Effects of aminolevulinic acid on growth, antioxidant activity and anthocyanin accumulation of apple explants under salinity stress in in vitro culture conditions

The present study was carried out to evaluate the effect of 5-aminolevulinic acid (ALA) on physiological and biochemical changes of in vitro-cultured Budaguvsky 9 (Bud 9) apple cultivar under NaCl induced salinity stress. Virus-free shoots and callus  of Bud 9 apple  were cultured on MS medium containing different levels of NaCl (0, 30, 60 and 90 mM) and ALA (0, 2.5, 5, 10 and 20 µM). Four weeks later phytochemical variations of regenerated plantlets with or without NaCl and/or ALA treatments were recorded.  Shoot explants and callus treated with 5-aminolevolinic acid at 2.5 to 20 µM concentrations demonstrated reduction in catalase and peroxidase and enhancement in superoxide dismutase and ascorbate peroxidase enzyme activity. The highest chlorophyll a and b values were observed at shoot explants treated with concentration of 10 μm of aminolevolinic acid. Also, salinity stress was performed an effective role on increasing the amount of anthocyanins of explants and the highest amount was obtained in 90 mM salinity stress. Increasing the intensity of salinity stress and amino acid concentration (2.5-10 μm) in culture media had synergic effect on the antioxidant activity, total phenol as well as flavonoids content of studied explants.