Peanut study targets net blotch genes

Student shines light on peanut pathogens


Innovation
Shona Wood's PhD has seen her growing net blotch-infected peanuts in glasshouse trials to develop better screening tools. PHOTO Rebecca Thyer

Shona Wood's PhD has seen her growing net blotch-infected peanuts in glasshouse trials to develop better screening tools. PHOTO Rebecca Thyer

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Molecular markers are being sought in bid to breed resistance to peanut fungal disease.

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What started as a desire to find out more about food production has led PhD student Shona Wood on a journey to better understand an emerging fungal pathogen.

Through the Australian Peanut Breeding Program, Ms Wood (pictured top right) aims to develop rapid phenotyping and genotyping tools to improve selection for resistance to net blotch, caused by Phoma arachidicola. The end result could see the development of molecular markers for resistance and resistant varieties released more quickly.

Left uncontrolled, net blotch can cause yield losses of up to 50 per cent in peanut crops. It is a threat to peanut production in cooler, moist, growing regions, such as Queensland's South Burnett.

It is an important disease globally, especially in China. While fungicides are used to control it, little is known about the pathogen's genetic diversity or sources of genetic resistance. Ms Wood says this is largely due to the difficulties of in-field screening.

"In unfavourable years - mostly hotter, drier ones - other prominent leaf diseases, like late leaf spot and rust, can rapidly take over. This limits the ability to effectively screen for net blotch resistance," she says.

One of her first steps has therefore been to develop a screening method to identify resistant cultivars. This has been done by allowing net blotch to grow in glasshouse trials without competition from other leaf diseases. The method has already enabled distinctions between resistant and susceptible lines.

Net blotch-infected peanuts in a glasshouse at Kingaroy, Queensland. PHOTO Rebecca Thyer

Net blotch-infected peanuts in a glasshouse at Kingaroy, Queensland. PHOTO Rebecca Thyer

"I have been able to confirm a soon-to-be-released peanut variety, Alloway (PBR), which has not previously been screened for net blotch, has a very high level of resistance," Ms Wood says.

Ms Wood's study through the University of Southern Queensland also aims to develop markers for net blotch resistance, while evaluating the genetic diversity within the pathogen's population.

Molecular markers open up the possibility of accurate early selection of resistance within the breeding program. To date, globally no markers have been developed that relate to net blotch resistance. However, work to identify relevant markers is being made easier and cheaper due to a new tool - the 50k single nucleotide polymorphism (SNP) chip.

Ms Wood says the chip, developed by the International Peanut Genome Initiative at the University of Georgia in the US, contains uniformly distributed markers across the peanut genome. "By sending my leaf DNA to them, the chip can identify potential markers associated with net blotch resistance more quickly and cheaply than previously possible. Global peanut breeding programs have successfully used the chip to develop markers for resistance to rust and late leaf spot." If validated, these markers would be used in the program to select for net blotch resistance in early generations, when genetic variability is the greatest. Studying the pathogen's genetic diversity could help the breeding program understand if the pathogen is likely to overcome any inherent genetic resistance, she says.

More information: Shona Wood, shona.wood@usq.edu.au

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