As we face the future with fewer chemical tools in the toolbox, plus a demand for a further reduction in chemical usage, we need access to the new plant-breeding technologies to provide alternative solutions for plant protection.

The European Green Deal (EGD) recently published by the European Commission aims to achieve significant reductions in fertiliser and chemical inputs in European agriculture. Attaining these ambitious targets requires a multi-disciplinary approach that will need to exploit all available innovations to deliver the required sustainability goals.

It is very clear that a forced reduction in chemical inputs will severely affect tillage enterprises, particularly in this country. Potential losses cause by lower chemical usage will be compounded by any further requirement to reduce nutrient inputs. If we do not have crop varieties with increased resilience to pests/pathogens and/or enhanced nutrient use efficiency, margins will be eroded further and the economic sustainability of crop production in Ireland will be seriously compromised.

Dramatic advances

Over the last five years, plant breeding techniques have advanced dramatically, with the emergence of precision breeding approaches. These have arisen due to our ability to understand, through genomics, more about a plant’s genetic processes and machinery in response to a specific stress. Precision breeding enables us to target very specific changes in that genetic machinery of a plant which, when used as part of an integrated pest management strategy, has real potential to deliver for European farmers and consumers.

One of these precision techniques uses a specific protein, much like a molecular scissors, to trim/edit specific plant genes. This can then be used, for example, to make the plant more resistant to specific fungal diseases.

The breeding technique is called CRISPR and the protein (Cas) is guided to its target using a molecular satnav. This makes the process (CRISPR-Cas editing) several hundred-fold more precise in achieving a desired trait than traditional breeding techniques.

Generating genetic diversity

Success in plant breeding necessitates the existence of specific gene(s) within the plant to produce that trait. Such solutions were not always present and breeders used irradiation to generate additional genetic diversity in plants.

These traditional techniques (known as mutagenesis) rely on the use of heavy chemicals/irradiation to attempt to make desirable changes in a plant’s genetic machinery. However, because of its non-specific nature (no satnav), the process has the regrettable impact of causing thousands of unwanted genetic changes in the plant.

As a result, while the sought-after trait (disease resistance) may be induced, it is typically linked with other undesirable traits (eg delayed maturity, lower yield or increased susceptibility to another disease).

Precision breeding

Precision breeding efficiently addresses this problem and accelerates the breeding process. This means that an existing successful variety with strong agronomic characteristics can be rapidly engineered and enhanced. And this can be done without losing all the good traits that already exist as these work for the farmer (eg yield) and carry the specifications required by the consumer/processor (eg quality and taste).

These capabilities are increasingly important for farmers, especially given the loss of chemical actives to the marketplace and the newly stated objective of further decreasing chemical use. These techniques will be extremely useful to help counter both the loss of actives and the need to decrease chemical use through the delivery of genetic-based solutions in the crops we grow.

Take a specific example. The industry has lost many of its insecticide actives as they have been revoked for various safety reasons. We are also witnessing increased insecticide resistance in aphid populations.

Together, these two factors cause very serious concern, given our need to control specific aphids as they can carry and transmit virus infection to plants. We need some way to control the problem. Again, genetic resistance in our plants and crops could provide an important solution to this problem.

Using CRISPR-Cas technology, researchers from China and Germany have successfully generated Potato Virus Y (PVY) resistant potato plants. Indeed, research groups all over the world are delivering novel varieties with important traits (Table 1) each year using CRISPR-Cas techniques.

Issues within the EU

At present, plant breeders in the US, Canada, Japan, India, Brazil, Argentina, Paraguay, Australia, Israel, Chile and others are benefiting from precision breeding techniques such as CRISPR/Cas. However, for European farmers, access to such genetically enhanced material is not allowed currently. This follows the clarification by the European Court of Justice (ECJ) as to where gene engineering sits within existing GMO legislation.

The ECJ decided in 2018 that plants obtained by the new breeding techniques are GMOs within the legal meaning of the existing EU Directive 2001/18/EC. This was surprising to many as plants developed using the traditional form of mutagenesis are exempt from Directive 2001/18/EC. The decision conflicted with the scientific advice provided by European breeders, scientists and the Commission’s own scientific advice mechanism.

Not surprisingly, the ECJ decision has been controversial. In 2019, scientists from 127 research facilities across Europe published an open statement supporting the application of precision-breeding techniques to assist the EU in meeting its sustainability goals. In response, multiple recommendations have been made stating that the EU must revise/amend what is now out-dated legislation from 2001. It is seen by many as important that precision-breeding techniques also be exempted from the scope of this old legislation.

Looking forward

Varieties developed or enhanced using CRISPR/Cas have their agronomic/processing characteristics improved by merely editing their own DNA. There is no additional DNA added. This is different to GMOs, which have had a foreign gene from another species added to bring in new characteristics. The CRISPR/Cas techniques merely edit the existing genetic profile of a variety to provide an additional trait from the same set of original genes.

Looking ahead, the European Green Deal strives to achieve important targets for EU food production. On top of this, we also have many climate-related challenges to face along the way. We can already see the impact of climate volatility, with unpredictable weather patterns delivering shorter windows to till, sow, manage and harvest. This volatility is predicted to continue and to get more extreme.

While we cannot control the climate we can – and must – capitalise on scientific advancements that have the ability to deliver robust cropping systems.

Breeding techniques such as CRISPR/Cas can generate high-performance novel varieties with increased stress resilience and/or consumer-driven traits that heretofore were not possible. If we wish to achieve the goals that are being set for us, we need, as a society, to re-examine our perceptions of plant breeding and allow science to be the major part of the decision-making process.