Breeding method of corn with high southern rust resistance

Abstract

The invention relates to the technical field of corn breeding, and particularly discloses a breeding method of corn with high southern rust resistance, which comprises the following steps: firstly, six inbred lines are sown, a high-resistance inbred line A is respectively positively and negatively crossed with a high-susceptibility corn inbred line B, a high-susceptibility corn inbred line C, a high-susceptibility corn inbred line D and a high-susceptibility corn inbred line E; the disease-resistant inbred line M and the high-sensitivity corn inbred line B are only orthogonal, and the high-resistance corn inbred line A and the disease-resistant inbred line M are hybridized to obtain at least ten F1-generation hybrid seeds; then, six inbred lines and ten parts of F1-generation hybrid seeds are sown in one row, bagging selfing is carried out, and after maturation, harvesting is carried out according to single ears, and threshing storage is carried out; secondly, spraying and inoculating pathogenic bacteria to all plants within a week after the tasseling stage and within two weeks after the tasseling stage, and recording the disease resistance of the plants. By the adoption of the cultivation method, the cultivated corn seeds can have the effect of highly resisting the southern rust disease, and damage of the southern rust disease in the corn planting process is avoided or reduced.

Description

Technical Field

[0001] The invention relates to the technical field of corn breeding, in particular to a breeding method for corn with high resistance to southern rust. Background Art

[0002] Corn is one of the main food crops in my country. Corn kernels are rich in vitamins, which can effectively promote metabolism and prevent cardiovascular and cerebrovascular diseases. Corn can also be used to make corn oil. Southern rust of corn is a leaf disease caused by infection with the biotrophic fungus Puccinia multiflora. The disease can cause a 20% to 30% reduction in corn yield, and more than 50% in severe cases. The fungus affects corn growth, causing corn susceptibility and yield reduction. In order to reduce the occurrence of southern rust, it can be prevented by applying fungicides, but the abuse of fungicides will lead to damage to soil quality and ecology. Discovering and breeding corn varieties with high resistance to southern rust can improve the resistance of corn to Puccinia multiflora, thereby reducing the occurrence of diseases and reducing corn yield reduction.

[0003] At present, the breeding methods for highly resistant corn to southern rust include molecular marker-assisted breeding, which analyzes and identifies molecular markers for resistance to southern rust in the corn genome. Most of them are in the theoretical stage, and no effective molecular marker-assisted breeding operations have been carried out. As a result, there is still a lack of many varieties of highly resistant corn seeds to southern rust in the existing technology, and thus there is a need for better highly resistant corn seeds to southern rust. Summary of the invention

[0004] In view of the technical problem that there are still many varieties of corn seeds with high resistance to southern rust in the prior art, and thus more excellent corn seeds with high resistance to southern rust are needed, the present invention provides a breeding method for corn with high resistance to southern rust.

[0005] The technical solution adopted by the present invention is: a breeding method for corn with high resistance to southern rust, which specifically comprises the following steps:

[0006] Select the high-resistance maize inbred line A;

[0007] Select highly susceptible corn inbred line B;

[0008] Select highly susceptible corn inbred line C;

[0009] Select highly susceptible corn inbred line D;

[0010] Select highly susceptible corn inbred line E;

[0011] Select disease-resistant inbred line QiM;

[0012] Six inbred lines are sown, and the highly resistant inbred line A is respectively cross-crossed with the highly susceptible corn inbred line B, the highly susceptible corn inbred line C, the highly susceptible corn inbred line D, and the highly susceptible corn inbred line E, the disease-resistant inbred line QiM and the highly susceptible corn inbred line B are only cross-crossed, and the highly resistant corn inbred line A is cross-crossed with the disease-resistant inbred line QiM, to obtain at least ten F1 hybrid seeds in total;

[0013] Six inbred lines and ten F1 hybrid seeds were sown in each row, bagged and self-pollinated, harvested as single ears after maturity, threshed and stored;

[0014] All plants were sprayed with pathogens within one week and two weeks after the tasting stage, and their disease resistance was recorded;

[0015] Sow single ears of seeds from ten hybrid F2 populations, with one row of the corresponding parent from each population, and thirty to fifty plants planted next to them as disease-resistant and disease-susceptible controls;

[0016] Sow all the seeds of a single ear of the orthogonal F2 population of highly resistant corn inbred line A, highly susceptible corn inbred line B, highly susceptible corn inbred line C, and highly susceptible corn inbred line D;

[0017] Plant F2:3 families derived from self-pollination of ten F2 fruit ears, plant one to two rows of each family, spray-inoculate all plants with pathogens, and then record their disease resistance;

[0018] Plant a large population of multiple F2 high-resistant corn inbred line A, highly susceptible corn inbred line B, and highly susceptible corn inbred line C, sample the leaves of all individual plants before tasseling, identify and record the disease resistance of each individual plant after spraying and inoculation with pathogens, and retain the cultivated seeds after fruiting.

[0019] Furthermore, the steps of pathogen spray inoculation are as follows:

[0020] Collect southern corn rust pathogens and put them into sterile water. Add 3 to 4 drops of Tween-20 per 100 mL of water and adjust the concentration of the bacterial solution to 4 JD to 45 spores per field of view under a 100x microscope.

[0021] When corn is in the 4-5 leaf stage, use a brush to paint the leaves for the first inoculation, and then strengthen the inoculation once more by spraying five to seven days later.

[0022] Furthermore, two weeks after the pathogen inoculation, the resistance of different maize inbred lines was investigated and graded;

[0023] The grading standard is as follows: Grade 1 (resistant, R), no lesions; Grade 2 (moderately resistant, MR), extremely small summer spores, and local tissues have chlorotic and necrotic spots; Grade 3 (moderately susceptible, MS), summer spores are of medium size and connected in pieces, and some host epidermis is torn; Grade D (susceptible, S).

[0024] Furthermore, the method further comprises the following steps:

[0025] The SNP loci of the parental high-resistant corn inbred line A and the high-susceptible corn inbred line C were screened by corn chip;

[0026] SNP markers evenly distributed on ten chromosomes of maize were selected from all polymorphic loci, and KASP genotyping was performed on thirty highly resistant and highly susceptible plants in the orthogonal population of the F2 parental highly resistant maize inbred line A and highly susceptible maize inbred line C.

[0027] New SNP markers were developed around the chromosome fragments linked to the resistance gene obtained by typing, and SNP markers were used to perform marker typing on the orthogonal population of the F2 parent highly resistant maize inbred line A and highly susceptible maize inbred line C.

[0028] Furthermore, the method further comprises the following steps: the method further comprises analyzing molecular markers, the steps of which are as follows:

[0029] DNA was extracted and purified by 2×CTAB method. The southern rust resistance gene was located on chromosome 10. 50 pairs of markers on the linkage group of maize chromosome 10 were selected from MaizeGDB.

[0030] The resistant-susceptible pool was used for polymorphism screening, and linkage analysis of the segregating populations was then performed on markers with polymorphisms between the resistant-susceptible pools.

[0031] Furthermore, the method further comprises a PCR amplification reaction, wherein the specific steps are as follows:

[0032] The reaction was performed by PCR instrument with a total volume of 20 μL, including 0.2 mmol / L dNTPs, 0.25 μmol / L primers and 20 ng template DNA, and sterile water was added to make up the volume;

[0033] The PCR amplification procedure was 94°C pre-denaturation for 5 min; 94°C for 40 s, 60°C for 35 s, 72°C for 45 s, 30 cycles; 72°C extension for 10 min; the amplified product was electrophoresed on a 6% non-denaturing polyacrylamide gel, and the staining process was carried out on a low-speed horizontal shaker. The method was as follows:

[0034] Fix with 10% ethanol + 0.5% glacial acetic acid for 15 min;

[0035] 0.2% silver nitrate penetration for 15 min;

[0036] Rinse twice with distilled water;

[0037] 1.5% sodium hydroxide + 0.4% formaldehyde was used for color development until a clear band appeared, then the color development was stopped and the results were analyzed by photograph.

[0038] Furthermore, the method further comprises the following steps:

[0039] From the large population of orthogonal crosses between the F2 high-resistant maize inbred line A and the highly susceptible maize inbred line C, multiple consecutive plants were selected as test materials, and DNA was extracted from leaves of some susceptible plants.

[0040] All available multiple markers on the corn chip were selected for SNP marker typing.

[0041] Furthermore, the method further comprises the following steps:

[0042] Genetic mapping software was used to construct a local genetic linkage map by using the data obtained from marker typing of a large population of F2 high-resistant maize inbred line A and high-susceptible maize inbred line C after orthogonal crosses. Functions were used to calculate the genetic distances between markers and rank the markers.

[0043] The beneficial effects of the present invention are as follows: compared with the prior art, in the present invention, firstly, six inbred lines are sown, and the high-resistance inbred line A is respectively cross-crossed with the high-susceptibility corn inbred line B, the high-susceptibility corn inbred line C, the high-susceptibility corn inbred line D, and the high-susceptibility corn inbred line E, the disease-resistant inbred line QiM and the high-susceptibility corn inbred line B are only cross-crossed, and the high-resistance corn inbred line A is cross-crossed with the disease-resistant inbred line QiM, so as to obtain at least ten F1 hybrid seeds in total; then, six inbred lines and ten F1 hybrid seeds are sown in one row each, bagged and self-pollinated, harvested as single ears after maturity, threshed and stored; secondly, all plants are sprayed and inoculated with pathogens within one week after the tasseling period and within two weeks after the tasseling period, and their disease resistance is recorded; furthermore, single ear seeds of ten hybrid F2 populations are single-grained Sowing, each group has a row of corresponding parents, and 30 to 50 plants are planted next to them as disease-resistant and disease-susceptible controls; then, the highly resistant corn inbred line A and the highly susceptible corn inbred line B, the highly susceptible corn inbred line C, and the highly susceptible corn inbred line D are orthogonal to the F2 group, and the seeds of single ears are all sown; then, the F2:3 families from ten F2 ears are planted, and each family is planted in one to two rows, and all plants are sprayed and inoculated with pathogens, and then their disease resistance is recorded; finally, a large group of multiple F2 highly resistant corn inbred lines A and highly susceptible corn inbred lines B and highly susceptible corn inbred lines C are planted, and all single leaves are sampled before tasseling, and the disease resistance of each single plant is identified and recorded after the pathogen is sprayed and inoculated. After the results are obtained, the cultivated seeds are retained. The above-mentioned cultivation method can make the cultivated corn seeds have the effect of high resistance to southern rust, so that the damage of southern rust can be avoided or reduced during corn planting. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In order to solve the problems existing in the background technology, the present application proposes the following technical solution: a breeding method for corn with high resistance to southern rust, specifically comprising the following steps:

[0046] Step S101, selecting a high-resistance corn inbred line A;

[0047] Step S102, selecting a highly susceptible corn inbred line B;

[0048] Step S103, selecting a highly susceptible corn inbred line C;

[0049] Step S104, selecting a highly susceptible corn inbred line D;

[0050] Step S105, selecting a highly susceptible corn inbred line E;

[0051] Step S106, selecting disease-resistant inbred line QM;

[0052] Step S107, sowing six inbred lines, cross-crossing the highly resistant inbred line A with the highly susceptible corn inbred line B, the highly susceptible corn inbred line C, the highly susceptible corn inbred line D, and the highly susceptible corn inbred line E, cross-crossing the disease-resistant inbred line QM and the highly susceptible corn inbred line B only, and cross-crossing the highly resistant corn inbred line A with the disease-resistant inbred line QM, to obtain at least ten F1 hybrid seeds in total;

[0053] Step S108, sowing six inbred lines and ten F1 hybrid seeds in each row, bagging and self-pollinating, harvesting by single ear after maturity, threshing and storing;

[0054] Step S109, spraying and inoculating all plants with pathogens within one week and two weeks after the tasting period, and recording their disease resistance;

[0055] Step S1010, sowing single ears of seeds from ten hybrid F2 populations, with each corresponding parent of each population in one row, and thirty to fifty plants planted next to them as disease-resistant and disease-susceptible controls;

[0056] Step S1011, sowing all seeds of single ear of the orthogonal F2 population of the highly resistant corn inbred line A, the highly susceptible corn inbred line B, the highly susceptible corn inbred line C, and the highly susceptible corn inbred line D;

[0057] Step S1012, planting F2:3 families derived from self-pollination of ten F2 fruit ears, planting one to two rows for each family, spraying and inoculating all plants with pathogens, and then recording their disease resistance;

[0058] Step S1013, planting a large group of multiple F2 high-resistant corn inbred line A, highly susceptible corn inbred line B, and highly susceptible corn inbred line C, sampling the leaves of all individual plants before tasseling, identifying and recording the disease resistance of each individual plant after spraying and inoculating with pathogens, and retaining the cultivated seeds after the results are obtained.

[0059] Among them, the steps of spraying and inoculating pathogens are as follows:

[0060] Step S101, collecting southern corn rust pathogens and putting them into sterile water, adding 3 to 4 drops of Tween-20 per 100 mL of water, and adjusting the concentration of the bacterial solution to 4 JD to 45 spores per field of view under a 100x microscope;

[0061] Step S102, when the corn is in the 4-5 leaf stage, the leaves are painted with a brush for the first inoculation, and five to seven days later, the inoculation is strengthened once more by spraying.

[0062] Among them, the resistance of different maize inbred lines was investigated and graded two weeks after the pathogen was inoculated;

[0063] The grading standard is as follows: Grade 1 (resistant, R), no lesions; Grade 2 (moderately resistant, MR), extremely small summer spores, and local tissues have chlorotic and necrotic spots; Grade 3 (moderately susceptible, MS), summer spores are of medium size and connected in pieces, and some host epidermis is torn; Grade D (susceptible, S).

[0064] The following steps are also included:

[0065] Step S101, screening SNP loci of parental high-resistant corn inbred line A and high-susceptible corn inbred line C through corn chip;

[0066] Step S102, selecting SNP markers evenly distributed on ten chromosomes of maize from all polymorphic loci, and performing KASP genotyping on thirty highly resistant and highly susceptible plants in the orthogonal population of the F2 parent highly resistant maize inbred line A and the highly susceptible maize inbred line C;

[0067] Step S103, developing new SNP markers around the chromosome fragments linked to the resistance gene obtained by typing, and using the SNP markers to perform marker typing on the orthogonal population of the F2 parent highly resistant corn inbred line A and the highly susceptible corn inbred line C.

[0068] The steps include: molecular marker analysis, the steps are as follows:

[0069] Step S101, extracting and purifying DNA using the 2×CTAB method, the southern rust resistance gene is located on chromosome 10, and 50 pairs of markers on the linkage group of maize chromosome 10 are selected from MaizeGDB;

[0070] Step S102, using the resistance-susceptibility pool to perform polymorphism screening, and then performing linkage analysis of the segregating population on the polymorphic markers between the resistance-susceptibility pools.

[0071] Among them, it also includes PCR amplification reaction, and the specific steps are as follows:

[0072] Step S101, carried out by PCR instrument, the total reaction volume is 20 μL, including 0.2 mmol / L dNTPs, 0.25 μmol / L primers and 20 ng template DNA, and sterile pure water is added to make up the volume;

[0073] Step S102, the PCR amplification program is 94°C pre-denaturation for 5 min; 94°C for 40 s, 60°C for 35 s, 72°C for 45 s, 30 cycles; 72°C extension for 10 min; the amplified product is electrophoresed on a 6% non-denaturing polyacrylamide gel, and the staining process is carried out on a low-speed horizontal shaker, the method is as follows:

[0074] Step S1, fixation with 10% ethanol + 0.5% glacial acetic acid for 15 min;

[0075] Step S2, 0.2% silver nitrate infiltration for 15 min;

[0076] Step S3, rinsing with distilled water twice;

[0077] Step S4, 1.5% sodium hydroxide + 0.4% formaldehyde color development, until a clear band appears, stop the color development, and take photos for analysis.

[0078] The following steps are also included:

[0079] Step S101, selecting a plurality of consecutive plants from a large population of orthogonal F2 high-resistant corn inbred line A and highly susceptible corn inbred line C as test materials, and extracting DNA from leaves of some of the rust-susceptible plants;

[0080] Step S102, selecting all available multiple markers on the corn chip for SNP marker typing.

[0081] The following steps are also included:

[0082] Genetic mapping software was used to construct a local genetic linkage map by using the data obtained from marker typing of a large population of F2 high-resistant maize inbred line A and high-susceptible maize inbred line C after orthogonal crosses. Functions were used to calculate the genetic distances between markers and rank the markers.

[0083] All F2 populations showed resistance segregation, and the number of resistant and susceptible isolates in each population is shown in Table 1.

[0084]

[0085] Table 1

[0086] In summary, as can be seen from the table, except for the F2 population of A×Qi M, the resistance and susceptibility ratios of the F2 populations of the other A are both 3:1. Among them, most of the individual plants in the F2 population of A×C showed high resistance (R level) or high susceptibility (S level). Therefore, by using the above cultivation method, the cultivated corn seeds can have the effect of high resistance to southern rust, and avoid or reduce the damage of southern rust during the corn planting process.

[0087]

[0088]

[0089] Table 2

[0090] As can be seen from Table 2, when the F2 disease level is resistant, 40 families showed high resistance.

[0091] Table 3 Leaf disease level, symptoms and resistance, reference standard.

[0092]

[0093] Table 3

[0094] To sum up, in the present invention, first, by sowing six inbred lines, the highly resistant inbred line A is reciprocally crossed with the highly susceptible maize inbred lines B, C, D, and E respectively, and the resistant inbred line Qi M is only orthogonally crossed with the highly susceptible maize inbred line B, and the highly resistant maize inbred line A is crossed with the resistant inbred line Qi M, obtaining at least ten F1 hybrid seeds in total;

[0095] Then, sow one row of each of the six inbred lines and ten F1 hybrid seeds, bag them for self-crossing, harvest by single ear after maturity, and thresh and store;

[0096] Secondly, within one week and two weeks after the tasseling stage, spray inoculate all plants with the pathogen and record their disease resistance;

[0097] Furthermore, sow the single-grain seeds of the single ears of the ten hybrid F2 populations, one row of the corresponding parents of each population, and plant thirty to fifty plants beside them as disease-resistant and susceptible controls;

[0098] Subsequently, sow all the single-grain seeds of the single ears of the F2 populations obtained by the orthogonal crosses of the highly resistant maize inbred line A with the highly susceptible maize inbred lines B, C, and D;

[0099] Next, the F2:3 families derived from the self-pollination of ten F2 fruit ears were planted, with one to two rows of each family, all plants were spray-inoculated with pathogens, and their disease resistance was recorded;

[0100] Finally, a large population of multiple F2 high-resistant corn inbred line A, highly susceptible corn inbred line B, and highly susceptible corn inbred line C were planted, and leaves of all individual plants were sampled before tasseling. After spraying and inoculation with pathogens, the disease resistance of each individual plant was identified and recorded. After the results were obtained, the cultivated seeds were retained.

[0101] By adopting the above-mentioned breeding method, the cultivated corn seeds can have a high resistance to southern rust, so that the damage caused by southern rust can be avoided or reduced during the corn planting process.

[0102] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for breeding corn with high resistance to southern rust, characterized in that: The specific steps include: Select the high-resistance maize inbred line A; Select highly susceptible corn inbred line B; Select highly susceptible corn inbred line C; Select highly susceptible corn inbred line D; Select highly susceptible corn inbred line E; Select disease-resistant inbred line QiM; Six inbred lines are sown, and the highly resistant inbred line A is respectively cross-crossed with the highly susceptible corn inbred line B, the highly susceptible corn inbred line C, the highly susceptible corn inbred line D, and the highly susceptible corn inbred line E, the disease-resistant inbred line QiM and the highly susceptible corn inbred line B are only cross-crossed, and the highly resistant corn inbred line A is cross-crossed with the disease-resistant inbred line QiM, to obtain at least ten F1 hybrid seeds in total; Six inbred lines and ten F1 hybrid seeds were sown in each row, bagged and self-pollinated, harvested as single ears after maturity, threshed and stored; All plants were sprayed with pathogens within one week and two weeks after the tasting stage, and their disease resistance was recorded; Sow single ears of seeds from ten hybrid F2 populations, with one row of the corresponding parent from each population, and thirty to fifty plants planted next to them as disease-resistant and disease-susceptible controls; Sow all the seeds of a single ear of the orthogonal F2 population of highly resistant corn inbred line A, highly susceptible corn inbred line B, highly susceptible corn inbred line C, and highly susceptible corn inbred line D; Plant F2:3 families derived from self-pollination of ten F2 fruit ears, plant one to two rows of each family, spray-inoculate all plants with pathogens, and then record their disease resistance; Plant a large population of multiple F2 high-resistant corn inbred line A, highly susceptible corn inbred line B, and highly susceptible corn inbred line C, sample the leaves of all individual plants before tasseling, identify and record the disease resistance of each individual plant after spraying and inoculation with pathogens, and retain the cultivated seeds after fruiting.

2. The method for breeding corn with high resistance to southern rust according to claim 1, characterized in that: The steps for pathogen spray inoculation are as follows: Collect southern corn rust pathogens and put them into sterile water. Add 3 to 4 drops of Tween-20 per 100 mL of water and adjust the concentration of the bacterial solution to 4 JD to 45 spores per field of view under a 100x microscope. When corn is in the 4-5 leaf stage, use a brush to paint the leaves for the first inoculation, and then strengthen the inoculation once more by spraying five to seven days later.

3. The method for breeding corn with high resistance to southern rust according to claim 1, characterized in that: Two weeks after inoculation with pathogens, the resistance of different maize inbred lines was investigated and graded; The grading standard is as follows: Grade 1 (resistant, R), no lesions; Grade 2 (moderately resistant, MR), extremely small summer spores, and local tissues have chlorotic and necrotic spots; Grade 3 (moderately susceptible, MS), summer spores are of medium size and connected in pieces, and some host epidermis is torn; Grade D (susceptible, S).

4. The method for breeding corn with high resistance to southern rust according to claim 3, characterized in that: The following steps are also included: The SNP loci of the parental high-resistant corn inbred line A and the high-susceptible corn inbred line C were screened by corn chip; SNP markers evenly distributed on ten chromosomes of maize were selected from all polymorphic loci, and KASP genotyping was performed on thirty highly resistant and highly susceptible plants in the orthogonal population of the F2 parental highly resistant maize inbred line A and highly susceptible maize inbred line C. New SNP markers were developed around the chromosome fragments linked to the resistance gene obtained by typing, and SNP markers were used to perform marker typing on the orthogonal population of the F2 parent highly resistant maize inbred line A and highly susceptible maize inbred line C.

5. The method for breeding corn with high resistance to southern rust according to claim 4, characterized in that: The following steps are also included: It also includes molecular marker analysis, the steps are as follows: DNA was extracted and purified by 2×CTAB method. The southern rust resistance gene was located on chromosome 10. 50 pairs of markers on the linkage group of maize chromosome 10 were selected from MaizeGDB. The resistant-susceptible pool was used for polymorphism screening, and linkage analysis of the segregating populations was then performed on markers with polymorphisms between the resistant-susceptible pools.

6. The method for breeding corn with high resistance to southern rust according to claim 5, characterized in that: It also includes a PCR amplification reaction, and the specific steps are as follows: The reaction was performed by PCR instrument with a total volume of 20 μL, including 0.2 mmol / L dNTPs, 0.25 μmol / L primers and 20 ng template DNA, and sterile water was added to make up the volume; The PCR amplification procedure was 94°C pre-denaturation for 5 min; 94°C for 40 s, 60°C for 35 s, 72°C for 45 s, 30 cycles; 72°C extension for 10 min; the amplified product was electrophoresed on a 6% non-denaturing polyacrylamide gel, and the staining process was carried out on a low-speed horizontal shaker. The method was as follows: Fix with 10% ethanol + 0.5% glacial acetic acid for 15 min; 0.2% silver nitrate penetration for 15 min; Rinse twice with distilled water; 1.5% sodium hydroxide + 0.4% formaldehyde was used for color development until a clear band appeared, then the color development was stopped and the results were analyzed by photograph.

7. The method for breeding corn with high resistance to southern rust according to claim 6, characterized in that: The following steps are also included: From the large population of orthogonal crosses between the F2 high-resistant maize inbred line A and the highly susceptible maize inbred line C, multiple consecutive plants were selected as test materials, and DNA was extracted from leaves of some susceptible plants. All available multiple markers on the corn chip were selected for SNP marker typing.

8. The method for breeding corn with high resistance to southern rust according to claim 7, characterized in that: The following steps are also included: Genetic mapping software was used to construct a local genetic linkage map by using marker typing data from a large population of F2 high-resistant maize inbred line A and high-susceptible maize inbred line C after orthogonal crosses. Functions were used to calculate the genetic distances between markers and to rank the markers.

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