Comprehensive quality evaluation method for blackberry interspecific hybridization single plant

Abstract

The invention discloses a method for evaluating the comprehensive quality of blackberry interspecific hybridization single plants, which comprises the following steps: 1) taking blackberries as female parents and wild rubus corchorifolius as male parents to obtain blackberry F1 generation interspecific hybridization seedling groups; (2) collecting mature fruits of each single plant of the F1 interspecific hybrid population, and measuring various appearance quality indexes and nutritional quality indexes of the fruits to obtain character data of each fruit; (3) obtaining a correlation rule among the characters through correlation analysis; and 4) performing principal component analysis by calculating and comparing the contribution rate and the characteristic value of the fruit character, calculating to obtain the weight of each principal component, constructing a fruit comprehensive evaluation model, and obtaining the comprehensive evaluation score of the hybrid F1 single plant according to the model. The method for optimizing the interspecific hybrid plants of the blackberries through comprehensive evaluation of fruit characters is explored for the first time, the evaluation indexes obtained by the method can be used for rapidly and effectively screening out the hybrid single plants with excellent comprehensive characters, and the method has a good application prospect in quality breeding of the blackberries.

Description

Technical Field

[0001] This invention belongs to the field of plant germplasm resource evaluation technology, and relates to an evaluation method and identification technology for the excellent comprehensive quality of interspecific hybrid germplasm fruits of blackberry and wild Rubus idaeus. Background Technology

[0002] Blackberry (Rubus spp.) is a perennial economic forest shrub belonging to the genus Rubus Linn. and subgenus Eubatus Focke of the family Rosaceae. Blackberry fruits are rich in anthocyanins, polyphenols, vitamin C (Vc), dietary fiber, and minerals, possessing not only excellent antioxidant and health benefits but also pharmacological effects such as antibacterial, anticancer, blood sugar-lowering, and vascular-protective properties. It has become one of the five healthiest foods recommended by the Food and Agriculture Organization of the United Nations. With the increasing global consumer focus on health and nutrition, the blackberry industry in China is developing rapidly and has become one of the fastest-growing new fruit tree types in recent years.

[0003] The main breeding objectives for blackberries both domestically and internationally focus on improving fruit flavor and firmness, suitability for mechanical harvesting, high yield, adaptation to local environments, and enhanced resistance to pests and diseases. Research has revealed that blackberries exhibit complex ploidy, ranging from diploid (2n=2x=14) to dodecloid (2n=12x=84). The subgenus *Strombyx*, to which blackberries belong, possesses abundant natural ploidy variation, predominantly allopolyploid, with a relatively small proportion of homopolyploids. Blackberry breeding faces limitations and challenges, including the complex background resulting from species polyploidy and a scarcity of genetic resources. Analysis of blackberry germplasm genetic diversity using molecular marker technology indicates that homoploid blackberry varieties have a relatively narrow genetic base due to geographical proximity, becoming a key factor restricting further innovative breakthroughs in blackberry germplasm. Therefore, it is necessary to conduct hybridization and selection of blackberry germplasm from different sources, which can not only broaden the genetic base of existing varieties but also has significant practical implications for screening and cultivating new germplasm with superior traits.

[0004] Despite the rich nutritional content of blackberries, cultivated blackberry varieties often suffer from simple volatile aroma components and limited flavor complexity, restricting the improvement of their fresh-eating quality and market value. To improve the fruit quality of cultivated blackberries, interspecific hybridization using abundant wild germplasm within the genus *Rubus* holds great potential. *Rubuschingii*, a wild relative of *Rubus*, produces mature fruits with a delicate texture, rich nutrition, and extremely high nutritional and medicinal value. Compared to cultivated blackberries, its fruits exhibit higher titratable acidity and a more complex, layered flavor profile. Through interspecific hybridization of blackberries and *Rubuschingii*, and selection of F1 generation germplasm, it is hoped that superior germplasm with outstanding fruit nutritional and flavor qualities can be bred.

[0005] Because the genetic origins of blackberry cultivars are difficult to trace back to a single original species, they are mostly products of multiple hybridizations and polyploidizations of two or more species within the subgenus *Blackberry*. Therefore, cultivars typically have complex genetic backgrounds, incorporating parents at multiple ploidy levels, and tend to exhibit wide phenotypic segregation after varietal and interspecific hybridization. Currently, the evaluation and selection of superior F1 generation blackberry hybrids still mainly relies on observation and investigation of fruit phenotypic traits. This approach can only simply identify individual plants with excellent single fruit morphological traits, and cannot take into account nutritional quality evaluation to screen for hybrid offspring with superior overall traits in appearance and fresh eating quality. Therefore, the breeding process for blackberry hybrid offspring lacks a scientific, effective, and rapid technology for evaluating and selecting superior hybrid germplasm fruits based on their overall quality. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical difficulties in the breeding of F1 generation hybrid blackberry plants in the prior art, which lack the selection and identification of hybrid single plants with excellent comprehensive quality, and to provide a technical method for successfully obtaining hybrid single plant germplasm with excellent comprehensive quality that takes into account both appearance and nutritional quality through hybridization breeding and comprehensive fruit evaluation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A comprehensive quality evaluation method for single blackberry interspecific hybrids is used for the selection and breeding of blackberry and wild raspberry interspecific hybrids. This comprehensive quality evaluation method includes the following steps:

[0009] (1) Obtaining F1 hybrid single plants: Using blackberry as the female parent and wild raspberry as the male parent, artificial hybridization was carried out and hybrid seeds were collected. After sowing the seeds, F1 hybrid single plant seedlings were obtained.

[0010] (2) Determination of fruit trait indices of hybrid single plants: Collect fruits from each hybrid single plant and determine their fruit trait indices; the fruit trait indices include appearance quality indices and nutritional quality indices; the appearance quality indices include single fruit weight, fruit transverse diameter, fruit longitudinal diameter, fruit shape index and fruit firmness; the nutritional quality indices include flavonoid content, anthocyanin content, total phenol content, soluble sugar content, vitamin C content, titratable acid content, soluble solids content and solid acid ratio;

[0011] (3) Correlation analysis of fruit indicators: Correlation analysis was performed on the fruit trait data obtained in step (2);

[0012] (4) Principal component analysis of fruit traits: Based on the correlation analysis results in step (3), the fruit trait index data obtained in step (2) are analyzed by calculating the contribution rate and characteristic value of each trait. A comprehensive evaluation model of fruit is constructed based on the weight of each principal component. The comprehensive evaluation score of hybrid F1 single plant is obtained based on the model. The single plant with a higher score has better comprehensive quality.

[0013] This invention constructs a comprehensive fruit evaluation model based on principal component analysis of fruit appearance and nutritional quality indicators. This model is used to evaluate the selected hybrid plants, which not only demonstrate excellent fruit morphology but also take into account nutritional quality.

[0014] Furthermore, the comprehensive quality evaluation method of the present invention also includes:

[0015] (5) Screening of core evaluation indicators: Calculate the comprehensive weight coefficient of each trait indicator and screen out the trait indicators with high comprehensive weight coefficients as core evaluation indicators; the comprehensive weight coefficient of each trait indicator is obtained by calculating the principal component weight and the loading of each trait on the principal component.

[0016] In step (3), the correlation analysis uses Pearson correlation analysis.

[0017] The formula for calculating the comprehensive weight coefficient of each trait index in step (5) is as follows:

[0018] ;

[0019] In the formula, This represents the comprehensive weighting coefficient of the j-th trait index. This represents the weight of the k-th principal component. This represents the loading of the j-th trait index on the k-th principal component.

[0020] In some embodiments, as a preferred embodiment, the present invention uses the hexaploid cultivated blackberry 'Freida' as the female parent and the diploid wild Rubus 'Palm Leaf Rubus' as the male parent for hybridization, successfully obtaining hybrid germplasm, which provides feasibility for carrying out comprehensive quality evaluation and identification of hybrid offspring fruits.

[0021] Based on this, principal component analysis was conducted to construct a comprehensive fruit evaluation model. The cumulative variance contribution rate of the first four principal components was 55.96%, namely: PC1 had the highest positive loading on fruit longitudinal diameter, transverse diameter, fruit shape index, and single fruit weight, and was positively correlated with titratable acid and negatively correlated with the sugar-acid ratio. This component mainly reflects the size, shape, and basic acidity characteristics of the fruit, and is a fruit size-morphology factor; PC2 had the highest positive loading on the sugar-acid ratio, and was a loading on titratable acid and flavonoids. This component reflects the core flavor of the fruit's sugar-acid balance and is a flavor balance factor; PC3 had the highest loading on fruit firmness and vitamin C, and was mainly associated with the fruit's texture and firmness and key nutrient components (vitamin C), and is a texture-nutrient factor; PC4 had a high positive loading on total phenols and single fruit weight, and was a loading on flavonoids. This component mainly reflects the accumulation of phenolic substances and its positive correlation with fruit size, and is a phenol accumulation factor.

[0022] Based on the first four principal components, a linear weighted model is constructed to calculate the comprehensive evaluation value:

[0023] F =0.3563× F 1+0.2768× F 2 + 0.1868 × F 3 + 0.1801 × F 4;

[0024] In the formula, F is the comprehensive score of a single plant, F1, F2, F3, and F4 are the scores of the four principal components: fruit size-morphology factor, flavor balance factor, texture-nutrition factor, and phenolic accumulation factor, respectively, and 0.3563, 0.2768, 0.1868, and 0.1801 are the weights of the corresponding principal components.

[0025] To quantify the contribution of each original trait indicator to the overall score, the overall weight coefficient of each trait indicator was further calculated. This coefficient is obtained through principal component weights. Loadings of each trait index on the principal components The calculation is as follows: The core evaluation indicators were selected as follows: Fruit longitudinal diameter (FLD) had the highest weighting coefficient (0.2660), followed by fruit transverse diameter (FTD, 0.2525) and single fruit weight (SFW, 0.1832), indicating that fruit size is the most critical positive factor determining overall quality. Fruit shape index (FSI, 0.1635) and fruit firmness (FF, 0.1477) also made significant positive contributions.

[0026] The present invention has the following advantages over the prior art:

[0027] This invention overcomes the previous problem of not being able to comprehensively and objectively evaluate the quality of F1 generation blackberry hybrids in order to select the best individual plants. It successfully obtained a rapid and effective evaluation method for blackberry interspecific hybrid germplasm with complex genetic backgrounds. For the first time, it obtained a comprehensive evaluation model and core evaluation indicators based on principal component analysis of fruit appearance and nutritional quality traits. After screening using this model, high-scoring hybrid individual plants with excellent comprehensive quality were obtained.

[0028] Existing interspecific hybrid germplasm of blackberries has large variations in offspring, making it impossible to objectively determine whether it possesses excellent nutritional quality based on visual morphology alone. However, by applying the fruit quality comprehensive evaluation model and core evaluation indicators of this invention, hybrid plants with excellent comprehensive fruit traits can be accurately and objectively identified, which is significantly beneficial for screening superior blackberry plants with excellent comprehensive quality traits.

[0029] The method for identifying fruit quality traits of interspecific hybrid blackberry germplasm of the present invention has important guiding significance for cultivating superior comprehensive fruit germplasm types of blackberry with independent intellectual property rights. Attached Figure Description

[0030] Figure 1 Correlation analysis diagram of 13 quality traits of F1 generation blackberry fruit;

[0031] In the figure, red / ellipse indicates a positive correlation, and blue / ellipse indicates a negative correlation. The darker the color, the higher the correlation coefficient, and the size of the circle corresponds to the color depth. *: P≤0.05; **: P≤0.01; FL: Flavonoid content; ANT: Anthocyanin content; TPC: Total phenolic content; SS: Soluble sugar content; VC: Vitamin C content; TA: Titratable acid content; SSC: Soluble solids content; SSC / TA: Solid-acid ratio; SFW: Single fruit weight; FF: Fruit firmness; FTD: Fruit transverse diameter; FLD: Fruit longitudinal diameter; FSI: Fruit shape index;

[0032] Figure 2 This is a principal component analysis diagram of a single F1 blackberry hybrid based on fruit quality traits. Detailed Implementation

[0033] Unless otherwise stated, the terms used in this invention generally have the meanings commonly understood by those skilled in the art.

[0034] The present invention will be described in further detail below with reference to specific preparation and application examples and data. It should be understood that these examples are merely illustrative of the invention and are not intended to limit the scope of the invention in any way.

[0035] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. All nouns or parameter abbreviations used are indicated upon their first appearance, and subsequent uses of the same nouns or parameter names will retain the same meaning as their initial indication.

[0036] Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0037] Example 1

[0038] Correlation among fruit traits of F1 individual plants from interspecific blackberry hybrids revealed

[0039] Blackberry variety 'Freida' and wild Rubus palmatus parent plants and their F1 hybrid offspring were planted at the Lishui Baima Scientific Base of the Institute of Botany, Chinese Academy of Sciences in Jiangsu Province, and were managed under conventional field conditions.

[0040] During the fruit ripening period in May-June 2025, the fruit characteristics of 90 fruiting plants from the hybrid progeny were investigated. Ten black, mature fruits of uniform size from each plant were selected for appearance measurement. The transverse diameter (maximum width of the cross-section) and longitudinal diameter (maximum length of the longitudinal section) of the fruit were measured using an MNT-150 digital vernier caliper, and the fruit shape index was calculated as: fruit shape index = longitudinal diameter / transverse diameter. The weight of a single fruit was determined using an electronic analytical balance with a sensitivity of 0.01. Fruit firmness was measured using a GY-4 fruit firmness meter (TOP instrument Co., Hangzhou). Ten fruits were counted as one group, and the measurement was repeated three times. The average value was used for analysis.

[0041] Ten healthy, undamaged mature fruits were selected, and the soluble solids content was measured using a PAL-1 handheld refractometer (Atago China Branch, Guangzhou). 50 g of fruit from each individual plant was thawed, crushed, and mixed before being used for flavor quality determination; each indicator was measured three times. For titratable acid determination: 2 g of fruit at each developmental stage was placed in a mortar, 8 mL of double-distilled water was added, and the mixture was ground into a homogenate. After standing for 20 min, the pH of the supernatant was measured using a pH meter (Hangzhou Jinmai Instrument Co., Ltd.). 5 mL of the supernatant was taken, 15 mL of double-distilled water was added, and the titratable acid content in the fruit was determined using an acid-base potentiometric titration method with a ZD-2 automatic titrator (Hangzhou Jinmai Instrument Co., Ltd.). The total phenolic content in the fruit was determined using the Folin-Ciocerteu method. The anthocyanin content in the fruit was determined by pH differential method. The contents of soluble sugar, vitamin C and flavonoids were determined by kits. The soluble sugar assay kit (catalog number A145-1-1), vitamin C assay kit (catalog number A009-1-1), and flavonoid assay kit (A142-1-1) were all purchased from Nanjing Jiancheng Bioengineering Research Institute Co., Ltd.

[0042] Pearson correlation analysis was performed on appearance quality indicators and nutritional quality indicators (e.g.) Figure 1(As shown). Regarding fruit morphogenesis, single fruit weight (SFW) was significantly positively correlated with fruit longitudinal diameter (FLD), fruit transverse diameter (FTD), and fruit shape index (FSI). The fruit shape index (FSI) was also significantly positively correlated with single fruit weight (SFW), indicating a high degree of synergy among the factors involved in fruit morphogenesis. Among fruit flavor components, titratable acid (TA) showed a highly significant negative correlation with the sugar-acid ratio (SSC / TA), while it was significantly positively correlated with both single fruit weight (SFW) and fruit longitudinal diameter (FLD), suggesting that larger fruits may have a higher acid content. The sugar-acid ratio (SSC / TA) was significantly negatively correlated with fruit longitudinal diameter (FLD), indicating that longer fruits have a lower sugar-acid ratio. In contrast, total phenolic content (TPC) showed a significant positive correlation with single fruit weight (SFW), titratable acid (TA), and fruit transverse diameter (FTD), indicating that larger fruits can accumulate more phenolic substances. Flavonoid (FL) content and soluble sugar (SS) content and fruit transverse diameter (FTD) were all significantly negatively correlated, indicating that the accumulation of flavonoids and soluble sugars is difficult to achieve simultaneously.

[0043] Example 2

[0044] Principal component analysis of fruit traits in blackberry F1 individual plants

[0045] To extract the core evaluation dimensions, principal component analysis was performed on 13 major fruit quality evaluation traits of blackberries. The cumulative variance contribution rate of the first four principal components was 55.96%, reflecting most of the information in the original data of various blackberry fruit quality indicators.

[0046] Table 1 shows that PC1 has the highest positive loading on fruit longitudinal diameter, transverse diameter, fruit shape index, and single fruit weight. It is positively correlated with titratable acid and negatively correlated with the sugar-acid ratio. This component mainly reflects the fruit's size, shape, and basic acidity characteristics, and is a fruit size-morphology factor. PC2 has the highest positive loading on the sugar-acid ratio, and is a loading factor on titratable acid and flavonoids. This component embodies the core flavor of the fruit's sugar-acid balance and is a flavor balance factor. PC3 has the highest loading on fruit firmness and vitamin C, mainly related to fruit texture and firmness and key nutrient components (vitamin C), and is a texture-nutrient factor. PC4 has a high positive loading on total phenols and single fruit weight, and is a loading factor on flavonoids. This component mainly reflects the accumulation of phenolic substances and its positive correlation with fruit size, and is a phenol accumulation factor.

[0047] Table 1. Contribution rate and eigenvalues ​​of principal components of fruit traits in F1 hybrid blackberry plants.

[0048] Fruit quality traits PC1 PC2 PC3 PC4 Flavonoid content (FL) 0.0003 -0.3963 0.1398 -0.3139 Anthocyanin content (ANT) 0.1642 0.1519 -0.2026 0.1566 Total phenol content (TPC) -0.0363 -0.1068 0.2194 0.7244 Soluble sugar content (SS) -0.0031 0.1233 -0.2185 -0.1712 Vitamin C content -0.1520 0.0128 0.4452 0.0764 SSC / TA ratio -0.3068 0.5192 0.0246 0.1567 Single fruit weight (SFW) 0.3118 0.0447 -0.1524 0.4888 Fruit firmness FF -0.0411 0.1907 0.6663 -0.0825 Titratable acid content TA 0.3278 -0.4607 -0.0305 0.1190 Soluble solids content (SSC) -0.1671 0.3080 -0.3177 -0.0303 Fruit Shape Index (FSI) 0.3894 0.1965 -0.0818 -0.0795 Fruit transverse diameter FTD 0.4435 0.2822 0.1829 -0.0975 Fruit longitudinal diameter FLD 0.5214 0.2447 0.1886 -0.1263 Variance contribution rate (%) 19.9397 15.4897 10.4560 10.0772 Eigenvalue (λ) 2.5922 2.0137 1.3593 1.3100 Cumulative contribution rate (%) 19.9397 35.4294 45.8854 55.9626

[0049] Note: PC1-PC4 represent the first to fourth principal components, respectively.

[0050] Example 3

[0051] Comprehensive evaluation of fruit quality of F1 interspecific hybrid blackberry plants and screening of core evaluation indicators

[0052] To eliminate differences in dimensions and orders of magnitude among the various trait indicators, the raw data underwent standardization preprocessing. The Z-score standardization method was used to convert the original observations of each trait into standardized data with a mean of 0 and a standard deviation of 1. The specific calculation formula is as follows: .in, This represents the standardized value of the i-th sample (i.e., the fruit of the F1 hybrid plant to be evaluated) on the j-th trait; These are the original observations; and ...

[0053] Principal component analysis was performed using OriginPro 2024 software based on the standardized data matrix Z. Principal components were extracted based on the principle that the eigenvalue (λ) was greater than 1. The score of a sample on the principal components was calculated by the following formula: . Let be the loading of the j-th trait index on the k-th principal component, and p be the total number of trait indices. This study extracts the first four principal components whose cumulative variance contribution rate meets the requirements (e.g., ...). Figure 2 (as shown), and derive the score corresponding to each sample. to Based on the first four principal components, a linear weighted model is constructed to calculate the comprehensive evaluation value. The weights of each principal component are as follows: From its eigenvalues Decide, The overall score for each sample : .

[0054] According to weight The weights of each principal component are calculated as follows: w1 = 2.59215 / (2.59215 + 2.01366 + 1.35928 + 1.31003) ≈ 0.3563; w2 = 2.01366 / 7.27512 ≈ 0.2768. Similarly, w3 ≈ 0.1868, w4 ≈ 0.1801. Based on this, a comprehensive fruit quality evaluation model is constructed. F =0.3563× F 1+0.2768× F 2 + 0.1868 × F 3 + 0.1801 × F4. The model was used to comprehensively evaluate the fruit quality of 90 hybrid plants, with the calculated comprehensive score ranging from -1.9234 to 1.7052. Based on the comprehensive score characteristics, the fruit quality grades of F1 plants were divided into excellent, good, medium, and poor, accounting for 20%, 30%, 30%, and 20% respectively (as shown in Table 2 below). The principal component scores and comprehensive scores of the top 20% (18 plants) of superior plants are shown in Table 3. This result demonstrates that principal component score analysis can clearly distinguish the source of quality advantages of different superior plants, providing a direct basis for the precise selection of parents and targeted improvement of traits in subsequent breeding.

[0055] To quantify the contribution of each original trait to the overall score, the overall weight coefficient of each trait was further calculated. This coefficient is obtained through principal component weights. Loadings of each trait on the principal components The calculation is as follows: .according to Calculate the overall weighting coefficient for each trait, taking FL as an example: .

[0056] Similarly, the weighting coefficients of each trait were further calculated. The results showed that the fruit longitudinal diameter (FLD) had the highest weighting coefficient (0.2660), followed by the fruit transverse diameter (FTD, 0.2525) and single fruit weight (SFW, 0.1832), indicating that fruit size is the most critical positive factor determining overall quality. Fruit shape index (FSI, 0.1635) and fruit firmness (FF, 0.1477) also had significant positive contributions. Total phenols (TPC, 0.1290) and anthocyanins (ANT, 0.0910) were moderately positive influencing factors. The contributions of the sugar-acid ratio (SSC / TA, 0.0672), vitamin C (VC, 0.0463), and titratable acid (TA, 0.0050) were relatively weak. The weighting coefficient for flavonoid content (FL) was negative (-0.1400), indicating a negative correlation between flavonoid content and the overall score. This suggests that high flavonoid content in individual plants may result in weaker performance in core economic traits such as fruit size and firmness, revealing an important trait trade-off in this hybrid population. Soluble sugar (SS, -0.0386) and soluble solids (SSC, -0.0387) also had a slight negative impact on the overall fruit quality evaluation.

[0057] Table 2 Distribution of Overall Quality Scores of Hybrid Offspring

[0058] grade Number of individual plants Percentage (%) Overall score range Representative single plant excellent 18 20 0.7307～1.705 58, 101, 33, 19, 11, 74,14, 22, 4, 61, 25, 10, 57,3, 8, 121, 12, 75 good 27 30 -0.0526～0.729 107, 64, 47, 34, 79, 69,115, 9, 35, 98, 43, 124,86, 32, 66, 108, 62, 15,20, 1, 77, 53, 17, 16, 52,63, 73 middle 27 30 -0.6430～-0.1054 68, 83, 24, 28, 59, 84, 30,38, 7, 81, 103, 18, 60, 65,82, 80, 54, 21, 29, 2, 118,122, 46, 70, 6, 55, 100 Difference 18 20 -1.9234～-0.6651 120, 125, 26, 39, 40, 72,27, 71, 111, 45, 102, 88,89, 119, 105, 97, 123, 117

[0059] Table 3. Principal component comprehensive scores and ranking of fruits from F1 hybrid blackberries.

[0060] Single plant serial number F1 F2 F3 F4 Si 57 3.0449 0.9216 0.5188 0.0953 1.2662 61 2.0456 1.3253 0.7466 -0.7082 0.9878 8 0.5196 1.7440 0.5695 0.9273 0.9512 15 1.4879 -0.2120 1.6129 0.8205 0.9175 101 4.1092 -1.3155 0.6751 -0.3880 0.8935 70 3.3173 -0.3909 1.0402 -1.5118 0.7874 102 1.1133 1.5011 0.7230 -0.7320 0.7602 64 0.6123 1.0965 -0.5486 1.9472 0.7324 59 -0.1117 1.2087 1.5255 0.0905 0.6874 17 0.8767 -0.5351 1.1167 1.4876 0.6673 18 -0.1272 0.9144 0.6619 1.3095 0.6363 58 -0.0681 1.3948 -0.1508 1.5045 0.6286 34 -0.6917 1.5847 1.0243 0.6965 0.6257 120 -1.0125 1.5220 0.8873 1.3250 0.6090 20 -0.1288 1.4033 0.9418 0.0364 0.5848 75 0.9573 0.1458 0.0151 1.1973 0.5550 32 0.4082 0.9897 0.9588 -0.4028 0.5404 60 -1.0657 1.3555 1.7095 0.2549 0.5331

[0061] Note: - These represent the scores of the sample on the first to fourth principal components, respectively. The overall score is determined by the model. =0.3563× +0.2768× +0.1868× +0.1801× The calculation yielded the result.

[0062] The results above show that 90 interspecific hybrid F1 plants were obtained by crossing blackberry 'Freida' with wild Rubus palmatum. A comprehensive evaluation model based on principal component analysis was constructed for the systematic evaluation of fruit traits in the interspecific hybrid F1 population. This model can effectively identify plants with excellent fruit quality and comprehensive traits. Fruit trait evaluation indicators with high weight coefficients—fruit longitudinal diameter, fruit transverse diameter, single fruit weight, fruit shape index, and fruit firmness—were selected. These main quality traits have a significant positive contribution to the overall fruit quality score and can be prioritized for guiding the selection of hybrid plants. This model has broad application prospects in the creation of new Rubus interspecific hybrid germplasm and the breeding of new high-quality blackberry varieties.

Claims

1. A comprehensive quality evaluation method of blackberry interspecific hybrid single plant, the evaluation method is used for interspecific hybrid breeding of blackberry and wild raspberry; characterized in that, The comprehensive quality evaluation method comprises the following steps: (1) Hybrid F1 generation single plant is obtained: blackberry is used as the female parent, wild raspberry is used as the male parent, artificial hybridization is carried out, hybrid seeds are collected, the seeds are sown and F1 hybrid single plant seedlings are obtained; (2) Hybrid single plant fruit trait index determination: collect the fruits of each hybrid single plant, and determine the fruit trait indexes; the fruit trait indexes include appearance quality indexes and nutritional quality indexes; the appearance quality indexes include single fruit weight, fruit transverse diameter, fruit longitudinal diameter, fruit shape index and fruit hardness; the nutritional quality indexes include flavonoid content, anthocyanin content, total phenol content, soluble sugar content, vitamin C content, titratable acid content, soluble solid content and solid acid ratio; (3) Correlation analysis of fruit indexes: the fruit trait index data obtained in step (2) is subjected to correlation analysis; (4) Principal component analysis of fruit traits: according to the correlation analysis results in step (3), the fruit trait index data obtained in step (2) is subjected to principal component analysis by calculating the contribution rate and characteristic value of each trait, a fruit comprehensive evaluation model is constructed according to the weight of each principal component, and the comprehensive evaluation score of the hybrid F1 single plant is obtained according to the model, and the single plant with a higher score has better comprehensive quality.

2. The comprehensive quality evaluation method according to claim 1, characterized by The comprehensive quality evaluation method further comprises the following steps: (5) Selection of core evaluation indexes: calculate the comprehensive weight coefficients of each trait index, and select the trait indexes with high comprehensive weight coefficients as core evaluation indexes; the comprehensive weight coefficients of each trait index are calculated by the principal component weight and the load of each trait on the principal component.

3. The integrated quality evaluation method according to claim 2, characterized by, The correlation analysis in step (3) uses Pearson correlation analysis.

4. The comprehensive quality evaluation method according to claim 2, characterized by The comprehensive weight coefficient calculation formula of each trait index in step (5) is as follows: ； In the formula, denotes the comprehensive weight coefficient of the jth trait index, denotes the weight of the kth principal component, denotes the load of the jth trait index on the kth principal component.

5. The comprehensive quality evaluation method according to claim 4, characterized by In step (1), blackberry 'Furida' is selected as blackberry, and wild raspberry 'Zhangye Rubus' is selected as wild raspberry.

6. The comprehensive quality evaluation method according to claim 5, characterized by In step (4), the fruit comprehensive evaluation model is constructed by the following four principal components: fruit size-morphology factor, flavor balance factor, texture-nutrition factor and phenolic accumulation factor, and the calculation formula is as follows: F =0.3563× F 1+0.2768× F 2+0.1868× F 3+0.1801× F 4； In the formula, F is the comprehensive score of the single plant, F1, F2, F3 and F4 are the scores of the four principal components of fruit size-morphology factor, flavor balance factor, texture-nutrition factor and phenolic accumulation factor, and 0.3563, 0.2768, 0.1868 and 0.1801 are the weights of the corresponding principal components.

7. The integrated quality evaluation method according to claim 6, characterized by, The core evaluation indexes selected in step (5) include fruit longitudinal diameter, fruit transverse diameter, single fruit weight, fruit shape index and fruit hardness.

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