Adaptation of chickpea recombinant inbred lines to excess soil moisture stress: a phenotypic plasticity perspective

Phenotypic plasticity is a key mechanism enabling crops to adapt to environmental variability. This study quantified plasticity across agronomic, phenological, and physiological traits in chickpea, examined their interrelationships under contrasting moisture regimes, and assessed their contributions to yield stability. We evaluated 191 genotypes, including recombinant inbred lines (RILs) and commercial cultivars following a randomized complete block design under three field environments: normal (126.4 mm), high-moisture (232.4 mm), and rainfed (187.4 mm). The latter two, being characterized by erratic and excessive rainfall, were combined as excess soil moisture (ESM) stress conditions. Phenotypic plasticity was estimated using reaction norm slopes and percentage changes, whereas genotypic performance was assessed via the stress tolerance index (STI). Grain yield per plot declined by approximately 50 % under stress, alongside reductions in biomass (44 %), seed number (49 %), and yield per plant (47 %). In contrast, 100-seed weight increased (8 %), reflecting a compensatory adjustment. Seed number, biomass, and canopy height presented high plasticity, whereas harvest index and seed weight remained stable. Phenological traits were delayed with limited responsiveness, while NDVI at podding revealed the highest physiological plasticity (0.91-1.57). Plasticity in seed number, biomass, and NDVI was positively associated with yield stability. High-performing RILs such as 1_97 and 1_85 combined high STI values (≥0.93) with adaptive plasticity profiles. These findings underscore the potential of trait-specific plasticity as a selection target to improve stress resilience in chickpea. Breeding programs should prioritize genotypes with adaptive plasticity in seed number, biomass, and canopy traits to sustain yield under excess soil moisture stress.