COMPARATIVE-ANALYSIS OF CALLUS FORMATION AND REGENERATION ON CULTUREDIMMATURE MAIZE EMBRYOS OF THE INBRED LINES A188 AND A632

Induction, maintenance, differentiation and embryogenic capacity of ca llus obtained from immature embryos by culture on induction medium, pr oliferation medium, maturation medium and regeneration medium, respect ively, were compared for two inbred lines of maize, i.e. A188 and A632 . The callus of inbred line A188 was embryogenic and maintained embryo genic capacity for at least 1 year. Immature embryos of inbred line A6 32 formed callus that was not embryogenic. It only produced roots. Whe n sucrose was replaced by sorbitol to induce or improve embryogenesis, again only A188 formed embryogenic callus. Subculture of this callus, however, allowed 4 week intervals in stead of 2 week intervals withou t loss of embryogenic capacity. When A188 was pollinated with A632 pol len, embryogenic callus was obtained from cultured immature ''F-1'' em bryos, showing that embryogenic capacity was inherited, maternally. Th e callus did not differ from the embryogenic callus generated on selfe d A188 embryos. When A632 was pollinated with A188 pollen, embryogenic callus was obtained too, showing that embryogenic capacity was also i nherited paternally, though the embryogenic capacity diminished quickl y, and the stability of the callus was lower than in the reciprocal cr oss.