A method for breeding of a cotton aphid parasitic wasp

Abstract

The application discloses a breeding method of cotton aphid bracon. The specific breeding method of the cotton aphid bracon is constructed by adopting specific parents, mother parents and different subculture schemes of stage humidity and temperature, aiming at solving the technical problem that the existing cotton aphid bracon is prone to hyperparasitism when the number of cotton aphids is low, leading to a large number of cotton aphid reproduction and poor control effect. The breeding method provided in the technical scheme of the application has a significant influence on the parasitization rate of F5 generation individuals obtained by breeding, and the parasitization rate of the cotton aphid bracon is significantly different from that of the control group. Moreover, the survival rate in low-temperature feeding and high-temperature feeding is also significantly affected, which can improve the stress resistance of the cotton aphid bracon and is beneficial to realize the green and sustainable development of the cotton industry.

Description

Technical Field

[0001] This invention belongs to the field of animal production applications, specifically relating to the breeding technology of a cotton aphid wasp. Background Technology

[0002] With the long-term and extensive use of chemical pesticides, parasitic wasps, as a special group of Hymenoptera, are increasingly attracting attention for their specific and efficient control of agricultural and forestry pests. Parasitic wasps are diverse and numerous, forming a unique type of symbiotic organism that can parasitize the surface or interior of insects, feeding on the host's external or internal tissues. Studies have reported that parasitic wasps are important natural enemies of cotton aphids in North China cotton fields, with parasitism rates reaching up to 80%. Aphids parasitized by wasps do not immediately stop feeding or die; they continue to feed and grow until the parasitic wasp develops into a mature larva. However, within the parasitized aphid, the parasitic wasp regulates and modifies the aphid's physiology, metabolism, biosynthesis, and immunity, making the aphid's internal environment suitable for the wasp's growth and development. Cotton aphids can be parasitized by various parasitic wasps, among which the cotton aphid parasitoid wasp (Brachystomum spp.) is the dominant parasitic wasp in northern cotton fields, effectively suppressing aphid populations in early summer. The cotton aphid wasp belongs to the family Braconidae within the superfamily Ichthyophthidae of the order Hymenoptera. It is distributed in China, Japan, Indonesia, South Korea, and other countries. The cotton aphid wasp parasitizes aphids and exhibits relatively high host specificity. The cotton aphid wasp undergoes four developmental stages: egg, larva, pupa, and adult. Mated females produce hermaphroditic offspring, while unmated females reproduce parthenogenetically.

[0003] The cotton aphid wasp's control over cotton aphids extends beyond direct parasitism; it also alters the pest's growth, development, and reproduction through stress. The cotton aphid wasp plays a significant role in suppressing the initial cotton aphid population and controlling its field population, thus constituting a crucial role in the green control of aphids. When aphid populations are insufficient, the cotton aphid wasp spends more time searching for hosts. To ensure the timely laying of all its eggs, it may choose aphids that have already been parasitized as hosts. Regardless of whether superparasitism occurs, only one wasp emerges from each mummified aphid, leading to massive aphid reproduction and poor control efficacy. Therefore, breeding cotton aphid strains with strong resistance and high parasitism rates is of great significance for the green control of cotton aphid diseases. Summary of the Invention

[0004] The purpose of this invention is to address the technical problem that existing cotton aphid parasitoids are prone to hyperparasitism when cotton aphid populations are low, leading to massive aphid reproduction and poor control effects. The invention aims to propose a breeding method for cotton aphid parasitoids. The breeding method provided in this application, which involves alternating female and male parents undergoing low-temperature acclimatization, selects cotton aphid strains with strong resistance and high parasitism rates. This method significantly affects the parasitism rate of the F5 generation individuals obtained through breeding, showing a significant difference compared to the control group. Furthermore, it significantly impacts the survival rate under both low-temperature and high-temperature rearing conditions, thereby enhancing the resistance of cotton aphid parasitoids and contributing to the green and sustainable development of the cotton industry.

[0005] To achieve this technical objective, the present invention adopts the following technical solution.

[0006] This invention provides a method for breeding cotton aphid parasitic wasps, which is carried out using the following method:

[0007] (1) Before cotton harvest, collect healthy natural aphids that parasitize cotton stalks and leaves from the field, and transfer them to cotton seedlings that have been cultivated in the seed aphid greenhouse. Allow the aphids to develop and reproduce into virus-free seed aphids at 21℃-29℃ and 65%-75% humidity for later use.

[0008] (2) Before cotton harvesting, collect parasitic aphids that have been parasitized by natural aphid parasitoids on cotton stalks and leaves from the field, and attach them to the leaves of cotton plants that have been bred with aphids in the seed bee greenhouse obtained in step (1). Allow the aphid parasitoids on the parasitic aphids to develop and emerge into detoxified seed bees at 21℃-29℃ and 20%-40% humidity for later use.

[0009] (3) Use the male bees obtained by domestication in step (2) to crossbreed with female bees, and obtain the F1 generation of cotton aphid parasitic wasps through breeding;

[0010] (4) Select robust F1 generation cotton aphid parasitic wasps. After culturing male wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. Female wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps were then mated with male wasps to obtain the F2 generation of cotton aphid parasitic wasps through breeding.

[0011] (5) Select robust F2 generation cotton aphid parasitic wasps. After culturing the female wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. The male wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps then mated with the male wasps to obtain the cotton aphid parasitic wasps F3 through breeding.

[0012] (6) Select robust F3 generation cotton aphid parasitic wasps. After culturing male wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. Female wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps were then mated with male wasps to obtain cotton aphid parasitic wasps F4 through breeding.

[0013] (7) Select robust F4 generation cotton aphid parasitic wasps. After culturing the female wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. The male wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps then mated with the male wasps. Through breeding, stable genetic cotton aphid parasitic wasps F5 were obtained.

[0014] Preferably, in the cotton aphid corydalis breeding method provided by the present invention, the ratio of corydalis to aphids in step (2) is 1:100.

[0015] Preferably, the present invention provides a method for breeding cotton aphid parasitic wasps. In step (4), robust F1 generation cotton aphid parasitic wasps are selected. Male wasps are cultured at 14°C and 30% humidity for 5 days, and then the temperature is gradually increased to 25°C and 30% humidity for 10 days. Female wasps are cultured at 25°C and 30% humidity for 15 days.

[0016] Preferably, the present invention provides a method for breeding cotton aphid parasitic wasps. In step (5), robust F2 generation cotton aphid parasitic wasps are selected. After female wasps are cultured at 14°C and 30% humidity for 5 days, the temperature is gradually increased to 25°C and 30% humidity for 10 days, and male wasps are cultured at 25°C and 30% humidity for 15 days.

[0017] Preferably, the present invention provides a method for breeding cotton aphid parasitic wasps. In step (6), robust F3 generation cotton aphid parasitic wasps are selected. Male wasps are cultured at 14°C and 30% humidity for 5 days, and then the temperature is gradually increased to 25°C and 30% humidity for 10 days. Female wasps are cultured at 25°C and 30% humidity for 15 days.

[0018] Preferably, the present invention provides a method for breeding cotton aphid parasitic wasps. In step (7), robust F4 generation cotton aphid parasitic wasps are selected. After female wasps are cultured at 14°C and 30% humidity for 5 days, the temperature is gradually increased to 25°C and 30% humidity for 10 days, and male wasps are cultured at 25°C and 30% humidity for 15 days.

[0019] Preferably, the breeding method for cotton aphid parasitic wasps provided by the present invention involves feeding the wasps with 11% honey water throughout the entire rearing process.

[0020] Furthermore, this application provides the application of the above-mentioned method for breeding cotton aphid parasitoids in the breeding of cotton aphids.

[0021] Furthermore, this application provides the application of the above-mentioned breeding method of cotton aphid parasitoids in the control of cotton aphids.

[0022] By implementing the technical solution of the present invention, the following beneficial effects can be achieved:

[0023] (1) The present invention provides a method for breeding cotton aphid parasitoids. By adopting a specific breeding process, by adopting specific male and female parents for domestication with different humidity and temperature at different stages, and by constructing a specific method for breeding cotton aphid parasitoids through different generation culture schemes, it can effectively solve the technical problem that existing cotton aphid parasitoids are prone to hyperparasitism when the number of cotton aphids is low, which leads to the large-scale reproduction of cotton aphids and poor control effect.

[0024] (2) The breeding method of alternating female and male parents for low-temperature domestication provided in the technical solution of this application has a significant impact on the parasitism rate of the F5 generation individuals obtained through breeding. The parasitism rate of cotton aphid parasitoids obtained through the technical solution provided in this application is 74%-95%, which is significantly different from the parasitism rate of cotton aphid parasitoids (51%-69%) in the control group. It also has a significant impact on the survival rate in low-temperature and high-temperature feeding, with a survival rate of 24%-53%, which is significantly higher than the 8%-19% in the control group. This can improve the stress resistance of cotton aphid parasitoids and is conducive to achieving green and sustainable development of the cotton industry. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In this embodiment, cotton aphids were collected from cotton fields at the Korla Experimental Base of the Institute of Plant Protection, Xinjiang Academy of Agricultural Sciences (Kule Village, Heshilik Township, Korla City, Bayingolin Mongol Autonomous Prefecture, Xinjiang Uygur Autonomous Region, 41.75ºN, 85.81ºE). Cotton aphid parasitic wasps were collected from aphids on licorice and camel thorn plants surrounding the Korla Experimental Base of the Institute of Plant Protection, Xinjiang Academy of Agricultural Sciences, and were used for experiments after emerging as adults in the laboratory.

[0027] The relevant experiments were conducted in cotton fields at the Korla Experimental Base of the Institute of Plant Protection, Xinjiang Academy of Agricultural Sciences. The cotton variety used was Xinluzhong 67, and a wide-narrow row sowing method was adopted, with 6 rows per film and a sowing width of 200cm, a film spacing of 42cm, a row spacing of 13+62+13, and a plant spacing of 10cm. No insecticides were sprayed during the experiment.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0029] Example 1: A method for breeding cotton aphid parasitic wasps

[0030] This invention provides a method for breeding cotton aphid parasitic wasps, which is carried out using the following method:

[0031] (1) Before cotton harvest, collect healthy natural aphids that parasitize cotton stalks and leaves from the field, and transfer them to cotton seedlings that have been cultivated in the seed aphid greenhouse. Allow the aphids to develop and reproduce into virus-free seed aphids at 21℃-29℃ and 65%-75% humidity for later use.

[0032] (2) Before cotton harvesting, collect parasitic aphids that have been parasitized by natural aphid parasitoids on cotton stalks and leaves from the field, and attach them to the leaves of cotton plants that have been bred with aphids in the seed bee greenhouse obtained in step (1). Allow the aphid parasitoids on the parasitic aphids to develop and emerge into detoxified seed bees at 21℃-29℃ and 20%-40% humidity for later use.

[0033] (3) Use the male bees obtained by domestication in step (2) to crossbreed with female bees, and obtain the F1 generation of cotton aphid parasitic wasps through breeding;

[0034] (4) Select robust F1 generation cotton aphid parasitic wasps. After culturing male wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. Female wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps were then mated with male wasps to obtain the F2 generation of cotton aphid parasitic wasps through breeding.

[0035] (5) Select robust F2 generation cotton aphid parasitic wasps. After culturing the female wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. The male wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps then mated with the male wasps to obtain the cotton aphid parasitic wasps F3 through breeding.

[0036] (6) Select robust F3 generation cotton aphid parasitic wasps. After culturing male wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. Female wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps were then mated with male wasps to obtain cotton aphid parasitic wasps F4 through breeding.

[0037] (7) Select robust F4 generation cotton aphid parasitic wasps. After culturing the female wasps at 10℃-18℃ and 20%-40% humidity for 5 days, the temperature was gradually increased to 25℃ and 20%-40% humidity for 10 days. The male wasps were culturing at 21℃-29℃ and 20%-40% humidity for 15 days. The female wasps then mated with the male wasps. Through breeding, stable genetic cotton aphid parasitic wasps F5 were obtained.

[0038] Example 2: A method for breeding a cotton aphid wasp

[0039] A method for breeding cotton aphid parasitoids involves the following steps: Before cotton harvest, robust natural aphids parasitizing cotton stalks and leaves are collected from the field and grafted onto cotton seedlings already cultivated in a seed aphid greenhouse. The aphids are allowed to develop and reproduce into virus-free seed aphids at 21°C and 65% humidity for later use. Before cotton harvest, parasitic aphids formed by the natural aphid parasitizing cotton stalks and leaves are collected from the field and grafted onto the leaves of cotton plants already infested with aphids in a seed aphid greenhouse. The parasitic aphid parasitoids on the parasitic aphids are allowed to develop and emerge as virus-free seed aphids for later use. Domesticated male and female aphids are crossbred to obtain the F1 generation of cotton aphid parasitoids. Robust F1 generation cotton aphid parasitoids are selected, and male aphids are used to... After culturing at 0℃ and 20% humidity for 5 days, the temperature was gradually increased to 25℃ and 20% humidity for 10 days. Female wasps were then cultured at 21℃ and 20% humidity for 15 days. The females were then mated with males to obtain the F2 generation of *Aphidius rubra*. Robust F2 generation *Aphidius rubra* were selected, and the females were cultured at 10℃ and 20% humidity for 5 days, followed by a gradual increase to 25℃ and 20% humidity for 10 days. The males were then cultured at 21℃ and 20% humidity for 15 days. The females were then mated with males to obtain the F3 generation of *Aphidius rubra*. Robust F3 generation *Aphidius rubra* were selected and cultured using the same method as F2 to obtain the F4 generation. Robust F4 generation *Aphidius rubra* were selected and cultured using the same method as F3 to obtain the F5 generation of stably heritable *Aphidius rubra*. The entire rearing process involved feeding the females with 11% honey water.

[0040] Example 3: A method for breeding cotton aphid parasitic wasps

[0041] A method for breeding cotton aphid parasitoids involves the following steps: Before cotton harvest, robust natural aphids parasitizing cotton stalks and leaves are collected from the field and grafted onto cotton seedlings already cultivated in a seed aphid greenhouse. The aphids are allowed to develop and reproduce into virus-free seed aphids at 23°C and 67% humidity. Before cotton harvest, parasitic aphids formed by the natural aphid parasitizing cotton stalks and leaves are collected from the field and grafted onto the leaves of cotton plants already infested with aphids in a seed aphid greenhouse. The parasitic aphid parasitoids on the parasitic aphids are allowed to develop and emerge as virus-free seed aphids at 23°C and 25% humidity. Domesticated male and female aphids are crossbred to obtain the F1 generation of cotton aphid parasitoids. Robust F1 generation cotton aphid parasitoids are selected, and male aphids are used to... After culturing at 2℃ and 25% humidity for 5 days, the temperature was gradually increased to 25℃ and humidity for 10 days, followed by 15 days of culturing at 23℃ and 25% humidity for the females. The females were then mated with males to obtain the F2 generation of *Aphidius rubrum*. Robust F2 generation *Aphidius rubrum* were selected, and the females were cultured at 12℃ and 25% humidity for 5 days, followed by 10 days of culturing at 25℃ and 25% humidity for the males. The females were then mated with males to obtain the F3 generation of *Aphidius rubrum*. Robust F3 generation *Aphidius rubrum* were selected and cultured using the same method as F2 to obtain the F4 generation. Robust F4 generation *Aphidius rubrum* were selected and cultured using the same method as F3 to obtain the F5 generation of *Aphidius rubrum* with stable genetic traits. The entire rearing process involved feeding the females with 11% honey water.

[0042] Example 4: A method for breeding cotton aphid parasitic wasps

[0043] A method for breeding cotton aphid parasitoids involves the following steps: Before cotton harvest, robust natural aphids parasitizing cotton stalks and leaves are collected from the field and grafted onto cotton seedlings already cultivated in a seed aphid greenhouse. The aphids are allowed to develop and reproduce into virus-free seed aphids at 25°C and 69% humidity. Before cotton harvest, parasitic aphids formed by the natural aphid parasitizing cotton stalks and leaves are collected from the field and grafted onto the leaves of cotton plants already infested with aphids in a seed aphid greenhouse. The parasitic aphid parasitoids on the parasitic aphids are allowed to develop and emerge as virus-free seed aphids at 25°C and 30% humidity. Domesticated male and female aphids are crossbred to obtain the F1 generation of cotton aphid parasitoids. Robust F1 generation cotton aphid parasitoids are selected, and male aphids are used to... After culturing at 4℃ and 30% humidity for 5 days, the temperature was gradually increased to 25℃ and 30% humidity for 10 days, followed by 15 days of culturing at 25℃ and 30% humidity for females. The females were then mated with males to obtain the F2 generation of *Aphidius rubrum*. Robust F2 generation *Aphidius rubrum* were selected, and the females were cultured at 14℃ and 30% humidity for 5 days, followed by 10 days of culturing at 25℃ and 30% humidity for males. The females were then mated with males to obtain the F3 generation of *Aphidius rubrum*. Robust F3 generation *Aphidius rubrum* were selected and cultured using the same method as F2 to obtain the F4 generation. Robust F4 generation *Aphidius rubrum* were selected and cultured using the same method as F3 to obtain the F5 generation of *Aphidius rubrum* with stable genetic traits. The entire rearing process involved feeding with 11% honey water.

[0044] Example 5: A method for breeding a cotton aphid wasp

[0045] A method for breeding cotton aphid parasitoids involves the following steps: Before cotton harvest, robust natural aphids parasitizing cotton stalks and leaves are collected from the field and grafted onto cotton seedlings already cultivated in a seed aphid greenhouse. The aphids are allowed to develop and reproduce into virus-free seed aphids at 27°C and 71% humidity. Before cotton harvest, parasitic aphids formed by the natural aphid parasitizing cotton stalks and leaves are collected from the field and grafted onto the leaves of cotton plants already infested with aphids in a seed aphid greenhouse. The parasitic aphid parasitoids on the parasitic aphids are allowed to develop and emerge as virus-free seed aphids at 27°C and 35% humidity. Domesticated male and female aphids are crossbred to obtain the F1 generation of cotton aphid parasitoids. Robust F1 generation cotton aphid parasitoids are selected, and male aphids are used to... After culturing at 6℃ and 35% humidity for 5 days, the temperature was gradually increased to 25℃ and 35% humidity for 10 days, followed by 15 days of culturing at 27℃ and 35% humidity for the females. The females were then mated with males to obtain the F2 generation of *Aphidius rubrum*. Robust F2 generation *Aphidius rubrum* were selected, and the females were cultured at 16℃ and 35% humidity for 5 days, followed by 10 days of culturing at 25℃ and 35% humidity for the males. The females were then mated with males to obtain the F3 generation of *Aphidius rubrum*. Robust F3 generation *Aphidius rubrum* were selected and cultured using the same method as F2 to obtain the F4 generation. Robust F4 generation *Aphidius rubrum* were selected and cultured using the same method as F3 to obtain the F5 generation of *Aphidius rubrum* with stable genetic traits. The entire rearing process involved feeding the females with 11% honey water.

[0046] Example 6: A method for breeding a cotton aphid wasp

[0047] A method for breeding cotton aphid parasitoids involves the following steps: Before cotton harvest, robust natural aphids parasitizing cotton stalks and leaves are collected from the field and grafted onto cotton seedlings already cultivated in a seed aphid greenhouse. The aphids are allowed to develop and reproduce into virus-free seed aphids at 29°C and 75% humidity for later use. Before cotton harvest, parasitic aphids formed by the natural aphid parasitizing cotton stalks and leaves are collected from the field and grafted onto the leaves of cotton plants already infested with aphids in a seed aphid greenhouse. The parasitic aphid parasitoids on the parasitic aphids are allowed to develop and emerge as virus-free seed aphids for later use. Domesticated male and female aphids are crossbred to obtain the F1 generation of cotton aphid parasitoids. Robust F1 generation cotton aphid parasitoids are selected, and male aphids are used to... After culturing at 8℃ and 40% humidity for 5 days, the temperature was gradually increased to 25℃ and 40% humidity for 10 days, followed by 15 days of culturing at 29℃ and 40% humidity for the females. The females were then mated with males to obtain the F2 generation of cotton aphid wasps. Robust F2 generation cotton aphid wasps were selected, and the females were cultured at 18℃ and 40% humidity for 5 days, followed by 10 days of culturing at 25℃ and 40% humidity for the males. The males were then cultured at 29℃ and 40% humidity for 15 days, followed by mates for the females. The F3 generation of cotton aphid wasps was obtained through this process. Robust F3 generation cotton aphid wasps were selected and cultured using the same method as the F2 generation to obtain the F4 generation. Robust F4 generation cotton aphid wasps were selected and cultured using the same method as the F3 generation to obtain the F5 generation of cotton aphid wasps with stable genetic traits. Throughout the rearing process, the wasps were fed a diet consisting of 11% honey water.

[0048] Example 7: Comparison of the breeding effects of cotton aphid parasitic wasps

[0049] Based on the breeding methods for cotton aphid parasitic wasps described in Examples 2 to 6 above, the characteristics of the obtained F5 generation cotton aphid parasitic wasps were measured, and they were set as experimental groups 1, 2, 3, 4, and 5. Control groups 1, 2, 3, 4, and 5 were also established to breed F5 generations using the F1 generation breeding method described in Examples 2 to 6. Thirty single female and male wasps were selected, and small defatted cotton balls were inserted into their finger-shaped tubes. 11% honey water was dripped onto the defatted cotton using a disposable plastic dropper, and the groups were fed for 24 hours. After 2 hours of feeding, they were paired at a female:male ratio of 1:1 for 2 hours. One hundred 2nd-3rd instar cotton aphids were selected and placed in a small rearing cage. Each pair of mated cotton aphid wasps were introduced, and the cage was placed in an artificial climate chamber (temperature 25°C, relative humidity 80%, photoperiod 14L:10D). Once the aphids had formed, they were removed with a brush and placed in 2ml finger tubes. The number was counted, and the parasitism rate was calculated. The parasitism rate was calculated using the following method:

[0050]

[0051] Each treatment was repeated three times in both the experimental and control groups. Data were recorded and organized using Microsoft Excel 2010 software. Significance analysis was performed using SPSS 21.0 software, with a confidence probability of 0.95. P <0.05 indicates a significant difference.

[0052] Table 1: Comparison of breeding effects of cotton aphid parasitic wasps

[0053]

[0054] According to the results measured in Table 1 above, the parasitism rate of *Aphidius rubescens* in Experimental Groups 1 to 5 of Examples 2 to 6 of this application was significantly higher than that in Control Groups 1 to 5. This indicates that the breeding method of alternating male and female parents undergoing low-temperature domestication provided in this application has a significant impact on the parasitism rate of the F5 generation individuals obtained through breeding. The parasitism rate of *Aphidius rubescens* in Experimental Groups 1 to 5 of Examples 2 to 6 of this application showed a trend of first increasing and then decreasing, with significant differences between groups. Experimental Group 3 of Example 4 had the highest parasitism rate. During the domestication and breeding process of *Aphidius rubescens*, the parasitism rate of the offspring increased continuously with increasing temperature and humidity, but higher temperatures and humidity did not necessarily mean stronger parasitism in the offspring.

[0055] Example 8: Comparison of the breeding effects of cotton aphid parasitic wasps

[0056] Based on the breeding methods for cotton aphid parasitic wasps described in Examples 2 to 6, the characteristics of the obtained F5 generation cotton aphid parasitic wasps were measured, and they were set as experimental groups 1, 2, 3, 4, and 5. Control groups 1, 2, 3, 4, and 5 were also established, bred to the F5 generation using the F1 generation breeding method described in Examples 2 to 6. One hundred cotton aphid parasitic wasps were randomly selected from each group and placed in small rearing cages. Each group was reared at 5°C and 40°C for 24 hours, respectively. Each treatment was repeated three times for both experimental and control groups, and the survival rate was calculated.

[0057] Table 2: Comparison of stress resistance effects of cotton aphid parasitic wasps

[0058]

[0059] According to the results measured in Table 2 above, the stress resistance of the cotton aphid wasps in Experiment 1 to Experiment 5 provided in Examples 2 to 6 of this application is significantly higher than that in Control Group 1 to Control Group 5. It is evident that the breeding method of alternating male and female parents undergoing low-temperature acclimatization provided in this application has a significant impact on the stress resistance of the F5 generation individuals obtained through breeding. The survival rate of the cotton aphid wasps in Experiment 1 to Experiment 5 provided in Examples 2 to 6 of this application shows a trend of first increasing and then decreasing, with significant differences between groups. Experiment 3 provided in Example 4 had the highest survival rate. During the acclimatization and breeding process of cotton aphid wasps, as temperature and humidity increased, the survival rate of the offspring obtained under low or high temperatures continuously increased; however, higher temperatures and humidity do not necessarily mean stronger stress resistance in the offspring.

[0060] The embodiments described above are only some, not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A method of breeding of Aphidius gossypii comprising the steps of, The following methods are used: (1) Before the cotton is harvested, the natural source aphids that are parasitic on the cotton stalks and leaves are collected from the middle of the field, and are then grafted on the cotton seedlings in the greenhouse, which are grown at 21-29 DEG C and 65-75% humidity, so that the original aphids develop and reproduce into virus-free aphids for later use; (2) Before the cotton is harvested, the parasitic aphids that are parasitic on the cotton stalks and leaves and are parasitized by the natural source cotton aphid wasp are collected from the middle of the field, and are then grafted on the leaves of the cotton plants in the greenhouse, which are grown at 21-29 DEG C and 20-40% humidity, so that the cotton aphid wasp on the parasitic aphids develops and hatches into virus-free wasps for later use; (3) The male wasps and female wasps obtained in step (2) are crossbred, and the F1 generation of the cotton aphid wasp is obtained through breeding; (4) The F1 generation of the cotton aphid wasp is selected and bred, the male wasps are cultured at 10-18 DEG C and 20-40% humidity for 5 days, and then are cultured at 25 DEG C and 20-40% humidity for 10 days, the female wasps are cultured at 21-29 DEG C and 20-40% humidity for 15 days, and then are crossbred with the male wasps, and the F2 generation of the cotton aphid wasp is obtained through breeding; (5) The F2 generation of the cotton aphid wasp is selected and bred, the female wasps are cultured at 10-18 DEG C and 20-40% humidity for 5 days, and then are cultured at 25 DEG C and 20-40% humidity for 10 days, the male wasps are cultured at 21-29 DEG C and 20-40% humidity for 15 days, and then are crossbred with the female wasps, and the F3 generation of the cotton aphid wasp is obtained through breeding; (6) The F3 generation of the cotton aphid wasp is selected and bred, the male wasps are cultured at 10-18 DEG C and 20-40% humidity for 5 days, and then are cultured at 25 DEG C and 20-40% humidity for 10 days, the female wasps are cultured at 21-29 DEG C and 20-40% humidity for 15 days, and then are crossbred with the male wasps, and the F4 generation of the cotton aphid wasp is obtained through breeding; (7) The F4 generation of the cotton aphid wasp is selected and bred, the female wasps are cultured at 10-18 DEG C and 20-40% humidity for 5 days, and then are cultured at 25 DEG C and 20-40% humidity for 10 days, the male wasps are cultured at 21-29 DEG C and 20-40% humidity for 15 days, and then are crossbred with the female wasps, and the F5 generation of the cotton aphid wasp is obtained through breeding.

2. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, The ratio of the bees and aphids in step (2) is 1:

100.

3. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, In step (4), the F1 generation of the cotton aphid wasp is selected and bred, the male wasps are cultured at 14 DEG C and 30% humidity for 5 days, and then are cultured at 25 DEG C and 30% humidity for 10 days, and the female wasps are cultured at 25 DEG C and 30% humidity for 15 days.

4. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, In step (5), the F1 generation of the cotton aphid wasp is selected and bred, the male wasps are cultured at 14 DEG C and 30% humidity for 5 days, and then are cultured at 25 DEG C and 30% humidity for 10 days, and the female wasps are cultured at 25 DEG C and 30% humidity for 15 days.

5. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, In step (5), the F1 generation of the cotton aphid wasp is selected and bred, the male wasps are cultured at 14 DEG C and 30% humidity for 5 days, and then are cultured at 25 DEG C and 30% humidity for 10 days, and the female wasps are cultured at 25 DEG C and 30% humidity for 15 days.

6. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, The F1 generation of the cotton aphid braconid wasps selected in the step (5) is cultured at 14℃ and 30% humidity for 5 days, then the temperature is increased to 25℃ and the humidity is 30% for 10 days, and the female wasps are cultured at 25℃ and 30% humidity for 15 days.

7. The method for breeding cotton aphid parasitic wasps as described in claim 1, characterized in that, The whole feeding process adopts 11% honey water feeding.

8. Application of the breeding method of the cotton aphid braconid in claim 1 to claim 7 in the breeding of cotton aphids.

9. Application of the breeding method of the cotton aphid braconid in claim 1 to claim 7 in the prevention and treatment of cotton aphids.

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