TEMPORAL EFFECT OF 2,4-D ON INDUCTION OF EMBRYOGENIC NUCELLAR CULTURES AND SOMATIC EMBRYO DEVELOPMENT OF CARABAO MANGO

Embryogenic nucellar cultures were established on B5 major salts, MS m inor salts and organics, 400 mg/l(-1) glutamine, 60 g/l(-1) sucrose, 2 g/l(-1) gellan gum, and 4.5 mu M 2,4-dichlorophenoxyacetic acid (2,4- D). There was no clear relationship between developmental age of the n ucellar explants and induction of embryogenic cultures. The temporal r equirements for culture initiation and for induction of embryogenic co mpetence from nucellar explants were determined by pulsing the culture s for 0, 7, 14, 21, 28, 35, 42, 49, 56, and 63 d. Culture initiation r equired a minimum 7-14 d pulse with 2,4-D, and was maximum after a 56- d pulse; however, embryogenic competence was optimum after a minimum o f 28 d exposure to 2,4-D. Somatic embryogenesis occurred directly from the nucellar explants at low frequencies. Somatic embryo maturation o nly occurred following plating of suspensions onto semisolid medium, a nd was stimulated by 2.4-4.8 mu M kinetin and 4.4 mu M 6-benzyladenine .