Construction method of tomato multi-parent stepped hybrid superpopulation and application of tomato multi-parent stepped hybrid superpopulation in variety breeding

Abstract

The invention discloses a construction method of a tomato multi-parent stepped hybrid superpopulation (TSP). The method aims at the technical bottlenecks of narrow parent genetic basis, low multi-character polymerization efficiency and long breeding period in commercial breeding. Commercial hybrids with prominent target traits are screened, wherein the commercial hybrids are high in yield, high in quality, good in commodity, resistant to soil-borne diseases, resistant to virus diseases and resistant to stress, and a three-in-one technical path of'step hybridization design-mixed strategy-super-large-scale recombination 'is adopted for construction. Three double cross species F1AB, F1CD and F1EF are obtained through the first round of hybridization; in the second round of hybridization, male parent mixed pollination and female parent mixed harvesting are adopted to obtain a four-way hybrid F1CDEF; in the third round of hybridization, male parent powder mixing and female parent single plant seed harvesting are adopted to obtain a six-way hybrid F1ABCDEF; and in the fourth round, large-scale single plant selfing and mixing are carried out to form an F2 super group with abundant genetic diversity. The invention provides a material basis for breeding disease-resistant, high-yield and high-quality breakthrough tomato varieties.

Description

Technical Field

[0001] This invention belongs to the field of plant genetics and breeding, specifically relating to a method for constructing a tomato multi-parent ladder hybrid superpopulation (TSP) and its application in variety selection. Background Technology

[0002] As a globally important vegetable crop, the yield and quality of tomatoes are crucial to food safety and market demand. However, modern tomato breeding faces three major challenges in synergistically improving comprehensive traits such as high yield, high quality, and multiple resistances. First, commercial germplasm resources face significant intellectual property barriers. Due to strict protection under plant variety protection or patent laws, breeders cannot directly use these commercial varieties carrying key genes as parents, severely limiting the genetic basis of breeding materials. Second, traditional breeding methods are inefficient and time-consuming. Taking multi-parental advanced generation intercrossing lines (MAGIC) as an example, although they provide rich genetic diversity, their construction requires 6-8 rounds of repeated intercrossing and self-pollination, taking 6-8 years, which cannot meet the market demand for rapid variety iteration. Traditional backcrossing breeding can only improve a few traits at a time, making it difficult to achieve efficient aggregation of multiple traits. Third, there are serious genetic antagonisms and linkage burdens among key traits. Important economic traits and stress resistance traits in tomatoes often show significant negative genetic correlations. For example, the genetic correlation coefficient between high yield potential and resistance to soil-borne diseases (such as wilt and bacterial wilt) or viral diseases (such as TYLCV) can be as low as -0.71. This attrition caused by gene linkage or physiological competition makes it extremely difficult to breed varieties that combine high resistance and high yield, constituting a long-term technical bottleneck.

[0003] Therefore, the urgent technical problem to be solved is to develop new methods for constructing breeding materials that shorten the breeding cycle and break unfavorable linkages, and to quickly create super populations with rich genetic backgrounds and fully recombined genes through efficient hybridization design, so as to breed the next generation of breakthrough tomato varieties. Summary of the Invention

[0004] This invention provides a method for constructing genetically diverse superpopulations (TSPs) for tomatoes using a ladder hybridization and mixing strategy, and also provides the application of this method in breeding inbred lines and cultivating tomato varieties.

[0005] The technical solution of this invention:

[0006] A method for constructing a multi-parent ladder hybrid super population of tomatoes includes the following steps: screening for high-yield TSP-A, high-quality TSP-B, good marketability TSP-C, resistance to soil-borne diseases TSP-D, resistance to viral diseases TSP-E, and resistance to abiotic stress TSP-F.

[0007] (1) First round of hybridization: B×A, D×C, F×E are hybridized, with each combination producing ≥5 individual plants to obtain double cross F. 1AB F 1CD F 1EF ;

[0008] (2) Second round of hybridization: F1 1CD ×F 1EF Hybridization is performed using pollen from a mixture of at least 100 male plants for pollination, and pollination of the female plant using pollen from a mixture of at least 100 female plants to obtain a four-cross hybrid F1. 1CDEF ;

[0009] (3) Third round of hybridization: F1 1CDEF ×F 1AB Hybridization is performed using a mixture of pollen from at least 100 male plants for pollination, and single female plants are harvested and ≥1024 independent lines are retained to obtain a six-cross F1 hybrid. 1ABCDEF ;

[0010] (4) Population construction: The obtained six-cross F1 populations are constructed. 1ABCDEF The lines were planted separately, and ≥4 plants from each line were randomly selected for self-pollination. All self-pollinated seeds were mixed to form an F2 superpopulation of ≥4096 plants.

[0011] Preferably, the double cross F1 obtained after the first round of hybridization 1AB F 1CD F 1EF Plant in different areas and harvest seeds from the offspring of ≥5 hybrid fruits of a hybrid combination;

[0012] Parent F 1CD With F 1EF Planting conditions: Large-scale planting of F 1CD and F 1EF Each double-cross population should have at least 150 plants to ensure that at least 100 plants receive mixed pollen.

[0013] F 1EF Male parent selection: Randomly collect anthers from ≥100 plants with vigorous growth and abundant pollen to prepare flowers;

[0014] F 1CD Selection of mother plants: Select ≥100 plants with consistent growth and normal flower development as mother plants for further processing.

[0015] Demasculate and pollinate; at harvest, collect all successfully hybridized seeds together.

[0016] Preferably, the maternal parent F is planted on a large scale before the third round of hybridization. 1CDEF Group and parent F 1AB group;

[0017] Father F1AB Use mixed pollen from ≥100 plants to ensure that the genetic diversity of parents A and B is fully introduced;

[0018] Mother F 1CDEF Single-plant pollination and single-plant seed harvesting were implemented, and ≥1024 independent lineage seeds that showed normal growth vigor, flowering period and fruit setting were retained from ≥1000 female plants.

[0019] Preferably, F before group construction 1ABCDEF Cultivation and planting conditions for the strain: retain ≥1024 F1 cells. 1ABCDEF The strains are planted in separate areas under the same conditions, with at least 10 plants planted in each strain to ensure that there are enough healthy plants for self-pollination.

[0020] The application of the tomato multi-parent ladder hybrid super population in the selection of inbred lines and the cultivation of disease-resistant, high-yielding, and high-quality tomato varieties.

[0021] The beneficial effects of this invention are:

[0022] (1) High efficiency and strong controllability: This invention gradually aggregates six types of traits through a ladder-like hybridization method of "double cross, quadruple cross, and six cross" to avoid the uncontrollability of direct multiple crosses; in the second round of hybridization, the male parent is mixed with pollen and the female parent is mixed with pollen, which efficiently inputs diversity; in the third round of hybridization, the female parent is harvested as a single plant (1024 plants) to preserve the genetic differences within the population and form a multi-pedigree basis; from each of the 1024 subpopulations, 4 plants are randomly selected for self-pollination and the seeds of 4096 plants are mixed to maximize the capture of recombination variation.

[0023] (2) Rich genetic diversity and breaking unfavorable linkage: Through large-scale random self-pollination and seed mixing (finally mixing no less than 4096 plants), this invention captures all possible gene recombination events that may occur in the parents to the greatest extent. Molecular marker verification shows that the constructed TSP population exhibits allelic polymorphisms at multiple disease resistance gene loci that are much higher than those of the original parents, effectively avoiding the genomic characteristics of the original parents, breaking the unfavorable linkage between traits such as high yield and disease resistance, and laying a solid genetic foundation for the aggregation of multiple excellent traits.

[0024] (3) Shortened breeding cycle: Through optimized hybridization and mixing strategies, this invention can complete the entire process from parental hybridization to TSP population input for breeding in just 4 years while ensuring sufficient genetic recombination. Compared with the traditional MAGIC population construction method (which usually takes 6-8 years), the breeding cycle is shortened by nearly half, which greatly accelerates the breeding process.

[0025] (4) Significant advantages in breeding efficiency and cost: The TSP population constructed using this invention can be used to directly conduct large-scale inbred line selection and to rapidly screen target genotypes using molecular marker-assisted selection (MAS), greatly shortening the cycle of field phenotypic selection and improving selection accuracy and efficiency. At the same time, this method starts with commercial hybrids, avoiding the variety rights fees that may arise from directly using authorized parents, reducing the cost of obtaining original materials, and providing a new, efficient, and economical paradigm for commercial breeding. Attached Figure Description

[0026] Figure 1 Results of Ty2 molecular marker detection in some germplasms;

[0027] Figure 2 Results of Ty3a molecular marker detection in some germplasms. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described in detail below with reference to examples.

[0029] Example 1: Construction of a Tomato Multi-Parent Ladder Hybrid Superpopulation

[0030] Hybrids were screened for six target traits, including high-yield (A), high-quality (B), commercially viable (C), resistant to soil-borne diseases (D), resistant to viral diseases (E), and resistant to abiotic stress (F).

[0031] Among them, quality mainly refers to indicators such as sugar content, vitamin C, and sweet-sour ratio, while marketability mainly refers to storage resistance, color, and single fruit weight.

[0032] (1) First round of hybridization: B×A, D×C, F×E are hybridized, with each combination producing ≥5 individual plants to obtain double cross F. 1AB F 1CD F 1EF ;

[0033] (2) Second round of hybridization: F1 1CD ×F 1EF , father (F 1EF Pollination was performed using ≥100 mixed pollen plants, with the female parent (F) 1CD Harvest ≥100 plants together to obtain a tetracross F1. 1CDEF ;

[0034] (3) Third round of hybridization: F1 1CDEF ×F1 AB , father (F 1AB Pollination was performed using ≥100 mixed pollen plants, with the female parent (F) 1CDEF Harvest individual plants and retain ≥1024 independent lines to obtain six-cross F1 strains. 1ABCDEF ;

[0035] (4) Population construction: ≥1024 F 1ABCDEF The lines were planted separately, and ≥4 plants from each line were randomly selected for self-pollination. All self-pollinated seeds were mixed (≥4096 plants) to form an F2 superpopulation (TSP), as shown in Table 1.

[0036] To ensure the quality of hybrids and lay a good foundation for the next round of hybridization, the following specific planting conditions and selection criteria should be followed:

[0037] 1. General planting conditions

[0038] All generations of materials are cultivated in standard, modern greenhouses or environmentally controlled, isolated rooms, with strict spatial or temporal isolation to prevent contamination by non-target pollen. Cultivation management employs uniform high water and fertilizer standards to ensure healthy plant growth.

[0039] 2. Specific planting considerations at each stage

[0040] (1) F1 generation is obtained after the first round of hybridization (F1 generation) 1AB F 1CD F 1EF The three combinations need to be planted in separate areas for easier observation and operation. Hybrid selection considerations: Seeds are harvested from at least five hybrid fruit progeny from each hybrid combination (e.g., B×A). The core objective at this stage is to ensure successful hybridization and preserve the genetic makeup of all hybrid progeny, providing a genetically diverse population for the next round of hybridization, rather than performing single-plant selection.

[0041] Parent F 1CD With F 1EF Planting conditions: Large-scale planting of F 1CD and F 1EF Each population shall consist of at least 150 plants to ensure the supply and acceptance of mixed pollen / flowers from at least 100 plants.

[0042] Father (F) 1EF Selection: Fresh anthers from ≥100 vigorous plants with abundant pollen were randomly collected and mixed to prepare pollen, aiming to maximize the genetic diversity input of the paternal parent.

[0043] Parent (F) 1CD Selection: Select ≥100 plants with consistent growth and normal floral development as the female parent, and perform emasculation and pollination. At harvest, collect all successfully hybridized fruits and seeds mixed together. This aims to efficiently aggregate the genetic background of the two parents, C and D, while avoiding genetic drift caused by early artificial selection.

[0044] (2) Parental F1 generation before the third round of hybridization 1CDEF With F 1AB Cultivation: Large-scale planting of F1CDEF Group (as parent) and F 1AB The group (as the parent).

[0045] Father F 1AB Selection: Continue to use the mixed pollen strategy of ≥100 plants to ensure that the genetic diversity of parents A and B is fully introduced.

[0046] Mother F 1CDEF Selection: This is a crucial step in establishing genetic heterogeneity. Single-plant pollination and seed harvesting were performed on the maternal plants. From a large number of maternal plants (≥1000), ≥1024 independent lines exhibiting normal growth vigor, flowering time, and fruit set were successfully retained. This aims to fix the genetic background differentiation of the four-cross F1 generation, laying the foundation for the subsequent construction of a superpopulation with 1024 sublines.

[0047] (3) F before group construction 1ABCDEF Strain cultivation

[0048] Planting conditions: ≥1024 F cells will be retained. 1ABCDEF The strains are planted in separate areas under the same conditions, with at least 10 plants planted in each strain to ensure that there are enough healthy plants for self-pollination.

[0049] Hybrid selection considerations: From each line, ≥4 healthy plants of moderate growth are randomly selected for self-pollination to avoid bias introduced by selecting extreme phenotypes. Finally, the seeds of all ≥4096 self-pollinated fruits are physically mixed evenly to form the final F2 population. This large-scale random mixing strategy ensures sufficient random recombination and fixation of the original parental genes, maximizing the capture of all possible superior gene combinations.

[0050] Table 1. Design of ultra-large-scale multi-parent composite hybrid populations

[0051]

[0052] Example 2: Construction and breeding of super populations of disease-resistant and salt-tolerant new varieties Mufan No. 5 and Mufan No. 7

[0053] By utilizing multiple rounds of hierarchical hybridization among superior hybrids and large-scale self-pollination to construct super populations, unique and superior germplasm can be created, achieving an organic combination of resistance, yield, and quality.

[0054] Based on six commercially available pink-fruited hybrids with outstanding TYLCV resistance and excellent overall traits (A. high-yield type, Wofen 360; B. high-quality type, Fentaro 2; C. good-fruit type, Dongfangmei; D. soil-borne disease resistant type, Jingfan 203; E. virus resistant type, Vienna 2; F. stress-tolerant type, Xiafenba), a super population F was constructed through three rounds of hybridization and one round of self-pollination. 2ABCDEFRandomly seed 15,000 F seeds. 2ABCDEF Single plants, self-pollination, and single-plant harvesting were conducted. Through the detection of disease resistance genes (Ty1, Ty2, Ty3a, Tm2a, I2, Mi1-2, Fr1, Cf9) in single plants of the super population, a super population disease resistance gene bank of 15,000 strains was obtained, realizing the creation of unique and excellent germplasm by integrating multiple properties and aggregating superior disease resistance traits.

[0055] With TYLCV resistance as the germplasm innovation target, 20 candidate super populations resistant to TYLCV and also possessing other resistances and superior traits were screened. Through multiple generations of self-pollination of the candidate lines, and using large-scale seedling disease resistance molecular marker detection, phenotypic gene expression, and precise field identification, 28 new germplasm accessions resistant to TYLCV and leaf mold were created, including 5 accessions also resistant to nematodes, root rot, and wilt soil-borne diseases (Table 2).

[0056] Among them, JC26-12-3-12-17-8, KG1430, FB26, P-12-19, P=21=67, P190, and P124 exhibited excellent germplasm performance.

[0057] Table 2 Germplasm Breeding Process

[0058]

[0059] To verify the beneficial effects of the tomato superpopulation (TSP) constructed in this invention on genetic diversity, the following molecular marker verification experiment of the TSP population was conducted.

[0060] Fifty individual plants from the F2 generation of the TSP population constructed in this invention were randomly selected, and six original parents (AFs) were used as controls. Genomic DNA was extracted from the leaves of all materials using the CTAB method or a commercial plant genomic DNA extraction kit.

[0061] Eight molecular markers of resistance to major tomato diseases (Ty1, Ty2, Ty3a, Tm2a, I2, Mi1-2, Fr1, Cf9) were used as templates for PCR amplification of tomato DNA.

[0062] General process: Marker screening → PCR system optimization (for each marker) → High-throughput PCR on 156 DNA samples → Initial agarose gel screening → Precise genotyping by electrophoresis → Obtaining genotype data for each marker site (e.g., 950bp / 850bp).

[0063] The results are as follows Figure 1 , 2 As shown, Figure 1 In this study, the resistance gene is 950 bp, and the susceptibility gene is 850 bp. Figure 2The resistance gene was 650 bp, and the susceptibility gene was 320 bp. This indicates that germplasm with resistance bands is a disease-resistant resource that can be utilized in breeding; conversely, germplasm with susceptibility bands is a disease-susceptible resource and should be eliminated. Molecular marker identification significantly shortens the cycle of field disease resistance identification and selection, and significantly improves breeding efficiency. Simultaneously, the TSP population exhibited rich band polymorphism at different marker loci, indicating that the TSP population is genotyped differently from the original parents, proving that this invention effectively circumvents the genomic characteristics of the original parents. The results show that this invention successfully created a population with extremely high genetic diversity, laying the foundation for the aggregation of multiple desirable traits.

[0064] 1. Breeding of Mufan No. 5

[0065] The new germplasm JC26-12-3-12-17-8 (JC is the hybrid group code, combination number 26, 12 is the 12th selected plantlet in the next generation, 3 is the 3rd selected plantlet in the next generation, and so on) is a stable inbred line developed through multiple generations of single-plant and single-fruit directional selection. It exhibits indeterminate growth, vigorous growth, green shoulders on immature fruits, pink color on mature fruits, oblate fruit shape, smooth and without ridges, with a single fruit weight of 100-120 g, high fruit firmness, 4-6 flowers per inflorescence, uniform flowering period, and resistance to leaf mold.

[0066] The new germplasm FBE2-26-9-23-6zz inbred line, after multiple generations of self-pollination and molecular marker-assisted breeding, is a stable inbred line containing MI, TY1, and TY3a resistance genes. It exhibits indeterminate growth, strong growth, green shoulders on immature fruits, pink color on mature fruits, round fruit shape, high firmness, and a single fruit weight of 80-100 g. Each inflorescence bears 5-6 flowers. It is salt-tolerant and resistant to tomato yellow leaf curl virus and root-knot nematode disease.

[0067] Mufan 5 is a hybrid variety bred using JC26-12-3-12-17-8 as the female parent and FBE2-26-9-23-6 as the male parent. After selecting superior inbred lines from the superpopulation (TSP) constructed in this invention, we conducted combining ability tests on a total of 28 hybrid combinations in the spring of 2022. Among them, the combination using JC26-12-3-12-17-8 as the female parent and FBE2-26-9-23-6 as the male parent showed the most outstanding performance and was named Mufan 5. This hybrid exhibited strong heterosis in testing, displaying indeterminate growth, vigorous growth, dark green leaves, and a common variegated pattern. The first inflorescence appears on the 7th-8th node, spaced 3-4 leaves apart, with 4-6 flowers per inflorescence. It has strong continuous fruit set, producing round fruits with dark green shoulders when young, turning pink when fully ripe. Individual fruits weigh 80-100 g. It is transport-resistant, early-maturing, and resistant to tomato yellow leaf curl virus, nematodes, and leaf mold. It successfully combines the excellent disease-resistant traits of both parents, achieving combined resistance to tomato yellow leaf curl virus, root-knot nematodes, and leaf mold. The outstanding performance of Mufan 5 fully demonstrates the enormous potential of the TSP population from which its parent inbred lines originated in efficiently breeding breakthrough tomato varieties. National Plant Variety Protection was applied for in 2024.

[0068] 2. Breeding of Mufan No. 7

[0069] This is a stable inbred line developed through multiple generations of single-plant and single-fruit directional selection using the new germplasm KG1430. It exhibits indeterminate growth and vigorous development. Immature fruits have green shoulders, while fully grown fruits are pink. The fruits are oblate, smooth, and without ridges, with a single fruit weighing 200-220g. The fruits are firm, and each inflorescence bears 4-6 flowers with a uniform flowering period. It is also resistant to leaf mold.

[0070] The new germplasm FB26 was bred through multiple generations of self-pollination and molecular marker-assisted selection. It is a stable inbred line containing the resistance genes MI, TY1 and TY3a. It has indeterminate growth, strong growth, green shoulders on immature fruits, pink color on fully mature fruits, round fruit shape, high firmness, single fruit weight of 80-100 g, 5-6 flowers per inflorescence, and resistance to tomato yellow leaf curl virus and nematodes.

[0071] The new variety Moufan 7 is a hybrid bred from KG1430 as the female parent and FB26 as the male parent. In the spring of 2022, using 12 superior inbred lines as parents, a total of 35 hybrid combinations were created using the incomplete diallel hybridization method, and the agronomic traits and combining ability of each combination were systematically evaluated.

[0072] The results showed that the general combining ability (GCA) of the male parent FB26 was stable and outstanding in terms of disease resistance (especially resistance to TYLCV and root-knot nematodes), making it an excellent donor of disease resistance genes; while the female parent KG1430 showed high GCA in terms of early maturity and continuous fruit setting ability.

[0073] Specific Combining Ability (SCA): The hybrid KG1430×FB26 exhibits extremely high positive specific combining ability in key traits such as yield per plant, fruit firmness, and marketable fruit rate. Its heterosis is significant, and its overall performance far surpasses other hybrids. This hybrid is an indeterminate type with strong growth vigor, dark green leaves, and the first inflorescence appears at the 7th-8th node, demonstrating strong continuous fruit setting ability. The fruit is round, with dark green shoulders when young and pink when mature, weighing 80-100g per fruit. It has high fruit firmness and is suitable for storage and transportation. Disease resistance testing showed that Mufan 7 is highly resistant to Tomato Yellow Leaf Curl Virus (TYLCV) and root-knot nematodes, and moderately resistant to leaf mold, successfully achieving a perfect aggregation and complementarity of the superior traits of both parents. This variety has been submitted for national plant variety protection in 2024.

[0074] Mufan No. 7 is a hybrid variety with the most outstanding comprehensive traits selected from 35 candidate combinations. Its excellent performance fully demonstrates the scientific nature of its parent selection and the breakthrough advantages of the variety itself, as detailed in Table 3.

[0075] Table 3. Breeding process of Mufan No. 5 / Mufan No. 7

[0076]

[0077] Example 3: Breeding and Characterization of Superior Inbred Line FBE2-26-9-23-6zz

[0078] From the TSP population constructed in this invention, a stable inbred line FBE2-26-9-23-6zz was successfully bred through multiple generations of self-pollination and molecular marker-assisted selection.

[0079] 1. Genetic background and breeding process

[0080] Source: Selected from the tomato multi-parent ladder hybrid superpopulation (TSP) constructed in this invention.

[0081] Breeding method: Through continuous self-pollination of single plants for more than 6 generations, combined with molecular marker-assisted selection (MAS), a superior inbred line with stable genetic traits is finally obtained.

[0082] Molecular identification: Specific PCR marker detection showed that the following disease resistance genes were stably homozygous: Mi-1 gene (resistance to root-knot nematodes), Ty-1 gene (resistance to tomato yellow leaf curl virus, TYLCV), and Ty-3a gene (resistance to tomato yellow leaf curl virus, TYLCV).

[0083] 2. Botanical characteristics

[0084] Growth type: Indeterminate. Growth vigor: Robust; under standard cultivation conditions, the internode length remains stable at 8-10 cm. Leaves: Dark green leaves, approximately 25-30 cm in length, exhibiting a standard leaf shape. Fruit clusters: Racemes, each bearing 5-6 flowers; high fruit set rate; uniform fruit clusters.

[0085] 3. Fruit characteristics

[0086] The shoulder of the fruit is a distinct dark green (green shoulder), while the body is light green. Characteristics of mature fruit: Color: The fruit turns a uniform, bright pink when ripe. Shape: Round, with a shape index (longitudinal diameter / transverse diameter) of approximately 0.95-1.05 and a smooth surface. Firmness: The fruit is firm; using a firmness tester, the firmness value is ≥ 6.0 kg / cm², indicating good storage and transportability. Single fruit weight: The weight of a single fruit is consistently between 80-100 grams, classifying it as a medium-sized fruit. Number of locules: Usually 2-3.

[0087] 4. Stress resistance and disease resistance

[0088] Disease resistance: High resistance to Tomato Yellow Leaf Curl Virus (TYLCV): Under natural disease conditions in the field or under artificial inoculation and identification conditions, the disease index is ≤15 (the disease index of the susceptible control is >80).

[0089] High resistance to root-knot nematodes: When planted in soil infected with root-knot nematodes, the root knot index is ≤2 (0-10 standard), which is better than the infected control.

[0090] Salt tolerance: In the hydroponic stress test with a concentration of 100 mmol / L NaCl, the relative plant height inhibition rate and relative fresh weight inhibition rate of seedlings were both less than 30% (strong salt tolerance type), showing significant salt tolerance.

[0091] The advantages of this invention are as follows:

[0092] 1. Breakthrough variety selection: The TSP population can be screened simultaneously for resistance to two types of diseases (soil-borne diseases and viral diseases) + stress + high yield + high-quality genotype, which solves the contradiction in tomato breeding that high yield does not mean disease resistance and high quality does not mean high yield;

[0093] 2. Reduce breeding costs: Avoid variety rights fees, and the cost of original materials is close to zero;

[0094] 3. Sustainable genetic effects: The 1,024 subpopulations retained within the population can serve as a long-term improvement library, continuously discovering new allele combinations.

[0095] This invention achieves an exponential increase in genetic diversity and simultaneous improvement of complex traits in tomato breeding populations through a three-pronged approach combining tiered hybridization design, mixed harvesting strategy, and large-scale recombination. The successful breeding of the Mufan series of varieties validates the high efficiency of the TSP population in breakthrough variety breeding, providing a new paradigm for commercial breeding.

Claims

1. A method for constructing a tomato multi-parent ladder hybrid superpopulation, characterized in that, Includes the following steps: The screening included high-yield TSP-A, high-quality TSP-B, good marketability TSP-C, soil-borne disease resistant TSP-D, virus disease resistant TSP-E, and abiotic stress resistant TSP-F. (1) First round of hybridization: B×A, D×C, F×E are hybridized, with each combination producing ≥5 individual plants to obtain double cross F. 1AB F 1CD F 1EF ; (2) Second round of hybridization: F1 1CD ×F 1EF Hybridization is performed using pollen from a mixture of at least 100 male plants for pollination, and pollination of the female plant using pollen from a mixture of at least 100 female plants to obtain a four-cross hybrid F1. 1CDEF ; (3) Third round of hybridization: F1 1CDEF ×F 1AB Hybridization was performed, with the male parent being pollinated using a mixture of pollen from at least 100 plants, and the female parent being harvested individually and ≥1024 independent lines retained to obtain a six-cross F1 hybrid. 1ABCDEF ; (4) Population construction: The obtained six-cross F1 populations are constructed. 1ABCDEF The lines were planted separately, and ≥4 plants from each line were randomly selected for self-pollination. All self-pollinated seeds were mixed to form an F2 superpopulation of ≥4096 plants.

2. The construction method according to claim 1, characterized in that, The double cross F1 strain obtained after the first round of hybridization 1AB F 1CD F 1EF Plant in different areas and harvest seeds from the offspring of ≥5 hybrid fruits of a hybrid combination; Parent F 1CD With F 1EF Planting conditions: Large-scale planting of F 1CD and F 1EF Each double-cross population should have at least 150 plants to ensure that at least 100 plants receive mixed pollen. F 1EF Male parent selection: Randomly collect anthers from ≥100 plants with vigorous growth and abundant pollen to prepare flowers; F 1CD Female parent selection: Select ≥100 plants with consistent growth and normal flower development as female parents, and perform emasculation and pollination; at harvest, collect all successfully hybridized seeds together.

3. The construction method according to claim 1, characterized in that, Before the third round of hybridization, a large-scale planting of the maternal parent F1 was carried out. 1CDEF Group and parent F 1AB group; Father F 1AB Use mixed pollen from ≥100 plants to ensure that the genetic diversity of parents A and B is fully introduced; Mother F 1CDEF Single-plant pollination and single-plant seed harvesting were implemented, and from ≥1000 female plants, ≥1024 independent lineage seeds that showed normal growth vigor, flowering period and fruit setting were retained.

4. The construction method according to claim 1, characterized in that, Before group construction F 1ABCDEF Cultivation and planting conditions for the strain: retain ≥1024 F1 cells. 1ABCDEF The strains are planted in separate areas under the same conditions, with at least 10 plants planted in each strain to ensure that there are enough healthy plants for self-pollination.

5. The application of the tomato multi-parent ladder hybridization super population construction method as described in claim 1 in the selection of inbred lines and the cultivation of disease-resistant, high-yielding, and high-quality tomato varieties.

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