Interview with Bernd Holtschulte: “There are plant diseases that cannot be controlled with chemicals.”

December 14, 2017, Reading time: 5 minutes

Bacteria, fungi, viruses: Plants are targeted by countless attacks. The pathogens “want” to multiply in energy-rich leaves or fruits and often cause serious damage. Bernd Holtschulte is Head of Plant Diseases at KWS. In the interview he reports on what plant breeding has to offer.

Why do plants need to be protected at all? Are they not able to do that for themselves?

Many plants are naturally resistant to pathogens. This defense has evolved over the course of evolution over hundreds and thousands of years. In nature, however, there is a constant race between plants and microorganisms. Fungi, viruses or bacteria infect plants to multiply in them. The plants in turn create new defenses. Thanks to their high level of adaptability and reproduction potential, some pathogens manage to overcome the adapted barrier. This race is never finished. Breeding for high resistance (plant breeders call it resistance breeding) occurs in order to protect plants in the field from harmful organisms. Resistance breeding is particularly important if there are no other protective measures against a pathogen. This is the case with some viral diseases or fungi. This shows that: Plant protection works with chemical compounds, and also for breeding. And sometimes only with it.

What’s your biggest enemy today?

Fusarium fungi are one of our most important enemies. In cereals and corn, these pathogens release a high level of toxins and can destroy entire harvests. In addition, they reduce the germination capacity of seed and endanger the health of humans and animals. The ergot fungus, which causes poisoning in humans and animals, is well known. Additionally, there are plant diseases that cannot be controlled using chemical, biological or agronomic methods such as adequate crop rotation.

An example of this is beet necrotic yellow vein virus (rhizomania) in sugarbeets: This soil-borne fungus transmits a disease-causing virus to plant roots. There, it can multiply and cause damage that significantly reduces yield. In many countries breeding of rhizomania-resistant varieties is the only way to support sugarbeet cultivation. But resistance breeding plays an important role in almost all plants. This, however, requires perseverance: Until a new variety arrives on the market, intense breeding effort can take up to ten years. It helps that KWS is an independent company that can make its own breeding decisions independently.

How does resistance breeding work?

We bring properties that are present in nature, such as a plant present in the wild, into our cultivated crops. This is often done by crossing. With the new properties incorporated, plants can then fend off fungi, bacteria or viruses. In nature, there are many mechanisms for plant resilience. We can somewhat differentiate between existing and post-infection resistance. Examples of existing resistance are, for example, thicker coats of wax on leaves. An example of post-infection resistance is the emergence of thick-walled deposits in cell tissue which makes it more difficult for fungi to develop in the plant.

How important is climate change in your work?

Very important! Climatologists expect more mild, wet winters and warm, dry summers. For people that may sound pleasant at first. For plants, it means the occurrence and spread of increased harmful organisms from southern regions. We need to react to this now: Depending on the type of crop, breeding new varieties can take between ten and twelve years. Apart from anticipated higher disease pressure, resistance to drought is also important. Plant breeding therefore requires long-term planning; this also applies to research at KWS. We spend about 17 percent of our revenue on research.

Sustainable development is becoming increasingly important. What contribution does your work make?

Legislators have set integrated plant protection as an important objective. In short this means: Farmers need to further reduce plant protection chemicals. A common phrase is “As little as possible, as much as necessary”. This is where progress in resistance breeding can make an important contribution: Plants with more resistance require less plant protection chemicals. Additionally, biological plant protection and arable and crop-friendly methods should be able to contribute to sustainable management practices of agricultural land.

If that works so well: Why are chemical treatments used at all?

If we agree on the goal of achieving the highest possible yield per acre to supply a growing world population, then this is currently only possible with the best possible combination of plant breeding and plant protection. Plants need to be protected by seed treatments in the early stages of their development, because natural resistance is insufficient at this early stage of growth, or because resistance characteristics only emerge at a later stage of plant development.

What contribution does plant breeding make to nutrition?

The world population is expected to grow to an estimated 9.7 billion people by 2050. At the same time, agricultural and arable land is limited. So yield on the same available land needs to increase. Plant breeding is already helping reduce disease and pest losses, and increase crop yields by about 1.5 percent per year. Resistance breeding will play an even greater role in the future: It is currently becoming apparent that many chemical treatments will no longer be approved in the next few years. As a result, fewer plant protection products will be available. Plant breeding can make an important contribution here.

Pathogens are resistant to some pesticides. Can resistance against plant breeding also occur? Do you have to keep breeding new varieties over and over again?

Harmful organisms repeatedly break through any resistance. In many cases, it is only a matter of time. If resistance is controlled by only one gene in the plants, it can be overcome very quickly, i.e. in a few years. If two, three, or even more resistance genes are involved in one variety, it is assumed that resistance will last much longer.

When did human beings start resistance breeding?

The start of seed breeding dates back about 12,000 years. At that time, seeds of the most productive and healthiest plants were selected and sown again the following year. Yield and resistance improved slowly. We use the term “selective breeding” today. By further crosses with wild cereals, our cereals finally emerged. Seen in this way, resistance breeding in cereals is very old. But breeding alone is insufficient. Our daily bread is a product of resistance breeding, agronomic progress and plant protection chemicals. This is true not only for wheat and rye, but also for many other crops.

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Thilo Resenhoeft
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