Cultivation method of full-aroma long-grain hybrid japonica rice
By using molecular marker-assisted selection and synergistic directional selection between sterile and restorer lines, the problem of linkage redundancy of multi-target traits in rice breeding has been solved, improving breeding efficiency and certainty, and enabling the efficient breeding of full-fragrant long-grain hybrid japonica rice.
Patent Information
- Application Number
- CN202511151771.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-11-04
AI Technical Summary
Existing technologies for combining multiple target traits in rice breeding suffer from chain redundancy and lag in the breeding process, making it difficult to achieve all target traits simultaneously, resulting in low breeding efficiency and high uncertainty.
By employing molecular marker-assisted selection technology, through forward selection of aroma-related major genes and reverse screening of linked undesirable genes, combined with synergistic directional selection of sterile and restorer lines, undesirable genes can be identified and eliminated in advance, optimizing parental combining ability and shortening the breeding cycle.
This approach enables early fixation of target genes and elimination of undesirable genes, improving breeding efficiency and certainty, and ensuring the aggregation of superior traits and the stability of hybrid combinations.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of plant genetic breeding, in particular to a breeding method of full-flavor long-grain hybrid japonica rice. BACKGROUND
[0002] Hybrid rice breeding using cytoplasmic male sterile lines is a mature and widely used technical path to improve rice yield. With the change of market demand, the goal of rice breeding has shifted from single pursuit of high yield to simultaneous improvement of yield and quality traits. Among them, japonica rice varieties with aroma and long-grain grain type have attracted widespread attention from the market due to their excellent eating quality.
[0003] In existing breeding practices, the technology of introducing single target traits (such as aroma or long-grain) into target materials through conventional crossing is known. However, when multiple excellent traits from different parents are expected to be aggregated (for example, strong restorer genes, aroma genes, and long-grain genes are aggregated in the same restorer line), the existing technology faces inherent technical obstacles. The breeding process often causes target traits and undesirable traits to be difficult to separate due to linkage of genes. When a target trait (such as long-grain) is introduced from a certain donor parent, other gene segments that affect rice quality, resistance, or yield that are tightly linked to it are also introduced into the offspring. This linkage drag significantly hinders the effective aggregation of multiple excellent traits, resulting in the materials bred compromising on some traits and failing to achieve the breeding goal in terms of comprehensive traits.
[0004] In addition, traditional breeding methods mainly rely on phenotypic selection and identification of high-generation populations in the field. This approach requires planting large-scale segregating populations and identifying target traits at the late stage of plant growth and development, resulting in a long cycle and large resource input. More importantly, for hybrid rice breeding, the combining ability of sterile lines and restorer lines is the key to determining the superiority or inferiority of the final hybrid combination. In the existing technical process, the combining ability is usually evaluated after the sterile lines and restorer lines have been basically bred. Once the combining ability between the two is found to be poor, the years and resources invested in the parent selection process are wasted, which makes the acquisition of excellent hybrid combinations uncertain and reduces the overall efficiency of breeding. SUMMARY
[0005] To overcome the shortcomings of the prior art, the present application provides a breeding method of full-flavor long-grain hybrid japonica rice, which solves the problem of the prior art that it is difficult to balance target traits, the breeding efficiency is low, and the uncertainty is high when aggregating multiple target traits such as aroma and long-grain in hybrid rice breeding due to linkage drag and lagging breeding process.
[0006] In order to achieve the above object, the present application is implemented by the following technical scheme: a breeding method of full-flavor long-grain hybrid japonica rice, comprising the following steps:
[0007] S1, by hybridization and backcross, the aroma trait, long-grain trait is introduced into the sterile line background, and a candidate long-grain japonica rice sterile line is obtained;
[0008] S2, by hybridization, the aroma trait, long-grain trait and the restorer gene are aggregated, and in the offspring segregation population, molecular marker assisted selection is applied for screening, and a candidate long-grain japonica rice restorer line is obtained;
[0009] S3, the obtained candidate sterile line and the obtained candidate restorer line are predicted to be hybridized, and the final long-grain japonica rice sterile line and long-grain japonica rice restorer line are determined according to the performance of the offspring of the predicted hybridization;
[0010] S4, the final long-grain japonica rice sterile line is used as the female parent, and the final long-grain japonica rice restorer line is used as the male parent to carry out hybridization, and full-flavor long-grain hybrid japonica rice is obtained.
[0011] Preferably, in the step S2, the long-grain japonica rice restorer line is obtained by hybridizing a strong restorer japonica rice restorer line with a long-grain japonica rice material, and the offspring is further hybridized with a long-grain japonica rice material to construct an offspring segregation population.
[0012] Preferably, the strong restorer japonica rice restorer line is C418, the long-grain japonica rice material is Jiahe 218, and the long-grain japonica rice material is Ewan 17.
[0013] Preferably, in the step S2, the molecular marker assisted selection comprises:
[0014] The offspring segregation population is positively selected for the aroma gene;
[0015] The offspring segregation population is negatively screened for the undesirable trait gene linked to the long-grain trait donor.
[0016] Preferably, the positive selection of the aroma gene is specifically:
[0017] The genomic DNA of each individual in the offspring segregation population is extracted;
[0018] PCR amplification is carried out by using specific primers of the molecular marker linked to the rice aroma major gene badh2;
[0019] The amplification product is detected, and individuals presenting the corresponding map of the homozygous recessive genotype of the aroma gene are screened out.
[0020] Preferably, the negative screening is specifically:
[0021] PCR amplification is performed on the individuals retained by the positive selection using specific primers associated with the molecular markers linked to the undesirable genes in the long grain trait donor that cause a decrease in rice quality or resistance;
[0022] The amplified products are detected, and individuals presenting the profile corresponding to the undesirable genes are eliminated.
[0023] Preferably, in step S1, the step of breeding a long-grain japonica rice sterile line with an aroma type is:
[0024] A plurality of parents with an aroma type or broad compatibility are subjected to bulk hybridization, and the resulting offspring are crossed with a BT-type cytoplasmic male sterile line to obtain a primary hybrid population carrying sterile cytoplasm;
[0025] A new maintainer line is selected from the offspring of the obtained primary hybrid population, and the new maintainer line is continuously backcrossed with the sterile offspring, thereby breeding a candidate long-grain japonica rice sterile line with an aroma type.
[0026] Preferably, in step S3, the step of predicting hybridization specifically comprises:
[0027] In a generation in which the main traits of the candidate restorer line with an aroma type tend to be stable but are not yet homozygous, pollen is given to the candidate sterile line with an aroma type that is in the process of backcrossing.
[0028] Preferably, in step S3, the specific way of determining the final long-grain japonica rice sterile line and the final long-grain japonica rice restorer line is:
[0029] According to the heterosis and combining ability performance of the offspring of the predicted hybridization, the selection of the candidate sterile line in subsequent backcrossing is guided.
[0030] According to the heterosis and combining ability performance of the offspring of the predicted hybridization, the final purification selection of the candidate restorer line is guided.
[0031] Preferably, in step S4, obtaining a full-aroma long-grain hybrid japonica rice specifically comprises: according to the growth period characteristics of the final long-grain japonica rice sterile line and the final long-grain japonica rice restorer line, staggered sowing the final long-grain japonica rice sterile line and the final long-grain japonica rice restorer line to make their flowering periods meet, thereby hybridizing for seed production.
[0032] The present application provides a breeding method of a full-aroma long-grain hybrid japonica rice.
[0033] 1. This invention applies molecular marker-assisted selection technology in restorer line breeding, including positive selection of the aroma-related major gene badh2 and reverse screening of linked undesirable genes. This enables direct identification of individuals carrying the target gene at the genotype level, achieving early fixation of the target gene and elimination of undesirable genes. Compared with relying entirely on field phenotypic identification in the later stages of breeding, this shortens the breeding selection cycle and reduces the workload of later field identification and screening.
[0034] 2. This invention addresses the linkage redundancy problem that may accompany the introduction of long-grain traits in restorer line breeding by incorporating a molecular marker reverse screening step. This step utilizes molecular markers associated with unfavorable genes linked to long-grain trait donors that lead to decreased rice quality or resistance to actively eliminate individuals carrying these unfavorable genes. This technique overcomes the limitations of conventional hybridization breeding, where the physical linkage between the target gene and unfavorable genes makes it difficult to simultaneously achieve both the aggregation of the target trait and the removal of linked undesirable traits.
[0035] 3. This invention, through the coordinated directional selection of sterile and restorer lines, performs predictive hybridization in the mid-to-late stages of sterile and restorer line breeding. This allows for the early acquisition of combining ability data between candidate parents, which is then used as a decision-making basis to guide the selection of sterile lines in subsequent backcrosses and the final purification of restorer lines. This avoids the loss of early breeding investment caused by discovering poor combining ability only after the parental materials have been fully developed, and increases the certainty of obtaining superior hybrid combinations with strong heterosis. Attached Figure Description
[0036] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention.
[0037] Figure 2 This is a schematic diagram of the process for cultivating aromatic long-grain japonica rice male-sterile lines according to the present invention;
[0038] Figure 3 This is a schematic diagram of the process for cultivating aromatic long-grain japonica rice restorer lines according to the present invention;
[0039] Figure 4 This is a schematic diagram of the gel electrophoresis pattern for marker-assisted selection according to the present invention.
[0040] Figure 5 This is a schematic diagram of the predictive hybridization matrix for the synergistic directional selection of sterile and restorer lines according to the present invention;
[0041] Figure 6 This is a schematic diagram illustrating the principle of staggered sowing technology in hybrid seed production according to the present invention. Detailed Implementation
[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0043] Please see the appendix Figure 1 -Appendix Figure 6 This invention provides a method for cultivating a fully aromatic long-grain hybrid japonica rice, comprising the following steps:
[0044] S1. By hybridization and backcrossing, the aroma and long grain traits were introduced into the sterile background to obtain candidate aromatic long grain japonica rice male-sterile lines.
[0045] S2. By hybridization, the aroma trait, long grain trait and restorer gene are combined, and molecular marker-assisted selection is used to screen in the segregating population of the offspring to obtain candidate aroma-type long grain japonica rice restorer lines.
[0046] S3. Perform predictive hybridization between the obtained candidate male-sterile lines and the obtained candidate restorer lines. Based on the performance of the predicted hybrid offspring, determine the final aromatic long-grain japonica rice male-sterile lines and aromatic long-grain japonica rice restorer lines respectively.
[0047] S4. The determined final aromatic long-grain japonica rice male-sterile line is used as the female parent and crossed with the final aromatic long-grain japonica rice restorer line as the male parent to obtain fully aromatic long-grain hybrid japonica rice.
[0048] See attached document Figure 1 , Figure 1 This is a flowchart illustrating the cultivation method of a fully aromatic long-grain hybrid japonica rice according to an embodiment of the present invention. The preparation process of the experimental materials used in the cultivation method provided by the present invention is described below.
[0049] The breeding method described in this embodiment uses parental groups for breeding aromatic long-grain japonica rice male-sterile lines and parental groups for breeding aromatic long-grain japonica rice restorer lines as starting materials.
[0050] The parental groups used for cultivating sterile lines are composed and functionally allocated as follows:
[0051] Parental materials used for polymerizing target traits include fragrance parents. Widely compatible parent And another fragrance parent .in, . , The symbol is defined in this method.
[0052] The material providing the cytoplasmic male sterility is a BT type cytoplasmic male sterile line . Wherein, is a symbol defined in the method.
[0053] The parent group for breeding the restorer line, its composition and function distribution are as follows:
[0054] Strong restorer long grain indica restorer line parent : C418 is selected as the restorer line. The material has strong restorative ability to BT type sterile cytoplasm. Wherein, is a symbol defined in the method.
[0055] Long grain indica material parent : Jiahe 218 is selected as the long grain indica variety. The ratio of grain length to width of the material is greater than 3.0. Wherein, is a symbol defined in the method.
[0056] Scented indica material parent : Ewan 17 is selected as the scented indica variety. The material carries the homozygous recessive allele of the main gene badh2 of the scent, and has the scent trait. Wherein, is a symbol defined in the method.
[0057] In the subsequent steps, the above parent materials will be combined according to the preset hybridization path. The complex hybridization process for breeding the restorer line can be represented as:
[0058] ;
[0059] In the formula, represents the F1 generation population carrying the genetic material of three parents generated by the complex hybridization of the parents , and .
[0060] The hybridization and backcrossing process for breeding the sterile line can be represented as:
[0061] ;
[0062] ;
[0063] ;
[0064] In the formula, represents the F1 generation population generated by the three-way cross of the parents , , ;
[0065] represents the cross of and the sterile line The F1 generation population produced by four-cross crosses, which was introduced with sterile cytoplasm;
[0066] Representative from Sterile lines isolated from the offspring;
[0067] Representative from Newly selected descendants, and Matching retaining system;
[0068] Representatives utilize right The offspring population obtained by backcrossing n consecutive generations.
[0069] See attached document Figure 2 , Figure 2 The steps of a method for cultivating a fragrant long-grain japonica rice male-sterile line according to an embodiment of the present invention are illustrated. The steps include:
[0070] First, construct the basic target trait aggregation population. This involves using pre-prepared fragrance parents. As the maternal parent, a widely compatible parent The male parent was used for crossbreeding to obtain the F1 generation. Then, this F1 generation was used as the female parent and crossed with another fragrance-type parent. Three crosses were performed using the parent as the paternal line to obtain the three-cross F1 generation population. The purpose of this process is to aggregate the genetic backgrounds of multiple parents, such as aroma and broad compatibility, into the same population.
[0071] Subsequently, the introduction of sterile cytoplasm and the selection of new maintainer lines were carried out. The obtained... The population, acting as the male parent, conferred its pollen upon a BT-type cytoplasmic male-sterile line, which served as the female parent. Obtain the four-cross F1 generation population . All individuals within the group carry from The sterile cytoplasm.
[0072] Will The group engages in self-fertilization to obtain Separated groups. In Within the population, fertility segregation occurs due to the segregation of the restorer gene. Pollen fertility identification can distinguish between sterile plants with completely aborted pollen and fertile plants with normal pollen. From this population, fertile plants whose comprehensive agronomic traits meet the breeding objectives are selected, and their pollen is used to gift sterile plants from the same line with consistent phenotypes for testcrosses. If all progeny of the testcross are sterile, the fertile plant is identified as the new maintainer line. The pollinated sterile plants then serve as the initial sterile material for this maintainer line. .
[0073] The pollen fertility assessment can be specifically performed using the I2-KI (iodine-potassium iodide) staining method. Under a microscope, pollen grains stained round or nearly round, dark brown or black, are considered normal fertile pollen; pollen grains that are unstained, deformed, or only stained pale yellow are considered sterile pollen. The standard for sterile plants is a fertile pollen rate of less than 1%. In the population, fertile plants whose comprehensive agronomic traits meet the breeding objectives are selected. The selection criteria include: compact plant type, upright leaves, moderate growth period, and no obvious diseases.
[0074] Finally, backcrossing and genetic background purification were performed. The newly selected maintainer lines were then used. As the recurrent parent (paternal parent), it uses its matching initial sterile material. The parent (mother) is a non-reincarnated parent, and continuous backcrossing is performed.
[0075] The specific operation is as follows: and hybridization, to obtain Generation. In the next growing season, The replacement plant was used as the mother plant and then received... pollen, to obtain Generation. This backcrossing process is repeated for 5 to 7 generations.
[0076] In each backcross generation, the cytoplasm of the sterile offspring originates from the initial non-recurrent parent. The genetic material within its cell nucleus is then transferred from the reincarnated parent. The genetic material is replaced generation by generation. After multiple generations of backcrossing, the resulting high-generation backcross population is obtained. The genetic background has been linked to the new maintainer line. The genetic backgrounds of the rice plants are highly consistent, and they stably maintain male sterility. At this point, the lines with stable traits and consistent phenotypes within the population are selected as candidate male-sterile lines for subsequent steps.
[0077] See attached document Figure 3 , Figure 3 The method steps for cultivating aromatic long-grain japonica rice restorer lines according to an embodiment of the present invention are illustrated. These steps include:
[0078] First, a composite hybrid population with the target traits was constructed. This involved using strong resilience japonica rice restorer lines as parents. (C418) was used as the female parent, and the long-grain japonica rice material was used as the parent. (Jiahe 218) was used as the male parent for hybridization to obtain the F1 generation. Subsequently, this F1 generation was used as the female parent and crossed with aromatic japonica rice materials. (Example 17) The composite hybrid is performed to produce a composite hybrid F1 population carrying three genetic materials of the parents
[0079] The population is selfed to obtain a segregating population The population is selfed to obtain a segregating population The population is selfed to obtain a segregating population The population is selfed to obtain a segregating population In this population, the recovery gene, the long-grain trait gene and the aroma gene are simultaneously segregated. At the seedling stage, the young leaves of each single plant in the population are extracted to obtain the genomic DNA of each individual using the CTAB method, which is used for the subsequent molecular marker assisted selection.
[0080] Subsequently, the aroma gene is positively selected for all individuals in the population. In this step, a pair of molecular marker specific primers which are tightly linked to the rice aroma major gene badh2 are used to perform PCR amplification with the genomic DNA of each single plant as the template. In this embodiment, the molecular marker used for the positive selection of the aroma gene is the marker badh2-E7 which is linked to the 8-bp deletion functional site on the 7th exon of the badh2 gene. For the reverse selection, the molecular marker type related to the adverse gene can be a simple sequence repeat marker (SSR) or a sequence tag site marker (STS), which is obtained by constructing a linkage map between the long-grain parent and the recurrent parent or by group segregation analysis. Referring to the attached
[0081] The PCR amplification products are subjected to electrophoresis detection in a 3% agarose gel. According to the DNA band pattern formed after electrophoresis, the individuals presenting only the specific band corresponding to the homozygous recessive genotype of the aroma gene (badh2 / badh2) are screened out and these individuals are retained. Figure 4 After the positive selection is completed, the reverse selection of the linkage adverse trait gene is performed for all the retained individuals. In this step, the molecular marker specific primers related to the adverse gene site which is known to cause the decrease of rice quality or the decrease of disease resistance and is linked to the long-grain trait donor
[0082] The PCR amplification products of this round are also subjected to gel electrophoresis detection. According to the electrophoresis pattern, all the individuals presenting the specific band corresponding to the adverse gene are identified and eliminated. The purpose of this step is to break the genetic linkage between the long-grain trait and the adverse trait.
[0083] The PCR amplification products of this round are also subjected to gel electrophoresis detection. According to the electrophoresis pattern, all the individuals presenting the specific band corresponding to the adverse gene are identified and eliminated. The purpose of this step is to break the genetic linkage between the long-grain trait and the adverse trait.
[0084] The individuals remaining after the above forward selection and reverse screening are the preferred single plants that have both the aroma gene and the linkage drag broken. These preferred single plants are planted in the field to enter the subsequent generation of purification and selection.
[0085] Starting from the F3 generation, the progeny lines of the preferred single plants are identified for field agronomic traits, mainly including the selection of recovery degree, plant height, growth period, grain type and resistance. Through continuous line identification and selection of multiple generations, the line with stable inheritance of target traits and comprehensive agronomic traits meeting the breeding goal is determined as the candidate aroma type long grain japonica rice restorer line for subsequent steps.
[0086] Referring to the accompanying drawings Figure 5 , Figure 5 The method steps of the sterile line and the restorer line of the embodiment of the application are illustrated. The steps include:
[0087] First, a predictive hybrid system is established and operated. The starting time point of this step is when the candidate aroma type long grain japonica rice restorer line enters the F4 to F5 generation, and the candidate aroma type long grain japonica rice sterile line enters the BC2 to BC3 backcross generation. At this time, the main agronomic traits of the restorer line have been basically stable, but there is still a certain degree of gene separation within the population, and the sterile line is in the process of purifying the genetic background.
[0088] Specifically, from a plurality of candidate restorer line populations, a single plant with agronomic traits meeting the target is selected as the father; at the same time, from a plurality of candidate sterile line populations in the backcross process, the corresponding sterile plant is selected as the mother. The pollen of the aforementioned father is pollinated on the stigma of the mother to construct a predictive hybrid matrix composed of a plurality of micro test combinations as shown in the accompanying drawings Figure 5 Each hybrid combination is bagged and labeled to record its parentage.
[0089] Among them, the candidate restorer line population (for example, line numbered ), the candidate sterile line population (for example, line numbered ).
[0090] Subsequently, two-way guided selection based on the performance of the F1 generation after the predictive hybridization is carried out. The F1 generation seeds harvested from the above predictive hybrid combinations are planted in the field in the next growing season. When planting, each F1 combination is taken as an independent unit, and the backcross generation population of its corresponding restorer line parent and sterile line parent is taken as a control.
[0091] The field performance of each combination is observed, recorded and evaluated systematically during the whole growth period of the predicted hybrid F1 generation. The evaluation indexes include heterosis performance and combining ability level. The specific observation parameters of heterosis performance include plant height, tiller number, grain number per spike, seed setting rate and 1000-grain weight; the combining ability level is evaluated comprehensively in terms of yield potential, rice quality traits, disease resistance, lodging resistance and the like.
[0092] Specifically, the yield of each predicted hybrid F1 combination is compared with that of a local main cultivar (CK) as a control. If the yield of an F1 combination is increased by more than 5% compared with the CK, it is considered to have strong heterosis. The comprehensive evaluation of the combining ability level is performed by multi-point comparison and weighted scoring, and the multiple indexes such as yield, rice quality and resistance are given different weights and ranked by comprehensive index.
[0093] According to the above evaluation results, the selection process of the sterile line and the restorer line is bidirectionally guided.
[0094] On the one hand, the evaluation results are used to guide the selection of the candidate sterile line in subsequent backcrossing. If the F1 generation of a candidate sterile line (for example, line A) and multiple candidate restorer lines hybridize, and the F1 generation generally exhibits strong heterosis and combining ability, it is proved that the backcross family to which the line A belongs is an excellent family with high combining ability. Therefore, in the subsequent backcrossing and selection, the line A is mainly retained and continuously backcrossed and selected. On the contrary, if a candidate sterile line exhibits poor performance in the predicted hybridization, the corresponding backcross family is terminated. On the other hand, the evaluation results are used to guide the final purification selection of the candidate restorer line. If the F1 generation of a candidate restorer line (for example, line B) and multiple candidate sterile lines hybridize, and the F1 generation all exhibit excellent traits, it is proved that the line B has wide combining ability. The line B is determined as a key breeding material, and its offspring are mainly purified and expanded. On the contrary, if a candidate restorer line exhibits poor performance in the predicted hybridization, the line is directly eliminated.
[0095] Through the cooperative directional selection step, the combining ability data between the parents are obtained before the parents are bred, and the final sterile line and restorer line of the fragrant long-grain japonica rice are determined according to the data. The specific evaluation method is as follows: the yield of each predicted hybrid F1 combination is compared with that of a local main cultivar (CK) as a control. If the yield of an F1 combination is increased by more than 5% compared with the CK, it is considered to have strong heterosis. The comprehensive evaluation of the combining ability level is performed by multi-point comparison and weighted scoring, and the multiple indexes such as yield, rice quality and resistance are given different weights and ranked by comprehensive index.
[0096] The steps of the creation and identification method of the excellent hybrid combination of the embodiment of the application are illustrated. The steps include:
[0097] The specific evaluation method is as follows: the yield of each predicted hybrid F1 combination is compared with that of a local main cultivar (CK) as a control. If the yield of an F1 combination is increased by more than 5% compared with the CK, it is considered to have strong heterosis. The comprehensive evaluation of the combining ability level is performed by multi-point comparison and weighted scoring, and the multiple indexes such as yield, rice quality and resistance are given different weights and ranked by comprehensive index. Figure 1 , Figure 1 The steps of the creation and identification method of the excellent hybrid combination of the embodiment of the application are illustrated. The steps include:
[0098] First, hybrid seeds are produced. The final long-grain fragrant japonica sterile line is used as the female parent, and the final long-grain fragrant japonica restorer line is used as the male parent to produce hybrid F1 seeds. In order to ensure that the parents meet at the flowering stage to complete effective pollination, staggered sowing technology is used.
[0099] Referring to the drawings Figure 6 The operation of staggered sowing is based on the differences in the growth periods of the parents. Before seed production, the parents are planted separately, and the number of days from sowing to the beginning of heading of both is accurately recorded to calculate the difference in the flowering period between the two. According to the difference, a sowing plan is developed. If the flowering period of the male parent is earlier than that of the female parent, the female parent is sown earlier, and the number of days is equal to the difference in the flowering period. Conversely, the female parent is sown earlier.
[0100] In the seed production field, the male and female parents are planted according to a row ratio of 2:10. During the flowering period of the female parent, artificial assisted pollination is performed between the male parent rows, such as rope pulling to chase pollen or fan-assisted pollen delivery during the active pollination period (10:00 to 12:00) each day, and the operation is repeated 3 to 5 times to improve the outcrossing seed setting rate. After the seeds mature, the seeds of the female parent rows are harvested separately, and this batch of seeds is the obtained full-fragrance long-grain hybrid japonica F1 generation.
[0101] Subsequently, the created hybrid combination is systematically identified. The harvested F1 generation seeds are used as new variety combinations to participate in multi-point, multi-year (usually 2 to 3 years) regional variety comparison tests. In the test, excellent japonica rice varieties that have been promoted in the local area are set as the control group.
[0102] During the regional variety comparison test, the agronomic traits of the test hybrid combinations are comprehensively collected and analyzed. The main identification indicators include: yield components (effective panicle number, panicle number, seed setting rate, and 1,000-grain weight) and final yield; rice quality analysis (appearance quality, milling quality, physicochemical indicators, and cooking and eating quality); resistance grades of major diseases and pests (such as rice blast, white leaf blight, and brown planthopper); and growth period performance and adaptability in different ecological test points.
[0103] At the same time, the final harvested hybrid F1 generation rice is confirmed for fragrance traits. This confirmation includes: organizing an expert and consumer group to form a product evaluation team to taste and score the fragrance intensity of rice;
[0104] Gas chromatography-mass spectrometry (GC-MS) and other instrument analysis methods are used to detect and quantify the content of 2-acetyl-1-pyrroline, a fragrance substance in rice, to ensure that its content meets the standard for fragrant rice.
[0105] The hybrid combination with outstanding performance and stable traits will enter the production test after regional variety comparison test, in order to verify its high yield and stability under large-scale production conditions. Finally, a hybrid combination that reaches or exceeds the standard of the control variety in the comprehensive performance of various tests is finally determined as a new excellent full-flavor long-grain hybrid japonica rice variety.
Claims
1. A method for cultivating a full-fragrant long-grain hybrid japonica rice, characterized in that, Includes the following steps: S1. By hybridization and backcrossing, the aroma and long grain traits were introduced into the male-sterile line background to obtain candidate aroma-type long grain japonica rice male-sterile lines; S2. By hybridization, the aroma trait, long grain trait and restorer gene are combined, and molecular marker-assisted selection is used to screen in the segregating population of the offspring to obtain candidate aroma-type long grain japonica rice restorer lines. S3. Perform predictive hybridization between the obtained candidate male-sterile lines and the obtained candidate restorer lines. Based on the performance of the predicted hybrid offspring, determine the final aromatic long-grain japonica rice male-sterile lines and aromatic long-grain japonica rice restorer lines respectively. S4. The determined final aromatic long-grain japonica rice male-sterile line is used as the female parent and crossed with the final aromatic long-grain japonica rice restorer line as the male parent to obtain fully aromatic long-grain hybrid japonica rice.
2. The method for cultivating a full-fragrant long-grain hybrid japonica rice according to claim 1, characterized in that, In step S2, the aromatic long-grain japonica rice restorer line is constructed by hybridizing a strong-resilience japonica rice restorer line with long-grain japonica rice material, and then performing compound hybridization of the offspring with aromatic japonica rice material to construct a segregating population of offspring.
3. The method for cultivating a full-fragrance long-grain hybrid japonica rice according to claim 2, characterized in that, The strong resilience japonica rice restorer line is C418, the long-grain japonica rice material is Jiahe 218, and the aromatic japonica rice material is Ewan 17.
4. The method for cultivating a full-fragrant long-grain hybrid japonica rice according to claim 1, characterized in that, In step S2, the molecular marker-assisted selection includes: Positive selection of the aroma gene was performed on the segregating population of the offspring. The offspring segregating population was subjected to reverse screening for undesirable trait genes linked to the long-grain trait donor.
5. The method for cultivating a full-fragrant long-grain hybrid japonica rice according to claim 4, characterized in that, The positive selection of the aroma gene specifically refers to: Genomic DNA was extracted from each individual in the progeny segregating population; PCR amplification was performed using specific primers for a molecular marker linked to the major aroma gene badh2 in rice. The amplification products were tested to screen out individuals that exhibited the pattern corresponding to the homozygous recessive genotype of the aroma gene.
6. The method for cultivating a full-aroma long-grain hybrid japonica rice according to claim 5, characterized in that, The reverse filtering specifically refers to: PCR amplification was performed on individuals retained by the positive selection using specific primers associated with molecular markers linked to unfavorable genes in donors of long grain trait that lead to decreased rice quality or resistance. The amplification products were tested, and individuals that presented the pattern corresponding to the unfavorable genes were removed.
7. The method for cultivating a full-aroma long-grain hybrid japonica rice according to claim 1, characterized in that, In step S1, the step of cultivating aromatic long-grain japonica rice male-sterile lines is as follows: Multiple aromatic or broadly compatible parents are hybridized, and the offspring are then hybridized with BT-type cytoplasmic male sterile lines to obtain a primary hybrid population carrying sterile cytoplasm. New maintainer lines are selected from the offspring of the obtained primary hybrid population, and the new maintainer lines are continuously backcrossed with the sterile offspring to cultivate candidate aromatic long-grain japonica rice sterile lines.
8. The method for cultivating a full-fragrant long-grain hybrid japonica rice according to claim 1, characterized in that, In step S3, the step of predicting hybridization specifically includes: Pollen is granted to candidate sterile lines in the backcrossing process during a generation in which the main traits of the candidate restorer lines are stable but not yet homozygous.
9. The method for cultivating a full-fragrant long-grain hybrid japonica rice according to claim 8, characterized in that, In step S3, the specific method for determining the final aromatic long-grain japonica rice male-sterile line and aromatic long-grain japonica rice restorer line is as follows: Based on the predicted heterosis and combining ability of the hybrid offspring, guide the selection of candidate sterile lines in subsequent backcrosses; Based on the predicted heterosis and combining ability of the hybrid offspring, the final purification selection of candidate restorer lines is guided.
10. The method for cultivating a full-aroma long-grain hybrid japonica rice according to claim 1, characterized in that, In step S4, obtaining the full-fragrant long-grain hybrid japonica rice specifically includes: according to the growth period characteristics of the final fragrant long-grain japonica rice sterile line and the final fragrant long-grain japonica rice restorer line, the final fragrant long-grain japonica rice sterile line and the final fragrant long-grain japonica rice restorer line are sown at different times so that their flowering periods coincide, thereby carrying out hybrid seed production.