“Anything that will speed up plant breeding is a good option”

An interview with Professor Dr. Thomas Miedaner, head of the rye group at the State Plant Breeding Institute of the University of Hohenheim

Gene technology – are you for or against it? The ability of this question to divide people into two camps is something Professor Dr. Thomas Miedaner, head of the rye group at the State Plant Breeding Institute of the University of Hohenheim, is all too familiar with. Why this is so, whether and how this polarization can be counteracted, and which risks and opportunities emerging technologies offer when it comes to plant breeding, were questions TRANSFER magazine asked him, as another expert in the #techourfuture series of events.

This slideshow requires JavaScript.

Hello Professor Miedaner. Plants have been a part of the staple diet of humans for thousands of years, and they will remain indispensable in the future. But the growing global population, climate change, and the trend toward sustainable and healthy nutrition pose a challenge to plant breeding. What kinds of new technology can people use to address these challenges?

Plant breeding is a very time-consuming process. We assume it will take eight to ten years to develop and breed a new plant variety. As a result, we’re not in a position to react quickly to developments when it comes to plant breeding. This is also why anything that will speed it up is a good option. For example, this includes hybrid breeding, which was actually developed more than 100 years ago, but also new technology, such as marker technologies, which are the main focus of my work, but also genetic engineering and genome editing.

These technologies can help significantly accelerate plant breeding, which of course would be beneficial if you think about the issues you just mentioned. In terms of actual time savings, this depends on what kinds of traits you’re dealing with. If it’s a simply inherited resistance to diseases, that doesn’t take so long to develop, but if it’s a complex trait like drought tolerance, you can bank on it taking decades. One of the biggest problems is that many of the plant traits we work on are complex, so they’re inherited through a whole host of genes. Also, with genetic engineering and genome editing, initially you can only modify or add individual genes. The issue this raises is whether regulator genes can be found that will really change complex gene networks leading to the final traits, such as those required for  grain yield or complex disease resistances. At the moment, that’s certainly not the case. As things stand now, we’re not able to use this approach to breed perfect varieties, neither using genetic engineering nor with genome editing.

One of the big problems with plant breeding is the global spread of the aforementioned pathogens. What can be done about this?

As I just mentioned, there are some disease resistances that are only inherited through a single gene. These are relatively easy to work with, although often the effects are not durable. As a result, pathogens are often able to adapt relatively quickly to the new resistance because pathogens also keep changing. So if I’m dealing with a really simply, inherited disease resistance, it can either work for ten years or it could become ineffective again after three years. If you’re working with so-called quantitative resistance, there can be five, ten, or twenty genes inherited simultaneously and each one makes its own small contribution.

These resistances are more durable, but of course this entails a lot more time and effort. This is where we want to improve processes by using DNA marker technology, as this allows us to select for several genes simultaneously.

DNA marker technology, gene technology, genome editing – these are all technologies that can be used to accelerate plant breeding and make it more efficient. What opportunities do they offer, but also what are the risks?

All three techniques have to be dealt with separately because they’re based on different principles. For example, DNA markers are purely diagnostic procedures. We look for favorable variants in the genome of a plant, such as disease resistance or early ripening plants. To do this, we scan the genome and use relatively complex calculation methods to determine which regions of the genome are responsible for a certain trait. We can then pick the most favorable variants and use DNA markers to select these variants in the lab already at the seedling stage. The main advantage of this is that no changes are made to the plants itself. Instead, we breed them by classical methods and the only addition we make to the process is that we also run a DNA diagnosis. That’s why I see no risk in this area.

With gene technology, we have a completely different situation because entire genes are introduced to plants from foreign organisms. This is usually done with bacterial genes, because they’re easier organized and a lot easier to find in their small genomes.

This allows new traits to be created that were not previously available in certain plants, such as resistance to herbicides or special insects. One thing I’d like to point out in this respect is that genetically modified plants have been grown worldwide on vast acreages of land for 25 years now. To date, none of the anticipated or dreaded risks, such as a collapse of ecosystems, have been identified. That said, it’s only the well positioned, multinational corporations that can afford genetic engineering because of the high costs involved and the very complex approval procedures.

Unlike genetic engineering, genome editing is an approach that can also be used in technical terms by medium-sized companies with the support of scientists. It’s already fairly common practice in Germany for science to work together closely with plant breeding. With genome editing, no foreign genes are introduced. Instead, genes already present in the plants are modified by exchanging individual base pairs, the building blocks of DNA, and that’s what makes this process so special. There’s a nice example for the results from Israel, where scientists have succeeded in creating resistance to three different plant viruses by modifying a single gene. Now if you ask about risks, of course there are risks that something might go wrong – there always are.

For example, one thing that could happen is that you don’t just alter the gene you wanted to change but other genes in the genome with similar motifs as well, even though you didn’t actually want to influence them. But all plants – whether modified or bred conventionally – have to be tested in the greenhouse first, and then in the field, and naturally that’s where such defects become noticeable. At the end, there must always be a field test. I don’t see any other risks in this approach.

There’s a lot of talk at the moment about the CRISPR/Cas method. Could you explain in as simple terms as possible how this works?

In principle, you’re dealing with a tiny section of an RNA sequence that ensures the gene you want to modify is targeted specifically. That’s the big difference to conventional genetic engineering, because that introduces genes into the plant but you can’t influence exactly where they are integrated in the genome. And then there are Cas enzymes, which cause a double-strand break such that DNA is separated at the exact spot you targeted via the RNA sequence. This results in a split and the cell has two ways to repair this. Either it slaps other base pairs into the break, which usually causes the gene to stop functioning, or you offer the plant a repair sequence. And that’s exactly what the CRISPR/Cas method involves. Either you switch genes off, so you render them inoperable, or you alter them by changing individual base pairs. The latter method does require further research, however, before it can be offered by every laboratory.

There’s a lot of skepticism about genetic engineering. What reservations do you encounter in your work, and how do you deal with them?

Of course, as a scientist you’d immediately like to say that education and explanation are tremendously important; we have to show people what a new technology or a new process is all about. But on the other hand, that’s precisely what’s been happening for more than 20 years. There are clearly two fronts in ideological terms and they’ve become entrenched. I suspect there are a lot of people who don’t really think much about this topic. But then there are also activists who fundamentally oppose it, and you can’t win them over with factual reasoning.

If we take the issue of genome editing as an example, the biggest bone of contention is how to classify genome editing. The European Court of Justice has ruled that it’s the same as genetic engineering so it should be regulated exactly the same way.

This means that genome editing will not be carried out commercially in Europe because there are strict requirements that products must be labeled as genetically modified. They’ve adopted a different approach in other countries. In the USA, for example, results are checked by the government and if an alteration doesn’t include foreign DNA, but only the DNA found in the plant, and the characteristics that are produced also exist naturally in a plant, that doesn’t constitute genetic engineering – so it can be applied without restriction, cultivated, and even marketed. Those are the two different views on the matter at the moment.

In your opinion, what can scientists do to reach out to the general public and ease inhibitions when it comes to new technology?

Naturally, for the younger generation it’s important to share all information with them. But if you’re talking about the people who have already formed an opinion on certain technologies, and it’s negative, I believe the tricky issue is then whether we can still reach out to them at all, or whether they actually want to be reached out to.

But I would say I find it misleading if all kinds of products are labeled GM-free, because with the exception of small regions of Spain, there are no genetically modified plants being grown at all in Europe. You’ll neither find them in the fields nor in the market, so you can’t actually have any products at all from genetically modified crops. But if some products are labeled GM-free, it implies there are certain products out there that have been genetically modified.

That makes the whole topic more complicated. And then there’s one issue we really struggle to comprehend as people who work with plants: Lots of modern medicines are produced with the help of bacteria that have been genetically modified. Even vitamins and many of the additives you find in food are produced with genetically modified bacteria. Nobody seems to be interested in that bit, but with plants it always turns into a huge debate.


Prof. Dr. Thomas Miedaner (author)
Director of the rye division at the State Plant Breeding Institute University of Hohenheim (Stuttgart)