Abstract
In acid soils, the toxic form of aluminium, Al3+, significantly inhibits root growth and elongation, leading to less water and nutrient uptake. Previous research had shown differential Al toxicity tolerance among cultivated Cicer arietinum L. (chickpea); however, the potential for developing tolerant cultivars is limited by the narrow genetic diversity of cultivated chickpeas. Recent collections from Turkey of wild Cicer species, Cicer reticulatum, and Cicer echinospermum, have increased the available gene pool significantly, but there has been no large-scale screening of wild Cicer for acid tolerance or Al3+ toxicity tolerance. This study evaluated 167 wild Cicer and 17 Australian chickpea cultivars in a series of screenings under controlled growth conditions. The pH of 4.2 and Al concentrations of 15 and 60 μM Al were selected for large-scale screening based on dose response experiments in a low ionic strength nutrient solution. The change in root length showed better discrimination between tolerant and sensitive lines when compared with shoot and root dry weights and was used as a selection criterion. In a large-scale screening, 13 wild Cicer reticulatum accessions had a higher root tolerance index (≥50%), and eight had higher relative change in root length (≥40%) compared with PBA Monarch, which showed greater tolerance among the Australian domestic cultivars screened. In general, C. reticulatum species were found to be more tolerant than C. echinospermum, while genetic population groups Ret_5, Ret_6, and Ret_7 from Diyarbakir and Mardin Province were more tolerant than other groups. Among C. echinospermum, Ech_6 from the Siv-Diyar collection site of the Urfa Province showed better tolerance than other groups. In this first detailed screening of aluminium toxicity tolerance in the new wild Cicer collections, we identified accessions that were more tolerant than current domestic cultivars, providing promising germplasm for breeding programs to expand chickpea adaptation to acid soils.
Highlights
Chickpea (Cicer arietinum L.) is the largest pulse crop after common bean, with annual global production of 17.2 million tonnes from 17.8 Mha, and is a primary source of food protein for about 20% of the world population (Vadez et al, 2020)
Multiple studies showed that crop wild relatives (CWR) of Cicer possess a superior tolerance to various parameters, making them a valuable resource for chickpea improvement (Abbo et al, 2003; Reen et al, 2019), and this paper explores the Al tolerance at low pH in CWR of Cicer and compares them with cultivars of C. arietinum L
The objectives of this study were to (i) determine the effect of low pH and Al on plant growth of Australian domesticated Cicer cultivars; (ii) characterise the response of wild Cicer accessions to growing at low solution pH with increasing Al to identify the range of tolerance; and (iii) determine if there is any differentiation in tolerance to low pH and Al among the Cicer accessions based on the species or genetic population group
Summary
Chickpea (Cicer arietinum L.) is the largest pulse crop after common bean, with annual global production of 17.2 million tonnes from 17.8 Mha, and is a primary source of food protein for about 20% of the world population (Vadez et al, 2020). The widespread occurrence of soil acidity is one of the main limitations to chickpea production worldwide. Lime application is commonly used to manage soil acidity, while the addition of P-containing fertilisers can increase bioavailable P and reduce Al3+ toxicity (Liao et al, 2006). These methods are not always economically feasible, and lime application is ineffective in acid subsoil without deep tillage (Dai et al, 2011). An effective approach is to develop acid tolerant cultivars to increase crop productivity. Despite being an important pulse crop, no acid tolerant chickpea cultivars have been developed. In order to breed cultivars for acid tolerance, the first step is to identify Al-tolerant genetic resources (Foy et al, 1967)
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