A major constraint to expanding Australian lentil cropping is the prevalence of acid soils. Pulses strongly prefer alkaline soils, which is why production is focused on the Yorke Peninsula in South Australia and the Wimmera and Mallee regions of Victoria.

At Agriculture Victoria, this barrier to wider adoption is of particular concern to Dr Garry Rosewarne.

“To select for acid tolerance, a hydroponic assay has been established as a high-throughput platform for trait discovery work,” he says.

“It allows us to concurrently assess germplasm for acidity combined with aluminium or manganese toxicity tolerance. This is important because aluminium can stunt root growth and manganese can retard canopy growth.”

A major constraint to expanding Australian lentil cropping is the prevalence of acid soils. Photo: Barry Haskins

The hydroponic assay was established by Dr Vani Kulkarni during her PhD research. Dr Kulkarni assessed 111 lines that included material from the Australian Grains Genebank. Material was collected from regions with known acid soils, as well as lines from the breeding program and released varieties.

“Six lines with high levels of tolerance were identified and a further 10 lines were classified as tolerant,” Dr Rosewarne says.

“Included in the pool of tolerant material were lines from the national breeding program and the cultivars PBA Ace and Boomer. This indicates that mechanisms for acid soil tolerance are already in our breeding gene pool.”

This prior research led to the current GRDC co-investment in which the hydroponic assay is used to screen a larger set of germplasm. It is screened for acidity, aluminium and manganese toxicity tolerance, before being extended to other acid soil constraints such as phosphorus deficiency.

Field trials at four sites are underway in Victoria, WA and NSW to validate whether the glasshouse findings translate to the paddock. The trial sites are testing lentil yields of a subset of the genetically diverse germplasm on limed and non-limed plots.

Early indications show that while field conditions provide a complex screening environment, findings do appear to correlate with the hydroponic assay. Further validation work is underway.

Useful materials identified from the hydroponic screens are entered into the AI-driven genomic prediction breeding pipeline. This fast-tracks the development of “locally adapted breeder-friendly lines” with improved acid soils tolerance for lentil breeders nationally.

To validate the materials generated, testing of fourth generation progeny in both hydroponic and field sites in Victoria and the expansion zones will be undertaken.

In the final stages of this work, we plan to tap the additional gains that are possible by including acid soil-tolerant rhizobia into the package.

“This includes selecting genetics that optimise the synergistic interactions with rhizobia in order to deliver a step change in tolerance levels,” Dr Rosewarne says.

This work is a collaboration with the departments of Primary Industries and Regional Development in WA and NSW.