Stress gradients select for ecotype formation in Cicer judaicum Boiss., a wild relative of domesticated chickpea

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The investigation of plant adaptive strategies has been enhanced by the advent of high resolution climate models facilitating greatly improved fine-scale habitat characterization. We have used this approach in the evaluation of C. judaicum Boiss., an annual wild relative of chickpea. 54 accessions from 12 Israeli populations representing three separate habitats differing in temperature and terminal drought stress intensity were evaluated in a common garden experiment, measuring phenology and growth. The results indicate that C. judaicum formed distinct ecotypes along environmental stress gradients, with stress avoidance as a key adaptive strategy: (1) germination is delayed with increasing collection site altitude and associated decreasing temperatures; (2) flowering date and productivity (as estimated by mainstem length) are inversely related to habitat stress, as defined by site climate or soil type. Populations from stressful sites escape drought stress through early flowering at the likely cost of biomass production. We conclude that precise habitat characterization facilitates the study of specific adaptation over relatively short geographic distances. This is particularly pertinent today because many of the key crop production system stresses (i.e., terminal drought, the impact of climate change) can be modelled climatically to identify potentially-adapted germplasm from ex situ and in situ collections.