Cutting propagation is a rapidly propagating and widely used asexual propagation method in fruit tree seedlings. New plants propagated through cuttings can maintain the excellent traits of the mother plant, bloom and bear fruit early, and obtain neat female and male plants according to gender, which is important for the breeding and commercial production of dioecious kiwifruit varieties (strains). practical significance. Currently commonly used methods include hard branch cuttings, green branch cuttings and root cuttings.
(1) Hard branch cuttings
Use lignified annual branches for cuttings. Generally, it can be carried out from after the leaves fall to before germination in the next spring. The specific time depends on the local temperature and cutting conditions (such as the heating of the cutting bed). In most cases, in central my country, it is suitable to do it from mid-to-late February to early to mid-March. If there are insulation facilities (such as hotbeds, greenhouses, greenhouses, etc.), it can be carried out as early as January.
① Preparation of the planting bed. The planting bed for hard branch cuttings should be selected in a leeward and sunny place. There are many types of planting beds, which can be roughly divided into hotbeds and cool beds. The former refers to a hotbed where the temperature and humidity can be controlled within a certain range using facilities such as a greenhouse or greenhouse, while the latter refers to a hotbed at natural temperature.
Preparation of the cooling bed: Level the ground at the selected location. The size of the planting bed depends on the number of cuttings. It is generally 1 to 1.5 cm wide, 25 to 30 cm high or deep, and the length is variable. Choose loose, fertile, well-ventilated sandy loam soil and add an appropriate amount of fine sand, vermiculite, perlite, etc. as the soil mixture matrix. The soil must be disinfected before use. Spray 1 to 2 formalin solutions evenly while spraying. Turn over, then stack, seal with plastic film for about 1 week, remove the cover 3 to 4 days before use, turn, ventilate, and finally flatten as required.
Preparation of hotbed: A hotbed can be built where conditions permit to promote early rooting of cuttings. Currently, electric hotbeds are commonly used. The preparation process is as follows: determine the length of the heating wire and the distance between the wires according to the area of ??the hotbed. A 1000-watt heating wire can be laid in an area of ??10 meters 2 and the temperature can reach 21 to 25°C. First, lay a layer of pebbles, pine needles, straw, etc. at the bottom of the bed as an insulation layer and drainage layer. Spread 3 to 4 cm thick planting soil on top. After leveling, lay out electric hot wires with a spacing of 15 to 20 cm. Then add another layer on top. Spread about 15 cm of plugging soil and connect the heating wire, conductivity thermometer and electronic relay. The conductivity thermometer has a control device and multiple thermometer probes, which are plugged into the bed at different locations, and relays are connected to the 220-volt power supply. Before starting work, adjust the temperature threshold of the conductivity thermometer to 20~25±1℃, and adjust the adjustable transformer to about 180 volts. When the temperature in the bed is lower than the preset value, the automatic control device on the conductivity thermometer starts heating. When the temperature in the bed reaches 25±1℃, the power will be automatically cut off. It needs to be emphasized that safety must be paid attention to when using the electric hot socket.
You can also use biological fermentation hotbeds (such as horse dung, cow dung and other fermentation heat released as hotbed heat sources) for cuttings.
②Selection and treatment of cuttings The selection and storage of cuttings are the same as the selection and storage of scions.
Cutting treatment: Take out the cuttings before cutting and cut them into 10-15 cm long branch segments. Each branch segment has about 3 sections. The lower incision is cut into an inclined plane and the upper incision is above the terminal bud. Cut flat at 1.5cm. Generally, the upper incision is coated with wax and the lower incision is treated with growth regulator. When treated with growth regulators, high-concentration indolebutyric acid (IBA) (5000 mg/kg) is currently commonly used for rapid immersion for 3 to 5 seconds.
③ For cuttings, level the cutting soil and mark lines with a row spacing of 15 to 20 cm. Take the treated cuttings and cut them with a spacing of 10 to 15 cm. The insertion depth is 2/3 of the total length of the cuttings. Can be inserted straight or diagonally. Depending on the looseness of the soil, you can insert it directly or use a shovel to dig a trench before inserting it. After inserting, compact the bed soil with your hands and then spray it with water.
④Post-insertion management After insertion, special attention should be paid to the temperature of the soil and the temperature of the air on the bed surface. In the early stage of cutting, the temperature is low, the cuttings have not yet germinated, and the water demand is small, so the water supply should not be too much at this time. Generally, watering once every 7 to 10 days is sufficient.
After budding and sprouting, water consumption increases rapidly, and the water supply should also be increased. Water it once every 2 to 3 days on sunny days. While maintaining the appropriate humidity of the inserted soil, the relative humidity of the air in the bed should be increased to reduce the leaf surface. Evaporation. In practice, the stability of relative humidity is mainly maintained by covering the planting bed with film or plastic sheds. If an electric hotbed is used, the temperature should be kept at 20-25°C in the early stage of cutting. After most of the cuttings have taken root, stop increasing the temperature.
In terms of light, it depends on the weather conditions. Shade on sunny days to avoid sun exposure, and appropriate light at other times is beneficial to growth.
When the new shoots grow to 2 to 3 centimeters, they should be pinched in time and 2 to 3 leaves should be retained to reduce transpiration and promote rooting and survival. When most of the root system of the seedlings reaches more than 10 cm, the seedlings can be transplanted at a density of 30 cm x 30 cm. Water thoroughly after planting. Note that this is usually done on a cloudy day or in the evening after rain, and should be properly shaded. After survival, promptly set up pillars, weed, loosen soil, and topdress to promote vigorous growth of the seedlings.
(2) Green branch cuttings
Green branch cuttings are made by using the semi-lignified new shoots of kiwi fruit in that year, also called "twig cuttings". Using green branches for cuttings has high cell differentiation ability, rapid callus formation, and high cutting survival rate.
The appropriate period for cutting is after the first growth peak of the new shoots. The branches are more substantial at this time and have more nutrients. In central my country, this period is around early or mid-June. The selection and handling of green branch cuttings are very important. Experience shows that choosing semi-lignified branches with substantial growth, dark green leaves or thick leaves, and no disease will take root easily and have a high survival rate. It is best to collect cuttings on a cloudy day or in the morning on a sunny day. At this time, the water content of the branches is high, the air is cool, and the transpiration effect is weak. It is required to collect cuttings and handle them as needed. Generally, 2 to 3 nodes are left on the cuttings, 10 to 12 cm long. The base of the node is flattened diagonally on the opposite side of the axillary bud, and the upper part is cut flat 3 cm away from the node. 1 to 2 leaves are left on the cutting. In order to reduce transpiration, the leaves are You can leave only half of it; treat the base of the cut cuttings with auxin or make longitudinal wounds at the base deep into the wood, and then treat it with auxin. Commonly used auxins and their concentrations and times are IBA or NAA 200-500 mg/kg for 3 hours, ABT rooting powder 500-800 mg/kg for 5-10 seconds, IBA 3-5 g/L for quick dipping. After this treatment, insert the cuttings into the inserting bed immediately (the requirements for the inserting bed and the cutting operation are the same as for hard branch cuttings).
The management requirements after green branch cuttings are very strict. The cuttings must be kept from drying out, rotting, and falling leaves, and the photosynthetic capacity of the leaves must be maintained. Therefore, appropriate humidity must be controlled in moisture management. In addition to shading, bamboo arc-shaped supports must be set up and covered with plastic films to keep the humidity above 90%, the soil temperature around 25°C, and atomized water spraying several times a day to keep the leaves moist and not wilted. The bed soil should be moist without water accumulation and maintain good air permeability; if the temperature of the bed soil is high, use watering or spraying water to cool down, or uncover both ends of the film to ventilate and cool down, so that the temperature is controlled below 30°C. According to experimental observations, if the cuttings are well managed, callus will form in about 10 days, and roots will begin in about 20 days. The general survival rate is about 50, and the highest can be as high as 97.
(3) Root cutting propagation
Use the residual roots left in the soil when seedlings, tissue culture seedlings or seedlings emerge from the nursery in late autumn or early spring. The root system of kiwi fruit is fleshy, rich in nutrients and water. Cuttings are easy to survive and have a high germination rate.
Use the remaining root segments in the garden or the root segments cut when the seedlings emerge from the nursery. Select a thickness of about 0.5 cm, cut the root segments to a length of about 10 cm, and tie them into small bundles of sand according to species, strains, and strains. Hide and take out the cuttings from February to March the following spring.
The cutting bed preparation is the same as for hardwood cuttings. Cut the upper end of the root segment flat and the lower end diagonally. Cuttings can be made at a density of 10 to 15 cm x 20 to 30 cm. They can be inserted straight, diagonally or buried flat. Pay attention to the upper end pointing upward (the thicker end is the upper end), the cutting level is flush with the ground or 0.5 cm higher than the inserting bed, and the depth of flat burial is 2 to 3 cm. After planting, water enough and cover with straw and other straw. If possible, set up a small shed to maintain temperature and humidity to promote rooting and germination. In terms of management, keep the bed surface moist, but not too dry or too wet.
Generally, new roots and adventitious buds can be produced in 30 to 40 days; branches and leaves can be produced in 50 to 60 days. Select a strong growth among all the sprouting branches and wipe out the rest as soon as possible. Because it is easier to produce new roots, auxin treatment is generally not used in the production of root cuttings. After careful management, most of them can be grafted or released from the nursery in the summer or autumn of that year.
No matter which of the above types of cutting propagation (hard branch cuttings, green branch cuttings, root cuttings) takes root and survives, transplanting must be done as soon as possible, and the seedling border must be prepared in advance. Dig the transplanting hole (cm x 30 cm), apply manure and mix it with the soil. When transplanting, cut the overly long root system short, leaving 10 to 15 cm. The transplanting depth is equivalent to the depth of the cutting, not too deep or too shallow. Water it immediately after planting. After the water seeps down, seal the hole. Keep it moist. In the future, pay attention to shading, irrigation, setting up pillars and fertilizing outside the roots to promote the growth of seedlings.