A team of Chinese researchers have engineered genetically modified (GM) wheat that resists infection by the destructive take-all fungus.1 The fungus infects wheat roots, causing up to a 40-60% reduction in wheat yields.2
Take-all infects wheat grown in temperate regions worldwide. It devastated Australian wheat crops during the 1800s. Hence, farmers named it ‘take-all’. Now Chinese wheat is increasingly at risk. This might be a reason why a government research council funded this research. Another reason is that attempts at selective cultivation have not yielded take-all resistant wheat, and the infection is difficult to eradicate once it spreads. As a result, new technology is urgently needed for abating the take-all fungus.
First the researchers performed experiments to confirm that a gene found in a wild relative of wheat might help defend against a take-all infection. The gene was chosen because it is known to help the flowering plant rockcress resist disease. The wild relative of wheat contains a gene similar to the one found in rockcress. In addition, the wild relative of wheat is particularly resistant to viral infections.
The researchers infected the wild relative of wheat with take-all. They measured the number of gene copies, an indicator of gene activity, made over the course of 21 days:
The number of gene copies peaked after seven days. This indicates that the gene from the wild relative of wheat was activated after a take-all infection, potentially for defence purposes.
Next the researchers created GM wheat using a gene gun. Heavy metal particles were coated with the gene from the wild relative of wheat and then shot into a developing seed. The heavy metal particles pierced through the seed’s cell barriers, carrying the piggybacking gene with them. In this manner, the gene from the wild relative of wheat was inserted into the wheat seedlings.
The researchers double-checked that the gene was inserted. Finally they grew four wheat plants, one control plant (no gene inserted) and three GM plants (gene inserted), and infected their roots with take-all:
Both the control and GM wheat plant roots were infected with black take-all fungi, but the GM wheat plants were less infected than the control wheat plant. This was confirmed with further quantitative experiments. The researchers succeeded in engineering a take-all resistant strain of wheat.
Although this GM wheat is resistant to take-all in the lab, it is unknown how it would fare in a typical farmer’s field. One potential pitfall could be that the GM wheat might harbour low levels of the fungus, allowing it to spread further and cause minor destruction of many crops. If more disease-resistant genes could be inserted into this GM wheat, it might be possible to generate plants that are more resistant to take-all. These improved GM wheat plants could then be tested on a small scale before being grown more widely. The fungus could soon need a new name as it might no longer ‘take-all’.
For further reading:
Genetically Modified (GM) Crops- Friend or Foe?: An overview of how GM crops are made
1 Liu X, Yang L, Zhou X, Zhou M, Lu Y, Ma L, Ma H, & Zhang Z (2013). Transgenic wheat expressing Thinopyrum intermedium MYB transcription factor TiMYB2R-1 shows enhanced resistance to the take-all disease. Journal of experimental botany, 64 (8), 2243-53 PMID: 23547108