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Conventional breeding and genetic engineering go hand in hand

People, the environment and farm animals can benefit from cereals that have been bred to contain larger amounts of phytase – an enzyme that increases the availability of phosphate and other minerals. Conventional plant breeding methods cannot stand alone, but may be combined with the process of cisgenesis.

2014.02.27 | Janne Hansen

The grain from the genetically modified barley is manually harvested using scissors. All other plant material apart from the ears is then collected in containers and sent for incineration. After the harvest, the field is sprayed with Roundup to kill all seedlings produced from spilt grain. Photo: Inger Holme

Scientists from Aarhus University have examined the feasibility of increasing the availability of phosphate and other minerals from cereals using a type of genetic engineering called cisgenesis – and found that it can be done.

- With cisgenesis, only genes from the same species or from species that can be cross-bred in the conventional way are transferred. Furthermore, the plants must not contain DNA sequences from distantly related species, such as bacterial antibiotic genes, which often happens in the production of genetically modified plants. Cisgenic plants are produced from the same gene pool as that used for conventional breeding.

Several survey studies in Europe and the US have shown that one of people’s main concerns with genetic engineering is the transfer of genetic material between distantly related species that would otherwise not cross-pollinate. This is not a problem with cisgenic plants.

Cisgenesis was introduced by Dutch researchers in response to this scepticism. Since the introduction of the concept back in 2006, several European studies have shown that cisgenic crops have gained a significantly higher acceptance by people than have crops genetically engineered using material from distantly related species.

Because cisgenic plants are very similar to traditionally bred species, there are movements afoot in both the EU and the US to have conventional plant breeding regulations – rather than the GMO regulations – apply to cisgenic plants.

Why phytase?

Phosphorus and other minerals are essential elements for plants and animals. Phytase is an enzyme naturally present in plant cells. It is able to break down plant phytic acid and in this way it releases phosphate that can be assimilated by animals. Since animals are not able to produce phytase themselves, it is important that they get the enzyme through their diet.

Increased phytase activity in barley grain used for animal feed may both reduce the amount of phosphate that is normally added to animal fodder and the amount of phosphorous that is excreted from the animals and ends up in the fields and aquatic environment.

Genetic doubling-up

Barley naturally contains relatively small amounts of phytase in its grain. Since there is little variation in the phytase level between barley cultivars, it is not possible to improve phytase activity in barley grain using traditional breeding methods.

The method that the scientists are developing involves breeding cereals with a double dose of the gene coding for the phytase enzyme, thus increasing the phytase activity in barley grains.

- The gene coding for phytase activity in the grain has been extracted from the barley and then reinserted into barley as an extra copy using genetic engineering, explains senior scientist Inger Holme from Aarhus University.

Between 2007 and 2010, scientists have engineered and propagated barley plants containing a double dose of the gene coding for phytase in the laboratory and in the greenhouse. Here they found a two- or threefold increase in phytase activity in barley grain with the extra copy of the gene. In 2011, the cisgenic plants were thoroughly studied to ensure that the new gene did not affect other genetic functions of the barley plant.

Looking good

The results achieved in a laboratory may be all well and good, but the situation may be quite a different one when the barley is grown in a field under normal growing conditions. Since the cisgenic barley does not contain antibiotic genes, permission can be obtained to grow it in the field. The cisgenic barley is therefore being planted in the field from 2012 to 2016. The results so far are looking good.

- The analysis of the first year's harvest shows that barley grains from plants grown in the field have an increased phytase activity with apparently no side effects or any other effects, says senior scientist Inger Holme.

When the field trials are over, the next natural step will be to start experiments with pigs, chickens or rats and to transfer the technology to other cereals.

You can also read the popular science article ‘Phosphorus in wheat can be made more readily available’.


Further information

Senior scientist Inger Holme
Department of Molecular Biology and Genetics
Aarhus University, Denmark
e- mail: inger.holme@agrsci.dk, telephone: +45 8715 8238

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