Key points

Researchers are looking for a genetic marker that will help improve peanut blanchability.

• Blanchability is an important market requirement for processing peanuts
• Finding a genetic marker will enable breeders to cull poor blanchers
• The trait has a strong genetic influence but has been mostly ignored thus far.

Research by the GRDC-supported Australian Peanut Breeding Program (APBP) is close to finding a genetic marker for blanchability. Its success would mean more efficient breeding for this important peanut trait.

Blanchability refers to how easy it is to remove the peanut's skin (testa) from the kernel following rapid heat treatment.

It is a key market requirement for those processing peanuts into peanut butter and confectionary, making it a vital economic trait in any newly released cultivar in Australia.

Peanut Company of Australia (PCA) peanut breeder Dr Graeme Wright says that a genetic marker - a DNA sequence with a known location on a chromosome - could help breeders release new varieties that meet this requirement earlier.

"What we have found - and still need to validate - is huge," he says.

"Poor blanchers could be culled earlier from the breeding pipeline, making breeding programs here and overseas much more efficient."

Genetic influence

Blanchability has been a vital trait for Australian breeders since the mid-1990s. New varieties have to achieve a blanching score of 85 per cent or more to be viable for release.

Although there is a strong genetic influence involved with this trait, it has been largely ignored in most global breeding programs. This is why Australian research with US collaborators is showing real promise, Dr Wright says.

The Australian team collaborated with Dr Steve Cannon's US Department of Agriculture (USDA) group at Iowa State University and Dr Josh Clevenger's team at Mars-Wrigley Confectionery, the University of Georgia.

Dr Wright says the need for the work was multi-faceted.

"Studies had indicated that blanchability was under strong genetic control, is highly heritable and should be responsive to effective selection. However, published data was scarce," he says.

Additionally, there was limited information available about the trait's stability across different environments.

"That is, there was not enough information about the extent of genotype by environment interaction, which is important to breeding efficiency," Dr Wright says.

Added to the lack of information are the timeframes involved in breeding for this trait.

Studies had indicated that blanchability was under strong genetic control, is highly heritable and should be responsive to effective selection. However, published data was scarce. - Peanut Company of Australia peanut breeder Dr Graeme Wright

Dr Wright says that although early generation selection is theoretically possible and desirable in a breeding program, a significant amount of seed is needed to accurately characterise (phenotype) single plants.

In practice, it means phenotyping and selecting has been conducted only in later generations when seed quantities are more plentiful.

"A breeder may have to wait multiple generations of inbreeding to determine whether a new line meets the blanchability standard," he says.

However, if the marker work is successful and blanchability accurately assessed on a smaller quantity of seed, it would be possible to phenotype individual plants or lines effectively and make earlier selection decisions.

The research

The collaborative research approach saw Australia provide extensive phenotying data for blanchability measured on the 100 lines from the US 'mini core' collection. This collection is a small representative subset of the overall peanut germplasm collection of 12,000 lines.

Early success came when a genomic study to search for blanching and other traits saw a certain DNA region consistently and frequently showing up.

The next step was to validate this result with the University of Georgia, to determine whether these genomic regions were actually associated with blanchability in peanut genotypes and, therefore, able to be potentially used as genetic markers.

Using 'poor blanchers' and 'superior blanchers' from populations that had the same parents, the team compared DNA, looking for differences.

Analysing the parental data, variations were found. In fact, 100,000 polymorphic SNPs (single nucleotide polymorphisms) were discovered.

Dr Clevenger used these to analyse the good and poor blanchers, identifying sections of DNA that correlate to blanchability (called quantitative trait loci or QTLs).

Dr Wright says the collaborative results are exciting.

"They provide clear evidence for the presence of a strong QTL, which may cover the exact region where the gene or genes for blanchability reside," he says.

"Interestingly and significantly is the fact that one of these QTLs lines up with the US mini-core's own blanching study."

Dr Wright says the team is now validating workable markers for the blanching trait in a separate recombinant inbred population (useful for mapping QTLs), with these peanut lines grown, harvested and about to undergo blanching tests.

"Then all the data will be analysed, and if found to agree with the USDA study, which we expect, we could have a genetic marker within a year," he says.

Culling poor blanchers

Dr Wright says a workable marker would allow breeding teams to cull poor blanchers earlier in the breeding pipeline with the confidence that potential new lines have acceptable blanching characteristics.

"At the moment, we have to wait until breeding stages F5, F6 or later until we have sufficient seed quantities to conduct a blanching assessment on," he says.

"Having the confidence that blanching was adequate would allow us to concentrate on other traits.

"We have had cases where we have had very promising breeding lines nearly get to release, and they have failed due to poor blanching characteristics."

Dr Wright says the project also shows the benefits of collaboration.

"This research highlights the value of this international collaboration with the International Peanut Genome Consortium," he says.

More information: Graeme Wright, 07 41 821834, graeme.wright@bega.com.au