Method for screening new high-quality watermelon variety based on rootstock-scion combination

Abstract

The invention discloses a method for screening a new high-quality watermelon variety based on stock-scion combination, and belongs to the technical field of agricultural planting and quality identification. The method comprises the following steps: cultivating a to-be-detected watermelon grafting combination and a self-rooted seedling as a contrast until fruits are mature; measuring appearance quality indexes of the fruits, including single fruit weight, fruit shape index, peel thickness and pulp color; measuring nutritional quality indexes, including the content of soluble solids in the center and the edge, the sugar-acid ratio, the hardness and brittleness of pulp and the content of lycopene; on the basis of the measured index data, the comprehensive quality score of each grafting combination is calculated through a weighted scoring model, and the weight of the nutritional quality index is higher than that of the appearance quality index; and screening out an optimal grafting combination according to the score. The method realizes systematic and objective evaluation of appearance and nutritional quality of watermelon grafted fruits, provides a scientific basis for screening high-quality grafting combinations, and has good operability and popularization and application values.

Description

Technical Field

[0001] This invention belongs to the field of agricultural planting and quality identification technology, specifically relating to a method for screening high-quality new watermelon varieties based on rootstock-scion combination. Background Technology

[0002] watermelon( Citrullus lanatus As a globally important economic crop, watermelon often faces challenges such as soil-borne diseases, continuous cropping obstacles, and abiotic stresses in its production. Grafting technology, by integrating the genetic characteristics of resistant rootstocks and high-quality scions, can significantly improve the disease resistance, environmental adaptability, and yield of watermelons, and has become a key measure in modern watermelon cultivation. However, while improving stress resistance, grafting may also have a significant impact on the appearance and nutritional quality of the fruit, such as fruit morphology, single fruit weight, fruit texture characteristics, soluble solids content, sugar-acid ratio, and flavor composition.

[0003] Existing research indicates that different rootstock varieties and scion combinations have varying effects on watermelon fruit quality. For example, Gao Junhong, Shi Xianfeng, and others, through metabolomics analysis, found that grafting treatment significantly improved key quality parameters such as single fruit weight, soluble solids content, and sugar-acid ratio. Liu Xunjia et al. pointed out that grafting combinations using loofah as rootstock showed excellent resistance to waterlogging, but the fruit texture did not change significantly. Furthermore, Xu Shengli et al.'s research confirmed that grafting can effectively suppress soil-borne pathogens, but a unified standard for systematic evaluation of post-grafting fruit quality still lacks.

[0004] Currently, the evaluation of watermelon grafting quality mainly focuses on single indicators or small-scale experiments, and a systematic and comprehensive evaluation method has not yet been developed. This makes it difficult to quickly and accurately screen high-quality grafting combinations that possess both excellent agronomic traits and meet market demands. Therefore, developing a systematic evaluation method based on appearance and nutritional quality is of great significance for optimizing watermelon grafting technology, enhancing commercial value, and promoting industrial development. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for screening high-quality new watermelon varieties based on rootstock-scion combination. This method is systematic, efficient and easy to operate.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for screening high-quality new watermelon varieties based on rootstock-scion combinations, comprising the following steps: (1) Cultivation of experimental materials: Using candidate watermelon varieties or combinations as scions, and cucurbitaceous crops such as forage watermelon, gourd, and pumpkin as rootstocks, grafting was performed on different candidate rootstocks to obtain grafted composites; and watermelon self-rooted seedlings and self-grafted seedlings were set up as controls. (2) The grafted composite is planted and cultivated under unified cultivation and management conditions until the fruit matures. During this period, the grafting survival rate and scion growth are screened to determine the grafting compatibility and remove rootstock-scion combinations that cannot grow and develop normally. (3) Determination of appearance quality indicators: Collect mature fruits and determine their single fruit weight, transverse diameter, longitudinal diameter, peel thickness and flesh color; (4) Nutritional quality index determination: Collect mature fruit samples and determine the content of soluble solids in the center and edge, sugar and acid composition and content, flesh firmness, crispness and lycopene content. (5) Comprehensive quality evaluation and selection of the best variety combination: For all the rootstock and scion combinations selected in step (2), after processing the data of various indicators measured in steps (3) and (4) using the minimum-maximum normalization method, the comprehensive quality score of each grafting combination is calculated using the pre-established weighted scoring model; the combination with the highest score is selected as the target grafting combination with excellent comprehensive quality.

[0007] Further, in step (3), the determination of the pulp color is carried out by spectrophotometry to quantify the lycopene content; the determination of the sugar and acid composition and content includes using liquid chromatography or a special kit to determine the content of sucrose, glucose, fructose and malic acid, and calculating the sugar-acid ratio.

[0008] Furthermore, in step (4), the determination of the flesh firmness is quantified using a texture analyzer (knife-shaped probe—HDP / BSB); the weighted scoring model assigns a greater total weight to the nutritional quality indicators than to the appearance quality indicators.

[0009] Furthermore, in step (5), the weights in the weighted scoring model are specifically as follows: Central soluble solids content: 25%, sugar-acid ratio: 25%, single fruit weight: 15%, fruit firmness: 15%, peripheral soluble solids content: 5%, fruit shape index: 5%, peel thickness: 5%, lycopene content: 5%.

[0010] The present invention also provides a new watermelon variety obtained by the above screening method, wherein the new watermelon variety is cultivated by grafting a combination of watermelon Zhemi 8 scion and pumpkin rootstock Nan Rootstock 17-C-1.

[0011] The beneficial effects of this invention are as follows: 1. Systematic: This invention is the first to integrate the core appearance indicators and internal nutritional indicators that affect the commercial value of watermelons into a unified identification system, realizing a multi-dimensional and systematic evaluation of the quality of grafted fruits.

[0012] 2. Scientific nature: Quantitative instruments (such as texture analyzers, liquid chromatographs, and spectrophotometers) are used to replace subjective sensory evaluation. Key indicators such as meat firmness, sugar and acid composition, and lycopene content are presented with precise data, and the results are objective and reliable.

[0013] 3. Strong guidance: The method is directly centered on the quality requirements of the end market. The selected grafting combinations not only have good agronomic traits, but also have more competitive market value and flavor quality in terms of fruit.

[0014] 4. Good operability: The testing methods used are all mature technologies in the fields of agricultural and food testing. The process is clear and easy to promote and implement in scientific research institutions and enterprises, providing a standardized tool for rootstock breeding and screening. Attached Figure Description

[0015] Figure 1 These are phenotypic and appearance quality variation diagrams of watermelons with Wm, Wm / Sq, and Wm / CA provided according to embodiments of the present invention, wherein (A) is a watermelon phenotypic image, (B) is a diagram showing the variation of single watermelon weight, (C) is a diagram showing the variation of watermelon rind thickness, (D) is a diagram showing the variation of watermelon transverse diameter, and (E) is a diagram showing the variation of watermelon longitudinal diameter.

[0016] Figure 2 These are variation diagrams of watermelon taste and flavor quality (Wm, Wm / Sq, and Wm / CA) provided according to embodiments of the present invention, wherein (A) is a variation diagram of watermelon hardness, (B) is a variation diagram of watermelon crispness, (C) is a variation diagram of soluble solids in the center of the fruit, (D) is a variation diagram of soluble solids in the edge of the fruit, (E) is a variation diagram of watermelon glucose, (F) is a variation diagram of watermelon fructose, (G) is a variation diagram of watermelon sucrose, (H) is a variation diagram of watermelon malic acid, and (I) is a variation diagram of watermelon lycopene. Detailed Implementation

[0017] The present invention will be further described in detail below through a typical embodiment, but the scope of protection of the present invention is not limited thereto.

[0018] Example 1 uses the method of the present invention to screen high-quality watermelon grafting combinations.

[0019] (1) Cultivation of experimental materials: Select the watermelon scion variety 'ZM8' (Zhemi No. 8).

[0020] Two candidate rootstocks were selected: pumpkin rootstock 'Sq' (Southern Rootstock 17-C-1) and forage watermelon rootstock 'CA' (Wild Rootstock 2).

[0021] Meanwhile, self-rooted seedlings 'Wm' were cultivated as a control, with the self-rooted seedlings being grafted from the scion variety 'ZM8'.

[0022] Grafting was performed using the grafting method, with at least three biological replicates for each treatment. Under identical field management conditions, graft compatibility was initially screened, including graft survival rate and scion growth, eliminating rootstock-scion combinations that failed to develop normally. Fruits of consistent maturity (collected based on pollination date, day, and fruit size) were collected at 36 and 39 days post-pollination for analysis. Phenotypic figures and appearance quality for each group are shown below. Figure 1 As shown.

[0023] (2) Appearance quality determination, the data results for each treatment group are as follows: Figure 1 As shown in B, 1C, 1D, and 1E, the results indicate that, overall, grafted watermelons show significant differences in size, weight, and flesh color compared to self-rooted watermelons in terms of appearance quality. In terms of quality, grafted watermelons exhibit a significant advantage throughout the entire developmental cycle. Figure 1 B); In terms of both horizontal and vertical diameters, the grafted watermelon had a horizontal and vertical diameter greater than Wm throughout the entire observation period (B); Figure 1 D, E); Regarding rind thickness, grafted watermelons from different rootstocks exhibit varying degrees of variation during ripening. Figure 1 C).

[0024] The specific measurement method is as follows: Individual fruit weight: Weigh each fruit individually using an electronic scale with an accuracy of 0.01 kg.

[0025] Horizontal and vertical diameters: Use a ruler to measure the maximum horizontal and vertical diameters of the fruit and calculate the fruit shape index (vertical diameter / horizontal diameter).

[0026] Peel thickness: Select three points at the equator of the fruit and use vernier calipers to measure the total thickness, including the outer peel and the white layer, and take the average value.

[0027] Fruit pulp color: Lycopene content was determined using a lycopene content assay kit (catalog number: G0170F, spectrophotometry 50T / 48 samples, Greens Biotechnology). The specific experimental procedure is as follows: Take 0.05 g of freeze-dried watermelon sample into a 2 mL EP tube, add 1 mL of anhydrous ethanol and homogenize. Wash five times with anhydrous ethanol (1 mL each time) until the eluent is colorless and transparent.

[0028] Add 1 mL of extraction buffer to the precipitate, vortex and mix for 10 min, then centrifuge at room temperature (12000 rpm, 10 min). Collect the supernatant and transfer it to a new EP tube. Wash the precipitate three times with the extraction buffer until the eluent is colorless. Combine all the supernatants from the above washings with the extraction buffer and dilute to 5 mL as the test solution.

[0029] The visible spectrophotometer was preheated for 30 minutes in advance, the wavelength was set to 502 nm, and the instrument was zeroed with distilled water before detection.

[0030] The final lycopene content is expressed in μg·g⁻¹ DW. (3) The methods for determining nutritional quality are as follows: Soluble solids content: Using a digital handheld saccharimeter, the soluble solids content of the center (a 3cm diameter area at the very center) and the edge (1cm from the inside of the white pulp) of each fruit were measured. Juice was collected from the center and edge of each fruit, and the juice was dropped onto the surface of a prism. The soluble solids content was read and recorded as a percentage (%).

[0031] Sugar and acid composition and content: Sugar composition: The contents of sucrose, glucose, and fructose in the pulp were determined by high performance liquid chromatography or commercial kits. The total sugar content is the sum of the three. In this example, sucrose was determined using a sucrose content (anthrone colorimetric method) kit (catalog number: G0506W, microplate method 96 samples, Greens Biotechnology); fructose and glucose contents were determined using a glucose and fructose content detection kit (catalog number: G0544W, microplate method 96 samples, Greens Biotechnology).

[0032] Organic acids: Using malic acid as the main indicator, the content of organic acids was determined by high performance liquid chromatography (HPLC), referring to the method (Gao Haiyan et al., 2005). The specific experimental procedure is as follows: Take about 1.0 g of freeze-dried watermelon pulp powder and put it into a 10 mL centrifuge tube. Add 1 g of pulp powder and 3 mL of 80% ethanol. Incubate in a 45℃ water bath for 25 min, centrifuge at 8000 rpm for 20 min, and aspirate the supernatant into a 10 mL centrifuge tube.

[0033] Add 2 ml of 80% ethanol to the centrifuge tube containing the pulp residue, incubate at 45°C for 25 min, centrifuge at 8000 rpm for 20 min, and transfer the supernatant to the 10 ml centrifuge tube from which the supernatant was first transferred. Repeat twice.

[0034] After thoroughly mixing the supernatants from the three batches, take 1 ml and evaporate it at 45°C for 46 hours. Once the liquid has completely evaporated, dilute it to 1 ml with water, vortex thoroughly, centrifuge at 10,000 rpm for 15 min, and take 0.8 ml and filter it through an aqueous filter membrane to a depth of 0.22 μm for analysis.

[0035] The mobile medium used in the liquid chromatography analysis was deionized water (pH adjusted to 2.1 with perchloric acid). The operating conditions of the detection system included: a detection wavelength of 210 nm, a mobile phase transfer rate of 0.5 mL / min, a sample injection volume of 10 μL, and a column temperature control at 30℃. The ultraviolet (UV) spectrometer was the core component of the detection system. The L-malic acid standard used in the experiment was purchased from Shanghai Yuanye Biotechnology Co., Ltd., and its purity met the standards. Other chemical reagents, such as ethanol, also met analytical purity requirements.

[0036] Malic acid content is expressed in mg / g. -1 DW indicates.

[0037] Sugar-acid ratio: The ratio of total sugar content (the sum of sucrose, glucose, and fructose in the pulp) to malic acid content.

[0038] Fruit firmness: measured using a texture analyzer. A knife-shaped probe (HDP / BSB) was used. Five points were evenly selected on the circumference of the fruit longitudinal section with a radius of 3 cm from the center for puncture testing. The maximum force value when the fruit breaks was recorded, which is the fruit firmness, expressed in Newtons (N).

[0039] Lycopene content: This indicator has been completed in the determination of appearance quality and pulp color, and the data is shared.

[0040] (4) Data calculation and filtering: Enter all the above measurement data into the database (such as an Excel spreadsheet).

[0041] A weighted scoring model is established as shown below.

[0042] The indicators and their weights are as follows: the highest weight of 25% is given to the central soluble solids content and sugar-acid ratio; the weight of a single fruit and the firmness of the fruit are each given a weight of 15%; and the weight of soluble solids content, fruit shape index, peel thickness and lycopene content at the edge are each given a weight of 5%.

[0043] The weighted scoring model assigns a greater total weight to nutritional quality indicators than to appearance quality indicators. The data for each indicator is standardized using the min-max normalization method (e.g., normalized to 0-100 points), then multiplied by the corresponding weight, and finally summed to obtain the overall quality score for each grafting combination.

[0044] The comprehensive quality score for each treatment group was calculated using the above model. The results showed that the "Wm-Sq" combination scored 75.5, the "Wm-CA" combination scored 47.5, and the "Wm" combination scored 10.

[0045] Compare the overall scores of 'Wm-Sq', 'Wm-CA', and 'Wm'. The 'Wm-Sq' combination score is significantly higher than the other treatments, thus identifying this combination as the grafting scheme with the best overall quality.

[0046] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A method for screening new varieties of high quality watermelon based on the combination of stock and scion, characterized by, The method comprises the following steps: a) cultivating the grafted combination to be tested and the self-rooted seedling as a control until the fruits are mature; b) determining the appearance quality indexes of the fruits, which at least include single fruit weight, fruit shape transverse diameter and longitudinal diameter, fruit peel thickness and flesh color; c) determining the nutritional quality indexes of the fruits, which at least include central and edge soluble solid content, sugar-acid ratio, flesh hardness and brittleness and lycopene content; d) converting the index data determined in steps b) and c) into standard scores of 0-100 by the minimum-maximum normalization method, and then calculating the comprehensive quality score of each grafted combination by a weighted scoring model; the weights in the weighted scoring model are as follows: central soluble solid content 25%, sugar-acid ratio 25%, single fruit weight 15%, fruit hardness 15%, edge soluble solid content 5%, fruit shape index 5%, fruit peel thickness 5%, and lycopene content 5%; e) screening the optimal grafted combination according to the comprehensive quality score.

2. The method of claim 1, wherein, In the step b), the flesh color is quantified by determining the lycopene content in the flesh by spectrophotometry.

3. The method of claim 1, wherein, In the step c), the sugar-acid ratio is the ratio of the total sugar content to the malic acid content in the flesh determined.

4. The method of claim 3, wherein, The total sugar content in the flesh is the sum of the contents of sucrose, glucose and fructose determined in the flesh.

5. The method of claim 4, wherein, The contents of sucrose, glucose and fructose in the flesh are determined by high performance liquid chromatography or a kit.

6. The method of claim 1, wherein, In the step c), the flesh hardness is determined by using a texture analyzer.

7. A new variety of watermelon, characterized in that, The new watermelon variety is screened by the method of claim 1.

8. The new variety of watermelon according to claim 7, characterized by, The new watermelon variety is cultivated by grafting the combination of the scion of watermelon Zhenmi No. 8 and the pumpkin stock of Nanzhen 17-C-1.

Images