News From The Small Grains Specialist:
Small Grains Focus

Low Proposed DON Tolerances in Europe May Make Scab International Issue

By Jochum Wiersma
U of M Small Grains Specialist
wiers002@umn.ed

As a number of you may know, I am currently on six months leave from the University of Minnesota. I’m in my native Netherlands and enjoying amongst other things a very mild but wet winter. One thing that it seems I can’t escape from is small grain diseases.

Across Europe, FHB (scab) has increasingly become a problem, with outbreaks reported in Germany, France, Belgium, and the Netherlands. Especially in Germany there are many concerns about it. This past year the central and northern parts of the country had a lot of problems with the disease, and recently I had the “good fortune” of participating in a seminar on FHB in Germany.

Unlike in Minnesota and North Dakota, it seems that FHB in Germany is affecting winter wheat production but not winter barley, spring barley or spring wheat production. It appears that these other crops escape infection.  This is interesting because these crops flower at least partially during the same period.

Within the EU, tolerances for DON (vomitoxin) have been discussed for the past 18 months or so.  The limits as they are currently proposed are very stringent and much lower than the recommended levels the USDA and FDA maintain, which is one part per million for finished flour.  Here, instead of talking about concentrations in part per million (ppm) they talk about parts per billion (ppb). At the EU level, the proposed maximum limit in the raw grain intended for food is not to exceed 500 ppb (or 0.5 ppm).

In addition, it is proposed not to allow blending of different lots of grain if any of the individual lots exceed the 0.5 ppm limit. Individual member countries within the EU can opt to even further lower the limits, and some researchers in Germany feel that German policymakers might actually decide to do so, largely out of food safety concerns and consumer protection motives. Target limits are also being proposed for the feed industry.  However, as one researcher commented, there is only two letters difference in the spelling of “food” and “feed,” and he worried that the same limits imposed for food could be imposed on the feed industry. 

The most common crop rotation in the central part of Germany has changed in the past ten years to the inclusion of winter wheat followed by corn for silage.  In addition, reduced till and no-till are also implemented. As many growers in the Northern Plains already know, this is a recipe for a disaster. 

German crop breeders realize this too, and have responded by selecting taller wheat types with better FHB tolerance.  Why taller wheat types? One thought is that a taller spike may catch more wind and dry up a bit faster, although I wouldn’t want to bet the farm on this.

They fully acknowledge that breeding taller varieties may result in more problems with lodging, especially given Germany’s intensive production system. 

Selecting for tall types looks to me like an escape mechanism rather than a true genetic resistance to the disease like breeders in the U.S. are developing with Chinese spring wheat lines.  Breeders in Europe have made some crosses with the same Chinese sources of resistance, but most of the material didn’t make it through the first rounds of selection. They all were very reluctant to spend much time and energy in working the Chinese sources of resistance into a European background. Why the reluctance? Because they know it’s a long-term proposition, as evident by how long and how difficult it is taking breeders in the U.S. to incorporate Chinese sources of FHB resistance.

It is apparent that FHB is an international issue, and it bears watching by the wheat and barley industry on the North American side of the pond.  The low European tolerances for DON that are being proposed could especially become a concern for the North American grain trade, as these limits might also be applied to grain that is imported from the U.S. and Canada.