SINGLE ANDROGENETIC STRUCTURES OF MAIZE (ZEA-MAYS L) FOR THE INITIATION OF HOMOGENEOUS CELL-SUSPENSION AND PROTOPLAST CULTURES

Induction of androgenesis in maize leads to heterogeneous callus types in terms of chromosome number and regeneration ability. In order to o btain homogeneous cell suspensions from androgenetic material we initi ated maize cultures from single microspore-derived structures. Culture s were established either by transfer of previously selected type-II c allus or by transfer of single aggregates directly into suspension med ium. During establishment no selection was performed. Independent susp ension lines were analysed with respect to their chromosome number, th eir embryogenic capacity, and their regeneration ability. Cytological analysis revealed that most of the cultures tested showed a constant c hromosome number over a period of 18 months, indicating a homogeneous constitution Within regenerable lines no difference in embryogenic cap acity could be observed when smaller (1mm) and larger (4mm) aggregates were compared. Furthermore, their homogeneous character was confirmed by the regeneration of only green or albino plants from the individua l lines. Chromosome analysis of regenerants by root tip cytology showe d that their numbers corresponded to that of the suspension they were regenerated from. Similar results showing the homogeneous nature of th e lines were obtained in protoplast culture and regeneration experimen ts.