Heuchera villosa ‘Caramel’, which is native to Mexico, is a perennial of the genus Heuchera in Saxifragaceae (Hosoki and Kajino, 2003). Because of its bright and color-changing leaves, cold resistence, and shade tolerance, H. villosa ‘Caramel’ has been widely used as groundcovers under forests. Heuchera villosa ‘Caramel’ can reproduce by seeds, but the germination is slow and irregular. Vegetative propagation is commonly used, but frequently leads to variety degeneration and low survival rate. For these reasons, the large-scale production of H. villosa ‘Caramel’ is limited.
In vitro propagation approach has contributed significantly to the large-scale plant multiplication (Li et al., 2016; Papafotiou and Martini, 2016; Rout et al., 2006). Although in vitro propagation of Heuchera is still comparatively rare, micropropagation of Heuchera sanguinea Engelm. has been reported (Hosoki and Kajino, 2003; Miura et al., 1995; Stapfer and Heuser, 1986).
Primarily, Stapfer and Heuser (1986) reported micropropagation of H. sanguinea by shoot tip culture on woody plant medium supplemented with 16 mm BA or kinetin. Then, Miura et al. (1995) succeeded in adventitious shoots induction by mature leaves and petioles of H. sanguinea culture on modified MS medium. The optimum hormonal concentrations were 0.19 or 1.9 mm NAA plus 4.4 mm BA for leaves and 0.19 mm NAA plus 0.44 mm or 4.4 mm BA for petioles. The percentage of regenerated shoots was 50% and 80% for leaf and petiole explants, respectively. Afterward, Hosoki and Kajino (2003) also reported successful shoot regeneration from petioles, leaves, and petioles with leaves on the same media as that used by Miura et al. (1995). But petioles or petioles with leaves regenerated more shoots than leaves alone. The highest regenerating rate was 60% in petiole cultures.
So in H. sanguinea, the regeneration rate was lowest in leaf cultures and highest in petioles (Hosoki and Kajino, 2003; Miura et al., 1995), suggesting petioles might be the optimum explants for shoot regeneration of Heuchera. Thus, in our experiments, petioles from the plants of H. villosa ‘Caramel’ were used as explants.
The objective of the study was to evaluate the effect of different growth regulators on in vitro propagation of H. villosa ‘Caramel’.
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