Morphological and Physiological Responses of Pak Choi (Brassica rapa subsp. chinensis) Genotypes Under Controlled Drought Stress

This study evaluated the growth performance and physiological responses of 24 Korean landrace accessions of pak choi (Brassica rapa subsp. chinensis) under polyethylene glycol (PEG)-induced drought stress to identify indicators for selecting drought-resistance genotypes. Electrolyte leakage (EL) and chlorophyll fluorescence (Fv/Fm) analyses showed that resistance accessions (IT262109(11), IT279432(12), IT293143(20)) had minimal increases in EL and maintained high Fv/Fm values under stress, indicating superior membrane stability and photosystem II activity. In contrast, sensitive accessions exhibited a sharp rise in EL and a decline in Fv/Fm to approximately 0.3 under 25% PEG treatment, reflecting severe physiological damage. Principal component analysis (PCA) biplot based on integrated growth and photosynthetic parameters differentiated resistance and sensitive groups, with PC1 representing photosynthetic efficiency versus membrane injury. Growth trait responses interaction analysis using GGE biplot of six representative accessions (three resistance, three sensitive) demonstrated that resistance genotypes had smaller positional shifts across treatments, indicating greater growth stability, while sensitive genotypes showed pronounced variability and environment-specific responses. This study provides a framework integrating growth and physiological indicators for identifying drought-resistance pak choi accessions, offering valuable implications for breeding programs aimed at climate-resilient cultivar development.