Community Research and Development Information Service - CORDIS

H2020

Crossover control — Result In Brief

Project ID: 703117
Funded under: H2020-EU.1.3.2.
Country: United Kingdom
Domain: Fundamental Research , Food and Natural Resources

Speedy wheat breeding

Growing crops is a constant battle against disease and weather conditions. Scientists have made it easier to transfer genes from wild wheat so future bread wheat crops can cope with adverse conditions such as drought.
Speedy wheat breeding
There are around 800 million people around the world that do not have enough food. To cope with this situation, farmers will need to produce as much wheat as has been produced since agricultural practices first started over 100 000 years ago.

Wheat, like most important food crops is polyploid, that is, it has more than two sets of chromosomes. In fact, the bread wheat grown today has six sets of chromosomes. When it comes to seed production, this creates difficulties as all the sets must pair up to produce viable pollen and egg cells during the cell division (meiosis). Wheat has evolved gene mechanisms to stabilise this polyploid situation.

The Crossover control project aimed to introduce new genes from wild wheat relatives to increase crop yield. To do this, researchers had to facilitate pairing between wild wheat chromosomes and their more recent relatives. Moreover, frequency of crossover, which mixes up the ancient genes with the modern, was increased. For the crop to maintain its fertility to produce wheat seed, balanced chromosome pairing must occur during sex cell or gamete production in meiosis.

A new tool for crop breeding – Ph1

Scientists with Crossover control discovered several mechanisms to achieve this, one of which involved the key gene Ph1. “Using wheat strains with different deletions showed that gene Ph1 increases crossover hybrids between wheat and its wild relatives. What’s more, pairing efficiency and therefore high fertility in the resulting bread wheat was only affected slightly,” Professor Graham Moore, project coordinator explains.

The Crossover control team then delved further into the action of Ph1. The first step was to generate mutants for the ZIP4 gene with ethyl methanesulfonate treatment, so-called TILLING mutants. “ZIP4 is known to reduce or eliminate crossover in certain species so is a good candidate for controlling the Ph1 phenotype,” Prof. Moore points out.

To confirm the TILLING results, they used clustered regularly interspaced short palindromic repeats, CRISPR technology, to delete the ZIP4 gene specifically. Again, the ZIP4 mutants showed an increase in the wheat/wild wheat hybrids and a low level of incorrect pairing, indicating good fertility in the bread wheat plants.

Essential nutrients increase gene transfer

During the experiments on mutants lacking Ph1, the researchers also tested the effects of different nutrients in the growing medium. Using Hoagland solution to supply all the essential nutrients necessary for plant growth, they observed that a high level of crossover at meiosis was induced.

“Further testing showed that the Mg2+ ion specifically was responsible for this increase,” Prof. Moore notes. Irrigating hybrid plants lacking Ph1 with a 1 mM Hoagland’s solution increased crossover frequency.

Confirming the importance of the results on Ph1, the data has been published in four peer-reviewed papers. Journals include Chromosoma, Molecular Breeding, Nature Plants and Frontiers in Plant Science.

Advancing crop research – bringing home the bread

In terms of impact, a number of breeders, both within the EU and outside, have requested the TILLING ZIP4 breeding material. The Crossover control project has provided these lines free of intellectual property restrictions and they are now being used in breeding programmes.

“More than 70 % of flowering plants are polyploid including the majority of the world’s most important crops such as coffee, strawberries and bananas,” Prof. Moore points out. Use of the now available TILLING ZIP4 material will provide information on the genetics of other polyploids and how they cope with seed production. "It will be interesting to ascertain how many other polyploids have exploited this gene to stabilise themselves during meiosis," Prof Moore concludes.

Keywords

Crossover control, wheat, Ph1, ZIP4, chromosome, breeder, CRISPR
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