Plant regeneration through callus initiation from thin mature embryo fragments of wheat

A wheat regeneration system was developed using mature embryos. Embryos were removed from surface-sterilised mature caryopses (winter wheat Odeon cultivar and spring wheat Minaret cultivar) and ground to pieces through a sterile nylon mesh. The fragments were characterised by means of the image analysis technique. They were 500 muM mean diameter and most of them were elongated. They were used as explants to initiate embryogenic calli on solid medium supplemented with 10 muM 2,4-dichlorophenoxyacetic acid. The morphogenic pathway of the initiated calli was followed for a 40-day culture period. Active cellular division occurred within 24 hours of cultivation. Several hundred calli were produced from 100 fragmented embryos within 3 days. A 90% callus induction rate was achieved and proembryos appeared by the 8th day of culture. The highest embryogenic calli induction rate of 47% was obtained when 2,4-dichlorophenoxyacetic acid was suppressed after a 3-4 week induction period. Two regeneration methods were finally compared. A total of 513 plantlets were produced. The optimal protocol produced 25-30 plants per 100 embryos. This regeneration method may be suitable for transformation applications.