Expectations
When breeding new plant varieties using conventional methods, there are some limitations which are due to certain protective mechanisms in the genome to preserve species-specific characteristics. As a result, conventional breeding methods (including random mutagenesis) cannot be used to achieve certain genetic changes, or only with great difficulty. However, new genetic engineering techniques (NGTs) can overcome these limitations and be used to develop completely new traits in plants. Genetic modification with NGTs is also much faster and more precise, thus significantly shortening the time it takes to develop new varieties. It is widely anticipated that the greater efficiency, speed and precision of NGTs in plant breeding will result in fewer side effects.

Reality
NGT modifications frequently result in ‘extreme’ or species-atypical breeding traits, which are often accompanied by undesirable side effects (‘trade-offs’). This is reflected in the very small number of NGT plants currently available on the market. One example: Calyxt developed NGT soybeans with altered oleic acid composition in 2019. The soybeans were subsequently brought to market where they failed due to low crop yields. Calyxt has meanwhile re-aligned its business operations.

In a further example, NGT wheat was modified by knocking out several gene copies responsible for susceptibility to mildew. New genetic engineering techniques are more efficient in this respect than conventional methods and can achieve a more ‘extreme’ expression of the desired trait. However, this can also result in undesirable effects: apart from the observed mildew resistance, unintended effects were also observed, e. g. leaf chlorosis (bleaching), which did not occur with conventional breeding methods.

In another case, NGTs were used in wheat to knock out several copies of a gene crucial for the formation of asparagine, which is an amino acid that is ultimately responsible for the formation of carcinogenic acrylamide during baking. However, asparagine is also important for germination, plant growth, stress tolerance and defence against plant diseases. In this instance, it was found that the seeds of some varieties of this NGT wheat had very poor germinability. Furthermore, initial results from field trials showed changes in weight and number of grains.

Consequences
The above examples show that new genetic engineering techniques can be used to produce ‘extreme’ traits that go beyond what can be achieved with conventional breeding. However, unintended side effects and interactions can occur even if the modification of the DNA sequence is targeted and precise. As such, these often ‘inevitable’ side effects can significantly slow progress in breeding. The ‘re-balancing’ of NGT plants may possibly require much more time to be spent on developing a trait compared to conventional breeding, thus making many breeding goals unattainable. n toxins, and thus to the destabilization of the affected agro-ecosystems. Furthermore, there is a risk that food and feed produced with the genetically engineered plants will typcially be loaded with a cocktail of these herbicide residues.

While NGTs offer great potential for genetic modification, it is not easy to translate this potential into actual benefits. Consequently, it is not possible to predict the time required between genetic modification and actual commercialisation of the final product.

Further information:
TA report
Video on sustainability