How could an in vitro propagation system for Alstroemeria be established using plant hormones?

Growth of in vitro cultures can be managed accurately by plant hormones. Alstroemeria is a popular cut flower grown from rhizomes. Varieties change frequently on the market and plant breeders depend on quick techniques to promote and propagate new cultivars in time. Read the paper indicated below and discuss how an in vitro propagation system might be established by using plant hormones.

The paper Micropropagation of Alstromeria x hyprida ‘Juanita’ shows the results of a study about the effects of auxins, cytokinins and growth retardant on the growth patterns of Alstroemeria. The study had been carried out in order to find a way to increase the efficiency of in vitro micropropagation of Alstroemeria.

Since Alstroemeria is grown from rhizomes, the aim was to obtain a high amount of branched and easy-to-root rhizomes containing numerous, short generative shoots. The experiments with different concentrations of auxins or cytokinins alone or combined with a growth retardant should demonstrate, from which method these quality characteristics will result.

The results show, that an application of the cytokine BAP at a high concentration is not advisable because the rooting ability of the rhizomes becomes poor. Also the combination of BAP at a low concentration with kinetin or 2iP did not stand the test. However, a low concentration of BAP together with paclobutrazol or flurprimidol resulted in a high number of aerial shoots, the reduction of their length and a high rooting ability of the rhizomes.

Therefore, (according to Fig. 2) this is the application that could be suggested: 1.5 mg/l BAP + 0.1 mg/l flurprimidol and a basic medium (BM).

If the auxin NAA was added to the medium, an application of paclobutrazol or flurprimidol had a positive effect on the number of roots per rhizome and suppressed areal shoot and root elongation. This effect was though reversed, if BAP was added in addition to one of the growth retardants (paclobutrazol or flurprimidol).

So this is a possibility to stimulate rhizome rooting while inhibiting the root and areal shoot elongation: Medium containing 1mg/l NAA + 0.1 mg/l paclobutrazol.

Nevertheless, the results do not show here, whether this combination increases the number of aerial shoots per rhizome. So if there is a need to increase aerial shoot growth, the first possibility should be chosen. 

Original paper:
Micropropagation of Alstromeria Hybrida ‘Juanita’: http://www.actahort.org/members/showpdf?booknrarnr=447_32