Breeding method of high temperature and humidity resistant silkworm variety

Abstract

The application provides a breeding method of a high-temperature and high-humidity resistant domestic silkworm variety, and belongs to the technical field of domestic silkworm new variety breeding.The application uses a strong and healthy variety with high combining force as a backbone material, and crosses the backbone material with a cocoon and silk excellent variety to obtain a first generation hybrid, then feeds the first generation hybrid in spring under a high temperature, feeds the first generation hybrid under good mulberry and satiation, feeds the first generation hybrid in early autumn under a high temperature and high humidity natural environment, does not select leaves, feeds the first generation hybrid in a rough way, feeds F1-F4 generations in a 1 / 2x4 mixed ant amount, mates in the same moth area, feeds F5 generation in a single moth, mates in the same moth area, adopts a method of removing two ends and leaving the middle part to improve the development uniformity of the variety, feeds F9 generation in a single moth, mates in different moth areas, and the traits gradually become stable after 11 generations, the spring and autumn are both focused on the selection of strong and healthy traits, and the selection of egg quality, cocoon quality and silk quality traits is simultaneously considered, and the high-temperature and high-humidity resistant domestic silkworm variety Z831xZ842 is obtained.The domestic silkworm new variety has the characteristics of thick cocoon layer and excellent silk quality, and is suitable for reeling high-grade raw silk of 5A level or above.

Description

Technical Field

[0001] This invention relates to the field of silkworm breeding technology, and in particular to a method for breeding silkworm varieties resistant to high temperature and humidity. Background Technology

[0002] With the adjustment and optimization of my country's agricultural industrial structure, rural labor is continuously shifting to other industries. Traditional mulberry cultivation and silkworm rearing, as a labor-intensive industry, has long been plagued by labor shortages, low levels of cultivation and rearing techniques, and low overall efficiency. Simultaneously, with intensifying competition in the international silk market, cocoon and silk processing enterprises are placing higher demands on the quality of raw cocoons. Faced with multi-faceted competitive pressure, the industry has made transforming the traditional mulberry cultivation and silkworm rearing model into an efficient, simplified, and labor-saving model, as well as improving the quality of raw cocoons, one of the key objectives of technological innovation research in the construction of a modern sericulture industry technology system. Therefore, it is essential to conduct breeding programs for high-quality, robust silkworm varieties suitable for simplified and labor-saving rearing in rural areas and for the reeling of high-grade raw silk by cocoon and silk processing enterprises. Summary of the Invention

[0003] To address the aforementioned problems, this invention employs systematic breeding and targeted selection to breed new silkworm varieties Z831 and Z842, and then creates a hybrid variety Z831×Z842. Through laboratory variety comparison and identification, joint identification in breeding collaboration areas, and pilot-scale trials, the new hybrid combination Z831×Z842 exhibits uniform development, robustness, ease of rearing, and excellent cocoon and silk quality, with all economic indicators meeting the breeding objectives. This invention's new silkworm varieties, intended for autumn use, are characterized by thick cocoon layers and superior silk quality, particularly excelling in single-cocoon silk length, unwinding silk length, unwinding rate, and silk yield. They also possess excellent purity, making them suitable for reeling high-grade raw silk of grade 5A or higher.

[0004] The specific breeding steps of the new silkworm variety described in this invention are as follows:

[0005] S1. Select robust varieties with high combining ability as backbone materials and cross them with varieties with excellent cocoon and silk quality. Combine them into Chinese × Chinese and Japanese × Japanese combinations for feeding identification and screening. After two years and three silkworm seasons of feeding, based on the economic traits of cocoon and silk quality, select combinations whose main economic traits all exceed the average value for crossbreeding to obtain the first generation of hybrids.

[0006] S2, after hybridization, the hybrids are fed a slightly higher temperature in spring, and the mulberry trees are well-fed;

[0007] S3. In autumn, choose a humid natural environment with a temperature of 30-32℃ in early autumn, do not select leaves, and raise them in an extensive manner.

[0008] S4 and F1-F4 generations of mixed ants were bred in 1 / 2×4 batches and mated in the same moth-producing area. Individuals that retained the high temperature and humidity tolerance and the economic traits of the target variety were selected.

[0009] S5 and F5 generations begin single-moth breeding, mating in the same moth area, and the "removing both ends and leaving the middle" method is used to improve the uniformity of variety development when the moths are raised into cocoons;

[0010] S6 and F9 generations are bred individually and mated in different moth areas. Comprehensive selection is made based on egg quality, body quality, cocoon quality, etc., to select individuals that retain the ability to withstand high temperature and humidity and retain the economic traits of the target variety.

[0011] After the S7 and F11 generations, the traits gradually stabilized. In spring and autumn, the focus was on robustness selection, while also taking into account the comprehensive selection of egg quality, cocoon quality, and silk quality, resulting in the high-temperature and humid heat resistant silkworm variety Z831×Z842.

[0012] Furthermore, the robust variety with high combining ability is one or more of the following: 801 (Chinese strain), 9903 (Chinese strain), Furong (Chinese strain), 812 (Japanese strain), Xianghui (Japanese strain), and Zhenfeng (Japanese strain).

[0013] Furthermore, the superior silk varieties are one or more of Z3 (Chinese), E Spring (Chinese), 129 (Chinese), Z4 (Japanese), Spring 54 (Japanese), and Autumn 54 (Japanese).

[0014] Furthermore, the optimal rearing temperature is 29℃-30℃ for the young silkworm stage and 26℃-27℃ for the mature silkworm stage.

[0015] Furthermore, during the early silkworm stage, use leaves that are moderately ripe and tender; during the mature silkworm stage, use good mulberry leaves when the silkworms are full and do not eat watery or tender leaves.

[0016] When using mulberry leaves during the early silkworm stage, they should be moderately ripe and tender, and carefully selected leaves should be chosen to promote uniform development. Mature silkworms eat mulberry leaves vigorously, so they should eat plenty of good quality mulberry leaves and not eat watery or tender leaves, so as to give full play to the superior traits of the silkworm variety in terms of high silk production.

[0017] Furthermore, expand the silkworm rearing area ahead of time during the early silkworm stage to ensure even density of the rearing area. Add molting nets earlier for 1st and 2nd instars, and raise the silkworms in batches for each instar. Keep the rearing area dry during the mature silkworm stage.

[0018] Young silkworms develop rapidly and exhibit strong phototaxis and a tendency to grow closer together, so it's important to expand the silkworm rearing area early to ensure even spacing. Adding molting nets to the 1st and 2nd instars should be done earlier, and different instars should be raised in batches. During the mature silkworm stage, the silkworms are robust and consume a lot of mulberry leaves; therefore, it's essential to frequently remove sand and keep the silkworm rearing area dry to reduce the occurrence of silkworm diseases.

[0019] Furthermore, timely ventilation during the silkworm rearing period and staggered feeding during the fourth instar molting period can alleviate the pressure on the silkworms as they begin to molt.

[0020] Furthermore, in S2, the 1-3 year olds are raised three times, the 4-5 year olds are raised four times, the 1-2 year olds are raised with full protection and dry care, and the 3-4 year olds are raised with partial protection and dry care.

[0021] Furthermore, in S3, the entire age is raised three times, the 1-3 year olds are raised with full protection and dry care, and the 4-year olds are raised with partial protection and dry care.

[0022] Furthermore, in S4, individual selection is the primary factor.

[0023] Furthermore, in S5, individual selection is combined with moth area selection.

[0024] Furthermore, in S6, selection is primarily based on the moth-growing area, with individual selection as a secondary method.

[0025] Furthermore, the cocooning process is uniform and sparse, which enhances dehumidification, ensures uniform light in the cocooning chamber, maintains a temperature of 25℃-27℃, reduces dead cocoons, increases the rate of healthy pupae, and maintains a target temperature of 23℃-24℃ within the cocooning chamber.

[0026] New varieties mature uniformly, so it is important to prepare for cocooning properly. Cocooning should not be too dense, and the cocooning area should not be stuffy or damp. Ventilation and dehumidification should be strengthened. The temperature should be relatively high when cocooning begins, which is conducive to increasing the cocooning rate and reducing the number of silkworms that do not spin cocoons.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0028] The new silkworm varieties Z831×Z842 for autumn use in this invention are robust, uniformly developed, have high yield per cocoon, and are highly productive. They are suitable for large-scale, labor-saving silkworm rearing and have good silk quality, especially in terms of cocoon silk length, unwinding silk length, and fresh cocoon silk yield. They are suitable for reeling high-quality raw silk.

[0029] Laboratory testing revealed that the new silkworm varieties Z831×Z842, used in autumn, exhibited a 92.70% pupation rate, a cocoon layer rate of 24.06%, a cocoon yield of 18.12 kg per 10,000 silkworms, a single cocoon silk length of 1160.4 m, a fully unwound silk length of 954.9 m, a silk yield from fresh cocoons of 19.96%, a purity score of 97.7, and a fiber density of 2.660D. Trial breeding at silkworm breeding farms demonstrated that the original silkworms were easy to raise and had a high reproduction rate, producing 18.06 sheets of seed for Chinese and 17.62 sheets for Japanese silkworms, respectively. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] Figure 1 This is a diagram illustrating the breeding technology roadmap of the present invention;

[0032] Figure 2 These are Z831 silkworm eggs;

[0033] Figure 3 These are Z842 silkworm eggs;

[0034] Figure 4 It is a fifth-instar silkworm, Z831;

[0035] Figure 5 It is a fifth-instar silkworm, Z842;

[0036] Figure 6 The cocoon is Z831.

[0037] Figure 7 The cocoon is Z842 silkworm cocoon;

[0038] Figure 8 The silkworms are fifth-instar silkworms, numbered Z831×Z842.

[0039] Figure 9 The cocoons are Z831×Z842. Detailed Implementation

[0040] The technical solution provided by the present invention will be further described below with reference to the embodiments.

[0041] Example 1: Breeding of new silkworm varieties Z831×Z842, the method is as follows:

[0042] The robust varieties with high combining ability, 801 (Chinese), 9903 (Chinese), Furong (Chinese), 812 (Japanese), Xianghui (Japanese), and Zhenfeng (Japanese), were selected as backbone materials and crossed with varieties of excellent cocoon and silk quality, such as Z3 (Chinese), Echun (Chinese), 129 (Chinese), Z4 (Japanese), Chun54 (Japanese), and Qiu54 (Japanese). These were crossbred to form 36 Chinese × Chinese and Japanese × Japanese combinations for feeding evaluation and screening. After two years and three silkworm seasons of feeding evaluation, the average cocoon and silk quality of the 36 combinations is shown in Table 1.

[0043] Table 1. Cocoon and silk quality scores of 36 combinations in feeding evaluation.

[0044]

[0045]

[0046] As shown in Table 1, based on the eight main economic traits of cocoon silk, the Chinese combinations Z3×801, E-Spring×801, and Z3×Furong all exceeded the average value for the eight main economic traits of cocoon silk. The Japanese combinations Z4×812 and 812×Qiu54 also exceeded the average value for the eight main economic traits of cocoon silk. Therefore, the Chinese combinations Z3×801, E-Spring×801, Z3×Furong, and the Japanese combinations Z4×812 and 812×Qiu54 were selected as the key combinations.

[0047] Early combining ability prediction was conducted on key Chinese and Japanese hybrids using the incomplete diallel hybridization method. The results showed that Z3×801 and Z4×812 had the best combining ability, and the first-generation hybrids produced by these hybrids exhibited strong hybrid vigor, good robustness, and stable cocoon silk quality. Therefore, Z3×801 and Z4×812 were selected and, after multiple generations of systematic selection, were fixed as Z831 and Z842, respectively. The target combination was determined to be Z831×Z842.

[0048] Using Z4, a high-quality spring-use, high-silk-yield variety (introduced from the Sericulture Research Institute of the Chinese Academy of Agricultural Sciences), as the female parent, and "Zhaoxia" (812) of Huanghe × Zhaoxia as the male parent, the result was obtained by systematic separation and selection and fixed as Z842. Using Z3, a high-quality spring-use, high-silk-yield variety (introduced from the Sericulture Research Institute of the Chinese Academy of Agricultural Sciences), as the female parent, and "Huanghe" (801) of Huanghe × Zhaoxia, bred in our province, as the male parent, the result was obtained by systematic separation and selection and fixed as Z831.

[0049] Characteristics of Z842: Two molts and four molts, common spotting. Eggs are grayish-brown with white shells. Silkworms are dark brown, hatching is uniform, with approximately 2360 ant heads per larva. Young silkworms are attracted to density and light, developing uniformly. Larger silkworms eat mulberry leaves quickly, without stepping on leaves, with slender bodies and bluish-white color. They cocoon quickly, building the upper layer of cocoons. Cocoons are long oval with a shallow waist, white, and moderately coarse with wrinkles. Moths emerge uniformly, are white, and have outstretched wings. They mate easily, lay eggs quickly, and male moths are resistant to cold storage. Each moth lays approximately 500 eggs. Spring hatching takes 10 days, the larval stage 25 days, the pupal stage 16 days, for a total lifespan of 51 days. When crossbred with Z831, ant harvesting should be done 2 days earlier. Spring breeding yields an average of 17.62 sheets of eggs per ant head.

[0050] Z831 characteristics: Two-stage, four-molt silkworm, Pygmy silkworm. Eggs are grayish-green with pale yellow shells. Newborn silkworms are dark brown, hatching uniformly, with approximately 2460 ant heads per larva. Young silkworms are attracted to density and light, developing evenly. Larger silkworms eat mulberry leaves quickly, without trampling, and are robust with a bluish-white body. They cocoon quickly and rapidly, building the upper layer of cocoons. Cocoons are short-oval and white. Moths emerge uniformly, are white, have outstretched wings, mate easily, and male moths are resistant to cold storage. Egg laying is slightly slow but good, with approximately 490 eggs per moth. Spring hatching takes 10 days, the larval stage approximately 24 days, the pupal stage 16 days, for a total lifespan of 50 days. When crossbred with Z842, ant harvesting should be delayed by 2 days. Spring breeding yields an average of 18.06 sheets of seed per ant head.

[0051] Hybrid offspring are given a slightly higher temperature for rearing in spring (29℃-30℃ for small silkworms and 26℃-27℃ for large silkworms). They are reared three times for the first to third instars and four times for the fourth to fifth instars. They are fully protected from dry rearing for the first to second instars and partially protected from dry rearing for the third to fourth instars. They are fed plenty of high-quality mulberry leaves to fully utilize the high silk content of the variety.

[0052] In autumn, choose a warm and humid natural environment in early autumn. Raise ants three times throughout the entire life cycle: fully protected from dry conditions for 1-3 instars, and partially protected from dry conditions for 4 instars. Do not select leaves and raise them extensively to enhance their resistance. For F1-F4 generations, raise ants in mixed batches of 1 / 2×4 and mate them in the same moth-producing area. Take advantage of the early generation's trait segregation and focus on individual selection.

[0053] Focusing on individual selection at the early generation stage of trait segregation allows for the early identification and selection of individuals exhibiting superior genetic traits during the breeding process of new varieties. This accelerates the breeding process and improves breeding efficiency and success rate. By conducting individual selection in the early generations, superior genes can be concentrated more quickly, leading to the cultivation of silkworm varieties with the desired traits. In summary, this invention, through the method of "focusing on individuals at the early generation stage of trait segregation," improves the accuracy of selecting superior traits, accelerates the breeding process, reduces unnecessary feeding and management costs, saves time and resources, and selects the optimal genetic combination while maintaining genetic diversity.

[0054] The F5 generation begins single-moth breeding, mating within the same moth-producing area. Individual selection is combined with moth-producing area selection. During the silkworm season, late-dormant silkworms and weak silkworms are eliminated, and the middle silkworms are removed from both ends and kept when entering the cocoon.

[0055] This invention involves single-moth breeding starting from the F5 generation, mating within the same moth-producing area, and combining individual selection with moth-producing area selection to improve the genetic stability and production efficiency of silkworm varieties. This method ensures that the selected silkworms possess excellent genetic characteristics while also increasing silk yield and quality. Furthermore, this method helps optimize specific quality characteristics of silkworms, such as cocoon size, shape, and silk quality, to meet market demands.

[0056] Furthermore, this invention implements these breeding measures starting from the F5 generation, which adapts to genetic characteristics and the breeding cycle. By carrying out these measures when genetic characteristics tend to be stable, the quality of the variety can be improved more effectively, which has a very positive impact on accelerating the breeding process and improving breeding efficiency.

[0057] The selective retention of the upper cocoon by "removing both ends and keeping the middle" ensures the consistency of cocoon quality, making the cocoons develop more uniformly and improving the overall quality of the cocoons.

[0058] The method described in this invention ensures a precise selection and elimination process, which guarantees that the bred new varieties have better genetic characteristics, improves genetic stability, increases production efficiency, optimizes specific quality characteristics, meets market demands, and optimizes variety characteristics.

[0059] F9 generation single moth breeding, cross-breeding in different moth areas, with selection based primarily on moth area and secondarily on individual selection, while also comprehensively selecting based on egg quality, body quality, cocoon quality, etc.

[0060] After the F11 generation, the traits gradually stabilized. In spring and autumn, the focus was on robustness selection, while also taking into account the comprehensive selection of egg quality, cocoon quality, and silk quality. Starting from the F12 generation, the cocoon and silk quality performance (yield, cocoon layer ratio, and live pupa silk quality performance) and robustness (cage mortality rate, pupal rate, etc.) were combined to divide Z831 and Z842 into cocoon and silk quality line A and robustness line B, respectively. By the F19 generation, Z842 had an average pupal rate of 90.25% and an average cocoon layer ratio of 23.85%, while Z831 had an average pupal rate of 90.48% and an average cocoon layer ratio of 23.34%. See Tables 2 and 3 for details.

[0061] Table 2 shows the pedigree results of Z842.

[0062]

[0063] Note: □ Mixed breeding; ○ Single moth breeding

[0064] Table 3 shows the pedigree results of Z831.

[0065]

[0066] Note: □ Mixed breeding; ⑧ Single moth breeding

[0067] The original Z842 silkworms develop slowly, so attention should be paid to regulating moth emergence. The hybrid fifth-instar silkworms are robust, and mature silkworms excrete more fluid, making them prone to external contamination of the cocoons, affecting cocoon quality and unwinding. Simultaneously, during breeding, attention needs to be paid to the timing of removal from storage and activating the cocooning process. Feeding during the final molt should be done in batches, and silkworms should be placed in cocoons in batches, strengthening the regulation of early moth emergence within the cocooning stage. Cocooning should be done at the appropriate time, with even and sparse placement of silkworms. The cocooning frames should be lined with absorbent materials such as short straw, rice husks, and scorched rice bran, while ensuring ventilation and dehumidification to keep the silkworm beds dry.

[0068] Example 2: Laboratory Variety Comparison Test

[0069] Three-phase hybridization tests were conducted, with the control variety being the autumn control variety Huanghe × Zhaoxia used for silkworm variety identification in Hubei Province. The results are shown in Tables 4 and 5.

[0070] Table 4. Laboratory identification results of cocoons Z831×Z842

[0071]

[0072] Table 5. Laboratory identification results of silk quality for Z831×Z842.

[0073]

[0074] Tables 4 and 5 show that the new varieties Z831×Z842 exhibited stable traits during autumn rearing, with uniform hatching, molting, and cocooning. They consumed mulberry leaves quickly, were robust, and had widespread spots. Individual variation within the same area was small, with slight variation between different areas. Their physical condition was robust, reaching 100.42% of the control variety. The total instar time was 21 hours longer than the control variety. The average cocoon layer ratio was 24.06%, 0.51 percentage points higher than the control variety. The cocoon yield per 10,000 silkworms was 18.12 kg, reaching 107.54% of the control variety. Although affected by high temperatures during autumn evaluation, the new variety still showed stable silk quality results, with a cocoon silk length of 1160.4 m, a fully unwound silk length of 954.9 m, and a fresh cocoon silk yield of 19.96%, reaching 106.76%, 109.37%, and 110.83% of the control, respectively. The unwinding rate was 83%, the purity score was 97.7, and the fiber density was 2.660D, all of which exceeded the Hubei Province's standards for the approval of new summer and autumn silkworm varieties.

[0075] Example 3: Collaborative Identification Test in the Collaborative Area

[0076] The new varieties Z831×Z842 participated in the joint identification of the Northern Collaboration Area of ​​the National Silkworm Variety Laboratory Identification Site, Shandong Academy of Agricultural Sciences Sericulture Research Institute and Anhui Academy of Agricultural Sciences Sericulture Research Institute. The control varieties were Jingsong×Haoyue, the national spring silkworm variety identification control variety, and Qiufeng×Baiyu, the summer and autumn silkworm variety identification control variety. The results are shown in Tables 6 and 7.

[0077] Table 6. Cocoon and silk quality results of the new silkworm varieties Z831×Z842 (Shandong site) through collaborative identification.

[0078]

[0079]

[0080] The identification results from the Shandong site showed that, compared with the control variety Jingsong×Haoyue, the new variety Z831×Z842 was more robust, with a pupation rate of 94.55%, similar to the control. The total cocoon weight, cocoon layer ratio, cocoon yield per 10,000 silkworms, and cocoon layer weight per 10,000 silkworms were 2.50g, 24.32%, 24.66kg, and 6.016kg, respectively, reaching 110.62%, 108.81%, 108.11%, and 117.52% of the control. Regarding silk quality, the length of silk per cocoon, the length of unwound silk, and the silk yield from fresh cocoons were 1496.7m, 1211.9m, and 20.52%, respectively, reaching 111.26%, 106.27%, and 106.93% of the control. The cleanliness score was 99, and the unwound silk rate was 80.97%, slightly lower than the control. The cocoon and silk quality traits were excellent, and the overall performance reached the level of spring-use varieties.

[0081] Table 7. Collaborative Identification Results of Cocoon and Silk Quality for New Silkworm Varieties Z831×Z842 (Anhui Province)

[0082]

[0083]

[0084]

[0085] The joint identification results at the Anhui site showed that, compared with the control variety Qiufeng × Baiyu, the new variety Z831 × Z842 had a pupation rate of 95.94%, reaching 100.18% of the control; the total cocoon weight, cocoon layer ratio, cocoon yield per 10,000 silkworms, and cocoon layer weight per 10,000 silkworms were 1.74g, 25.06%, 16.87kg, and 4.224kg, respectively, reaching 108.75%, 112.78%, 110.84%, and 124.78% of the control; the silk quality was excellent, with the length of a single cocoon silk, the length of unwound silk, and the silk yield from fresh cocoons being 1055.0m, 793.4m, and 18.67%, respectively, reaching 114.19%, 104.12%, and 106.50% of the control; the unwound rate was 75.20%, lower than the control; the cleanliness score was 95.0, similar to the control. Resistance was similar to the control, and the overall performance was better than the control.

[0086] Pilot-scale results of Example 4

[0087] To understand the adaptability of the new silkworm variety Z831×Z842 combination in production, production trials were conducted in Jiuzihe Town of Luotian County, Xunjian Town of Nanzhang County, and Gaobazhou Town of Yidu City, major silkworm producing areas in Hubei Province. The results are shown in Table 8.

[0088] Table 8. Cocoon Quality Results of Rural Production Trials

[0089]

[0090]

[0091] The average cocooning time for the new variety Z831×Z842 across all age groups was 24 days and 15 hours, 16 hours longer than the control. The total cocoon weight and cocoon layer rate were 1.74g and 22.54%, respectively, reaching 109.56% and 104.62% of the control. The healthy pupa rate was 95.23%, reaching 100.25% of the control. The yield per sheet was 40.9kg, an increase of 5.1kg compared to the control, reaching 114.10% of the control, showing a significant increase in yield.

[0092] The new varieties Z831×Z842 underwent rural breeding evaluation and showed good cocoon and silk quality, as shown in Table 9. On average over two years, the cocoon silk length was 998m, the unwound silk length was 749m, and the fresh cocoon silk yield was 16.92%, reaching 109.98%, 109.34%, and 107.91% of the control varieties Huanghe×Zhaoxia, respectively. The unwound silk yield was similar to the control at 75.59%. The silk cleanliness score was 93.5, and the fineness was 2.317D, demonstrating superior silk quality. The raw cocoon quality meets the requirements for reeling high-grade raw silk of 5A or above, which is beneficial for cocoon and silk processing enterprises in our province to reel high-grade raw silk, improving quality and efficiency.

[0093] Table 9. Silk Quality Results in Rural Production Trials

[0094]

[0095] Note: The silk quality was tested by the Sericulture Institute of Sichuan Academy of Agricultural Sciences, the designated unit for silk quality identification of silkworm varieties nationwide.

[0096] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A breeding method for a new variety of silkworm, characterized in that, The steps are as follows: S1. Select robust varieties with high combining ability as backbone materials and cross them with varieties with excellent cocoon and silk quality. Combine them into Chinese × Chinese and Japanese × Japanese combinations for feeding identification and screening. After two years and three silkworm seasons of feeding, based on the economic traits of cocoon and silk quality, select combinations whose main economic traits all exceed the average value for crossbreeding to obtain the first generation of hybrids. The first generation of hybrids is Z831 × Z842. Using Z4, a high-quality spring-use silk variety with abundant silk production, as the female parent and Huanghe × Zhaoxia 812 as the male parent, the hybrid was obtained by systematic separation and selection to become Z842. Using Z3, a high-quality spring-use silk variety with abundant silk production, as the female parent and Huanghe × Huanghe 801 as the male parent, the hybrid was obtained by systematic separation and selection to become Z831. The economic traits of the cocoon silk are eight indicators: cocoon layer ratio, pupa ratio, cocoon yield per 10,000 silkworms, cocoon layer yield per 10,000 silkworms, single cocoon silk length, unwound silk length, fresh cocoon silk yield, and purity. S2, after hybridization, the hybrids are fed a slightly higher temperature in spring, and the mulberry trees are well-fed; S3. In autumn, choose a humid natural environment with a temperature of 30-32℃ in early autumn, do not select leaves, and raise them in an extensive manner. S4 and F1-F4 generations of mixed ants were bred in 1 / 2×4 batches and mated in the same moth-producing area. Individuals that retained the high temperature and humidity tolerance and the economic traits of the target variety were selected. S5 and F5 generations begin single-moth breeding, mating in the same moth area, and the "removing both ends and leaving the middle" method is used to improve the uniformity of variety development when the moths are raised into cocoons; S6 and F9 generations were bred individually and mated in different moth areas. Comprehensive selection was made based on egg quality, body quality, and cocoon quality to select individuals that retained resistance to high temperature and humidity and preserved the economic traits of the target variety. After the S7 and F11 generations, the traits gradually stabilized. In spring and autumn, the focus was on robustness selection, while also taking into account the comprehensive selection of egg quality, cocoon quality, and silk quality, resulting in the high-temperature and humid heat resistant silkworm variety Z831×Z842.

2. The breeding method according to claim 1, characterized in that, The optimal rearing temperature is 29℃-30℃ for young silkworms and 26℃-27℃ for older silkworms.

3. The breeding method according to claim 1, characterized in that, Expand the silkworm bed ahead of time during the early silkworm stage to ensure even density. Add molting nets earlier for 1st and 2nd instars. Raise the silkworms in batches for each instar. Keep the silkworm bed dry during the mature silkworm stage.

4. The breeding method according to claim 1, characterized in that, In S2, the 1-3 year olds are raised three times, the 4-5 year olds are raised four times, the 1-2 year olds are raised with full protection and dry care, and the 3-4 year olds are raised with partial protection and dry care.

5. The breeding method according to claim 1, characterized in that, In S3, the entire age is raised three times, the 1-3 year olds are raised with full protection and dry care, and the 4-year olds are raised with partial protection and dry care.

6. The breeding method according to claim 1, characterized in that, In S4, individual choice is the primary factor.

7. The breeding method according to claim 1, characterized in that, In S5, individual selection is combined with moth area selection.

8. The breeding method according to claim 1, characterized in that, In S6, selection is primarily based on the moth-growing area, with individual selection as a secondary method.

9. The breeding method according to claim 1, characterized in that, The cocooning process involves uniform and sparse feeding, enhanced dehumidification, uniform light distribution in the cocooning chamber, and temperature protection at 25℃-27℃ to reduce cage death and increase the rate of healthy pupae. The target temperature within the cocooning chamber is 23℃-24℃.

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