Determination of salinity tolerance levels of various watermelon genotypes

In this study, reactions of 15 different watermelon genotypes were screened for salt stress (at 75 ve 150 mM NaCl) in nutrient solution culture. Tolerance of genotypes to salt stress was correlated by shoot and root dry matter production, symptom score degrees, sodium (Na), potassium (K), calcium (Ca) concentrations, K/Na and Ca/Na ratios. Moreover, changes of chlorophyll concentrations and relative water content of leaves were also studied. However, among the parameters used, the symptom scores and shoot Na concentration were more reliable parameters for salt stress tolerance of the genotypes. The genotype 216 which contained low Na concentration had lower symptom score in shoot under salinity which in turn had high tolerance degree. Moreover, at 150 mM NaCl, it was found that the genotypes 260 and 98 had also similar symptom scores with the genotype 216, and both were Na-excluder and tolerant. It was determined that the genotypes 59, 178, Crimson Sweet and Crimson Tide along with genotype 37, were Na-includer and sensitive types. The genotype 13 was sensitive and had semi-Na-exclusion mechanism. Based on the high NaCl dose, the genotypes 174, 242, 117, 181, 229 and 249 were Na-includer and moderately sensitive types.As a result, the higher salt tolerance was related to the low Na concentrations in shoots. The genotypes, selected as tolerant, primarily 216 along with 260 and 98 can be recommended for cultivation at sites under salinity risk. Among the studied parameters, shoot Na concentration and severity of leaf symptom scores were reliable parameters for classification of the salt stress tolerance of genotypes.Key words: Watermelon, salt stress, salt tolerance, K/Na ratio, Ca/Na ratio