Identification of salt tolerant chilli (Capsicum annuum L.) genotypes and reliable indicator traits at the germination stage using fuzzy comprehensive evaluation approach

Soil salinization is a major abiotic stress that significantly limits crop productivity, particularly during seed germination and early seedling development. Field-based screening for salinity to identify the salt tolerant genotypes is often unreliable due to environmental variability and soil heterogeneity. Present study aimed to develop a robust laboratory-based screening model and identify key morpho-physiological traits associated with salinity tolerance in chilli (Capsicum annuum L.). Ten genotypes were initially evaluated under NaCl concentrations of 0, 75, 100, 150, and 200 mM to determine the optimal salt threshold concentration. Based on the salt injury index, 150 mM NaCl was identified as the critical concentration, using germination percentage, root and shoot length, seedling length, dry weight, and vigour indices serving as key selection parameters. Subsequently, 109 genotypes were screened against identified concentration and categorized using membership function values into highly salt-tolerant (4), salt-tolerant (7), salt-sensitive (84), and highly salt-sensitive (14) categories. The identified genotypes (HSS and HST) were also validated in pot against 150 mM NaCl-induced salt stress at 45 days to confirm the reliability of laboratory screening. We formulated a mathematical evaluation approach and regression, pinpointing seedling length and vigour index-I as critical indicators of salinity tolerance in chilli genotypes at the germination stage. This study established a standardized, high-throughput screening protocol, traits that reliably represents tolerance and a mathematical model for salinity tolerance assessment. The identified salt-tolerant genotypes have significant potential for use in breeding programs and as rootstocks to enhance salinity resilience in commercial chilli production.