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Resistant regions mapped in RLN research

University of Southern Queensland senior research fellow Dr Rebecca Zwart is evaluating chickpea populations for improved root lesion nematode resistance. Here she holds one of the wild relatives that has been used to develop these populations.
Photo: courtesy University of Southern Queensland

Key points

  • Wild chickpea relatives collected from south-east Türkiye (Turkey) have been identified as superior sources of resistance to two species of root lesion nematodes
  • Populations derived from wild chickpea relatives and leading commercial chickpea varieties are being evaluated for improved root lesion nematode resistance
  • The University of Southern Queensland will map regions in the chickpea genome associated with resistance for future breeding opportunities

After letting nematodes reproduce in the roots of new chickpea populations, researchers from the University of Southern Queensland have begun evaluating increases in nematode numbers.

The number crunching will give an indication of which chickpea lines are susceptible and, importantly, which are resistant.

The work is part of a broader project to incorporate root lesion nematode (RLN) resistance from wild chickpea relatives, collected in the Republic of Türkiye (Turkey), into Australian commercial varieties.

University of Southern Queensland senior research fellow Dr Rebecca Zwart says the work will inject a mix of novel genetics that provide improved resistance into Australian commercial chickpea lines. “The next step is looking at the genomic regions involved in any resistance that has been found in the wild relatives.

“There are two major species of RLN that infect chickpeas. We are working with populations derived from crosses between elite Australian chickpea varieties and wild chickpea lines that show superior resistance to both RLN species.”

With that in mind, her team is building a genetic ‘mud map’ to key resistant regions. “Knowing the genomic regions associated with resistance and identifying closely linked molecular markers will enable RLN resistance to be tracked during each generation in a breeding program.”

The team is using quantitative trait locus (QTL) analysis to do this. QTL is a statistical method that links trait measurements (phenotypic data) and molecular markers (genotypic data).

“As well as enhancing germplasm, it is really about trying to provide molecular tools to breeders so that they can efficiently incorporate improved RLN resistance in breeding programs and speed up the breeding process.”

Up until the Turkey collection missions, conducted by CSIRO, Dr Zwart says chickpea breeders faced a lack of effective RLN-resistant sources.

RLNs are migratory endoparasites and can cause yield losses of up to 25 per cent in chickpeas.

In the northern region, where more than 80 per cent of chickpeas are grown, the predominant RLN species is Pratylenchus thornei. However, P. thornei and P. neglectus can often be found in the same paddock. In the southern and western chickpea expansion areas, P. neglectus is the more dominant of these species.

When nematode populations build up in the roots of susceptible chickpea crops, they can remain in the soil, infecting and causing yield losses in subsequent susceptible crops such as wheat. “When RLN is present, the value of growing chickpeas in rotation with wheat is diminished.”

Improving genetic resistance to both species of RLN is a priority for breeding programs.

Dr Zwart says wild relatives offer good opportunities to incorporate a diversity of new resistance into existing commercial varieties.

“At the start of the project, we used the information we already knew from PBA HatTrick’s resistance regions to search for similar genetic markers in the wild relatives. This confirmed that the wild relatives offer new diversity for RLN resistance that is not present in current chickpea varieties.

“That means we have the opportunity to combine resistances – that is the resistance found in PBA HatTrick and the new genetic regions coming from these wild relatives. It offers an unprecedented opportunity for chickpea crop improvement.”

The plan is for chickpea breeders to have access to improved chickpea germplasm by mid-2025, while a core set of adapted chickpea lines will have been identified that capture wild lines’ genetic diversity.

A series of GRDC-supported projects have helped the university’s current research. This includes the CSIRO collection missions from 2013 to 2016; the importation of wild Cicer germplasm into Australia by the Australian Grains Genebank and its distribution to researchers nationally; and Curtin University’s crosses between genetically diverse wild relatives and elite commercial chickpea varieties.

More information: Rebecca Zwart,  [email protected]

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