Pastoral Genomics publication with IBERS

A study by a fellowship of pastoral industry players has discovered a large untapped source of genetic potential for grass breeders.

As well as digging up hidden productivity bonuses, the study may direct the big role that grasses will play in beating global warming.

The Pastoral Genomics (PG) consortium, which includes Meat and Wool New Zealand, uses biotechnology to improve forage, taking advantage of leading-edge international research.

The study was published in the eminent journal Genetics in September and is part of a larger collaboration with forage researchers at the Institute for Biological, Environmental & Rural Sciences (IBERS) in Wales.

By comparing the genomes of rice and grass, the researchers found large genetic resources that breeders' artificial selection has yet to exploit.

Consortium manager Zac Hanley is also the chief scientist of dairy-giant Fonterra's Auckland-based ViaLactia Biosciences, which co-authored the paper.

He says breeders are looking for novel combinations of genes and traits but not all combinations are possible and not every trait is easy to measure.

The impracticalities mean nobody can afford the time or money for all of the possible arrangements.

"Breeders have too many frogs to kiss to find their grassy prince," Dr Hanley says.

But the biggest obstacle to checking all the possible variations is the nature of the genome, which is what the Genetics paper discusses.

Breeders cross and select to find the best combinations of gene variants that they can and have been very successful.

There are 30-40,000 genes in the genome strung along several chromosomes, and there are several versions (alleles) of most genes to be found if the whole species is examined.

Breeders rely on generating and examining offspring plants containing novel mixtures of these allelic variants.

"Crudely, it's as though there are no tall-and-green plants so you cross tall-and-brown ones with short-and-green ones and hope to get the novel combination you are after," Dr Hanley says.

Most alleles travel in packs down the generations, and packs of packs, and packs of packs of packs.

"Super-packs are called chromosomes," he says.

Occasionally, separate genes can come together to make a new pack due to a chance overlap-and-swap between paired chromosomes.

Such combinations are lucky breaks because they increase the breeder's chance of finding improved offspring, and breeders design their programmes so that this will occur.

But the data in the paper suggests some packs of co-travelling alleles are more likely to break up and mix around than others.

"And this means that breeders have mostly been getting their lucky breaks and finding the new combinations they need only within that subset of packs that break up frequently," Dr Hanley says.

These breakable packs seem to be located towards the ends of chromosomes.

Meanwhile, packs of gene variants nearer the heart of a chromosome are less likely to break up and contribute to new packs and newer, better plant offspring.

Although Pastoral Genomics is focussing on New Zealand forages the research has shown that the problem is widespread as a very similar situation exists in wheat and recent work in barley is also indicating similar findings.

"In a nutshell, this work at IBERS suggests breeding strategies may have only been playing with half the possibilities for the heritable improvement of traits in grass and the cereals with the remainder of gene loci being too tightly linked together to be separated and mixed around," Dr Hanley says.

Up until now that has been "good enough", but pressure on grass breeders to develop new varieties with increased productivity as well as environmentally friendly farming practises such as lower fertiliser inputs.

IBERS plant geneticist Julie King, who led the study, says new varieties needed include those able to meet the challenges of climate change such as tolerance to drought.

Grasses also have an important role to play in overcoming global warming, she says.

"Firstly, there is a strong drive to increase the fermentation proprieties of grass, through the manipulation of cell walls, for alcohol, i.e. biofuel, production," Dr King says.

A second major target is the development of grass varieties that reduce methane production from grazing animals, which contribute to global warming.

"Unlocking previously untapped genetic variation in the middle of chromosomes will be of critical importance in order to achieve these ambitious targets," she says.

"To do this we need to discover the genetic mechanism which controls how new gene combinations are produced, an area of joint research being undertaken in both New Zealand, the UK and internationally."

The future sequencing of the genes within the grass genome is a priority research area for IBERS, Pastoral Genomics and their European partners.

However, the mechanism controlling how new gene combinations are produced has to be determined and manipulated so handy genes can be isolated with a map-based cloning strategy, Dr King says.

Meat and Wool New Zealand's Pastoral Genomics director Cros Spooner says the potential ability to translate these results into improved grasses for New Zealand sheep and beef farmers is an exciting opportunity not to be missed.

"We're speeding up traditional techniques and opening up new boundaries of genetic potential using modern methods," he says.

Pastoral Genomics is funded by Meat and Wool New Zealand, Fonterra, AgResearch, Deer Industry NZ, FoRST and Dairy InSight.

The work at IBERS in the Crop Genomics and Biomathematics Programme is funded by the Biotechnology and Biological Research Council and the European Molecular Biology Organization.

Link to publication: http://dx.doi.org/10.1534/genetics.107.075515