A new technique which uses the tools of genetic engineering but does not introduce foreign DNA into a crop plant has been developed by Crop & Food Research.

Dr Tony Conner, who has been applying genetic modification tools to crop plants since the mid 1980s, has led the research team. He says the new technique has been welcomed by the international research community.

Over the years Dr Conner has often provided a scientific point of view in the public debate surrounding GM. He says one of the public’s main concerns has been the use of GM to transfer genes between unrelated organisms.

“To me, the real appeal of this new technique is that while it uses the tools of genetic modification, it does not introduce genetic material from unrelated species.

Precision breeding only transfers genetic material which would naturally cross with a particular plant. “We’re only using genes which are already available to traditional plant breeders. But we can transfer those genes responsible for a particular characteristic into a new plant very precisely, in one step.”

“In hindsight this seems like an obvious development for genetic modification – but science is like that. No one thought you could find the necessary gene sequences in plants to do this – they usually come from bacteria. But we found them and this has opened up vast new possibilities.”

He is pleased the technique has been developed in New Zealand. “This technique will have huge benefits for crop breeding both in New Zealand and internationally.” The intellectual property is held by Crop & Food Research, which is a government funded research institute responsible for adding value to the New Zealand economy.

Dr Conner presented his technique at three recent international science conferences in Germany, the Netherlands and Australia. It will be presented at a New Zealand conference in November.

“It was received enthusiastically by the science community and regulators, particularly those working to improve food production in the third world.”

“Plants produced using this technique are, by definition, not transgenic and this means the compliance costs involved in gaining approval for commercial use are minimised. This makes it viable for the technology to be used to develop cultivars suitable for local conditions in third world countries.

“Precision breeding also presents a viable option to develop improved cultivars of crops grown on a smaller scale around the world.”

Dr Conner says while the technique is particularly valuable in crops which are propagated vegetatively, such as potatoes, fruit trees, cassava and sugarcane, it will also have a role in the breeding of major crops such as maize, soybean, rice and wheat.

He says once the genomes of the world’s important crops are sequenced, precision breeding will become increasingly valuable. “It provides us with a tool to go into germplasm banks and find all the alternative variants of a gene, select the best one for what we want, and then insert it into the target crops in a single step without any foreign DNA.”

BACKGROUND

The idea which led to the development of precision breeding occurred to Dr Tony Conner in 1999 when he took nine months out from research to look after his young son. His first difficulty was in persuading people that precision breeding would work – a difficulty he has since overcome.

As a frequent science commentator in the public debate surrounding GM through the 1980s and 1990s, he was well aware of public concern regarding the transfer of genes from one species to an unrelated species. The new technique seemed to him to be a socially responsible way forward using the tools of genetic engineering.

To achieve success, Dr Tony Conner had to develop a vector system which only transferred DNA which was naturally available to breeders. He did this by identifying DNA sequences which occur within a particular plant genome and then used these to assemble vectors for gene transfer.

As a result, although the plants are derived using the tools of molecular biology and plant transformation, they are not transgenic – they do not contain genetic material from unrelated species. This raises important questions around the definition of GM, which has implications for regulators worldwide. It also means that the traditional tests used to detect whether or not a plant has been genetically modified, are not applicable.

Dr Conner started by designing a vector system for precision breeding in the species Arabidopsis thaliana, which has the smallest known genome of any crop and is often used by plant biotechnologists trying new techniques. He designed and developed a binary vector for Agrobacterium-mediated gene transfer in which all the DNA sequences destined for transfer to the plant were based on sequences which occur naturally in the Arabidopsis thaliana genome.

Dr Conner and his colleagues have now successfully demonstrated that the vector based on A. thaliana DNA can be used to transform A. thaliana. The genetic makeup of the resulting plants mimics chromosomal rearrangements of the endogenous DNA sequences equivalent to micro-translocations that could also arise during mutation breeding.

Precision breeding vectors have been developed for a wide range of plant species. They are now being tested in Solanaceous species, including potato and petunia.

Scientists’ understanding of plant genomes is advancing rapidly as the DNA of major crops are sequenced. This knowledge will increasingly enable researchers to identify specific genes of interest which code for a desired crop trait.