Outputs from prior projects – together with the application of new technologies and knowledge – will expand the productive area for chickpeas.

Among all the commercially grown pulses, chickpeas are the most sensitive to acid soils – and to further challenge this situation, there has been little variation in tolerance available in the breeding pool for the species.

It is a problem which has hampered the adoption of chickpeas outside their traditional eastern Australian environment, says Professor Chengdao Li, director of the Western Crop Genetics Alliance at Murdoch University. Professor Li has been applying his knowledge accumulated from investigating the issue in barley to chickpeas.

“In Western Australia’s grainbelt alone, more than 75 per cent of soils and subsoils are affected by acidity, which has been exacerbated with increased nitrogen input and climate change,” Professor Li says.

Both aluminium and manganese cause damage to crops when grown on acid soils; in WA, aluminium is the dominant cause. Insoluble aluminium is abundant in most soils, but under acidic conditions (pH less than 4.5), some forms of aluminium are solubilised to release ions that are highly toxic to both roots and beneficial bacteria such as rhizobia.

Aluminium toxicity inhibits cell division and reduces root elongation of plants. Such effects on root growth not only impair nutrient acquisition by crops but can also exacerbate drought by restricting access of roots to subsoil water storage.

“Management practices such as liming reduce the effects of toxicity, but this is a costly and inefficient means to ameliorate subsoil aluminium toxicity. An alternative would be to find a genetic solution through developing acid tolerant crop varieties,” Professor Li says.

“For chickpeas, we needed to start with developing an accurate and high-throughput hydroponic screening method and then methodically screen to look for variation – an analogous approach to what we had done for barley.”

Solid groundwork

A GRDC-invested pilot project lead by Dr Darshan Sharma from the WA Department of Primary Industries and Regional Development (DPIRD) did much of the groundwork for chickpeas.

The project identified and confirmed sources of inherent tolerance, bulked-up seed for future research, fine-tuned phenotyping methodology under glasshouse conditions and developed genetic information that chickpea pre-breeders and breeders will use in developing varieties that would sustain yield potential of new chickpea varieties on acidic soils.

“The team developed a high-throughput hydroponic system and used it for the rapid screening of aluminium tolerance in 1243 chickpea lines,” Professor Li says.

“Using 18 Australian chickpea cultivars as a reference, Australian chickpea cultivars were found to generally display susceptibility to aluminium toxicity.”

The pilot project also drew upon the outputs of recently completed GRDC investments with Murdoch University, CSIRO, the University of Western Australia, Curtin University and the Australian Grains Genebank, which collected worldwide chickpea germplasm and developed genetic populations

Of notable value have been the wild species from the pioneer work, supported by GRDC, by Professor Douglas Cook from University of California Davis, USA including some of the interspecific derived lines he initially identified as reputed sources of acid soil tolerance which our team has confirmed.

Although there are more than 40 chickpea species, only a select number are readily crossable and produce fertile offspring with domesticated chickpeas (Cicer arietinum).

Cicer reticulatum and C. echinospermum species are considered the closest progenitors that are readily crossable. Through screening, 13 wild C. reticulatum lines with better tolerance to soil acidity than the best-performing Australian line have already been found.

“Additionally, diagnostic molecular markers and specific candidate genes were identified for aluminium tolerance in chickpeas from this project,” Professor Li says.

“Together with the effective hydroponic screening system, this work laid the foundations for genomic assisted breeding, field validation and controlled-environment screening, and the potential to accelerate the transfer of tolerant genes to current elite chickpea varieties for improved aluminium-tolerance and grain production.”

The groundwork in previous GRDC investments has led to a five-year GRDC investment that commenced in 2023, ‘Developing genetic tools to facilitate breeder use and deployment of high-value acid soils tolerant chickpea germplasm.’

Built on identification of acid soil tolerant materials from the wild chickpea species, this project combines molecular markers, genomic prediction and rapid-cycling germplasm enhancement to transfer both major and minor genes into Australian elite varieties and evaluate their economic value in diverse Australian environments (western, southern and northern Australia).

Building on foundations

The new project is a collaboration between DPIRD, Murdoch University and Agriculture Victoria Research (AVR) and has several detailed goals over its five-year timeframe.

“We will establish a publicly accessible database to catalogue all phenotypic and genotypic data being generated from this project and other related projects and update it annually. This will be a valuable resource for chickpea improvement,” Professor Li says.

The screening method will be further refined for both aluminium and manganese toxicity and validated in southern NSW, Victoria and Western Australia and be made available to breeders and pre-breeders.

Advanced acid tolerant chickpea lines will be evaluated under acid paddock conditions for compatibility with commercial rhizobial strains and improved strains near release.

Simultaneously, the AVR team, led by Dr Sukhjiwan Kaur (senior research scientist, genomic and predictive breeding), will focus on implementing a genomic selection-assisted speed breeding approach. This innovative strategy aims to identify and synergistically combine both major and minor genes for acid tolerance.

The speed breeding facility at AVR expedites the development of fixed lines by significantly reducing the generation cycle time to just 50 to 60 days, a remarkable reduction when compared to the standard span of more than six months in a field environment. As the project advances, it will generate seed stocks that are enriched with both major and minor gene tolerances.

Acid soil tolerance has been effectively transferred from wild chickpea species (right) to commercial cultivars (left). Photo: Evan Collis

Field validation of these seed stocks will be carried out throughout the project and, once validated, these seed stocks will be delivered to chickpea breeders for deployment into breeding.

These technologies are accelerating the rate at which we can deliver material to breeders and ultimately to growers.

The project builds upon GRDC-invested research by the University of California-Davis developing crosses between aluminium tolerant and sensitive chickpeas.

“Drawing from this collection imported through the Australian Grains Genebank, this year a collection of 510 chickpea genotypes covering both genotype and phenotype diversity was chosen for 2023 field trials to identify additional genetic factors that impact chickpea production in acid soils. They have been planted in Merredin, WA.

“Field evaluation is very important as there can be complex interactions between aluminium, manganese and phosphorus that impact on chickpea growth which we cannot simulate in controlled environments.

“The investment by GRDC is also giving us the opportunity to investigate the potential of a chromosome block identified by Professor Rajeev Varshney in a chickpea line which reportedly confers abiotic stress tolerance such as tolerance to drought.”

Professor Varshney identified this chromosomal region of chickpeas while working at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Hyderabad, India, before joining Murdoch University. He is now the director of Murdoch University’s Centre for Crop and Food Innovation, director of the WA State Agricultural Biotechnology Centre, and international chair in agriculture and food security at Murdoch University’s Food Futures Institute.

Professor Li says a similar approach will be used to backcross and speed breed these genes into elite material and evaluate them in paddock conditions.

Collaboration and communication, sharing knowledge, technology and resources is key to ensure that we can deliver improved chickpea lines to grow on acid soils and expand the area of production for chickpeas in Australia.

“We anticipate delivering knowledge, tools and germplasm carrying multiple diverse sources of tolerance to acid soils for deployment in chickpea breeding programs by 2027.”

More information: Professor Chengdao Li, [email protected]