Ferrihydrite nanoparticles as inducers of regeneration of wheat callus culture

Regeneration in isolated tissue culture is a bottleneck in work on cell selection and genetic modification of plants. Ferrihydrite (Fh) nanoparticles (NPs) with high biological activity can stimulate morphogenesis in such systems. The effect of adding of Fh NPs to nutrient media at a concentration of 1 mg/l was analyzed at three stages of development of a wheat callus culture (CC) (induction of callus (IFh), callus proliferation (PFh), organ regeneration (RFh)). Transplanted calli from media with Fh and from control (IFh, IC) were randomly distributed between variants with and without Fh. There was no effect of a single contact with Fh on CC at any stage, in contrast to the cases of double interaction with Fh. Thus, the IFh-PFh samples had a twice as high frequency of formation of chlorophyll-containing regions and a third lower percentage of calli with signs of necrosis than all other variants. The presence of Fh in the induction medium stimulated regeneration on PC and PFh media. Contact with Fh at the proliferation stage increased the frequency of regeneration on the RC medium by 4 times in comparison with PC-RC, and halved the frequency of necrosis under these conditions. The maximum percentage of regenerants was obtained in the IFh-PFh-RC line (45%), slightly less in the IFh-PC-RFh and IC-PFh-RFh (35%). The maximum frequency of necrosis on RC and RFh media was recorded for IC-PC samples. IFh-PFh-RFh had a similar level of necrosis. IFh-PC calli switched to multiple rhysogenesis without any shoot on regeneration media. A low level of necrosis (<40%) was maintained on RFh medium until week 8 for IFh-PC and IC-PFh. Thus, Fh NPs contributed to the formation of highly regenerative callus. Contact with Fh at another stage stimulated the synthesis of chlorophyll and slowed down the tissue senescence. Fh NPs are promising growth regulators for any breeding programs connected with regenerant formation.