Factors affecting minimal growth conservation of potato microplants in vitro

Combined effects of sucrose, mannitol and photoperiod on microplant conservation were studied in four potato genotypes belonging to two different groups viz., Tuberosum and Andigena. Minimal growth medium was based on Murashige and Skoog (MS) supplemented with 6 different concentrations of sucrose (30, 40, 50, 60, 70 and 80 gl^-1) with 4 different concentrations of mannitol (0, 20, 40 and 60 gl^-1). The cultures were conserved under two photoperiod conditions i.e. continuous illumination and 16-h photoperiod at 6 ± 1 °C. There were significant interactions between photoperiod and sucrose, and between photoperiod and mannitol. Maximum microplant survival and desirable microplant growth were observed under 16-h photoperiod. Sucrose alone did not improve culture viability over 30 months of storage. Inclusion of mannitol in the conservation medium increased microplant survival. Sucrose x mannitol interaction showed that sucrose was effective in enhancing microplant survival in combination with 20 or 40 gl^-1 mannitol, but not with 60 gl^-1 mannitol. Combined effect of sucrose, mannitol and photoperiod showed that optimum microplant growth and maximum culture viability were obtained when the cultures were grown in MS medium containing 40 gl^-1 sucrose and 20 gl^-1 mannitol under 16-h photoperiod. Potato microplants can be conserved in this medium and cultural conditions up to 30 months without subculturing. This revised version was published online in July 2006 with corrections to the Cover Date.