The effects of different salt concentrations on seed germination in pepper cultivars

This study was conducted to determine the effects of different NaCl concentrations (0, 50, 100, and 150 mM) on the seed germination performance of four pepper (Capsicum annuum L.) cultivars (Karaisalı, BT Bursa Yağlık 016, Yalova Çorbacı 12, and Demre). The experiment was established under controlled conditions according to a factorial completely randomized design with four replications. Germination percentage, mean germination time, germination index, germination speed index, Timson index, and salt tolerance index (STI) were determined, and the obtained data were evaluated using principal component analysis (PCA). In addition, the microstructural characteristics and elemental composition of the seed coat were examined by scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS) in selected treatments. The results indicated that increasing NaCl concentrations generally reduced germination percentage and germination speed, with a pronounced inhibitory effect observed particularly at 100 and 150 mM NaCl levels. Significant differences were detected among cultivars; the Demre cultivar stood out by exhibiting high germination index and germination speed index values across all salinity levels. The Karaisalı cultivar showed a stable germination response and did not exhibit abrupt declines in germination performance even at high NaCl concentrations. In contrast, the Bursa cultivar exhibited the lowest performance at all salinity levels, while the Yalova cultivar displayed relatively higher tolerance under moderate salinity but became sensitive under severe salinity conditions. PCA results classified the cultivars into three distinct tolerance groups and confirmed that Demre and Karaisalı cultivars possessed high performance with minimal stress-related losses. These findings were further supported by the salt tolerance index (STI) values. SEM–EDS analyses revealed that Na and Cl contents in seed tissues increased with rising salinity levels, whereas essential nutrient elements such as K, Ca, and Mg decreased. Under high salinity conditions, cellular shrinkage and tissue damage were observed in the seed coat, indicating that the reduction in germination performance was associated not only with osmotic stress but also with ionic toxicity and antagonistic interactions among nutrient elements. In conclusion, the combined use of physiological indices and PCA during the germination stage enabled a reliable assessment of salt tolerance in pepper, and the results demonstrated that the Demre and Karaisalı cultivars are promising genotypes for cultivation and breeding programs in areas with salinity risk.