In-situ overwintering cross breeding method for cassava in subtropical zone

Abstract

The invention discloses an in-situ overwintering cross breeding method for cassava in a subtropical zone, and belongs to the technical field of cassava cross breeding. The overwintering cross breeding method comprises the following steps: promoting flowering of cassava, performing natural cross pollination after flowering, and harvesting hybrid seeds from February to March in the next year. The flower promoting method comprises the following steps: applying a high-phosphorus fertilizer and a high-potassium fertilizer to cassava; main branches of cassava are cut off in September, and branching is promoted; spraying a flower forcing agent on the cassava in October. According to the method, cassava cross breeding is carried out in the subtropical region, and cassava hybrid seeds can be harvested in the next year through the steps of flower promoting, cross breeding, seed harvesting and the like; by using a high-phosphorus fertilizer, a high-potassium fertilizer and a flower forcing agent, the cassava enters reproductive growth from vegetative growth after September, and conditions are created for cross breeding; according to the method, the cassava seeds are subjected to flower forcing in October, hybridization in November and harvesting in February to March of the next year, so that the hybrid cassava seeds have a growth and development cycle of 3-4 months, accumulated temperature required by seed maturation is ensured, and the harvested seeds have the advantages of large quantity and high germination rate.

Description

Technical Field

[0001] The invention belongs to the technical field of cassava hybrid breeding, and in particular relates to a cassava in situ wintering hybrid breeding method in subtropical areas. Background Art

[0002] Cassava (Manihot Esculenta Crantz) is a plant of the genus Manihot in the family Euphorbiaceae. It is one of the three major tuber crops in the world, the third largest food crop in tropical regions, and the sixth largest food crop in the world. It is known as the "king of starch" and the "underground granary". In addition to being used as food, cassava is also an important industrial raw material. For example, cassava root starch and dried flakes can be used to make modified starch, alcohol and sorbitol, becoming an important raw material for food, medicine, textile, papermaking and other industries.

[0003] Cassava originated in tropical regions and is a typical short-day tropical crop. It likes sunshine and high temperatures, is not resistant to frost, snow and shade, and is very sensitive to changes in light duration and ambient temperature. It is suitable for growing in sandy loam with good drainage, deep soil, loose soil, and rich organic matter and potassium. Cassava is grown in tropical and subtropical regions, horizontally distributed between 30° north and south latitude, and vertically distributed in areas below 2,300 meters above sea level.

[0004] Cassava was first introduced to China by overseas Chinese from tropical ASEAN countries in the early 19th century. Guangxi is the largest cassava planting and processing base in the country, with cassava planting area and output accounting for more than 60% of the country. Excellent varieties are the basis for high and stable yields of cassava planting, and hybrid breeding is the most important way to cultivate new cassava varieties. However, Guangxi is located in the subtropical region, which has obvious seasonal differences compared to the tropical regions where cassava originates. There are problems such as insufficient light intensity and light duration, and long low temperature time. Some cassava varieties, especially those from tropical regions, cannot bloom and bear fruit, so hybrid breeding cannot be carried out; most cassava varieties will reduce the number of hybrid seeds or have poor quality due to insufficient accumulated temperature time when hybrid breeding is carried out multiple times a year, which will affect the germination rate of seeds and further affect the efficiency of cassava breeding. Summary of the invention

[0005] The invention provides a subtropical cassava in situ overwintering hybrid breeding method to solve the above technical problems.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for in-situ overwintering hybrid breeding of cassava in subtropical areas comprises: promoting flowering of cassava, conducting natural hybridization and pollination after flowering, adopting cold-proof technical measures such as fertilizing, spraying flowering inducing agents, and covering with film to protect leaves and fruits, and harvesting hybrid seeds in February to March of the following year.

[0008] The methods to promote flowering are as follows: apply high-phosphorus fertilizer and high-potassium fertilizer to cassava; cut off the main branches of cassava in September to promote branching; spray flowering agents on cassava in October.

[0009] Phosphorus dosage of high phosphorus fertilizer (in P 2 O 5 8-15kg / mu; high potassium fertilizer (K 2 The potassium dosage (in terms of unit area) is 6-10kg / mu.

[0010] The flower-inducing agent comprises the following components: boron trace element fertilizer with a boron content of 10-20%, zinc trace element fertilizer with a zinc content of 20-50%, and 35-55g / L chitin; the method of use is as follows: 800-1200 times of the boron trace element fertilizer and the zinc trace element fertilizer are mixed with 500-1000 times of chitin, and then sprayed on the top and leaves of cassava, and the spraying amount is based on the amount of water just dripping from the leaves.

[0011] From October to December, cassava was sprayed with 0.0005% 28-homobrassinolide, and the spraying amount was based on the amount of water just dripping from the leaves.

[0012] Spray 28-homobrassinolide 5-6 times.

[0013] After cassava hybridization and pollination, when the outdoor temperature is below 4°C, use a light-transmitting film to wrap the cassava plants.

[0014] When the outdoor temperature is below 4℃ for 3 days, wrap the cassava plants with a transparent film; when the outdoor temperature is ≥10℃, remove the transparent film on the cassava plants.

[0015] Guangxi is located in the subtropical region, with high temperatures in summer and autumn. Cassava hybrid seeds can mature in 2-3 months, but the temperature is low in winter, and hybrid seeds need 3-4 months to mature. Moreover, the leaves of cassava plants stop growing when the temperature is below 16°C, and as winter progresses, the temperature is lower and the amount of leaf shedding increases; in subtropical regions, the average temperature is lowest in January, sometimes below 3°C, and almost all cassava leaves fall off. In an open-air environment, the second crop of cassava hybrid seeds lacks the nutrients needed for growth and cannot mature, resulting in a reduction in the number of seeds and a low germination rate; this application sprays cassava with 0.0005% 28-homobrassinolide in a concentration of 10-12 months to improve the cold resistance of the plant, slow down the rate of leaf shedding to extend the retention time of the leaves, and wrap the plant with a light-transmitting film to reduce the impact of the external environment, ensure sufficient time for reproductive growth, increase accumulated temperature, thereby increasing the number of second-crop seeds and improving seed quality.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Cassava hybrid breeding is carried out in subtropical areas. Through the steps of promoting flowering, hybrid breeding, and seed harvesting, cassava hybrid seeds can be harvested in the following year. Through the use of high-phosphorus fertilizer, high-potassium fertilizer, and flowering initiators, cassava can enter reproductive growth from vegetative growth after September, creating conditions for hybrid breeding. Moreover, flowering is promoted in October, hybridization is carried out in November, and seeds are harvested in February-March of the following year, so that hybrid cassava seeds still have a growth and development cycle of 4-5 months, ensuring the accumulated temperature required for seed maturation, and ensuring that the harvested seeds have the advantages of large quantity, good quality, and high germination rate.

[0018] 2. Guangxi is located in the subtropical region, with low temperatures in winter. When the temperature is below 16°C, the leaves of cassava stop growing, and as the temperature drops, the leaves gradually fall off, and even all the leaves fall off. The obstruction of photosynthesis will inevitably affect the growth and development of seeds. The present application uses a light-transmitting film to wrap the plants at low temperatures, which can keep warm and transmit light, reduce the risk of cassava leaf loss at low temperatures, and avoid the existing operation of moving cassava into a greenhouse at low temperatures, thereby achieving in-situ overwintering hybridization. The method is simple and effective, and is conducive to the development and maturity of seeds.

[0019] 3. The method of the present application can solve the existing cassava hybrid breeding, especially when tropical varieties of cassava are planted in the subtropics, the vegetative growth is vigorous in the first half of the year due to the suitable light and temperature, and the reproductive growth is inhibited, which in turn affects the development of hybrid breeding; by carrying out hybrid breeding after September, the light and temperature changes in the subtropical region at this time are used to inhibit the vegetative growth and promote the start of reproductive growth, and by increasing the accumulated temperature time, the winter cassava hybrid breeding efficiency is high, the seeds are more, and the germination rate is high; it is particularly suitable for varieties with vigorous growth, such as the tropical variety Indonesia UB4772. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is an illustration of the seed planting of the UB4772 variety after two harvests.

[0022] Figure 2 This is an illustration of the planting of seeds from two harvests of the SC9 variety.

[0023] Figure 3 Illustration of the seeds planted for two harvests of the AW40 variety.

[0024] Figure 4This is a diagram showing the planting of seeds from two harvests of the AW441 variety.

[0025] Figure 5 This is an illustration of the seed planting of the GR11 variety for two harvests.

[0026] Figure 6 This is an illustration of the planting of seeds from two harvests of the newly selected 048 variety.

[0027] Figure 7 This is an illustration of the planting of seeds from two harvests of the SC5 variety. DETAILED DESCRIPTION

[0028] To facilitate a better understanding of the present invention, the following examples are provided to illustrate the present invention in conjunction with the accompanying drawings. These examples belong to the protection scope of the present invention, but do not limit the protection scope of the present invention.

[0029] Example 1

[0030] A method for in-situ overwintering hybrid breeding of cassava in subtropical areas comprises: promoting flowering of cassava, conducting natural hybridization and pollination after flowering, and harvesting hybrid seeds in February to March of the following year.

[0031] The methods to promote flowering are as follows: apply high-phosphorus fertilizer and high-potassium fertilizer to cassava; cut off the main branches of cassava in September to promote branching; spray flowering agents on cassava in October.

[0032] Phosphorus dosage of high phosphorus fertilizer (in P 2 O 5 8kg / mu; high potassium fertilizer (K 2 The potassium dosage (in terms of unit area) is 6kg / mu.

[0033] The flower-inducing agent includes the following components: boron trace element fertilizer with a boron content of 10-20%, zinc trace element fertilizer with a zinc content of 20%, and 35g / L chitin; the method of use is as follows: 800 times the solution of the boron trace element fertilizer and the zinc trace element fertilizer is mixed with 500 times the solution of chitin and then sprayed on the top and leaves of cassava, and the spraying amount is based on the amount of water just dripping on the leaves.

[0034] From October to December, cassava plants were sprayed with 0.0005% 28-homobrassinolide, and the spraying amount was based on the amount of water just dripping from the leaves.

[0035] Spray 28-homobrassinolide 6 times.

[0036] After cassava hybridization and pollination, when the outdoor temperature is below 4°C, use a light-transmitting film to wrap the cassava plants.

[0037] When the outdoor temperature is below 4℃ for 3 days, wrap the cassava plants with a transparent film; when the outdoor temperature is ≥10℃, remove the transparent film on the cassava plants.

[0038] Example 2

[0039] A method for in-situ overwintering hybrid breeding of cassava in subtropical areas comprises: first promoting flowering of cassava, conducting natural hybridization and pollination after flowering, and harvesting hybrid seeds in February to March of the following year.

[0040] The methods to promote flowering are as follows: apply high-phosphorus fertilizer and high-potassium fertilizer to cassava; cut off the main branches of cassava in September to promote branching; spray flowering agents on cassava in October.

[0041] Phosphorus dosage of high phosphorus fertilizer (in P 2 O 5 11kg / mu; high potassium fertilizer (K 2 The potassium dosage (in terms of unit area) is 8kg / mu.

[0042] The flower-inducing agent includes the following components: a boron trace element fertilizer with a boron content of 15%, a zinc trace element fertilizer with a zinc content of 40%, and 45g / L chitin; the method of use is as follows: a 1000-fold solution of the boron trace element fertilizer and the zinc trace element fertilizer is mixed with an 800-fold solution of chitin and then sprayed on the top and leaves of cassava, and the spraying amount is based on the amount of water just dripping from the leaves.

[0043] From October to December, cassava plants were sprayed with 0.0005% 28-homobrassinolide, and the spraying amount was based on the amount of water just dripping from the leaves.

[0044] Spray 28-homobrassinolide 5 times.

[0045] After cassava hybridization and pollination, when the outdoor temperature is below 4°C, use a light-transmitting film to wrap the cassava plants.

[0046] When the outdoor temperature is below 4℃ for 3 days, wrap the cassava plants with a transparent film; when the outdoor temperature is ≥10℃, remove the transparent film on the cassava plants.

[0047] Example 3

[0048] A method for in-situ overwintering hybrid breeding of cassava in subtropical areas comprises: first promoting flowering of cassava, conducting natural hybridization and pollination after flowering, and harvesting hybrid seeds in February to March of the following year.

[0049] The methods to promote flowering are as follows: apply high-phosphorus fertilizer and high-potassium fertilizer to cassava; cut off the main branches of cassava in September to promote branching; spray flowering agents on cassava in October.

[0050] Phosphorus dosage of high phosphorus fertilizer (in P 2 O 5 The potassium dosage of high potassium fertilizer is 15kg / mu; the potassium dosage of high potassium fertilizer is 10kg / mu.

[0051] The flower-inducing agent includes the following components: boron trace element fertilizer with a boron content of 20%, zinc trace element fertilizer with a zinc content of 50%, and 55g / L chitin; the method of use is as follows: 1200 times the mixture of boron trace element fertilizer and zinc trace element fertilizer is mixed with 1000 times the mixture of chitin, and then sprayed on the top and leaves of cassava, and the spraying amount is based on the amount of water just dripping on the leaves.

[0052] From October to December, cassava plants were sprayed with 0.0005% 28-homobrassinolide, and the spraying amount was based on the amount of water just dripping from the leaves.

[0053] Spray 28-homobrassinolide 6 times.

[0054] After cassava hybridization and pollination, when the outdoor temperature is below 4°C, use a light-transmitting film to wrap the cassava plants.

[0055] When the outdoor temperature is below 4℃ for 3 days, wrap the cassava plants with a transparent film; when the outdoor temperature is ≥10℃, remove the transparent film on the cassava plants.

[0056] To facilitate seed collection, when the cassava plants are 2M-2.5M after pollination, you can use a net bag to cover the branches with fruits to prevent the seeds from falling and being lost after the fruits crack.

[0057] After the first batch of seeds is harvested, the main branches of the cassava plants are cut off (maintaining a height of 0.8-1.2m after pruning) to promote branch growth.

[0058] The 28-homobrassinolide used can improve the cold resistance of cassava plants, delay the yellowing and falling of leaves, and ensure the nutritional supply of the fruit.

[0059] The high-phosphorus fertilizer, high-potassium fertilizer, boron trace element fertilizer, zinc trace element fertilizer, chitin and 28-homobrassinolide used in the present invention are all existing products purchased from the market; wherein the high-phosphorus fertilizer can be superphosphate, and the high-potassium fertilizer can be potassium dihydrogen phosphate, which are applied 1.5 months after cassava planting; the flower inducing agent is used once a week for a total of 4 times.

[0060] test

[0061] The male and female parents of the hybrid cassava were planted in the cassava germplasm nursery of the Guangxi Subtropical Crops Research Institute in Nanning on February 16, 2023, with a plant row spacing of 1.4 meters × 1 meter; the first hybridization was a conventional management and planting method, and the seeds were harvested after hybridization; the second hybridization began in September, using the method of Example 3.

[0062] The first hybridization: flowering in May, pollination in June, and seed harvest in September.

[0063] The second hybridization: cut off the main branches after the first batch of seeds is harvested in September, induce flowering in October, pollinate in November, and harvest seeds in February-March of the following year.

[0064] The harvested cassava seeds were sown in the film greenhouse of Guangxi Subtropical Crops Research Institute in Nanning on April 1, 2024, with the same seed planting environment. The germination rate was counted on May 10, 2024. Figure 1-Figure 7 The figure shows some diagrams of seed germination. See Tables 1 and 2 for the seed number and germination rate of the first and second hybrid seeds.

[0065] Table 1 Statistical results of the first batch of cassava hybrid seeds

[0066] Serial number variety Female parent source / variety Mother plant / tree Number of seeds / grain Number of germination / grain Germination rate / % 1 Indonesia No. 3 Indonesia / Tropical 30 0 0 / 2 Indonesia No. 2 Indonesia / Tropical 30 0 0 / 3 UB4772 Indonesia / Tropical 60 167 108 64.7 4 Burmese flower leaves Myanmar / Tropical 20 0 0 / 5 CR24-16 Vietnam / Tropical 20 0 0 / 6 HN1 Vietnam / Tropical 20 0 0 / 7 SC9 China / Subtropical 40 79 65 82.3 8 AW40 China / Subtropical 40 251 151 60.2 9 AW441 China / Subtropical 40 319 205 64.3 10 GR11 China / Subtropical 30 86 61 70.9 11 New Selection 048 China / Subtropical 50 162 93 57.4 12 SC5 China / Subtropical 50 310 213 68.7

[0067] Table 2 Statistical results of the second crop of cassava hybrid seeds

[0068] Serial number variety Maternal origin / region Mother plant / tree Number of seeds / grain Number of germination / grain Germination rate / % 1 Indonesia No. 3 Indonesia / Tropical 30 234 162 69.2 2 Indonesia No. 2 Indonesia / Tropical 30 229 89 38.9 3 UB4772 Indonesia / Tropical 60 944 805 85.3 4 Burmese flower leaves Myanmar / Tropical 20 17 10 58.8 5 CR24-16 Vietnam / Tropical 20 101 71 70.3 6 HN1 Vietnam / Tropical 20 100 50 50.0 7 SC9 China / Subtropical 40 127 112 88.2 8 AW40 China / Subtropical 40 144 93 64.6 9 AW441 China / Subtropical 40 270 186 68.9 10 GR11 China / Subtropical 30 51 41 80.4 11 New Selection 048 China / Subtropical 50 450 287 63.8 12 SC5 China / Subtropical 50 700 509 72.7

[0069] The cassava varieties No. 1-6 in Table 1 and Table 2 are all tropical varieties, and the planting areas are in subtropical regions. Except for UB4772, the cassava varieties No. 1-6 in Table 1 are all seedless in the first crop. The reason may be that the light, temperature and rainfall in the subtropical region in the first half of the year are suitable for cassava growth. At this time, it is in vegetative growth or the vegetative growth is too vigorous, which inhibits the reproductive growth. Hybrid breeding requires cassava plants to maintain reproductive growth for a considerable period of time. Due to insufficient reproductive growth time, there is no flowering, hybridization or only male flowers without female flowers, and hybridization and pollination cannot be performed, so there are no hybrid seeds or the amount of seeds is very small.

[0070] The first batch of seeds of No. 3 cassava UB4772 had 106 seeds, 108 germinated seeds, and a germination rate of 64.7%, while the second batch had 944 seeds, 805 germinated seeds, and a germination rate of 85.3%. There were significant differences in indicators such as seed number and germination rate. The reason was that the cassava had vigorous nutritional growth in the first half of the year, resulting in an imbalance in the ratio of female flowers to male flowers, with very few female flowers and more male flowers, which in turn affected the number of seeds.

[0071] From the data comparison of the number of seeds, number of germinations, and germination rates of the subtropical varieties No. 7-12 in Table 1 and Table 2, it can be seen that the method of the present invention has a greater improvement in the number of harvested seeds, number of seed germinations, germination rate, and other indicators compared with the common method of hybrid breeding, indicating that increasing and extending the reproductive growth time has a significant effect on improving the seed quality of hybrid breeding; the reason is that subtropical early flowering varieties, such as SC9, Xinxuan 048, SC5, etc., bloom early in the first crop (summer), while other cassava parents do not bloom, and "hybrid breeding" cannot be carried out. The general cassava flowering rule is that female flowers bloom earlier than male flowers, and such cassava parents cannot carry out "self-pollination breeding", so it is easy to have the situation of "male and female flowers do not meet in flowering period and breeding efficiency is low". By adopting the method of the present invention, such cassava parents meet in flowering period with other cassava parents in the second crop (autumn), and "hybrid breeding" can be carried out, thereby improving the efficiency of hybrid breeding and obtaining more seeds by hybridization.

[0072] From the data in Table 2, it can be seen that by adopting the method of the present invention for hybridization, through the steps of promoting flowering, cross pollination, harvesting seeds, etc., taking advantage of the changes in conditions such as light and temperature after September, the vegetative growth of cassava is restricted and gradually enters into reproductive growth, thus laying a foundation for the growth and maturity of seeds.

[0073] In addition, cassava plants are protected under low temperature conditions by means of light-transmitting films, etc., to ensure the normal photosynthesis of leaves and young capsules, and to supply nutrients for seed development; in addition, pollination and hybridization in November, and seed harvesting in February-March of the following year, increase the cassava temperature accumulation time and extend the reproductive growth time, thus significantly increasing the number of seeds harvested from hybrid breeding cassava. From the seed germination rate, it can be seen that the seeds harvested overwintering have better vitality and higher germination rate.

[0074] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the statement "including an element defined by ... does not exclude the existence of other identical elements in the process, method, article or device including the element".

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for in situ overwintering hybridization of cassava in subtropical areas, It is characterized in that include: Cassava is promoted to flower, and then naturally hybridized and pollinated after flowering, and the hybrid seeds are harvested in February or March of the following year.

2. A subtropical cassava in situ wintering hybrid breeding method according to claim 1, It is characterized in that The methods to promote flowering are as follows: Apply high-phosphorus fertilizer and high-potassium fertilizer to cassava; cut off the main branches of cassava in September to promote branching; spray the cassava with flowering agents in October.

3. A subtropical cassava in situ wintering hybrid breeding method according to claim 2, It is characterized in that Phosphorus dosage of high phosphorus fertilizer (in P 2 O 5 8-15kg / mu; high potassium fertilizer (K 2 The potassium dosage (in terms of unit area) is 6-10kg / mu.

4. A subtropical cassava in situ wintering hybrid breeding method according to claim 3, It is characterized in that The flower-inducing agent includes the following components: Boron trace element fertilizer with a boron content of 10-20%, zinc trace element fertilizer with a zinc content of 20-50%, and chitin at 35-55g / L; Here’s how to use it: Mix 800-1200 times of trace element fertilizer and 500-1000 times of chitosan, and spray them on the top and leaves of cassava. The spraying amount should be enough to wet the leaves until water just drips.

5. A subtropical cassava in situ wintering hybrid breeding method according to claim 4, It is characterized in that After cross pollination of cassava, cassava was sprayed with 0.0005% 28-homobrassinolide in October-December.

6. A method for in situ wintering hybridization of cassava in subtropical areas according to claim 5, It is characterized in that Spray 28-homobrassinolide 5-6 times.

7. A method for in situ wintering hybridization of cassava in subtropical areas according to claim 6, It is characterized in that After cassava hybridization and pollination, when the outdoor temperature is below 4°C, use a light-transmitting film to wrap the cassava plants.

8. A subtropical cassava in situ wintering hybrid breeding method according to claim 7, It is characterized in that When the outdoor temperature is below 4℃ for 3 days, wrap the cassava plants with a transparent film; when the outdoor temperature is ≥10℃, remove the transparent film on the cassava plants.

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