Comparative germination and early seedling responses of five chickpea genotypes (Cicer arietinum L.) under hexavalent chromium stress

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Abstract Hexavalent chromium [Cr(VI)] is among the most phytotoxic heavy metals entering the agricultural ecosystems of South Asia. It originates almost entirely from industry and is discharged in the untreated effluents of leather tanning, chrome plating and electroplating, textile dyeing, pigment and paint manufacture, wood preservation and metal finishing units, from where it reaches farmland through canal and groundwater irrigation. Chickpea ( Cicer arietinum L.) is the leading rainfed pulse crop of Pakistan, yet the Cr(VI) tolerance of its locally released varieties has never been compared. We hypothesised that Pakistani chickpea genotypes differ significantly in germination and early seedling tolerance to Cr(VI), and that root-related traits discriminate genotypes more effectively than shoot-related traits. Five chickpea genotypes (Paider-91, Punjab-2008, Bhakkar-2011, Thal-2020, and Bittle-2021) were subjected to five concentrations of potassium dichromate (K₂Cr₂O₇): 0, 25, 50, 75, and 100 mg L⁻¹ in a completely randomized factorial design with five replicates. Nine morpho-physiological traits were evaluated over 14 days: germination rate (GR), mean germination time (MGT), seedling vigor index (SVI), shoot length (SL), root length (RL), seedling length (S.L), root collar diameter (RCD), fresh weight (FW), and dry weight (DW). Data were analysed by two-way ANOVA, Fisher’s LSD post-hoc test, and Pearson correlation. Chromium stress induced dose-dependent, statistically significant ( p ≤ 0.001) inhibition across all traits. Grand mean GR declined from 94.4% (control) to 80.8% at 100 mg L⁻¹ (-14.4%), while MGT increased by 79.2% (1.97 to 3.53 days). SVI suffered the greatest relative suppression (-69.0%). Punjab-2008 and Bhakkar-2011 consistently outperformed the other genotypes, retaining superior GR, SVI, root and shoot lengths and biomass at maximum stress. Bittle-2021 was the most sensitive genotype for almost every trait measured. Pearson correlation analysis revealed highly significant positive relationships among the growth- and biomass-related traits ( r = 0.561-0.966) and significant negative relationships between MGT and all growth parameters ( r = -0.491 to -0.550). Pakistani chickpea varieties differ appreciably in Cr(VI) tolerance, confirming the study hypothesis. Punjab-2008 and Bhakkar-2011 are accordingly prioritised as donor genotypes for breeding chromium-tolerant varieties, and root length and SVI are recommended as discriminating traits for rapid genotypic screening. The findings provide a practical basis for varietal selection on chromium-affected agricultural soils in Pakistan.