Shoot apical meristem:: In vitro regeneration and morphogenesis in wheat (Triticum aestivum L.)

We report a less genotype-dependent in vitro regeneration system capable of producing multiple shoot clumps and whole plants in four different wheat genotypes. Shoot apical meristems from 7-d-old seedlings produced axillary and adventitious shoots and somatic embryos on media containing N-6-benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D). All four genotypes responded positively to shoot multiplication depending upon media composition. Scanning electron microscopies of cultures showed a proliferating budding state that gave rise to adventitious shoots and somatic embryos on further multiplication. The percentage of relative shoot apical meristem multiplication was 80-90%, and the average number of shoot meristems per multiplied shoot was 40-50 in all genotypes. Among different concentrations of phytohormones, 2 and 4 mg l(-1) BA (8.8 and 17.7 muM) in combination with 0.5 mg l(-1) 2,4-D (2.26 muM) gave the best results. Actively multiplying shoot clumps were recovered with high frequency among 3-mo.-old cultures. These shoot clumps regenerated normally and produced fertile plants containing viable seeds. This in vitro system might prove useful for the production of transgenic plants of wheat in a relatively genotype-independent manner.