Enhanced shoot regeneration in nine Australian wheat cultivars by spermidine and water stress treatments

The regeneration potential of ageing calli initiated from isolated scutella of immature embryos was increased in nine elite Australian cultivars (QT7208, QT9685, QT7709, Kennedy, Lang, Sunvale, Giles, Petrie and Veery) of wheat (Triticum aestivum L.). Firstly, the effects of 4–32 h of dehydration stress on regeneration of 4- to 20-week old calli were evaluated. Cultivars such as Veery, Kennedy and Sunvale showed significant improvement in regeneration from calli up to 12-weeks old that had undergone 16 h of dehydration stress. Secondly, 4- to 20-week old callus cultures were treated with 0.05–5 mM spermidine to evaluate its effect on regeneration. While spermidine had a negative effect on regeneration from 4-week old calli at all tested concentrations (as compared with untreated controls), there was a 3–50% improvement in the regeneration ability of older calli (16- to 20-week old) of all cultivars. Finally, exogenous application of 1 mM spermidine to 16-week old cultures, in combination with 16 h dehydration stress, improved plant regeneration by 10–65% in all nine cultivars.