The improvement of Iris pallida propagation by somatic embryogenesis

Iris spp. rhizomes are used in cosmetics and perfumery thanks to the presence of irones, violet-scented ketonic compounds. Between the several Iris species, Iris pallida Lam. is rich in irones and is the most valuable. In Tuscany, the cultivation of I. pallid is an integral part of the rural tradition. The aim of the research is to study the possibility of producing I. pallid plants by micropropagation and to overcome some critical factors of traditional cultivation. This study was based on the induction of somatic embryogenesis from flower buds and from leaf tissues of in vitro plantlets. Results demonstrated that the most suitable factors to begin the induction of embryogenic callus were the medium, a modified MS medium named i1B containing 0.1 mg L-1 Kinetin (Kin) and 1 mg L-1 2,4-dichlorophenoxy acetic acid (2,4-D), and the explant, the petal hafts (the base of the petals) of the flower buds. Another medium, named i1A, containing 1 mg L-1 Kin and 1 mg L-1 2,4-D was the most appropriate for the successive subcultures of the embryogenic callus among the tested ones. To induce and maintain embryo formation, an expression medium, named i2, containing a modified Knudson C macro elements, 1 mg L-1 Kin and 0.1 mg L-1 indole-3-butyric acid (IBA) was efficient. The protocol was subsequently improved with the use of in vitro microplant leaf tissues for the production of embryogenic callus. Transferring the embryos onto a modified MS medium named i3 with 0.1 mg L-1 of 6-benzyladenine (BA) and α-naphthaleneacetic acid (NAA), allowed us to obtain microplants to acclimatize ex vitro. As regards the presence of irones precursors, the HPLC chromatographic profile of the rhizomes from micropropagated I. pallida plants after acclimatization in open field, was comparable to that of rhizomes from mother plants cultivated in the place of origin.