Jiangtao Hu

Strawberry (Fragaria × ananassa Duch.) can be easily propagated with daughter plants or through crown division, which are developed from the axillary bud at the axils of leaves. This study was conducted to investigate the effects of different cytokinins, auxins, and their combinations on the axillary bud growth in strawberry. Four cytokinins (6-benzyladenine, kinetin, zeatin, and thidiazuron (TDZ)) and three auxins (indole-3-acetic acid, indole-3-butyric acid, and naphthaleneacetic acid) at a concentration of 50 mg·L⁻¹ were sprayed on the leaves three times in 10-day intervals. The expression levels of cytokinin, auxin, and meristem-related genes in the crowns were also investigated. The results showed that TDZ was the most effective hormone for the axillary bud growth, and also promoted plant growth. However, chlorophyll, soluble sugar, and starch contents in the leaves were lower after TDZ. TDZ activated the cytokinin signal transduction pathway, while repressing the auxin synthesis genes. Several meristem-related transcription factors were upregulated, which might be essential for the growth of the axillary buds. These results suggested that TDZ can improve the cultivation of strawberry, while further research is needed to explain the effect on phytochemistry.

The beneficial effects that silicon (Si) has on plant growth as well as resistance to biotic and abiotic stresses have been well documented for many crops in recent years. However, few studies focus on the effects of Si on plant growth during the propagation stage of strawberry (Fragaria × ananassa, Duchesne). This study was conducted to investigate the optimal method for Si application during the cutting propagation of strawberry in soilless cultivation. Strawberry mother plants were supplied with Si through foliar spray, runner spray, or root drench before the cutting propagation, then half of the daughter plants in each treatment received continued Si supply through foliar spray or through root drench after the cutting propagation. The results showed that the plant height, petiole length and diameter, leaf length and width, shoot fresh and dry weights, and root fresh and dry weights were significantly increased by Si root drench both before and after the cutting propagation. Moreover, plants absorbed more Si by drench than by spray, and the absorbed Si was only able to be transported from the root to the shoot, and from the mother plant to the daughter plant. Further research found that the chlorophyll fluorescence parameter of the maximum quantum efficiency of the photosystem II (Fv/Fm) and the activities of superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase were also enhanced while catalase did not change under a high temperature stress in strawberry treated with Si before and after cutting propagation by root drench. Thus, Si application by drenching the roots during the whole propagation period is recommended to increase the quality of the strawberry daughter plants in soilless cultivation.