Method for improving cross efficiency and parent seed setting rate of sweet potato in northern region

Abstract

The present application relates to sweet potato cultivation technical field, specifically to a kind of method for improving sweet potato hybridization efficiency and parent seed setting rate in northern region: S1, site selection builds shed and pool;S2, preferred parent, cultivation and direct sowing, need to create adversity artificially, according to weather condition and soil moisture content, create drought stress treatment and dark treatment stress, control stem growth rate, timely induce flowering;S4, apply phosphorus and potassium fertilizer;S5, early determination of parent combination seed setting;S6, cluster hybridization pollination;S7, picking, dry preservation.This method is simple in operation, and the amount of labor is small, and the parent transplanting survival rate is high, the flowering quantity is more and the seed setting rate is high, has strong replicability and universal applicability, will greatly promote the efficiency of sweet potato seed production in northern China, and lays a solid foundation for sweet potato breeding work.

Description

TECHNICAL FIELD

[0001] The application relates to a method for improving the hybridization efficiency and parent seed setting rate of sweet potatoes in northern areas and belongs to the technical field of sweet potato cultivation. BACKGROUND

[0002] Sweet potato (pomoea batatas L.) is also known as red potato, sweet potato and sweet potato, belongs to the Convolvulaceae family, is the fourth largest food crop in China, and is inferior to rice, wheat and corn. According to the statistics of FAO, the planting area of sweet potato in China accounts for 36.5% of the world in 2017, and the total output accounts for 63.84% of the world. With the adjustment of the structure of planting industry and the improvement of people's living standards, sweet potato plays an increasingly important role in people's life and diet.

[0003] Sweet potato is a short-day crop and likes warm and is not cold-resistant. Existing research shows that sexual hybridization by traditional free pollination is the main means for cultivating new sweet potato varieties in China at present. The method mainly uses Brazilian morning glory, yingluo and the like as stock, uses parent sweet potato as scion, uses the split grafting method for grafting, is transferred into a hybridization pot after survival, and starts hybridization pollination after flowering. Except for individual varieties, sweet potato cannot flower under natural conditions in northern areas of China, and therefore, inducing sweet potato parent to flower is a necessary condition for hybridization pollination of sweet potato in northern areas of China. The traditional hybridization pollination method is to control the length of day and the high and low temperature of the hybridization pot by moving the hybridization pot in and out of the dark room. However, the light and temperature control links such as parent grafting and pot moving require a large amount of time and labor, and the high temperature and rain in summer and the frequent frost in autumn in northern areas of China greatly affect the flowering quality of sweet potato and reduce the work efficiency of hybridization pollination. In addition, the genetic basis of sweet potato is complex and the seed separation degree is high, and the phenomena of self-sterility and extremely low seed setting rate of hybridization between varieties are common, which further affect and limit the efficiency of sweet potato seed production in northern areas. SUMMARY

[0004] The application provides a method for improving the hybridization efficiency of sweet potato in northern areas, and has the advantages of simple operation, small labor intensity, high survival rate of parent transplanting, high flowering quantity and high seed setting rate, strong replicability and universal applicability, and can greatly promote the efficiency of sweet potato seed production in northern areas of China and lay a solid foundation for sweet potato breeding.

[0005] The technical scheme for solving the above technical problems is as follows: a method for improving the hybridization efficiency and parent seed setting rate of sweet potato in northern areas, the method comprises the following steps:

[0006] S1, site selection, shed construction and pool construction

[0007] The plastic greenhouse frame is selected, and the insect-proof net, the ordinary sunshade net, the high-density sunshade net and the drip-free transparent plastic film are sequentially laid from inside to outside, and the hybridization pool is arranged in the greenhouse; wherein the ordinary sunshade net is 3-4 needles, and the high-density sunshade net is 8-10 needles;

[0008] S2, selecting the best parent, strengthening and directly planting

[0009] S2.1 parent selection: according to the breeding target, the parent materials with complementary advantages are selected, specifically, based on high yield, taking high starch, high anthocyanin or high carotene type sweet potato varieties as the target, and considering short vine, early maturity, germination, storage resistance or disease resistance (one or more of root rot, black spot or soft rot) and other advantages.

[0010] S2.2 seedling raising: the parent seed potatoes are put into the spring shed for seedling raising, and then the seedlings are raised, and after the seedling raising is completed, the healthy high pruning seedlings are harvested;

[0011] S2.3 ridging, soil moistening and direct planting;

[0012] S3, artificially creating adversity

[0013] After the sweet potato seedlings are cured, a conical frame is built around the sweet potato seedlings, drought stress treatment and dark treatment stress are created according to the weather conditions and soil moisture content, the stem vine growth rate is controlled, and flowering is induced in time;

[0014] Among them, the dark treatment stress is 30-40 days after the sweet potato seedlings are transplanted, and the above-ground part of the sweet potato seedlings is 40-60 cm long, the sweet potato seedlings in the greenhouse are subjected to dark treatment stress, so that the light time of the sweet potato seedlings in the greenhouse is 8-9h per day, and the temperature in the greenhouse is 20-28℃;

[0015] S4, applying phosphorus and potassium fertilizer

[0016] S5, early determination of seed setting of parent combination

[0017] According to the breeding target, the parent combination mode is determined, the number of pollination flowers of the hybrid parent combination is evenly distributed according to the number of flowers, and early pollination is performed, and the compatibility between parents is predicted according to the number of seed setting and the seed setting rate of the parent combination;

[0018] S6, cluster hybridization pollination

[0019] During the flowering period of the parents, according to the compatibility between the parents determined in S5, pollination is performed;

[0020] S7, picking, drying and preservation

[0021] After the hybrid parent fruit matures, it is picked in time and stored in a cool and dry place. Specifically, the capsule is generally yellow about 35 days after pollination, and then gradually turns brown. When more than 1 / 3 of the capsule handle near the capsule is brown, it means that the seed is close to complete maturity. Collect all the capsules of the same parent into a bag and label them well. Choose a well-ventilated and dry place, and naturally air dry the capsules with the handle for about 7-10 days. When the capsule handle is dry and easy to crack, rub and sieve the honest and full seeds from the capsule, and then repackage them in a kraft paper bag and store them in a cool and dry place.

[0022] Further, in step S2.2, 30-35 days before transplanting, the parent seed potato is placed in a springhouse for seedling. When the sweet potato seedlings grow to 15-17 cm, stop watering. According to the transplanting plan, the seedlings are hardened off in advance. The hardening-off method is as follows: 4-5 days before transplanting, gradually open the greenhouse for ventilation and cooling during the day. The greenhouse ventilation opening can be opened all day and night 2-3 days before transplanting, except in extreme weather. Ensure that the temperature in the seedling greenhouse is reduced to 20-22°C, and the soil moisture content is less than 20%. The sweet potato seedlings are bent around the fingers and are not easy to break, which is considered to be hardened off.

[0023] Further, in step S2.2, the cutting method of the healthy high-cut seedling is as follows: when the sweet potato seedlings grow to 25-28 cm, select healthy sweet potato seedlings with a stem diameter of more than 0.5 cm. Use sterilized and disinfected scissors to cut the sweet potato seedlings at least 5 cm above the base of the seedbed. The length of the obtained seedlings is 20-23 cm, which is considered to be a healthy high-cut seedling.

[0024] Further, in step S2.3, the method of ridging, soil moistening and direct planting is as follows: 90-110 g / m 2 The amount is uniformly scattered in the hybrid pool, and 0.4-0.6 kg / m 2 The fully decomposed cow and sheep manure is used in step S2.3. The mass ratio of N:P2O5:K2O:Mg in the slow-release fertilizer potassium dihydrogen phosphate is 6:(40-45):(5-8):(12-18);

[0025] Each hybrid pool is two ridges according to the standard of ridge height 10-15 cm, ridge width 15-20 cm, and ridge spacing 20-25 cm; on the day of transplanting, fill the ditch with water to moisten the ridge; after 3 pm, dip the root of the high-cut seedling into the root-dipping agent containing thiophanate-methyl and phoxim and let it stand for 2-4 min; vertically insert the parent sweet potato seedling into the ridge, with a depth of more than 10 cm, while ensuring that the aboveground part has a height of 5-10 cm. The two ridge seedling positions are staggered, and the root of the sweet potato seedling is pressed to form a nest after planting.

[0026] Further, in step S3, the method of drought stress treatment is: 20-25 days after the sweet potato seedlings are transplanted, the sweet potato seedlings are no longer watered, and the opening and closing state of the drip-free transparent plastic film on the top of the shed is adjusted according to the weather. When it is rainy, the plastic on the top of the shed is closed to keep the rain out, and after the sun comes out, it is opened to facilitate ventilation and reduce the temperature in the shed.

[0027] Further, in step S3, the method of controlling the growth rate of stems and vines is to control the growth rate of stems and vines by pruning. When the parent sweet potato seedlings branch to 20-22 cm, 2-4 strong main stem branches are retained, and are spirally bound and fixed around the periphery of the conical frame in the same direction according to the growth, 1-2 times a week. The side branches at the flower buds are removed in time every day with sterilized scissors, and 1 cm of the length close to the root is retained. If the main branches still do not have obvious flower buds 40 days after transplanting and the average internode length of the part within 40 cm from the front end of the stem is longer (≥10 cm), the main branch apices are removed artificially to reduce the elongation growth rate.

[0028] Further, in step S4, the method of applying phosphorus and potassium fertilizer is: 48-52 days after transplanting, evenly spread slow-release potassium dihydrogen phosphate fertilizer around the roots, and spread 20-30 g / m 2 The amount is evenly spread into the rhizosphere of the sweet potato seedlings, the soil is loosened and the fertilizer is covered, and the slow-release potassium dihydrogen phosphate fertilizer is spread once every 20-30 days, a total of 3-4 times during the whole hybridization period.

[0029] Further, in step S5, the method of early determination of the fertility of the parent combination is:

[0030] (1) Open the high-density shading net and retain the ordinary shading net for heat insulation on the top of the shed. At 8:00-10:00 in the morning, use a fine-tipped forceps to collect pollen, and pollinate according to the hybridization combination plan. 3-5 flowers are pollinated each time when determining compatibility in the early flowering stage;

[0031] (2) Timely close the flowers, that is, gather the edges of the flowers together, turn them 30°-60°, and lightly pinch them to close the flowers. Timely hang a sign, and after all the combinations are pollinated, completely open the ordinary shading net for light, and close the ordinary shading net and the high-density shading net again at 16:00-17:00 in the afternoon;

[0032] (3) One week after pollination, investigate the number of seeds of each parent combination and calculate the seed setting rate. According to the seed setting rate, determine the compatibility. The parent combination with a seed setting rate ≥60% is considered to have strong compatibility, the parent combination with a seed setting rate of 20%≤seed setting rate<60% is considered to have moderate compatibility, and the parent combination with a seed setting rate <20% is considered to have weak compatibility.

[0033] Further, the cluster hybridization pollination method in step S6 is as follows: before the parent flowering period, according to the affinity determination result in S5, combinations with medium affinity or above are collected and counted, and a parent cluster hybridization plan is formulated again, each female parent is determined one by one, and the pollen of multiple or all male parents with medium affinity or above is taken off and mixed, and the female parent stigma is pollinated in the same culture dish, and there is no need to carry out closed flower treatment at this period; according to the need, pollination insects are introduced to achieve artificial and insect cooperative pollination.

[0034] Further, in step S1, the size of the greenhouse is (10-11) m* (7-8) m, the top height is (2.5-2.8) m, and the shoulder height is (1.5-1.7) m.

[0035] The soil is taken in place, and six hybridization pools are arranged in place in the greenhouse. The greenhouse width is the longitudinal direction of the hybridization pool, the hybridization pool width is 0.8-0.9 m, adjacent hybridization pools are separated by a 0.7-0.8 m walkway, the walkway on both sides of the hybridization pool edge is slightly wider by about 0.8-0.85 m, and a 0.8-1 m corridor is reserved at the middle position of the longitudinal direction of the hybridization pool.

[0036] The beneficial effects of the present application are:

[0037] (1) Compared with the existing hybridization greenhouse, the size of the hybridization greenhouse is moderate, and the disassembly and assembly are simple and easy to operate, which improves the work efficiency of building the greenhouse by more than 100%; at the same time, it is convenient for the management of net and film, reduces the labor intensity, and saves labor by more than 50%; the temperature and humidity of the greenhouse can be controlled, and the overall flowering period is prolonged by about 20 days, and the overall seed setting rate is improved by 22%. The greenhouse in the technical scheme of the present application is sequentially laid with an insect-proof net, an ordinary sunshade net (3-4 needles), a high-density sunshade net (8-10 needles), and a drip-free transparent plastic film, which is more conducive to the coordinated comprehensive control of the ventilation, sunlight, and temperature in the greenhouse; in addition, the setting of the insect-proof net can play a role in preventing and controlling insects, and is also conducive to the later human-insect cooperative pollination.

[0038] (2) Selecting parents with outstanding traits and obvious complementary advantages for combination, the probability of breeding offspring materials with excellent comprehensive traits is improved by more than 5% compared with random combination, and the selection rate of hybrid selection is significantly improved; the trained healthy high-cut seedlings are directly transplanted into the ridge after chemical treatment, which saves the grafting link, improves the transplanting survival rate by more than 10%, improves the work efficiency by 50%, and at the same time, effectively shortens the seedling time by 2-3 days, so that the seedlings can be transplanted as needed, and the seedlings can be supplemented in time; the staggered arrangement of the sweet potato seedlings facilitates the later pollination, pruning, and harvesting of capsules; in addition, compared with the seedlings, the high-cut seedlings can avoid the connection of sweet potato seedlings with tubers or soil-borne pathogens, thereby being more conducive to the healthy growth of sweet potato seedlings and cultivating high-quality parent materials.

[0039] (3) Drought and dark stress effectively solves the problem of not easy to flower in northern hybrid sweet potato, and advances the flowering period of the parent by 10-20 days, providing sufficient time for accurate determination of the compatibility of the parent combination, and significantly improving the precision of efficient seed production combination; branch removal and top control can ensure the supply of nutrients required for the present bud flowering branch, and improve the hybrid seed setting rate;

[0040] In addition, 30-40 days after the sweet potato seedlings are transplanted, and when the above-ground part of the sweet potato seedlings grows to 40-60 cm, dark treatment stress is carried out on the sweet potato seedlings in the greenhouse, which can effectively improve the number of flowers and ultimately improve the seed setting rate of the parent; if the sweet potato seedlings are too long and dark treatment stress is carried out, the initial flowering period will be delayed, and even no flowering will occur; if the dark treatment stress is carried out when the sweet potato seedlings are too short, the growth of the sweet potato seedlings will be very slow, the sweet potato seedlings will be too short, and the total number of flowers will be reduced.

[0041] (4) Heavy application of phosphorus and potassium fertilizer and less application of nitrogen fertilizer can effectively control the excessive growth of stems and leaves, increase the number of root system groups and the thickness of the main stem, prolong the flowering period by 7-10 days, and increase the number of flowers by 63.9%.

[0042] (5) During the morning pollination period, 3-4 needle sunshade nets are retained to cover the greenhouse, which effectively reduces the pollination temperature in the greenhouse, and increases the hybrid seed setting rate by more than 21%; evenly distributing the pollination quantity and timely closing the flowers reduces the statistical workload, saves the time-consuming and labor-intensive process of bagging, effectively prevents indirect pollination by bees, ants and other insects, ensures the accuracy of the determination of the compatibility of the hybrid combination, and improves the work efficiency by more than 8%.

[0043] (6) Cluster hybridization can take multiple parent pollen at the same time, and pollinate the target female parent, which avoids the complexity of traditional single taking and single pollination, saves more than 60% of labor, and improves the pollination efficiency by more than 30%; after pollination, the flowers are not closed, and the pollination efficiency can be further improved with the help of insect pollination.

[0044] (7) The capsule stalk is picked when more than 1 / 3 of the part close to the capsule is brown, which effectively avoids the mixing and even loss of seeds caused by bursting after complete maturity, and the after-ripening treatment promotes the complete maturity of the seeds, and improves the seed germination rate by more than 15%. DETAILED DESCRIPTION

[0045] The specific embodiments of the present application will be described in detail below. The present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, therefore the present application is not limited by the disclosed specific embodiments.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms used are only for the description of the specific embodiments, and are not intended to limit the present application.

[0047] A method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions (the method is used in Examples 1-5 below), the method is as follows:

[0048] S1. Site selection, shed construction, and pond building

[0049] (1) Select a plot of land that is slightly elevated, not prone to water accumulation, well-ventilated, and has not been planted with sweet potatoes in the past 5 years as the site for building the greenhouse;

[0050] (2) The soil should be tilled and loosened in the winter before the shed is built. Tillage should be done but not broken up. The tillage depth should be about 20cm. Depending on the soil type of the plot, imported soil can be mixed during winter tillage. The principle of "mixing clay with sand and sand with clay" should be followed for adjustment.

[0051] A simple and practical plastic greenhouse frame is constructed using stainless steel pipes. Insect-proof netting, ordinary shade netting, high-density shade netting, and drip-free transparent plastic film are laid out sequentially from the inside out. Hybridization ponds are set up inside the greenhouse. The ordinary shade netting has 3-4 needles, and the high-density shade netting has 8-10 needles.

[0052] The greenhouse measures 10m x 7m (length x width), with a top height of 2.5m and a shoulder height of 1.5m. A slot is provided at the shoulder height for easy fixing and opening of insect-proof netting, high-density shade cloth, and drip-free transparent plastic film. Six hybridization ponds are constructed on-site using locally sourced soil. The width of the ponds is 0.8m, with the greenhouse width serving as the longitudinal axis. Adjacent hybridization ponds are separated by a 0.7m walkway, with slightly wider walkways (approximately 0.85m) along the edges of the two side ponds. A 1m corridor is reserved in the middle of the longitudinal axis of the hybridization ponds.

[0053] S2. Select superior parent plants and cultivate robust seedlings for direct planting.

[0054] (1) Parent selection: Based on high yield, the goal is to select sweet potato varieties with high starch, high anthocyanin or high carotene, while taking into account the advantages of short vines, early maturity, many sprouts, good storage or strong disease resistance (one or more of root rot resistance, black spot resistance or soft rot resistance), and select parent materials with complementary advantages according to the breeding objectives.

[0055] (2) Hardening off seedlings: 30-35 days before transplanting, the parent seed potatoes are placed in the spring greenhouse for seedling cultivation. When the sweet potato seedlings grow to 15-17cm, watering is stopped. Harden off seedlings in advance according to the transplanting plan. The hardening off method is as follows: 4-5 days before transplanting, gradually open the greenhouse for ventilation and cooling during the day on sunny days. 2-3 days before transplanting, the greenhouse vents can be fully opened day and night, except in extreme weather. Ensure that the temperature inside the seedling greenhouse drops to 20℃-22℃ and the soil moisture content of the seedbed is below 20%. When the sweet potato seedlings are not easily broken when bent around a finger, it is considered that the hardening off is complete. Then, harvest strong, tall-cut seedlings.

[0056] The method for picking and cutting the healthy high-cut seedlings is as follows: when the sweet potato seedlings grow to 25-28 cm, select the healthy sweet potato seedlings with a stem diameter of more than 0.5 cm, and cut the sweet potato seedlings at the base at least 5 cm above the seedbed by using sterilized and disinfected scissors, so as to obtain the seedlings with a length of 20-23 cm.

[0057] (3) Raising ridges, moistening soil and directly planting:

[0058] The small granular slow-release fertilizer potassium dihydrogen phosphate (N:P205:K20:Mg mass ratio 6:40:6:15) is applied at 100 g / m 2 The amount is uniformly scattered into the hybrid pool, and 0.5 kg / m 2 The completely decomposed cattle and sheep manure is applied according to the standard of two small ridges with a ridge height of 10-15 cm, a ridge width of 15-20 cm, and a ridge spacing of 20-25 cm; on the day of transplanting, the ridges are filled with water to wet the back of the ridges, and the healthy high-cut seedling roots are treated with a medicament before being directly planted into the ridges in a staggered manner.

[0059] The method for directly planting in a staggered manner is as follows: after 3:00 pm, the high-cut seedling roots are dipped into a root-dipping medicament containing thiophanate-methyl and phoxim for 3 min; a simple seedling inserting tool is used to vertically insert the parent sweet potato seedlings into the ridge body, with a soil depth of more than 10 cm, while ensuring that the aboveground part has a height of 5-10 cm; the two-ridge seedling positions are arranged in a staggered manner, and the seedling roots are pressed by hand to complete the nest after planting.

[0060] Preparation of the thiophanate-methyl and phoxim root-dipping medicament: according to the requirements of the drug instruction, a single volume of thiophanate-methyl is diluted with 800 times water to obtain a thiophanate-methyl medicament, and a single volume of phoxim is diluted with 1000 times water to obtain a phoxim medicament; the thiophanate-methyl medicament and the phoxim medicament are mixed in a volume ratio of 1:1 to obtain the thiophanate-methyl and phoxim root-dipping medicament to be used.

[0061] S3, artificially creating adversity

[0062] After the sweet potato seedlings are acclimated, a three-mitre conical bamboo frame is built around the sweet potato seedlings; 20-25 days after the sweet potato seedlings are transplanted, drought and darkness are created according to the weather conditions and soil moisture conditions to control the stem growth rate and induce flowering in a timely manner.

[0063] (1) Drought stress treatment: 20-25 days after the sweet potato seedlings are transplanted, the sweet potato seedlings are no longer watered, and the opening and closing state of the drip-free transparent plastic film on the top of the shed is adjusted according to the weather; when it is rainy, the plastic on the top of the shed is closed to keep out the rain, and after it is sunny, it is opened to facilitate ventilation and reduce the temperature in the shed.

[0064] (2) Dark treatment stress: 30-40 days after the sweet potato seedlings are transplanted and the above-ground growth reaches 40-60cm, the hybrid parents in the greenhouse are subjected to dark treatment stress. The specific method is as follows: From 16:00 to 17:00 every afternoon, cover the entire hybrid greenhouse with a double-layer shade net to simulate the dark environment. Starting at 8:00 the next morning, first open the high-density shade net (8-10 needles) and keep the ordinary shade net with 3-4 needles to ensure that the temperature in the greenhouse does not exceed 28℃ during pollination and the temperature in the greenhouse is maintained at 20-28℃. After pollination is completed, open the ordinary shade net with 3-4 needles to ensure that the hybrid parents in the greenhouse have light exposure time of 8-9 hours per day for about 90 days. After that, for the next 30 days, as the temperature difference between day and night increases in the north, the light exposure time can be extended. That is, open the shade net after the morning temperature rises and close the shade net when the sun is about to set.

[0065] (3) Pruning and controlling the top: When the branches of the parent sweet potato seedlings grow to 20-22cm, retain 2-4 strong main branches and tie them in a spiral manner around the outside of the conical frame in the same direction according to their growth, and fix them 1-2 times a week; use sterilized scissors to remove the side branches at the flower buds in time every day, leaving 1cm of length close to the root; if the main branches still do not show obvious flower buds 40 days after transplanting and the average internode of leaves within 40cm of the front end of the stem is relatively long (≥10cm), manually remove the terminal bud of the main branch to reduce its elongation growth rate.

[0066] S4, Apply more phosphorus and potassium, and less nitrogen.

[0067] Approximately 50 days after planting, evenly apply potassium dihydrogen phosphate slow-release fertilizer around the roots. Specific method: Mix small granular slow-release potassium dihydrogen phosphate with an N:P₂O₅:K₂O ratio of 0:51:34 at a concentration not exceeding 30g / m³. 2 Dosage (20-30g / m²) 2 Spread the fertilizer evenly around the roots, loosen the soil and cover with fertilizer. Apply the fertilizer every 20-30 days, for a total of 3-4 applications during the entire hybridization period.

[0068] S5. Early testing of parental hybrid viability

[0069] The parental combination method is determined according to the breeding objectives. The number of pollinated flowers of the hybrid parental combination is evenly distributed according to the number of flowers, and pollination is carried out in advance. The compatibility between the parents is predicted based on the number and rate of fruit set of the parental combination.

[0070] (1) Open the high-density shade net and keep the ordinary shade net on the roof for heat insulation. At 8:00-10:00 am, use fine-tipped tweezers to collect pollen and pollinate one by one according to the hybridization combination plan. When testing compatibility at the beginning of flowering, pollinate 3-5 flowers for each combination each time.

[0071] (2) Timely do the closed flower treatment, that is, gather the flower edges together after pollination, rotate 30°-60° and pinch the flower to close, timely hang the label, completely open the ordinary sunshade net after all the combination pollination is finished, until 16:00-17:00 in the afternoon, close the ordinary sunshade net and the high-density sunshade net again;

[0072] (3) After pollination for one week, investigate the seed setting quantity of each parent combination and calculate the seed setting rate, judge the affinity according to the seed setting rate, the parent combination with the seed setting rate ≥60% is regarded as a relatively strong affinity combination, the parent combination with 20%≤seed setting rate<60% is regarded as a moderate affinity combination, and the parent combination with the seed setting rate<20% is regarded as a relatively weak affinity combination.

[0073] S6, cluster hybridization pollination, human and insect cooperation pollination

[0074] Before the parent flowering period, according to the affinity determination result in step S5, collect and count the combinations with moderate affinity or above, formulate the parent cluster hybridization plan again, determine each female parent one by one, take the pollen of multiple or all male parents (the hybridization seed setting rate is above 20% in the previous determination) combined with the female parent with moderate affinity or above, mix uniformly, and place in the same culture dish to pollinate the stigma of the female parent. In this period, no closed flower treatment is needed. According to the need, appropriately introduce pollination insects such as wall bees or male bees to realize human and insect cooperation pollination.

[0075] S7, picking, drying and preservation

[0076] After the hybridization parent seed setting capsule matures, timely picking, and preservation in a cool and dry place.

[0077] Picking specific method: the capsule is generally yellow about 35 days after pollination, then gradually turns brown, when more than 1 / 3 of the capsule handle near the capsule turns brown, it indicates that the seed is close to complete maturity, at this time, the capsule is picked together with the capsule handle into a kraft paper bag.

[0078] After-ripening treatment: select a well-ventilated and dry place, naturally air dry the capsule together with the capsule handle for about 7-10 days, when the capsule and the capsule handle are dry and easy to burst, rub and sieve the capsule to select the honest and full seeds, re-pack them into a kraft paper bag, and preserve them in a cool and dry place.

[0079] I. Example results of different greenhouses

[0080] Example 1

[0081] The above method (the method described in the application) is used to carry out sweet potato hybridization experiments in the northern region.

[0082] Comparative Example 1

[0083] Using the same sweet potato as in Example 1, a traditional hybridization darkroom (referred to as "traditional darkroom") for northern sweet potato is used for sweet potato hybridization experiment. The traditional darkroom is a well-lit and ventilated bungalow, which is equipped with 6 hybridization cars. The length of light and the high and low temperature are controlled by moving the hybridization car in and out of the darkroom.

[0084] The hybridization shed described in the application is used in the example, and the traditional darkroom is used in Comparative Example 1, and the relevant data comparison is shown in Table 1.

[0085] Table 1 Comparison of temperature control and flowering and fruiting of Example 1 and Comparative Example 1

[0086]

[0087] Note: The amount of labor for daily management is "person / 8h".

[0088] From the data comparison in Table 1, it can be seen that the average daily temperature in the hybridization shed of the method of the application in Example 1 can be controlled at about 27-28℃, which is 2-3℃ lower than the temperature outside the darkroom; at the same time, the highest and lowest temperature in the hybridization shed can be controlled between 17-30℃, and the temperature difference is less than the extreme value of the darkroom environment, which prolongs the flowering period by about 18 days, and the average hybridization and fruiting rate can be increased by 21%.

[0089] II. Effects of different pretreatment methods on parent grafting and transplanting

[0090] Example 2

[0091] Using tobacco-sweet potato 29 as parent test material, the above method (the method described in the application) is used, and the high cutting seedlings described in the application are used for transplanting.

[0092] Comparative Example 2

[0093] Using tobacco-sweet potato 29 as parent test material, the same method as in Example 2 is used, except that the ground seedlings are used for transplanting.

[0094] Comparative Example 3

[0095] Using tobacco-sweet potato 29 as parent test material, the same method as in Example 2 is used, except that the ground seedlings are used for transplanting.

[0096] The high cutting seedlings, ground seedlings and survived grafted seedlings with uniform thickness and consistent height in Example 2, Comparative Example 2 and Comparative Example 3 are simultaneously transplanted into the hybridization shed, and the survival rate and efficiency of transplanting are counted, and the specific data are shown in Table 2.

[0097] Table 2 Effects of different pretreatment methods on parent grafting and transplanting

[0098]

[0099] From the above table 2, it can be seen that: high pruning and ground pulling seedlings are directly transplanted as parents, which eliminates the grafting link, reduces the risk of grafting dead seedlings, and the transplanting (grafting) efficiency is increased from 10 plants / h to 300 plants / h, which is 30 times of the grafting transplanting. The seedling recovery time after transplanting is the shortest, which is 1-2 days earlier than that of the grafted seedlings. The survival rate of high pruning seedlings transplanted according to the method of the present application is the highest, which is more than 2.8% and 6.2% higher than that of ground pulling seedlings and grafted seedlings, respectively.

[0100] III. Experimental results of different dark treatment stress opportunities

[0101] Example 3

[0102] Using tobacco potato 29 as parent test material, using the above method (the method of the present application), after the sweet potato seedlings were transplanted for 30-40 days, and the above-ground part of the sweet potato seedlings grew to 40-60 cm, the sweet potato seedlings in the greenhouse were subjected to dark treatment stress, and the flowering condition was counted.

[0103] Comparative Example 4

[0104] The same method as in example 3 was used, except that the dark treatment stress was applied to the sweet potato seedlings in the greenhouse when the above-ground part of the sweet potato seedlings grew to 30-35 cm, and the flowering condition was counted.

[0105] Comparative Example 5

[0106] The same method as in example 3 was used, except that the dark treatment stress was applied to the sweet potato seedlings in the greenhouse when the above-ground part of the sweet potato seedlings grew to 65-75 cm, and the flowering condition was counted.

[0107] The flowering number statistics of example 3, comparative example 4 and comparative example 5 are shown in table 3.

[0108] Table 3 Effects of dark treatment stress on the flowering number of sweet potato parents

[0109]

[0110] Note: More than 10 flowers per plant per day is considered as full bloom period.

[0111] As can be seen from the above table, in the method of the present application, the sweet potato seedlings are subjected to dark treatment stress 30-40 days after transplanting and the aerial part of the sweet potato seedlings grows to 40-60 cm (Example 3), which can effectively increase the number of flowers and ultimately increase the seed setting rate of the parent. If the sweet potato seedlings are too long and subjected to dark treatment stress (Comparative Example 5), the initial flowering period is delayed, resulting in a significant decrease in flowering effect. If the sweet potato seedlings are too short and subjected to dark treatment stress (Comparative Example 4), the growth of the sweet potato seedlings is very slow, and the short height of the sweet potato seedlings also leads to a decrease in the number of flowers.

[0112] In addition, in the specific test, tobacco potato 29 was not subjected to dark treatment stress, and it was found that the flowering was late. However, the method of dark treatment stress of the present application can promote early flowering of sweet potato (about 15 days earlier). In the test, Zhenghong 23 sweet potato was also used for comparison, and it was found that if no dark treatment stress was performed, Zhenghong 23 did not flower at all, but if the method of dark treatment stress of the present application was used, Zhenghong 23 could achieve good flowering.

[0113] IV. Experimental results of different fertilization

[0114] Example 4

[0115] Tobacco potato 29 was used as the parent test material, and the above method (the method of the present application) was used. About 50 days after transplanting, slow-release potassium dihydrogen phosphate was uniformly applied around the roots. The specific method was as follows: small particle slow-release fertilizer potassium dihydrogen phosphate with a mass ratio of N:P2O5:K2O of 0:51:34 was uniformly applied around the roots at 20-30 g / m 2 The amount was uniformly applied around the rhizosphere, the soil was loosened and the fertilizer was covered, and the application was performed once every 20-30 days.

[0116] Comparative Example 6

[0117] The same method as in Example 4 was used, except that the slow-release potassium dihydrogen phosphate was replaced with organic fertilizer of cow and sheep manure.

[0118] Comparative Example 7

[0119] The same method as in Example 4 was used, except that the slow-release potassium dihydrogen phosphate was replaced with conventional compound fertilizer of nitrogen, phosphorus and potassium (N:P2O5:K2O mass ratio of 15:15:15).

[0120] The light shielding conditions of Example 4, Comparative Example 6 and Comparative Example 7 were kept the same, and the number of days in the full flowering period and the number of flowers in the full flowering period were counted, as shown in Table 4.

[0121] Table 4 Effect of fertilization on the number of flowers of sweet potato parents

[0122]

[0123] As can be seen from the data in Table 4, the longest flowering period is achieved by using the potassium dihydrogen phosphate slow-release fertilizer in the method of the present application, which can reach 36 days, and the flowering period is extended by 7-10 days compared with the application of organic fertilizer and conventional compound fertilizer; in addition, the parent flowering number of the parent in the flowering period is 658 flowers per plant by applying the potassium dihydrogen phosphate slow-release fertilizer in the method of the present application, which is 231 flowers and 297 flowers more than the application of organic fertilizer and conventional compound fertilizer, respectively, significantly improving the flowering number in the flowering period.

[0124] V. Experimental results of pollination methods

[0125] Ten parent plants of tobacco potato 29 were selected and divided into two groups, 5 plants per group. In the flowering period, more than 50 flowers were selected as pollination female parents for 1:1 pollination and group pollination for a week. The two treatments were consistent with each other except for the pollination method.

[0126] 1:1 pollination: the determined single male pollen was pollinated to the female stigma one by one, and after 5-10 flowers were pollinated by each male, other parents were changed in turn;

[0127] Group pollination: all male pollens planned for hybridization were concentrated in one culture dish at one time, ensuring that the pollen dosage did not need to be taken again, and the pollen was pollinated to 50 female stigmas in turn, and bees, ants and other insects were released or induced to assist pollination. Different pollination methods were marked with red and green playing cards, and the pollination efficiency (according to the time required for pollination of 50 flowers) and the seed setting rate were calculated. The specific results are shown in Table 5.

[0128] Table 5 Effect of pollination method on pollination efficiency and seed setting rate

[0129] Treatment Pollination efficiency flo / h Seed set % 1:1 pollination 75 60 Clustered human-wasp pollination 93 85

[0130] Compared with the traditional 1:1 pollination, the group of insects pollination increased the pollination efficiency by 18 flowers / h and the seed setting rate by 25%, and the seed setting rate could reach 85%.

[0131] The technical features of the above-described embodiments can be combined arbitrarily, and in order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not exhaustively listed, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0132] For those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application, and the protection scope of the present application is subject to the appended claims.

Claims

1. A method for improving the hybridization efficiency and parental seed setting rate of sweet potatoes in northern regions, characterized in that, The method is as follows: S1. Site selection, shed construction, and pond building A plastic greenhouse frame is selected, and insect-proof netting, ordinary shade netting, high-density shade netting, and drip-free transparent plastic film are laid out from the inside to the outside. A hybridization pool is set up inside the greenhouse. The ordinary shade netting has 3-4 needles, and the high-density shade netting has 8-10 needles. S2. Select superior parent plants and cultivate robust seedlings for direct planting. S2.1 Parental selection: Select parental materials with complementary advantages according to the breeding objectives; S2.2 Hardening off seedlings: Place the parent seed potatoes in a spring greenhouse for seedling cultivation, and then harden off the seedlings. After hardening off the seedlings, harvest the strong, tall-cut seedlings. S2.3 Ridge the soil, moisten it, and plant directly; S3, Artificially Created Adversity After the sweet potato seedlings have recovered from transplant shock, a cone-shaped frame is built around the seedlings. Drought stress treatment and dark stress treatment are created according to the weather conditions and soil moisture to control the growth rate of the stems and vines and induce flowering in a timely manner. Among them, the dark treatment stress is to apply dark treatment stress to the sweet potato seedlings in the greenhouse 30-40 days after transplanting, when the sweet potato seedlings have grown to 40-60cm above ground. This ensures that the sweet potato seedlings in the greenhouse have 8-9 hours of light per day and the temperature in the greenhouse is 20-28℃. S4, Apply phosphorus and potassium fertilizer S5. Early testing of parental hybrid viability The parental combination method is determined according to the breeding objectives. The number of pollinated flowers of the hybrid parental combination is evenly distributed according to the number of flowers, and pollination is carried out in advance. The compatibility between the parents is predicted based on the number and rate of fruit set of the parental combination. S6, Cluster hybridization pollination During the peak flowering period of the parent plants, pollination was carried out based on the compatibility between the parent plants as determined in S5. S7. Harvesting, drying and preservation Harvest the mature capsules of the hybrid parents in a timely manner and store them in a cool, dry place.

2. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S2.2, 30-35 days before transplanting, the parent seed potatoes are placed in a spring greenhouse for seedling cultivation. When the sweet potato seedlings grow to 15-17cm, watering is stopped. Seedlings are hardened off in advance according to the transplanting plan. The hardening-off method is as follows: 4-5 days before transplanting, gradually open the greenhouse for ventilation and cooling during the day on sunny days. 2-3 days before transplanting, the greenhouse vents can be fully opened day and night, except in extreme weather. Ensure that the temperature inside the seedling greenhouse drops to 20℃-22℃ and the soil moisture content of the seedbed is below 20%. When the sweet potato seedlings are not easily broken when bent around a finger, the hardening-off is considered complete.

3. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S2.2, the method for harvesting robust high-cut seedlings is as follows: when the sweet potato seedlings grow to 25-28cm, select healthy sweet potato seedlings with a diameter of more than 0.5cm, and use sterilized scissors to cut the sweet potato seedlings at the base at least 5cm away from the seedbed. Seedlings with a length of 20-23cm are considered robust high-cut seedlings.

4. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S2.3, the method for ridging, moistening the soil, and direct planting is as follows: apply slow-release potassium dihydrogen phosphate fertilizer at a concentration of 90-110 g / m². 2 Apply evenly to the hybridization pool, along with 0.4-0.6 kg / m² of other fertilizer. 2 The fully decomposed cow and sheep manure, and the slow-release potassium dihydrogen phosphate used in step S2.3, has a N:P2O5:K2O:Mg mass ratio of 6:(40-45):(5-8):(12-18). Two ridges are prepared for each hybridization pond, with a ridge height of 10-15cm, a ridge width of 15-20cm, and a ridge spacing of 20-25cm. On the day of transplanting, the furrows are filled with water, just enough to moisten the back of the ridges. After 3 pm, the roots of the high-cut seedlings are dipped into a root-dipping agent containing methyl thiophanate and phoxim and left to stand for 2-4 minutes. The parent sweet potato seedlings are then vertically inserted into the ridges, with a soil depth of more than 10cm, while ensuring that the above-ground part is left with a height of 5-10cm. The seedlings are arranged in staggered positions on the two ridges. After planting, the roots of the sweet potato seedlings are pressed down by hand to seal the planting hole.

5. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S3, the drought stress treatment method is as follows: starting 20-25 days after planting sweet potato seedlings, stop watering the sweet potato seedlings. At the same time, adjust the opening and closing status of the drip-free transparent plastic film on the greenhouse roof according to the weather conditions. When it is cloudy or rainy, close the plastic film on the greenhouse roof to keep out the rain, and open it again on sunny days to facilitate ventilation and lower the greenhouse temperature.

6. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S3, the growth rate of stems and vines is controlled by removing branches and controlling the top. When the branches of the parent sweet potato seedlings grow to 20-22cm, retain 2-4 strong main branches and tie them around the conical frame in a spiral manner in the same direction according to their growth, fixing them 1-2 times a week. Use sterilized scissors to remove the lateral branches at the flower buds every day, leaving 1cm close to the root. If no obvious flower buds appear on the main branches 40 days after transplanting and the average internode length of leaves within 40cm of the stem tip is ≥10cm, manually remove the terminal buds of the main branches to reduce their elongation growth rate.

7. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, The method for applying phosphorus and potassium fertilizer in step S4 is as follows: 48-52 days after planting, evenly spread slow-release potassium dihydrogen phosphate fertilizer around the roots, using a slow-release fertilizer with an N:P2O5:K2O ratio of 0:(50-52):(32-35) at a rate of 20-30 g / m³. 2 Apply the fertilizer evenly around the roots of the sweet potato seedlings, loosen the soil and cover with fertilizer. Apply the fertilizer once every 20-30 days, for a total of 3-4 applications during the entire hybridization period.

8. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, The method for determining the fertility of parental combinations in step S5 is as follows: (1) Open the high-density shade net and keep the ordinary shade net on the roof for heat insulation. At 8:00-10:00 am, use fine-tipped tweezers to collect pollen and pollinate one by one according to the hybridization combination plan. When testing compatibility at the beginning of flowering, pollinate 3-5 flowers for each combination each time. (2) Timely flower closure treatment, that is, after pollination, gather the edges of the flowers together, rotate 30°-60° and gently pinch to close the flowers, hang the label in time, and after all the pollination is completed, open the ordinary shade net completely to let in light, and close the ordinary shade net and high-density shade net again at 16:00-17:00 in the afternoon. (3) One week after pollination, investigate the number of seeds produced by each parent combination and calculate the seed set rate. Based on the seed set rate, determine the affinity. Parent combinations with a seed set rate ≥ 60% are considered to have strong affinity, parent combinations with a seed set rate ≤ 20% and a seed set rate < 60% are considered to have medium affinity, and parent combinations with a seed set rate < 20% are considered to have weak affinity.

9. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 8, characterized in that, The cluster hybridization pollination method in step S6 is as follows: Before the peak flowering period of the parents, based on the affinity test results in S5, the combinations with medium or higher affinity are collected and statistically analyzed, and a parent cluster hybridization plan is formulated again. Each female parent is identified one by one, and pollen from multiple or all male parents with medium or higher affinity is collected, mixed, and placed in the same petri dish to pollinate the stigma of the female parent. No flower closure treatment is required at this stage. Pollinating insects are introduced as needed to achieve artificial and insect collaborative pollination.

10. The method for improving the hybridization efficiency and parental seed setting rate of sweet potato in northern regions according to claim 1, characterized in that, In step S1, the greenhouse dimensions are (10-11)m long * (7-8)m wide, (2.5-2.8)m high, and (1.5-1.7)m shoulder height. Six hybridization ponds were set up on-site in the shed using soil sourced locally. The width of the shed served as the longitudinal axis of the hybridization ponds, with each pond being 0.8-0.9m wide. Adjacent hybridization ponds were separated by walkways of 0.7-0.8m. The walkways along the edges of the two hybridization ponds were slightly wider, about 0.8-0.85m, and a 0.8-1m corridor was reserved in the middle of the longitudinal axis of the hybridization ponds.

Images