Determination of salt stress tolerance levels of differentsquash genotypes

This research was conducted to determine the salt stress tolerance levels of twenty different squash genotypes. In the study, seeds of the genotypes were sown in 12 L pots containing a 2:1 mixture of peat and perlite. Stress treatments were started on the 39th day after sowing and an initial dose of 50 mM NaCl was used until the salt concentration was gradually increased until a final level of 150 mM NaCl was reached. Plants exposed to salt stress for eighteen days were harvested and subjected to various measurements and analyses. Scale assessment was carried out to determine the salt stress tolerance levels of the genotypes; in addition, green part fresh and dry weight, stem length and thickness, leaf area, leaf relative water content, membrane injury index (MII), SPAD value as well as Na, Cl, K and Ca ion contents in green part were analyzed. In the scale assessment, GTK-11 and GTK-13 genotypes exhibited the closest development to control plants with values of 1.33; On the other hand, GTK-18 genotype was determined to be the most affected and damaged genotype by salt stress with a scale value of 5.0. The applied 150 mM NaCl salt stress caused decreases in green parts fresh and dry weight, stem length and diameter, leaf area, leaf relative water content (RLWC) and SPAD values at different rates. Compared to control plants, the genotypes with lower losses were GTK-6, GTK-10, GTK-11 and GTK-13; the highest losses were observed in GTK-5, GTK-14, GTK-17, GTK-18 and GTK-29 genotypes. Salt stress increased the membrane damage index (MII) by an average of 43%. In addition, as a result of stress application in all genotypes, Na and Cl ion contents increased by an average of 570% and 589%, respectively, compared to control plants. While the genotypes that were more selective in terms of toxic ion accumulation and accumulated lower levels of Na and Cl ions were GTK-6, GTK-10, GTK-11 and GTK-13, the accumulation of these ions was highest in GTK-4, GTK-8, GTK-14 and GTK-19 genotypes. On the other hand, K and Ca ion contents decreased by 45.76% and 43.00%, respectively, with the application of 150 mM NaCl. While this decrease was more limited in GTK-10, GTK-11 and GTK-13 genotypes, losses in K and Ca ion contents were more pronounced in GTK-5, GTK-14, GTK-17 and GTK-18 genotypes. In the light of all the data obtained, it was concluded that GTK-6, GTK-10, GTK-11 and GTK-13 genotypes were tolerant to salt stress, while GTK-5, GTK-17, GTK-18 and GTK-19 genotypes were sensitive to salt stress in this study carried out in the early development period.