The study aimed to test the applicability of silver nanoparticles (AgNPs) as a mutagen in chrysanthemum breeding. Therefore, the biochemical activity of leaf explants during in vitro culture; the effectiveness of in vitro adventitious shoots regeneration; genetic and phenotypic variation among ex vitro-cultivated plants in Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Lilac Wonder’ and ‘Richmond’ in response to in vitro application of silver nanoparticles, were analyzed. The research hypothesis assumed that AgNPs, as a chemical mutagen added onto the micropropagation medium, can cause changes at the molecular level in the explant cells, and the emerging variation may be useful in chrysanthemum breeding.
Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Lilac Wonder’ and ‘Richmond’ leaf explants were cultured on the modified Murashige and Skoog (MS) medium supplemented with 0.6 mg L-1 BAP and 2 mg L-1 IAA and treated with silver nanoparticles (AgNPs; spherical; 20 nm-in-diameter size; 0, 50, and 100 mg∙L-1). The biochemical response of leaf explants during three successive weeks of in vitro culture was analyzed. The effectiveness of adventitious organogenesis was evaluated after 10 weeks. Produced shoots were rooted in vitro, acclimatized and cultivated ex vitro in glasshouse. At the full flowering stage chrysanthemums were subjected to phenotype verification. The genotype stability was evaluated using genetic marker systems: randomly amplified polymorphic DNA (RAPD) and start codon targeted polymorphism (SCoT).
AgNPs strongly suppressed the ability of leaf explants to form adventitious shoots and the efficiency of regeneration. The content of metabolites (chlorophyll a, chlorophyll b, total chlorophylls, carotenoids, anthocyanins, phenolic compounds), and the activity of enzymatic antioxidants (superoxide dismutase and guaiacol peroxide) in leaf explants, varied depending on the AgNPs treatment and age of culture. Phenotype variations of ex vitro cultivated chrysanthemums, covering the color and pigment content in the inflorescence, were detected in one 50 mg∙L-1 AgNPs-derived and five 100 mg∙L-1 AgNPs-derived ‘Lilac Wonder’ plants, and were manifested as the color change from pink to burgundy-gold. Stem height, number of leaves, and chlorophyll content in leaves varied depending on the AgNPs treatment and the cultivar analyzed. A significant influence of AgNPs on the genetic variation occurrence during adventitious organogenesis from leaf explants in chrysanthemum was proved.
This research was funded by The National Science Centre (NCN) in Poland, project „Badania nad zastosowaniem nanocząstek srebra w hodowli chryzantemy wielkokwiatowej/Studies on the use of silver nanoparticles in chrysanthemum breeding”, MINIATURA 4, no. DEC-2020/04/X/NZ9/01667 (2020-12-12 – 2021-12-11).
(2022-07-22)
