Figure 1. (a) Onion seed cutting showing mature embryos. (Modified from http://www.botany.hawaii.edu/faculty/webb/Bot201/Angiosperm/onion_embryo_developmentM.htm). (b) Callus from ME of Torrentina variety. (c) Calli after three months cultivation in selection medium. (d) Calli pieces selected after four months in selection medium showing β-glucuronidase expression. Bars represent 1 millimetre.

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