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Biotization of encapsulated in vitro derived propagules of Carrizo Citrange

Germana, Maria A., Maurizio, Micheli, Chiancone, Benedetta, Bianco, Carmen, Casales, Fabrizio G., Defez, Roberto
Acta horticulturae 2015 no.1065 pp. 663-669
Citroncirus webberi, Citrus, Citrus tristeza virus, Poncirus trifoliata, Sinorhizobium meliloti, artificial seeds, calcium alginate, developmental stages, encapsulation, fungi, hands, indole acetic acid, micropropagation, plant growth-promoting rhizobacteria, plantlets, rooting, rootstocks, seeds, shoots, somatic embryos, sowing, tissues
The encapsulation technology represents a new tool to integrate micropropagation into the nursery activity. It allows combining the advantages of zygotic or gamic seeds with those of micropropagation. The synthetic or artificial seeds have been defined as “artificially encapsulated somatic embryos, shoots or other tissues which can be used for sowing under in vitro or ex vitro conditions”. This will be a powerful propagation tool in the nurseryman hands, if the levels of the synthetic seeds conversion can be increased also in the nurseries, without the asepsis of in vitro laboratories and with the presence of many parasitic microorganisms, like bacteria and fungi, responsible for contamination and/or for trophic competition. This research was carried out in order to apply biotization into the synthetic seed technology of Carrizo citrange [C. sinensis (L.) Osb. × Poncirus trifoliate (L.) Raf.], one most extensively used citrus rootstock, because of its resistance to the Citrus tristeza virus (CTV). With this goal, preliminary experiments to set up protocols for biotization, through the introduction of Plant Growth Promoting Bacteria (PGPB) into calcium alginate capsules of Carrizo citrange in vitro-derived microcuttings, were carried out, in order to protect the plantlets from abiotic and biotic factors and to promote their growth during the first stages of development. Specifically, the Sinorhizobium meliloti wild type strain 1021 and its derivative RD64, that synthesizes 80-fold more IAA as compared to the wild type strain, was used to evaluate their performance in inducing rooting of encapsulated microcuttings.