February 2015 editorial

Anders Borgen, WP1 leader 

Anders Borgen

Anders Borgen, WP1 leader

COBRA is a big European project covering several topics and involving many partners. Some people would say that COBRA is more like a research program than a real research project. For this reason, it is difficult to give an overview of what happens throughout the project, and I will therefore focus only on a few hotspots from WP1 related to the “seed quality and health” topic.

Some tasks in WP1 deal with common bunt and dwarf bunt, and in particular, with resistance breeding against these wheat seed borne diseases. In order to identify resistance genes in the host and virulent races among the pathogens, a set of differential varieties with known resistance genes are required.

Most of the internationally recognised differential varieties are landraces collected a long time ago in Turkey and in other places. Their agronomic performances are not fit for all climatic conditions. Many COBRA partners faced problems with winter hardiness and lodging when they used these differential varieties. In the past, a project started with the aim of developing near isogenic lines (NILs) of the stiff straw and winter hardy variety Starke II to be used as a novel differential set for bunt resistance. Two COBRA partners, SLU and NordGen, found the germplasm from this project in NordGen collection, and in cooperation with the Danish and Austrian partners, this material will now be tested and further developed.

Using the available differential lines and the spores collected from the stakeholders, within the COBRA project, it has been discovered that virulence exists in Europe against most of the wheat resistance genes toward both dwarf bunt and common bunt. In breeding sector, therefore, it is necessary that new wheat lines with effective long-lasting resistance, the genes to which virulence are rare, are used. It seems that the most reliable resistance genes are Bt11 and Bt12.

For long-lasting resistance, this should not rely  only on one single gene, but on several genes. Pyramiding resistance genes, however, is difficult to be ensured because it is not possible by field assessment to see whether a healthy plant has one, two or more resistance genes. In order to solve this problem, COBRA partner BOKU will develop genetic markers to identify the presence of Bt11 and Bt12.

Many of the COBRA tasks are focused on how breeding can contribute to the control of plant diseases and ensure quality in diverse populations.

According to the traditional breeding methods, elite pure lines are selected from pure stands of head-rows or single plants, and healthy high quality candidates are multiplied from these to form a new pure line variety. The question for many partners is: “how is possible to identify and get rid only of the plants with negative traits within a population?”

Wind borne pathogens such as yellow rust (Puccinia striiformis) will affect the plant populations and, by means of a natural selection, will reduce the frequency of the most susceptible lines within a population. Many partners have observed that the populations indeed perform better against rust and analogous leaf diseases similarly to pure stands of the parents of the population.

However, in many cases, disease level in the populations still exceed normal acceptable thresholds in wheat. In seed borne diseases such as common bunt in wheat and loose smut in barley, the pathogen is maintained year after year within the crop, and while the population develops improved resistance due to the natural selection, also the pathogen reacts by increasing its virulence matching the resistance of the host.

Therefore, it seems to be necessary developing appropriate breeding tools for population breeding in order to accelerate the selection pressure on the populations to be ahead of the pathogens. The fulfillment of this purpose could be encouraged by the hand removal of plants susceptible to non lethal diseases, rising the disease pressure in breeding plots to increase natural selection or growing large selections of single plant descendants and recombining elite lines into complex mixtures. Different strategies are tested by COBRA partners.

All seed marketed in European countries must meet the requirements of the seed legislations in the respective countries. In all countries of the COBRA partners this means that seed production should be certified and varieties that are distinct, uniform, stable should be approved.

The latter requirement rules out legal distribution and trade of Composite Crosses Populations (CCPs) seeds and other diverse populations. As COBRA is a research project, it benefits from the general exemption for research and breeding, but this implies that many research results and germplasm from the COBRA project cannot be used by farmers and other stakeholders, as they have no legal access to the seed of the populations.

A new EU-directive, however, legalizes the market of heterogeneous plant reproductive material from 2015 onwards in a few EU countries. Thanks to this new regulation, several COBRA partners will use this opportunity to distribute the population developed in the project to external stakeholders in Europe.



Leave a Reply