In Vitro Micropropagation of Kale (<i>Brassica oleracea</i> var. <i>sabellica</i> L.)

In vitro micropropagation is used to rapidly shorten the breeding process of crops, such as kale, an internationally widespread winter vegetable. The aim of this study is to develop optimised micropropagation protocols for three kale varieties. First, it was determined which seed surface disinfection method resulted in the highest germination rate and the lowest infection rate. Secondly, it was investigated which of several existing <i>Brassica</i> protocols and one modified protocol from the literature provided the highest regeneration efficiency of kale explant types (cotyledons, hypocotyl, root, and intact seedlings as the control) after eight weeks of cultivation. Germination was highest and fastest after disinfection with 10% NaClO for 10 min for “Frostara” and at 5% for 2.5 min for “Schatteburg”. The infection rate and speed were lowest in treatments with 10% NaClO. The regeneration efficiency and number of newly formed leaves, roots, shoots, and stems varied between media, explant type, and kale variety. Most new leaves and shoots were formed when hypocotyls were used as explant type. Roots regenerated mostly more roots than shoots, stems, and leaves. A higher ratio of auxin to cytokinin in the culture medium partially increased leaf regeneration. The addition of AgNO₃ increased shoot regeneration and reduced yellowing and leaf drop. Phenotypic anomalies occurred less frequently in media with lower hormone concentrations. All tested protocols are suitable for kale micropropagation, but regeneration was highly dependent on the medium for different varieties and explant types. Therefore, this study builds a basis for future micropropagation of kale and the development of variety-specific protocols for maximum commercial success.