Abstract
Soil salinity results in reduced productivity in chickpea. However, breeding for salinity tolerance is challenging because of limited knowledge of the key traits affecting performance under elevated salt and the difficulty of high-throughput phenotyping for large, diverse germplasm collections. This study utilised image-based phenotyping to study genetic variation in chickpea for salinity tolerance in 245 diverse accessions. On average salinity reduced plant growth rate (obtained from tracking leaf expansion through time) by 20%, plant height by 15% and shoot biomass by 28%. Additionally, salinity induced pod abortion and inhibited pod filling, which consequently reduced seed number and seed yield by 16% and 32%, respectively. Importantly, moderate to strong correlation was observed for different traits measured between glasshouse and two field sites indicating that the glasshouse assays are relevant to field performance. Using image-based phenotyping, we measured plant growth rate under salinity and subsequently elucidated the role of shoot ion independent stress (resulting from hydraulic resistance and osmotic stress) in chickpea. Broad genetic variation for salinity tolerance was observed in the diversity panel with seed number being the major determinant for salinity tolerance measured as yield. This study proposes seed number as a selection trait in breeding salt tolerant chickpea cultivars.
Highlights
Chickpea (Cicer arietinum L.) is an important legume crop used as human food, animal feed and is grown in rotation with cereal crops to fix nitrogen in the soil and to act as a disease break[1]
Shoot ion independent stress results from hydraulic resistance imposed by NaCl in the plant xylem[13] as well as the reduction in external osmotic potential which interferes with water uptake leading to a reduction in plant growth rate[14,15,16]
A study conducted by Dias et al.[18] established differential accumulation of metabolites involved in the TCA cycle, carbon and amino acid metabolism in two chickpea genotypes (Genesis 836 & Rupali) that have been shown to contrast in salinity tolerance[4]
Summary
Chickpea (Cicer arietinum L.) is an important legume crop used as human food, animal feed and is grown in rotation with cereal crops to fix nitrogen in the soil and to act as a disease break[1]. Vadez et al.[7] did not find an association between salinity tolerance (seed yield per plant in saline soil) and accumulation of Na+ in total vegetative biomass at 50 days after sowing (DAS) in a germplasm collection of chickpea, whereas, Turner et al.[6] established a negative correlation between Na+ accumulation in the youngest fully expanded leaf at 98 DAS with salinity tolerance (seed yield under 40 mM NaCl) in 55 chickpea genotypes These differences could be attributed to different sampling strategies for leaf tissues (different time points and developmental stage) employed in the two studies. Characterisation of the Reference Set using 50 SSR markers revealed that it is rich in allelic diversity[26] and can be mined for genetic variation of value in breeding
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