ETH Zürich: new way to accelerate plant breeding

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Researchers at ETH Zürich have developed a method for generating unreduced gametes for use in plant breeding.

In plants, sexual polyploidization by the formation of unreduced (2n) gametes is an important feature in both nature and breeding programmes. Many of the world’s leading crops are polyploid, indicating that human breeding activities have unwittingly selected for plants with increased ploidy. Although there is now much interest in the formation of unreduced gametes or polyploid plants for plant breeding, as yet there is no technology available that allows the generation of unreduced gametes by targeted deletion of a defined locus.

The formation of unreduced gametes has a wide range of applications. It can be used to overcome incompatibility barriers in inter-species or interploidy crosses, the production of seedless fruits and the generation of homozygous diploids. However, mutants producing unreduced pollen are only available in few crop species or varieties, and the affected loci have not yet been identified.

Thus far, production of polyploid plants is mainly achieved by colchizine treatment, a laborious, time-consuming and inefficient technique. Therefore, the targeted generation of unreduced plant gametes could have widespread application in plant breeding.

The researchers have developed a technique for the generation of unreduced pollen (2n) by mutations in the conserved plant gene called Jason. Lack of Jason causes a failure in chromatid separation during meiosis II, leading to the formation of unreduced microspores and pollen at high frequency.

Based on the observed production of unreduced male gametes, the techniques should prove useful in generating interploidy crosses, production of seedless fruits and the generation of homozygous diploids.

This is a transgene-free technology, involving as it does a targeted deletion of a single locus. It could be used to overcome crossing barriers that exist when crossing original varieties with crops, for the generation of seedless fruits and of homozygous diploids (2n).