Detailed Explanation of Rhododendron Tissue Culture and Cultivation Management Techniques

As a high-grade ornamental flower, rhododendron is not easy to propagate and grow in North China. This is mainly because most of the soil in North China is alkaline, while rhododendrons prefer typical acidic soil, thus making propagation and planting somewhat difficult, and they can only be grown as greenhouse flowers. Rhododendron propagation methods include seed sowing, cuttings, layering and grafting, and tissue culture. Tissue culture does not require seeds; it only needs the stem tips of the current year's branches of the rhododendron. In a very short time, a large number of small rhododendron seedlings can be cultured in test tubes, and it is not restricted by season; rhododendron seedlings can also be cultivated in winter.

Method: First, take the terminal buds of the current year's young branches of the rhododendron, rinse them under running tap water for 5 min, then place them in a beaker, pour in washing solution, add an appropriate amount of water, stir with a small brush, repeat 2 times, then rinse clean with clean water. Place the cleaned stem tips into 75% alcohol and soak for 1 min, rinse 4 to 5 times with sterile water in a sterile ultra-clean workbench, then soak in 0.1% mercuric chloride for 3 min, then rinse 4 to 5 times with sterile water, and finally inoculate onto the differentiation medium. The differentiation medium is modified MS medium, in which KI is removed and the ratio of NH4+ to NO3- is adjusted from the original 1:2 to 1:1, with a pH value between 5.0 and 6.5.

MS (modified) + 6BA 1.0-2.0 (mg/l) + NAA (0.1-0.5 mg/l)

After 1 month, clustered buds differentiate on the stem tips. After 20 d, they grow into clustered shoots. Cut off the clustered buds and inoculate them onto rooting medium. After 15 d, white young roots form; after 20 d, the roots are 2-3 cm long. The rooting medium is:

MS + IBA 1.0-2.0 mg/l + NAA 0.1-0.5 mg/l. When the small rhododendron seedlings have grown in test tubes for 20 d and the roots are about 2-3 cm long, the test-tube plantlets can be moved into a greenhouse for hardening, so that the test-tube plantlets adapt to the external environment. After the test-tube plantlets have been hardened in the field for about 4-5 d, gently take the small rhododendron seedlings out of the test tubes and place them in a carbendazim solution with a water temperature of 25°C, a pH value of 5.0, and a 0.1% solution to rinse off the agar on the fine roots.

Then plant them in a mixed soil of humus soil, moss, and mountain soil at a ratio of 2:1:7. When potting in a greenhouse, attention should be paid to drainage, watering, misting, and other work. The small seedlings transplanted out on the same day should be fertilized once. When fertilizing, note that it is better to apply light fertilizer than heavy fertilizer, because rhododendron roots are extremely fine, and heavy fertilizer can easily cause root rot. In the Heze area, the water is mostly alkaline, so alum fertilizer water should be applied at appropriate times. Alum fertilizer water is prepared with 3 kg ferrous sulfate, 5 kg sesame oil residue, 5 kg soybean cake, and 200 kg water. It must be thoroughly decomposed before being diluted and used for watering. After the rhododendron blooms, appropriately increase nitrogen fertilizer, and in summer provide appropriate shading.