Moderate desiccation dramatically improves shoot regeneration from maize (Zea mays L.) callus

Tissue and cell culture systems are vital to many areas of maize research and improvement. Efficient shoot regeneration remains a limiting factor for most elite lines. To enhance shoot regeneration, calluses derived from immature embryos of four genotypes were subjected to 6, 12, 24, 48, and 72 h of desiccation on sterile filter paper before shoot induction. We achieved up to 32% desiccation (measured as mass) and 48% imbibition (measured as mass gain in 48 h incubation) which was 3.4-fold higher than nondesiccated controls. This rapid desiccation/imbibition procedure enhanced shoot regeneration and development, but its efficiency was crucially dependent on the degree and duration of desiccation. All four genotypes calluses regenerated shoots best after 48 h of desiccation corresponding to a 23.7% average desiccation percentage, and regeneration frequencies reached 42-74%, which increased 1.5-2.1-fold compared with that of nondesiccated calluses. The effect of desiccation treatment on the shoot regeneration increase took place mainly during the early phase of induction. The weekly average shoot regeneration frequency of calluses with 48 h desiccation in the first wk reached 8.8% (the control was no regeneration); then it increased 3.0 and 2.3-fold in the second and third wk induction, respectively. We demonstrate that the moderate desiccation of calluses increases the yield of shoot regeneration and speeds up regeneration course in maize.