Selection and characterization of NaCl tolerant cells from embryogenic cultures of Pennisetum purpureum schum. (Napier grass)

Sodium chloride (salt) tolerant callus was selected from leaf-derived embryogenic callus of Pennisetum purpureum. The tolerant callus was obtained after repeated subculture on medium containing 1.25% NaCl (direct selection), or after gradually increasing salt concentration to 2% during serial subculture (step-wise selection). For both types of callus optimal growth occurred on 0.25% NaCl. Fresh weight to dry weight ratios (FW/DW) decreased in unselected callus grown on high (1.25–2%) salt concentrations, but not in tolerant callus. The callus obtained by direct selection was less sensitive to KCl than unselected callus. After 30–40 weeks under selection, the tolerant callus became necrotic, but healthy callus was recovered from it after transfer to salt-free medium. The callus recovered showed no retention of tolerance and preliminary experiments indicated that plants regenerated from it were more sensitive to salt irrigation than those regenerated from unselected callus.