Preliminary Study: Micropropagation Using Five Types of Chelated Iron and the Subsequent Acclimation of Blue Honeysuckle (Lonicera caerulea var. kamtschatica Sevast.)

Abstract

Blue honeysuckle (Lonicera caerulea var. kamtschatica Sevast.) is a valuable berry crop with a unique biochemical composition. It is rich in vitamins, minerals, and biologically active substances. Different species and cultivars of honeysuckle require different cultivation conditions in the field of accelerated reproduction in vitro. Taking into account the high clonal replication potential of the plant, we conducted research on the chelated-iron form’s influence on the micropropagation productivity of the blue honeysuckle “Lulia” cultivar at the multiplication, rooting, and subsequent acclimatization stages of microplants. In a preliminary study, five types of iron chelates were tested with carboxyl- and phosphorus-containing ligands: Fe(III)-EDTA, Fe(III)-DTPA, Fe(III)-EDDHA, Fe(III)-HEDP, and Fe(II)-HEDP. Each type of iron chelate was applied at four concentrations: standard, decreased by 2 times, and increased by 1.5 times and 2 times in the basic Murashige and Skoog (MS) nutrient medium. It was found that the blue honeysuckle “Lulia” had a selectivity to the type of iron chelate that was used. The nutrient-medium modifications with iron chelates, which caused the plant response, contributed to a significant improvement in the plant’s physiological status and increased its survival rate during the microplant’s acclimation to the nonsterile conditions stage. At the rooting stage, an increase in the rooting rate of up to 100% (Fe (III)-EDDHA), an increase in the number of shoots by 1.5–2 times, and an increase in the number of roots by 1.4–1.9 times were observed. The positive effect of the iron’s chelated forms was also observed at the acclimation stage. According to the results of the research, the most suitable iron forms for clonal micropropagation of blue honeysuckle were carboxyl-containing Fe(III)-EDDHA and phosphonate-containing Fe(II)-HEDP. Moreover, the effectiveness of both complexonates was confirmed in a wide concentration range: Fe(III)-EDDHA from (×1.0) to (×2.0), and Fe(II)-HEDP from (×0.5) up to (×1.5).

Plant Growth Regulation in Cell and Tissue Culture In Vitro

“…The optimal concentration of iron in the medium is 70–100 µM, in the form of iron(II) sulfate heptahydrate (FeSO 4 ·7H 2 O), a commonly used salt. However, Fe is not soluble and is rarely accessible to plants; therefore, it is used more effectively in a Fe chelate form, as ferric ethylenediaminetetraacetic acid (FeEDTA) chelated from FeSO 4 , or in a directly chelated form, as ethylenediamine di-2-hydroxyphenyl acetate ferric (FeEDDHA), among others [ 54 ]. The chelated form FeEDDHA is more stable at different pH levels and has shown relevant results for different species evaluated, including date palm [ 55 ], walnut [ 56 ], and hazelnut [ 57 ].…”

Plant Regeneration via Somatic Embryogenesis and Indirect Organogenesis in Blue Honeysuckle (Lonicera caerulea L.)

“…After the first study that focused on shoot proliferation of blue honeysuckle (L. caerulea and L. caerulea var. edulis) [24], subsequent research studies have demonstrated the micropropagation efficiency of blue honeysuckle is influenced by genotypes [25], base medium compositions (MS, 3/4 MS, 1/4 MS, and MS supplemented with wheat starch) [24,[26][27][28], plant growth regulators (6-BA and thidiazuron + IAA) [25,29], chelated irons (FeNaEDDHA, Fe(III)-EDTA, Fe(III)-DTPA, Fe(III)-EDDHA, Fe(III)-HEDP, and Fe(II)-HEDP) [27,28], and culture temperatures [24]. To the best of our knowledge, there have been no reports about plant regeneration through the ISE pathway on blue honeysuckle.…”