Making the most of wild genes

Rusts and Barley Yellow Dwarf Virus (BYDV) are among the most damaging wheat diseases worldwide. Developing new varieties resistant to diseases such as these is a constant battle for wheat breeders, who often rely on wild relatives of wheat as sources of effective resistance genes.

Unfortunately genes from wild relatives usually come in large blocks and often include undesirable genes that are difficult to separate.

A new technique pioneered by a CSIRO team led by Dr Phil Larkin in Canberra, in collaboration with the International Maize and Wheat Improvement Center (CIMMYT) and Sydney University, targets potentially valuable genes but leaves other genes behind.

The team began with two blocks of genes from two different Thinopyrum grass species, each positioned on the same wheat chromosome and with a number of resistance genes. Conditions were then created to 'recombine' the blocks to bring together rust and BYDV resistances but exclude detrimental genes.

The new recombined chromosomes involve pieces from three different species; they are trigenomic chromosomes - a world first.

The result is a stable disease resistance 'package' for wheat breeders without the associated undesirable genes giving breeders highly useful disease resistance traits in a package that can be easily used in breeding.

It is hoped other examples will follow and the genetic diversity available in wild species can be recruited more extensively for wheat improvement.

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