Abstract
The specificities of tissue culture of wheat greatly limit the use of chloroplast transformation technologies in this crop. One limitation in wheat tissue culture is that it is difficult to regenerate plantlets from leaf tissue explants of regenerated plantlets, resulting in difficulty in obtaining homoplastic plants via multiple rounds of antibiotic selection of chloroplast transformants. Thus, a repeated in vitro regeneration system from leaf tissues was studied in this research. Our results showed that 2 mm leaf basal segments of the 4 cm high leaves from regenerated plantlets can give the best callus induction at present study. The best callus induction medium was Murashige and Skoog (MS) basal medium supplemented with 2 mg/L 2,4-dichlorophenoxyacetic acid and 1 mg/L naphthalenacetic acid, which gave a callus induction rate of up to 87.2%. The optimal differentiation medium was MS basal medium supplemented with 10 mg/L silver nitrate and 1 mg/L 2,3,5-triiodobenzoic acid, which gave a regeneration rate up to 33.7% for the wheat lines tested. This is the first report showing that leaf basal segments of in vitro regenerated plantlets can be used for regeneration of wheat. The establishment of a repetitive regeneration system should pave the way for the development of chloroplast transformation and the plant regeneration systems starting from leaf material of in vitro regenerated wheat and other cereal crops.
Highlights
For wheat (Triticum aestivum) and other cereal crops, regenerated plants from tissue culture have mainly been from calli derived from immature embryos or inflorescences
The three concentrations of naphthalenacetic acid (NAA) caused signifycantly different callus induction rates. These results suggested that the growth regulator NAA was a key factor for callus induction from leaf basal tissues (Table 1)
Immature embryos or inflorescences of cereal crops are usually used as the starting material in their tissue culture and transgenic research
Summary
Regenerated plants from tissue culture have mainly been from calli derived from immature embryos or inflorescences. Leaf basal segments of seedling have frequently consisted of mixed tissues including leaf tissue and other tissues, usually coleoptile tissue [1] It is not clear whether the regenerated plants were only from leaf tissues or not. The green leaf tissues of in vitro regenerated plantlets, not seedlings, were used as explants in wheat tissue culture and a repeatable wheat regeneration from leaf to leaf was accomplished. This method will be of importance for plastid transformation of graminaceous species and for improved plant regeneration systems starting from in vitro produced leaf material
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