Overview and Background
Grain legumes were not beneficiaries of the Green Revolution. Policy and investment since the 1960’s have favored Green Revolution cereal crops, which were planted on the best agricultural land and also received the lion’s share of inputs. Legumes, on the other hand, were often relegated to marginal lands where elevated temperatures, rain fed cropping systems, short growing seasons and poor soils conspire to limit yield potential. As a result, enhancing climate resilience – including resilience to environmental extremes, variable climate and marginal soils – is an ongoing challenge to most legume crops. Moreover legume breeding has largely ignored legumes’ chief advantage, namely their capacity for biological nitrogen fixation, which underpins their agricultural sustainability and high content of nutritional nitrogen. Climatic factors such as moisture, heat and salinity impact nitrogen fixation, and thus developing climate-resilient nitrogen fixation is a corresponding need.
Currently grain legume production (chickpea, groundnut and pigeonpea) is ~7 million tons short of demand in impoverished, hungry countries. In the absence of a solution this gap is projected to increase sharply to 10 million tons by 2020. Fortunately, many developing countries are implementing policies that encourage greater use of legumes. This increases the potential impact of breeding gains that will be achieved by this project. The incomes of poor farmers in parts of Ethiopia, and elsewhere in sub-Saharan Africa, have increased markedly in recent years due to the export of chickpea to large, growing markets of South Asia, but there remains a critical need to stabilize this situation by developing climate-resilient chickpea varieties.
Chickpea as a crop: Cultivated chickpea first appears in the archeological record some 6.6-7.2 thousand years ago in Syria (Hillman, 1975). The immediate wild relatives (C. reticulatum and C. echinospermum, the primary and secondary gene pools respectively) are restricted to southeastern Turkey. Domestication likely happened earlier, as much as 10.5 thousand years ago, concurrent or soon after the domestication of other fertile crescent crops such as wheat, barley, pea, and lentil. Domesticated chickpea was likely brought to Syria by about 7 thousand years ago, while records for the dates of introduction into East Africa and the Indian subcontinent are limited.
Abbo et al. (2003, 2009) have speculated that chickpea is particularly genetically depauperate because the wild relatives have a narrow geographic distribution compared to other crops domesticated in the Fertile Crescent, and because cultivated C. arietinum has a phenology shifted originally towards later germination as a summer annual, compared to the wild relatives that germinate in the fall or winter and flower in the spring. In natural populations, modulation of flowering time can be an important mechanism for adaptation to varying environments (Wilczek et al. 2009, Banta et al. 2012, Leinonen et al. 2013, Friesen et al. in review, Castro et al. in review). Reduced responsiveness to environmental cues (temperature and photoperiod) during crop domestication has permitted range and seasonal expansion of crops, including chickpea (Bergeret al. 2011). Control of flowering is of particular relevance and increased importance to climate change. For example, to mitigate losses from heat and drought, chickpea breeders have selected short duration varieties that flower and mature early and thus avoid the risk of late season heat and drought (Gaur et al. 2008). In chickpea, tolerance to drought has been associated with the ability of plants to conserve water in the soil profile, mitigating the effects of terminal drought. Root system architecture is also likely important in chickpea, as has been observed in some other crop species. Phenotypic resistance is also known for heat and cold temperatures, as well as to major pathogen and pest species. In all cases the genetic bases and underlying mechanisms of these important traits are poorly understood.
The whole genome sequence of a Canadian chickpea genotype was reported by Varshney, Cook and colleagues in 2013, while an Indian initiative led by the National Institute for Plant Genome Resaerch in New Delhi, India, sequenced a second cultivated genotype and a wild C. reticulatum accession. Re-sequencing of numerous breeding lines reveals the imprint of human selection on the chickpea genome, while combined genetic and phenotypic analyses are beginning to yield genome intervals and genes involved in flowering time control, plant architecture, nodule number and disease resistance. Moreover, because of the substantial investment by the international community there exist standardized phenotyping protocols for drought and heat tolerance, and for assessing the other major phenotypes of this project, including flowering time, nutrient composition, and symbiosis.
Chickpea is grown widely around the globe, although by far the largest producer and consumer of chickpea is the country of India. Turkey is chickpea’s center of origin, and India and Ethiopia represent longstanding centers of secondary diversity. Partners in this project include six of the top ten chickpea producing countries, accounting for approximately 83% of the world’s total production.
Source: FAO Stats Website