In Vitro Propagation by Axillary Shoot Culture and Somatic Embryogenesis of Daucus carota L. subsp. sativus, ‘Polignano’ Landrace, for Biodiversity Conservation Purposes

Abstract

Carrots are a multi-purpose vegetable; hence, they have become a very popular consumers’ choice, also thanks to their nutritional value with health benefits. Several varieties and landraces exist of carrot (Daucus carota L. ssp. sativus). In Apulia (Italy), for example, a multicolored carrot landrace is present, the Polignano carrot (PC), threatened by the risk of genetic erosion. With the purpose of verifying the possibility of using in vitro culture for ex situ conservation purposes of PC, a rapid and reliable protocol for micropropagation and a highly efficient somatic embryogenesis protocol have been set up. For micropropagation studies, axillary buds from taproot were used as initial explants. Supplementation on basal medium (BM, a Murashige–Skoog modified medium) with low cytokinine (6-benzyladenine, BA, 0.22 μM) dosage was enough to obtain a good multiplication rate, also depending by the PC color. Rooting of proliferated shoots occurred easily in hormone-free medium and acclimatization was successfully reached in 6 weeks. Somatic embryos were formed from embryogenic callus induced by taproot sections placed on 2,4-dichlorophenoxyacetic acid (2,4-D)-added medium. After in vitro conversion in hormone-free medium, somatic embryos were also successfully acclimatized. Both microplants and somatic embryos produced true-to-type taproots (multicolored carrots), demonstrating the suitability of in vitro techniques for biodiversity conservation purposes.