Comparative responses of chickpea cultivars to water deficit
Chickpea (Cicer arietinum L.) yields in Mediterranean areas are restricted largely by drought, and little is yet known about adjustments to water deficit among cultivars. A gradient of water availability was imposed on chickpea cultivars differing in drought tolerance to study their differential responses in plant water relations, gas-exchange, growth, water-use, yield and yield components as a step toward increasing the efficiency of cultivar development for drought tolerance;Differences in stomatal conductance among cultivars were more consistently and predictably related to differences in water-use efficiency (WUE) than were genotypic variations in photosynthesis. Selection for increased WUE through reduction in leaf conductance would seem a straightforward proposition; however, photosynthetic limitations due to lowered leaf conductance will tend to limit yield potentials under favorable environments;Osmotic adjustment may have occurred in all the cultivars. However, the differences among cultivars were not large enough to influence plant performance significantly under drought stress. Leaf water potential showed good correlations with important plant functions, and thus, appears to be a better indicator of drought tolerance among cultivars;No significant differences were found among cultivars for crop growth rate, total dry-matter production or dry-matter WUE. The differences among cultivars in seed yield were associated with differences in seed growth rate, effective filling period, harvest index, seed WUE and rooting depth. High yields of droughted chickpea were due less to specific physiological responses than to ability to set pods under drought. Seed yield was improved because of a larger sink size and demand, and by partitioning a larger part of biomass into seed;In conclusion, genetic variation exists in many of the traits examined, offering promise for yield improvement for dryland conditions. While yield stability of the cultivars was associated mainly with physiological attributes, yield potential was determined by sink size, sink demand and partitioning of dry-matter from the vegetative source to the reproductive sink.