Effect of salinity on physiological characteristics, yield and quality of microtubers in vitro in potato

In vitro microtuberization provides an adequate experimental model for the physiological and metabolic studies of tuberization and the preliminary screening of potential potato genotypes. The effect of saline stress at 0-80 mmol concentration on in vitro tuberization of two potato cultivars were investigated in this study. With an increase in the salt concentration, the microtuberization of potato was either delayed by 5-10 days (20 and 40 mmol NaCl) or inhibited completely (80 mmol NaCl) in addition to the reduction in microtuber yields. The two potatoe genotypes studied showed different trends in total soluble sugars, sucrose and starch contents of microtubers under NaCl stress, while glucose and fructose levels remained unchanged. The vitamin C content in microtubers of two potato genotypes was reduced by salt stress. Salinity applied from 20 to 60 mmol progressively increased proline and malondialdehyde (MDA) levels in microtubers of both the potato cultivars. In genotype Zihuabai, NaCl at low concentration (20 mmol) led to a significant increase in peroxide (POD) and polyphenoloxiadase (PPO) activities, while in Jingshi-2, the PPO activity decreased progressively with an increase in NaCl concentrations. Genotype Zihuabai exhibited higher tolerance to salt stress than Jingshi-2 under in vitro conditions.