By Helena Tagg
Researchers from Durham University, in collaboration with Harran University and the University of California Davis, have uncovered one to three major genes that control flowering times in chickpeas. This facilitates the manipulation of flowering time to avoid localised abiotic and biotic stresses.
The trailblazing discovery has already birthed a new variety that is improving yields in Turkey and Syria, and its potential application in combating the intensifying food crisis, in the face of climate change, is palpable.
Chickpeas (Cicer arietinum) are a nutrient-rich legume bursting with health benefits; a source of plant-based protein and high in minerals such as zinc and iron. Comprising 20% of the world’s output of pulses, chickpeas are crucial to local and global economies and are a staple food in many low-income countries.
However, a deluge of climate-related consequences — the perfect storm of extreme weather conditions, water scarcity, and rising temperatures — rally against agricultural systems at the present. Recent estimates predict that climate change is set to thrust a third of crop production beyond ‘safe climatic space’, with effects concentrated near the tropics.
The necessity for improved crops is glaringly obvious, indisputably urgent. Modern molecular techniques, in collaboration with age-old field methodology, provide a sophisticated tool to investigate further.
Durham’s researchers curated ten crosses between cultivated C. arietinum and genetically diverse wild types, C. reticulatum and C. echinospermum, grown in Turkey. These were nurtured under identical conditions, such that differences in flowering time could be measured and attributed to inherited alleles.
Two of the lines were stringently tested using Nested Association Mapping, to unearth the genetic architecture underlying the flowering time phenotype. First used in studies of complex traits in corn, Nested Association Mapping monopolises upon the advantages of Linkage Analysis and Association Mapping, resulting in highly accurate mapping based on both recent and historic recombination events.
Flowering time was found to be highly heritable, and the researchers dexterously dissected the resulting frequency distributions in order to fit them to Mendelian ratios. When tested with goodness of fit statistics, five out of seven cultivars fitted a two gene model. Quantitative trait locus analysis revealed loci for flowering time on chromosomes three, five and six, which is supported by prior research in Arabidopsis.
Guar et al. estimate that heat stress and drought are culpable for 50% of yield losses in chickpeas due to abiotic stress, proving especially catastrophic during the plants’ vulnerable reproductive phase. Loss of membrane integrity, reducing chlorophyll content, depressed metabolism and lowered enzymatic efficacy are a blight upon yields, to name but a few.
However, following the identification of the major genes responsible, the researchers hint that the flowering times of individual varieties could be locally optimized to avoid these calamitous environmental stresses. This could bolster yields, despite escalating climate change, and expand the range of locations that chickpeas can be grown in.
The range of impacts that chickpeas hold in climate mitigation are remarkable. This ranges from improving food security, providing a more sustainable protein alternative to meat, and boosting soil fertility by naturally fixing nitrogen without the use of fertilizer (reducing costs and potential wider ecosystem effects).
Supporting work from the University of Saskatchewan illustrates how novel chickpea varieties could contribute to the UN’s Sustainable Development Goals by working towards zero hunger. The authors hold optimism that this target could be fulfilled by 2030, given that scientists capitalize upon genomic technology and the existing allelic diversity in wild varieties.
This research undoubtedly generates optimism for the scope of impact that the humble chickpea possesses and underlines the value of germplasm, extending beyond domesticated varieties. The authors highlight that further work is required to identify more genes controlling yield and resistance to environmental factors. Subsequent to the successful implementation of superior strains in Turkey and Syria, the practical value of such research is apparent and encouraging.
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