Adventitious shoot regeneration from in vitro leaves of Aronia mitschurinii and cotyledons of closely related Pyrinae taxa

The objective of this study was to develop an in vitro shoot regeneration procedure and to evaluate the frequency of adventitious shoot regeneration from: (1) in vitro leaves of a commercial cultivar of Aronia mitschurinii on various media treatments; (2) cotyledons of closely related Pyrinae taxa; and (3) 21 wild Aronia genotypes. Optimum regeneration of leaf explants occurred when they were wounded with two transverse cuts along the midrib and placed on Murashige and Skoog (MS) basal media containing 5 μM indole-3-butyric acid (IBA) and 10 μM thidiazuron (TDZ). TDZ was more effective than 6-benzylaminopurine (BAP) as a cytokinin, and IBA was more effective than the no auxin control, 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-naphthaleneacetic acid (NAA). Regeneration from cotyledons of seven Pyrinae taxa was evaluated using 10 μM BAP in combination with 0.1, 1 and 5 μM NAA. Adventitious shoot formation for A. melanocarpa and P. communis responded best to 1 μM NAA, whereas all other taxa formed a greater number of adventitious shoots on 5 μM NAA. A. mitschurinii cotyledon explants produced a significantly greater number of shoots compared with in vitro leaf explants. The number of shoots forming per cotyledon explant and the percent of explants forming shoots were both significantly different among the 21 Aronia genotypes. Significant differences were observed between the six Aronia taxonomic groups for the number of shoots forming per explant. Diploid and tetraploid Aronia genotypes produced a significantly greater number of shoots per explant than did triploid genotypes. Regenerated shoots were rooted in vitro and plants grew normally in the greenhouse. These results will be useful for future studies using leaf and cotyledon explants for genetic transformation, genome editing and mutation breeding with Aronia and related taxa.