Determination of Morphological and Biochemical Responses of Prunus Cerasifera Myrobolan 29C Rootstock to Stepwise Increasing NaCl Stress Under in Vitro Culture Conditions

Abstract

This study aimed to evaluate the morphological and biochemical responses of the clonal rootstock Prunus cerasifera Myrobolan 29C to stepwise increasing NaCl doses (target levels: 0, 40, 80, 120, and 160 mM) under in vitro culture conditions. Morphological assessments included regeneration rate, injury severity, shoot and leaf number, shoot length, and shoot fresh weight. Biochemical analyses comprised the activities of ascorbate peroxidase (APX), peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), as well as malondialdehyde (MDA) level, proline accumulation, total phenolics, total flavonoids, and total protein content. With increasing salinity doses, regeneration and vegetative growth parameters generally decreased; growth indicators were relatively preserved under the lower doses, whereas declines became more pronounced under the higher doses (120-160 mM NaCl). Biochemical responses suggested activation of salinity-associated defense responses, as reflected by increased proline accumulation, antioxidant enzyme activities, and total phenolic and flavonoid contents, particularly under the higher doses. In contrast, total protein content decreased at higher salinity, and elevated MDA levels indicated enhanced oxidative damage under severe conditions. Overall, the results indicate that Myrobolan 29C exhibits a limited capacity to maintain growth under low-to-moderate salinity, while growth and tissue integrity are more strongly constrained under severe salinity in in vitro culture.