Chickpea genotypes contrasting for seed yield under terminal drought stress in the field differ for traits related to the control of water use

Chickpea (Cicer arietinum L.) is often exposed to terminal drought, and deep, profuse rooting has been proposed as the main breeding target to improve terminal drought tolerance. This work tested whether plant water use at the vegetative stage and under non-limited water conditions could relate to the degree of sensitivity of chickpea to terminal drought. Transpiration response to a range of vapour pressure deficits under controlled and outdoor conditions was measured with canopy conductance using gravimetric measurements and thermal imagery in eight chickpea genotypes with comparable phenology and contrasting seed yield under terminal drought in the field. Additionally, the response of plant growth and transpiration to progressive soil moisture depletion was assayed in the same genotypes. Drought-tolerant genotypes had a lower canopy conductance under fully irrigated conditions at the vegetative stage; this trend was reversed at the early pod filling stage. While two sensitive genotypes had high early growth vigour and leaf development, there was a trend of lower growth in tolerant genotypes under progressive soil drying than in sensitive ones. Tolerant genotypes also exhibited a decline of transpiration in wetter soil compared to sensitive genotypes. Canopy conductance could be proxied by measuring leaf temperature with an infrared camera, although the relationship lost sensitivity at the pod filling stage. This work suggests that some traits contribute to water saving when water does not limit plant growth and development in drought-tolerant chickpea. It is hypothesised that this water would be available for the reproduction and grain filling stages.