Effect of media additives, incubation culture conditions and subculturing on control of oxidative browning in in-vitro culture of apple (Malus domestica)

An efficient in-vitro initiating culture system of forced primary explants of M7 and M9 apple (Malux domestica Borkh) rootstock was developed. Shoot explants (10-15 mm) comprising apical bud having 1 to 2 nodes were excized and aseptically cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) 0.5 mg/litre and indole-3-butyric acid (IBA) 0.1 mg/litre. The cultured explants immediately transferred to low temperature regime (4 ± 3°C) under complete darkness (0/24 hr photoperiod for 2-3 days) followed by subculture on fresh medium and incubated for 5 ± 1 weeks at 24 ± 1°C under 16/8 hr photoperiod and 3.5 ± 0.5 klx light intensity resulted in considerable reduction in explant browning and media exudation accompanied by enhancement in surviving explants. Media fortification either with ascorbic acid or polyvinyl pyrrolidone (PVP) did not markedly influence reduction in severity of oxidative browning and phenolic exudation of explants in culture medium.