMMYT in Turkey under pressure from fungi that cause cereal root rot. Though progress in winter wheat breeding is slower, promising, resistant winter wheats have been identified and are being tested in preliminary yield trials.

Through another GRDC project, a new International Root Disease Resistance Nursery will enable researchers in a number of locations to evaluate sources of resistance to nematode and root rotting fungi. Many of the researchers belong to Australia and the Root Disease Network, formed from the International Master Class on Soil Borne Pathogens of Cereals in Turkey in 2003 (see 2003 Annual Report story: "Underground Wheat Diseases: Out of Sight, Out of Mind").

Will Farmers See
the Results?

Breeding for resistance or tolerance to soil pathogens is one of the most economical and effective ways to help farmers cope with the problem, but it is not the only way. “We need to look at reduced tillage practices, crop rotations, and different ways of improving soil fertility,” says Nicol. “For example, Professor Elekcioglu has identified some genera of nematodes that can be used as soil health indicators and help determine more appropriate cropping systems.” Ever on the lookout for collaborators, she adds, “We could benefit from partners who want to study biological control, based on Elif Sahin’s work.”

For more information: j.nicol@cgiar.org

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January, 2005