Seed propagation and pest control cultivation technology of Rhododendron Huading

Seed propagation and pest control cultivation technology of Rhododendron Huading

Rhododendron huadingense is a deciduous shrub of rhododendron in the rhododendron family, discovered and named by Mr. Ding Bingyang in 1990 on Tops Of Huading Mountain [1]. The existing resources are only sporadically distributed in Tiantai Huading Mountain, Jinhua North Mountain, Pan'an Dapan Mountain and Ningbo Siming Mountain, which is endemic to Zhejiang Province. Rhododendron Huading has a narrow natural distribution area, a sparse population, serious human damage, and is of great value in phylogenetic research, and has been listed as a key protected wild plant and a protected plant with extremely small populations in Zhejiang Province [2-3]. In addition, Rhododendron Huading blooms in early spring, flowers first and leaves later, and the flowers are colorful, which is of great ornamental development value.

At present, the research on Rhododendron Huading mainly focuses on community characteristics, seed germination characteristics, genetic diversity, pollen activity, and endangerment factors [3-8], while the systematic breeding technology of its seeds has not been reported. In this paper, we summarize a set of seed propagation techniques for Rhododendron Huading, which aims to provide a scientific basis for its population conservation and community structure restoration, and also provide reference for the seed breeding of other alpine Rhododendrons.

1 Characteristics of the cuckoo

Rhododendron is a deciduous shrub. The tree is 1 to 4 m tall, the bark is gray-brown, and the deep longitudinal fissures are deep. The branches were green and hairless. The leaves are papery, often 4 to 5 pieces clustered at the top of the branches, ovate, ovate or oval, sharply pointed at the apex, broadly wedge-shaped or rounded at the base, with fine serrations and coarse margin hairs at the edges. Flowers 2 to 4 clusters form an umbrella-shaped, apical, densely glandular hairs on the peduncle, corolla funnel-shaped, 4.5 to 5.0 cm long, lilac or purple-red, 5 lobes, lobes oval, purple spots at the base of the upper 3 lobes, stamens 10; ovary ovoid, glabrous; capsules ovoid, 10 mm long, 8 mm in diameter, yellow, dark brown when dry. The flowering period is from the end of March to the beginning of April, and the fruiting period is from October to November. The community is mainly distributed in the Huangshan Pine Forest at an altitude of 800-1100 m and the mixed coniferous and broad-leaved forest.

2 Rhododendron huading seed propagation technology

2.1 Seed collection and storage

The seeds were collected from the natural community plants in the Huanghaitian forest area of Ningbo Forest Farm, at an altitude of 850 m, on the southwest slope, where the natural distribution of Rhododendron Huading is relatively concentrated, and the number of fruiting mother trees is large. The harvest takes place from late October to early November each year, when the skin of the capsule changes to a dark yellow or yellowish brown color. The collected seeds are placed in a dry and ventilated place to spread out in a cool shade, after the capsules are dried and cracked, the peel is crushed, the seeds are fully released, and then the peels, stalks and doped dead branches and leaves are removed, the seeds are sieved clean, and the seeds are placed in the gauze to dry and preserve.

2.2 Garden selection

The nursery land should be selected in a place similar to the natural habitat of Huading Rhododendron, with convenient irrigation, certain shade, thick soil, loose soil and good drainage. This nursery is located in the forest farm of Ganzhuling, Simingshan Town, Ningbo City, under the loose forest of Huangshan Mountain at an altitude of 800 m above sea level, with a depression closure of about 75%. The plot has a typical low mountain climate, with four distinct seasons, abundant sunshine, abundant rainfall, and cool summers, with an average temperature of about 24 °C in July and a maximum temperature of no more than 32 °C; a cold winter, an average temperature of -2.0 to 1.0 °C in January; and an average annual temperature of 11.6 to 12.0 °C. The average annual frost-free period is 203 d, the average annual rainfall is about 2 000 mm, and the average annual relative humidity is 83.0%.

2.3 Make a bed on the ground

Under the selected Huangshan pine forest, remove the weeds and vines under the forest in winter, and open the horizontal zone according to the terrain. Plough again before spring sowing, carefully prepare the land, remove weeds, stones, and finely crush the soil. Then make a bed with a width of 1.2 m and a groove between the beds of 25 cm and a depth of 10 cm. Prepare the humus and pine needles under the forest in sync.

2.4 Sowing

2.4.1 Sowing time and seed treatment. The sowing time should be selected after the temperature has risen steadily, and the seedlings in the Siming Mountains should be selected in mid-to-late March. Soaking the seeds in warm water for 24 h before sowing can effectively shorten the germination time.

2.4.2 Sowing methods. First of all, the humus soil under the 5 cm thick and coarse sieve forest is laid on the bed surface, the sowing method adopts strip sowing, the bed surface is opened every 10 cm, the horizontal ditch should be shallow and not deep, the treated seeds are evenly sprinkled in the horizontal ditch, and then covered with humus under the fine sieve forest 5 mm, and finally covered with a layer of clean pine needles, which is appropriate not to expose the bed surface, which can maintain the humidity of the seedbed and effectively prevent the erosion and splashing of the rainwater. Water once, pay attention to keep the bed surface slightly wet in time to replenish water, about 20 days can emerge.

2.5 Seedling management

In the seed germination stage and seedling stage, it is necessary to observe diligently, do not drought and lack of water, watering is mainly spraying, to prevent large water from washing the seedlings out of the bed. Weeding should be carried out regularly at the seedling stage, keep the bed surface clean, and fertilize once a month when the seedlings grow to 4 to 5 cm in the rapid growth stage, and foliar spraying with potassium dihydrogen phosphate + urea should not exceed 0.5%. During the rainy season, broad-spectrum fungicides such as carbendazim should also be sprayed monthly to prevent diseases such as standing blight at the seedling stage. If red spiders and other insect pests are found, insecticides should be sprayed in time.

2.6 Transplantation of seedlings

The seedling growth period is generally from May to October, and can be transplanted after the leaf withers in mid-to-late November or before the germination of new shoots in the second year. The transplanting time should choose a cloudy day with little wind, and the row spacing of the transplanted plants is 20 cm×30 cm, and the seedlings can also be transplanted into the container to cultivate the container seedlings. After transplanting, watering and proper shade can achieve a survival rate of more than 95%.

Habitats have been destroyed and plants have been stolen in large quantities, and the Rhododendron Huading is now endangered. Although some scholars have tried to explain the causes of endangerment in terms of community characteristics, population structure, seed germination, and pollen vigor [2-3, 7-8], they have not been able to draw consistent and effective conclusions. Rhododendron Huading has a high natural fruiting rate, large seed particles, and a germination rate that is not low, which provides good conditions for the seed breeding of Rhododendron Huading. The team has successfully cultivated more than 60,000 Rhododendron huading seedlings through the above seed breeding techniques, which provides sufficient seedling guarantee for the population recovery and development and application of Rhododendron Huading in the later stage.