Abstract
Accelerating genetic gain in crop improvement is required to ensure improved yield and yield stability under increasingly challenging climatic conditions. This case study demonstrates the effective confluence of innovative breeding technologies within a collaborative breeding framework to develop and rapidly introgress imidazolinone Group 2 herbicide tolerance into an adapted Australian chickpea genetic background. A well-adapted, high-yielding desi cultivar PBA HatTrick was treated with ethyl methanesulfonate to generate mutations in the ACETOHYDROXYACID SYNTHASE 1 (CaAHAS1) gene. After 2 years of field screening with imidazolinone herbicide across >20 ha and controlled environment progeny screening, two selections were identified which exhibited putative herbicide tolerance. Both selections contained the same single amino acid substitution, from alanine to valine at position 205 (A205V) in the AHAS1 protein, and KASP™ markers were developed to discriminate between tolerant and intolerant genotypes. A pipeline combining conventional crossing and F2 production with accelerated single seed descent from F2:4 and marker-assisted selection at F2 rapidly introgressed the herbicide tolerance trait from one of the mutant selections, D15PAHI002, into PBA Seamer, a desi cultivar adapted to Australian cropping areas. Field evaluation of the derivatives of the D15PAHI002 × PBA Seamer cross was analyzed using a factor analytic mixed model statistical approach designed to accommodate low seed numbers resulting from accelerated single seed descent. To further accelerate trait introgression, field evaluation trials were undertaken concurrent with crop safety testing trials. In 2020, 4 years after the initial cross, an advanced line selection CBA2061, bearing acetohydroxyacid synthase (AHAS) inhibitor tolerance and agronomic and disease resistance traits comparable to parent PBA Seamer, was entered into Australian National Variety Trials as a precursor to cultivar registration. The combination of cross-institutional collaboration and the application of novel pre-breeding platforms and statistical technologies facilitated a 3-year saving compared to a traditional breeding approach. This breeding pipeline can be used as a model to accelerate genetic gain in other self-pollinating species, particularly food legumes.
Highlights
Achieving food security under increasingly hostile environmental conditions1 requires rapid innovation across all sectors involved in food production (Varshney et al, 2021)
We describe the use of mutagenesis to develop a non-GM herbicide tolerance trait beneficial within the farming system
We provide a case study outlining the progression, in 4 years, from initial cross to Australian National Variety Trials (NVT) of herbicidetolerant chickpea breeding line CBA2061 using a combination of innovative platforms: accelerated homozygosity, markerassisted selection and advances in applied statistics optimal for achieving selection targets
Summary
Achieving food security under increasingly hostile environmental conditions requires rapid innovation across all sectors involved in food production (Varshney et al, 2021). Harnessing pre-breeding tools will be key to improving the rate of genetic gain in crop and horticultural species. Techniques to accelerate lifecycle turnover using modified single seed descent have been proposed to further truncate breeding pipelines in a range of species, including food legumes (Ochatt et al, 2002; Mobini et al, 2015; Croser et al, 2016; Mobini and Warkentin, 2016; Ribalta et al, 2017; Watson et al, 2018; Hickey et al, 2019; Cazzola et al, 2021). As a result, breeding programs need to be agile to maximize efficiency involving collaboration with public pre-breeding at other institutions. We present a case study of cross-institutional implementation of a compressed breeding pipeline to deliver an improved chickpea (Cicer arietinum L.) cultivar bearing a mutagenesis-derived gene for herbicide tolerance, a critical need of Australian grain growers for sustainably managing their farming system and improving production
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