Chickpea heat tolerance traits have been identified and are in the process of being transferred to chickpea breeders

High temperatures during chickpea’s critical flowering and pod-fill period reduce seed size and number. To mitigate these yield losses, GRDC in 2021 invested in a proof-of-concept study that searched for novel heat tolerance traits within the broader chickpea gene pool.

The project is headed by Professor Richard Trethowan, director of the Plant Breeding Institute at the University of Sydney.

Professor Trethowan explains that the targeted germplasm came from three sources:

• material from the Australian Grains Genebank (AGG) that was collected from hot climates around the world;
• Australian cultivars identified from an analysis of performance in hot environments in National Variety Trials; and
• lines from India with heat tolerance.

These materials were used to develop a unique germplasm in the Australian Research Council’s Legumes for Sustainable Agriculture (LSA) hub.

The LSA hub was established to  drive gains in chickpea growth rates, nitrogen sustainability and resilience against the effects of climate change. It was designed to link trait discovery to breeding outcomes and, therefore, drive up farm production, environmental sustainability and profitability.

“The high temperature project was a key subprogram and it was considered vital to achieving the hub’s overall objectives,” Professor Trethowan says. “Much of the initial work was conducted by Dr Angela Pattison, who left the university at the conclusion of the LSA. However, the evaluation and development of new materials continued with the support of GRDC after the hub’s closure.”

Screening the wider gene pool

Similar techniques to those deployed in wheat (see GroundCover™ Supplement story AI fast-tracking wheat heat tolerant gains) were used to expose chickpeas to heat stress. This includes staggered sowing dates (with the late-sown replicates experiencing higher flowering temperatures) and in-field heat chambers to deliver heat stress for five days during the sensitive flowering period.

The analysis performed during this project included the response to heat of anther and pollen development. This involved physiological and genetic analysis.

The in-field use of portable heat chambers at critical stages enabled a close assessment of the structural abnormalities that occur in reproductive organs under controlled levels of heat stress.

The data was augmented by large-scale late-sowing experiments that exposed different chickpea genotypes to more variable heat stress events, thereby widening the search for genetic diversity. This field work enabled the team to understand which traits to target to achieve improved heat tolerance.

As interesting traits were identified, the associated genetics were mapped using the Chickpea DArTseq technology. This is a DNA marker platform that was used to identify those quantitative trait loci (QTLs) linked to the novel heat tolerance traits.

A mapping population was developed and phenotyped for this phase of the project. These populations are in the final year of assessment at Narrabri, New South Wales, in field trials that used staggered sowing dates.

The heat-tolerant materials were also crossed with Australian-adapted chickpea germplasm to develop a population of pre-breeding lines. These new materials show substantial yield advantages under high temperatures, with some yielding almost double when grown in late summer.

The advantage is lower for late autumn or winter-sown materials (the usual sowing window for chickpeas) and depends on temperatures in spring. The warmer the conditions, the greater the advantage.

The strategy we used capitalises on advances made in screening wheat for high-temperature tolerance.

“However, the late summer screening is novel and has led to the identification of some truly unique materials that express a high level of heat tolerance independently of confounding gene-by-environment effects,” Professor Trethowan says.

Chickpea breeders have followed the progress of this project and have made requests to access the new, more heat-tolerant pre-breeding lines.

Sufficient chickpea seed quantities of the pre-breeding materials are being produced for distribution to multiple stakeholders upon request and GRDC permission, with the project on the cusp of starting the transfer to breeders. 

More information: Richard Trethowan, richard.trethowan@sydney.edu.au