Method for improving nutrient supply of female floral branches of Populus deltoides artificial hybridization

A method for improving nutrient supply of female floral branches of Populus deltoides artificial hybridization, comprising the following steps:

• step 1, cultivation of female floral branch nutrient-supply seedlings, i.e., floral branch inarching rootstocks
• in March of a year before cross pollination, branches of the same year of a hybrid female parent with a same pedigree number are selected to make cuttings, and then cuttage propagation is performed;
• after all seedlings have fallen leaves at end of November, a weakly lignified part of an upper part is cut off, keeping a seedling height of 1.5-2.0 m, and then a seedling container is moved from a field to a greenhouse;
• or for 1-year-old cuttings that are not easy to obtain female floral branch strain, Populus deltoides or P. euramerican poplar with a same genetic relationship or close genetic distance with the female branch strain is selected for cuttage or current year seedlings are transplanted in autumn of 1 year before a floral branch is picked, and the transplanting is completed before seedlings fall leaves;
• after the transplanting, weakly lignified parts of upper parts of the seedlings are truncated, and the number of the transplanted seedlings is 2-3 times the number of hydroponic floral branches, so as to select seedlings with similar thickness of the hydroponic floral branches as rootstocks for grafting;
• step 2, management of the female floral branch nutrient-supply seedlings, i.e., the floral branch grafting rootstocks
• 10-15 days before hydroponics of cross-pollination floral branch, the female floral branch nutrient-supply seedlings are placed in a room with a room temperature of 20° C. and a relative humidity of 50-60%, and gibberellin solution with a concentration of 10-50 mg/L is sprayed on upper parts of the female floral branch nutrient-supply seedlings every 5-7 days until the female floral branch nutrient-supply seedlings are wet, and the spraying is stopped after leaf buds germinate;
• watering with flowerpots, nutrient solution is poured on poplar rootstock growth substrate in the flowerpots, and the nutrient solution is composed of 0.02-0.05% of borax, 0.1-0.2% of superphosphate and 0.05-0.1% of compound urea aqueous solution;
• step 3, hydroponic management of male and female floral branches
• after the leaf buds of the female floral branch nutrient-supply seedlings start to germinate for 2-3 days, the hydroponics of the male floral branches is started;
• after 5-7 days of the hydroponics of the male floral branches, the hydroponics of hybrid female floral branches is started, keeping a room temperature at 20° C. and a relative humidity of 50-60% during the hydroponics;
• step 4, grafting of the hydroponic female floral branches and nutrient-supply seedlings, i.e., inarching rootstocks
• the female flower branches are hydroponically cultured indoors at the room temperature of 20° C. and the relative humidity of 50-60%;
• the female floral branches and the nutrient-supply seedlings are grafted, and the grafting method is an inarching method;
• step 5, after the grafting, management of the nutrient supply of the female floral branches, i.e. the inarching rootstocks
• watering is carried out timely according to moisture status of nutrient-supply seedling substrate every 5-7 days, and the nutrient solution is applied at the same time when the watering;
• and a substrate temperature for rootstock growth is kept at 20-22° C. to facilitate rapid absorption of substrate nutrients by rootstock roots;
• step 6, hydroponic management of the female floral branches after the inarching is completed
• the grafted female floral branches are then placed in a hydroponic container for hydroponics;
• an initial indoor temperature is kept at 20° C. during the day and no less than 5° C. at night, and water is changed every 2-3 days;
• when the temperature rises in a later stage, the water is changed every 1-2 days, and the nutrient solution is added when changing the water;
• and the nutrient solution is sprayed on backs of leaves of the female floral branches;
• wherein in step 3, a container used for the hydroponics of the female floral branches has a diameter of 25-35 cm and a depth of 40-50 cm, a circular water outlet with a diameter of 1.5-2 cm is opened 0.3-0.5 cm on a side of the container away from a bottom of the container, and the circular water outlet is equipped with a cylindrical rubber plug with a length of 3-5 cm;
• wherein in step 6, when changing the water, cuts of the grafted female floral branches are rinsed;
• if the cuts at lower ends of the grafted female floral branches have changed color or even rotted, the cuts are trimmed in time and a hydroponics container is cleaned;
• and oxygen is introduced into hydroponic solution once a day to ensure that there is enough oxygen in the water;
• wherein a soil ball is necessary when the transplanting in step 1, and a diameter of the soil ball is smaller than an inner diameter of a container to be transplanted, meanwhile a height of the soil ball is 6-10 cm lower than the container;
• a bottom and surroundings of the container are filled with turf and soil mixed in a volume ratio of 2:1, and after compaction, roots are irrigated with a mixed solution of 100-150 mg/L of indoleacetic acid and naphthylacetic acid when watering.