Humans have been growing crops for 10,000 years and in this time we’ve selectively bred for crops which are easier to harvest. In doing this important genes involved in plant defence could have been lost along the way. Palmgren et al. look into the potential for re-introducing old genes into modern crops.
Modern crop breeding started by breeding plants which each contained a desired trait, in the hope that the offspring would show a combination of these two traits.
This approach is based off the work of Gregor Mendel, who investigated the hereditary of traits in pea plants in the mid 19th century. Yet, it was not until the early 20th century that his work was properly appreciated and understood.
By the mid 20th century, radiation and mutagenic chemicals were being used to introduce mutations into plants. Mutations are changes in a gene which can affect the function of that gene. In many cases mutations have no effect, but sometimes the mutation can have a noticeable effect, be that either positive or negative. For example, exposure to radiation could cause mutations in multiple genes which make the plant produce a higher yield would be seen as a positive effect and these plants would be bred from. A plant which produced a small yield or reached maturity slowly would not be bred from.
Importantly these mutations are random, so could potentially affect any gene in the plant genome. Breeding for these higher yields and easier harvesting could have come at the expense of those genes needed to protect the plant from stresses- such as pathogens or droughts.
How Could We Re-Introduce These Lost Genes?
-Introgression (Conventional breeding)
Introgression has been used to introduce genes into a modern variety from a wild relative for years. To do this, the wild relative and modern variety are crossed. The resulting offspring is then back crossed with the modern variety to remove any unwanted ‘wild’ genes. This leaves a plant which is like the modern variety but which has the desired trait from the wild relative. This is shown below.
This technique can be time consuming, as you have to perform several back crosses and some unwanted genes can also be introduced into the modern cultivar.
This technique is similar to transgenesis, but the gene introduced is from a relative, rather than from a different species.
This involves the precise mutation of sequences which already exist in the plant. Precision mutagenesis is similar to the use of radiation or chemical mutagenesis but while these randomly mutate genes, precision mutagenesis mutates specific genes.
These three techniques do not involve transgenes, they use genes from wild relatives or modification of genes in a plant. Transgenesis involves the introduction of genes into a plant from different species, such as a rice gene into wheat. Whereas, cisgenesis would introduce a gene from a wild relative into a modern variety.
While these techniques are generally considered more natural than transgenesis, there are still problems associated with implementing them. Public opinion is important because farmers will only grow a crop if they believe they can make a profit. In general, the public have a negative opinion of genetically modified organisms. As cisgenesis is considered more natural than transgenesis, the technique holds promise for improving crops. However, surveys have suggested that the public do not see transgenesis and cisgenesis as different enough to warrant a different treatment.
There is also the potential to use the older crops themselves, as well as looking to see if they have traits which make them more resistant to disease.
Dr Sarah De Vos, at the John Innes Centre (JIC), was recently awarded a BBSRC/Royal Society of Edinburugh Enterprise Fellowship to revive heritage lines of barley for brewing.
Dr De Vos and Dr Chris Ridout (also based at the JIC) together own a brewing company known as Stumptail Brewery where they produce beers using a variety of barley known as Chevallier. Chevallier was used in brewing from the early 1800s up until the mid 1930s when it was replaced by hybrid crops. At Stumptail Brewery they aim to recreate beers brewed by the Victorians.
To conclude, introducing genes from old relatives has the potential to make plants more resistant to pathogens or environmental stresses (eg drought). However, while a negative opinion of genetically modified organisms persists these techniques are unlikely to be used.
Palmgren et al. (2014) Are we ready for back-to-nature crop breeding? Trends in Plant Science,
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