Evaluation of Kabuli Chickpea Genotypes for Terminal Drought Tolerance in Tropical Growing Environment

Terminal drought is the major constraint for chickpea production, leading to yield losses of up to 90% in tropical environments. Understanding the morphological, phenological, and physiological traits underlying drought tolerance is crucial for developing resilient chickpea genotypes. This study elucidates the drought-tolerant traits of eight kabuli chickpea genotypes under a controlled environment using polyvinyl chloride (PVC) lysimeters. Terminal drought was imposed after the flowering stage, and the response was assessed against non-stress (well-watered) treatment. Drought stress significantly impacted gas-exchange parameters, reducing the stomatal conductance (16-35%), chlorophyll content (10-22%), carbon assimilation rate (21-40%) and internal carbon concentration (7-14%). Principal component analysis (PCA) indicated three groups among these eight genotypes. The drought-tolerant group included two genotypes (AVTCPK#6 and AVTCPK#19) with higher water use efficiency (WUE), deep-rooted plants, longer maturity, and seed yield stability under drought stress. In contrast, the drought-susceptible group included two genotypes (AVTCPK#1 and AVTCPK#12) that were early-maturing and low-yielding with poor assimilation rates. The intermediate group included four genotypes (AVTCPK#3, AVTCPK8, AVTCPK#24, and AVTCPK#25) that exhibited medium maturity and medium yield, conferring intermediate tolerance to terminal drought. A significantly strong positive correlation was observed between seed yield and key physiological traits (stomatal conductance (gsw), leaf chlorophyll content (SPAD) and carbon assimilation rate (Asat)) and morphological traits (plant height, number of pods, and root biomass). Conversely, carbon discrimination (Delta 13C) and intrinsic WUE (iWUE) showed a strong negative correlation with seed yield, supporting Delta 13C as a surrogate for WUE and drought tolerance and a trait suitable for the selection of kabuli chickpea genotypes for drought resilience.