Learn about the variety characteristics and cultivation techniques of Sunshine No. 1 orange grapefruit!
Huang Zaifa et al
Bijiang District is located in the northeast of Guizhou Province, at the junction of Hunan and Guizhou provinces, is the central urban area of Tongren, known as the "Pearl of Eastern Guizhou", there are 28 large and small rivers in the district, the four seasons are distinct, the rain and heat are in the same season, the climate is pleasant, it belongs to the humid climate of the central subtropical monsoon, and the average annual temperature is 17.9 °C. Thanks to the favorable geographical and climatic conditions, pomelo has become one of the leading industries in Bijiang District, in recent years, the area of newly planted Sanhong pomelo alone is more than 1,300 hm 2, plus the area of traditional white-fleshed pomelo, the planting scale of pomelo in the whole district exceeds 3,300 hm 2. So far, most pomelos have entered the fruit-bearing stage, but the saturation of the domestic pomelo market has also forced the local pomelo industry to transform. Among the many grapefruit varieties, "Sunshine No. 1" has won the love of consumers due to its relatively stable biological characteristics, resistance, adaptability, and excellent taste, and has also pointed out the direction for pomelo farmers to implement high-graft planting.
1 Characteristics of the "Sunshine No. 1" orange grapefruit
1.1 Breed origin and genetic background
"Sunshine No. 1" is an excellent single plant selected by Cao Li, a teacher from the Citrus Research Institute of the Chinese Academy of Agricultural Sciences, with "Ehime 28" as the female parent and "Chunxiang" as the male parent, among many hybrid descendant groups, with stable horticultural traits. The variety has good yield, long hanging period, the market time is from late November to early December, and the tree can normally be left to keep the fruit until March of the following year, which is very resistant to storage and transportation, and can be stored for 3 months at room temperature after harvest. By analyzing and evaluating the genetic characteristics of these parent varieties, the research team carefully selected those parents with excellent disease resistance, high yield and high-quality fruit traits for crossing, so that "Sunshine No. 1" orange grapefruit not only integrates the excellent characteristics of the parent varieties such as large fruits, high sweetness and good taste, but also ensures the stable inheritance of agronomic traits such as early maturity.
1.2 Biological characteristics
Sunshine 1 has a strong tree potential, fast growth, thick leaves, extremely vigorous vitality, well-developed root system, can grow well in a wide range of soil types, and has strong adaptability to soil, which is conducive to the efficient use of water and nutrients. Sunshine 1 has a moderate flowering period and an abundant number of flowers, which is highly synchronized with the active period of pollinating insects, which helps to improve pollination efficiency and fruit setting rate. Its fruit is large, the skin is thin, the flesh is full, the sugar content is high, and the ratio of sweet and sour is moderate, which meets the market demand for high-quality grapefruit. When this kind of pomelo is ripe, the flesh is bright in color, juicy and delicious, with little bitterness, and its good commerciality and taste have been widely praised by consumers. In addition, the fruit of "Sunshine No. 1" orange pomelo has good storage and transportation characteristics, which reduces its loss during transportation and provides greater economic benefits for fruit farmers and merchants.
1.3 Resistance and Adaptability
Sunshine No. 1 has strong resistance to pests and diseases, and has a certain degree of resistance to common diseases such as citrus canker and huanglongbing, and the strong disease resistance of the plant itself also reduces the amount of chemical pesticides used by pomelo farmers in the planting process, effectively reduces the pollution of soil resources, and indirectly has a positive impact on environmental protection. In line with resistance, Sunshine 1 also showed strong environmental adaptability, with stable growth and consistent fruit quality in both warm, humid and arid climates. This wide adaptability allows it to be grown in multiple regions, expanding the geographical distribution of pomelo cultivation. In addition, Sunshine 1 can adapt well to changes in soil pH, and can maintain growth and fruit quality in both acidic and alkaline soils. Thanks to its strong adaptability, Sunshine 1 has become the preferred variety for the next generation of pomelo planting.
2 Cultivation conditions of the "Sunshine No. 1" orange grapefruit variety
2.1 Soil environment
In order to ensure the healthy growth of plants, the fruit and vegetable flower plantation in Wuling Mountain, Guizhou Province should control the pH value of the planting soil of "Sunshine No. 1" orange pomelo at 5.5 ~ 6.5 to maintain the effectiveness of nutrients in the soil. At the same time, due to the high requirements of the root system of this variety for soil permeability and drainage capacity, it is recommended to use deep, fertile and well-drained loam or sandy loam. The ideal soil organic matter content should be maintained at more than 2%, and the heavy metal content should be strictly controlled below the national safety standard, such as cadmium content should be lower than the limit of 0.2 mg·kg-1 stipulated in the national standard "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018) to avoid heavy metal pollution. In addition, the available phosphorus content in the soil should be more than 20 mg·kg-1, and the available potassium content should be more than 100 mg·kg-1, which is helpful to promote the growth and development of "Sunshine No. 1" pomelo and improve the fruit quality. In terms of trace elements, iron should be above 200 mg·kg -1 and zinc at 30 mg·kg -1. Ensuring that the soil conditions meet these criteria creates a favourable environment for Sunshine 1 orange grapefruit to grow, thereby improving the health of the plant and increasing the commercial value of the fruit.
2.2 Climate and light conditions
Sunshine No. 1 is suitable for planting in warm areas with an average annual temperature of 15 ~ 28 °C, which is conducive to the growth of grapefruit trees and fruit development. The annual precipitation is 1 200 ~ 1 500 mm, and it is evenly distributed, which can keep the soil moist and provide sufficient water for the growth of pomelo. The relative humidity should be kept at 70% ~ 90%, too low humidity will increase the irrigation demand and may lead to water stress, while too high humidity may induce disease. Bijiang District belongs to the subtropical humid mountain climate, with an average annual temperature of 16 ~ 18 °C, an annual precipitation of 1 400 ~ 1 500 mm, four distinct seasons and a long frost-free period, which is an ideal environment for the growth of pomelo. At the same time, in order to ensure that the acidity, sweetness and pulp size meet the expectations of consumers, the plants need sufficient light intensity to complete photosynthesis and sugar accumulation, so the effective light time of "Sunshine 1" should not be less than 6 hours per day, if the light is insufficient, it will affect the quality of the fruit. Specifically, the light intensity should be kept in the range of 2 000 ~ 3 000 μmol·m -2·s -1 to ensure the formation of color and unique flavor of grapefruit.
3 Cultivation techniques of the "Sunshine No. 1" orange grapefruit variety
3.1 Preparation before planting
The soil in Bijiang District is brown soil, which is deep and fertile, with uniform distribution of heat and water, which is suitable for growing crops, and is one of the important soil types in the local area. Brown soils are acidic and suitable for the growth of orange pomelo, but they need to be adjusted by the appropriate amount of quicklime, and in order to meet the nutritional needs of Sunshine 1 orange pomelo, soil preparation must be carried out before planting. Winter is the best time to apply winter fertilizer, when the application of ripened organic fertilizer can provide sufficient nutrients for orange pomelo in spring. Under normal circumstances, the amount of 3 000 ~ 5 000 kg per 667 m 2 should be used to ensure that the organic matter content in the soil is more than 2%, and the carbon and nitrogen ratio should be ensured to be (25:1)~(30:1) when fertilizing to promote microbial activities and nutrient release. The application of organic fertilizer mixed with green manure and livestock and poultry manure as base fertilizer can not only improve the physical properties of the soil, increase the air permeability and water retention of the soil, but also provide rich nutrient sources for soil microorganisms, promote their activities, and accelerate the decomposition of organic matter and the circulation of nutrients. If the nitrogen content in the soil is too high, the carbon source (rice husk, straw, etc.) can be appropriately increased to achieve the ideal level of carbon and nitrogen ratio, so as to ensure that nitrogen fertilizer will not be wasted or lost due to excess. At the same time, combined with green manure planting technology, green manure crops with short growth cycle, wide coverage and developed root system, such as milk vetch and vetch, can not only reduce soil compaction through their root structure, but also increase soil nitrogen content through nitrogen fixation. After the green manure crops grow to a certain stage, through the green manure pressing and in-situ fermentation technology, that is, the green manure crops are pressed on the ground and let them decompose quickly in situ, which can quickly increase the soil organic matter content without affecting the soil structure, and at the same time provide immediate nutrients for orange grapefruit planting.
3.2 Cultivation techniques
The planting of "Sunshine No. 1" orange pomelo should be carried out in the spring or autumn when the climate is mild and the precipitation is moderate, and Bijiang District is located in the slope area of the transition from the Guizhou Plateau to the Hunan and Hunan mountains, and the local mountain characteristics require the selection of planting techniques suitable for the slope. After ensuring that the soil is deeply turned, choose the right season for planting so that the seedlings can grow in the right environment. Bijiang is usually planted after frost in spring or when there is sufficient rain in autumn, when the climatic conditions are conducive to seedlings rooting and reduce stress due to adversity. When planting, it is necessary to add organic water and fertilizer fermented by microorganisms, such as humic acid, potassium dihydrogen phosphate and other water-soluble organic fertilizers, and mix with water in a ratio of 1:10 to ensure that the root system of seedlings is in close contact with the soil and promote the rapid development of the root system. Depending on the size of the seedlings, the size of the planting pit should be 80 cm×80 cm×80 cm, and the planting row spacing and plant spacing should be kept at 4 m×3 m to ensure that the fruit trees have enough space for photosynthesis.
3.3 Cultivation management
Using the balanced topdressing technology of organic, inorganic and microbial fertilizers, according to the growth cycle and nutritional needs of orange pomelo, the application ratio and timing of major elements such as nitrogen, phosphorus and potassium are reasonably arranged to ensure the growth and development of plants. For example, in the early stage of plant growth, increase the application of nitrogen fertilizer to promote the growth of branches and leaves, and at the flowering and fruiting stage, increase phosphorus and potassium fertilizer appropriately to improve fruit quality and yield, and at the same time, the application of microbial inoculants can not only improve soil fertility, but also enhance the resistance of plants to diseases and pests. In terms of pest control, priority should be given to biological control and physical control methods, such as the application of pheromone trapping technology or the release of natural enemies for biological control, so as to minimize the use of chemical pesticides to ensure the balance between fruit safety and ecological environment. It should be noted that due to the large precipitation in Bijiang District, pomelo seedlings should be planted with reasonable drainage measures to avoid root rot caused by water accumulation at the roots, and timely irrigation should be carried out in the dry season to keep the soil moderately moist.
4 Maturity management and harvesting techniques of "Sunshine No. 1" orange grapefruit variety
4.1 Identification of maturity period
For Sunshine No. 1 orange grapefruit, accurate identification of ripening stage is of great significance to ensure fruit quality and maximize market value. Generally speaking, the ripening of orange pomelo is manifested by the change of peel from blue-green to bright yellow, and at the same time, the fruit volume increases, the peel becomes thinner and the whole begins to show luster. The monoculture performance of "Sunshine No. 1" variety is seedless, the peak production period is 667 m 2, the yield is 3~5 t, the appearance is beautiful, golden, large, and the weight of a single fruit is 200 ~ 300 g. In terms of chemical indicators, the ratio of total solublesolid (TSS) to total acid (TA) (TSS/TA ratio) is an important reference for evaluating the ripeness of grapefruit. In general, a TSS/TA ratio of 12:1 or higher is considered ripe, but the exact value needs to be adjusted according to the characteristics of the variety and local climatic conditions. In addition, the sugar and vitamin C content inside the fruit increases significantly during ripening, which can be quickly detected on site with a portable Brix meter and vitamin C tester. In addition, Bijiang District can predict the ripening period by collecting meteorological data for several consecutive years, combined with fruit growth models, which is especially important for commercial planting. From the fruit point of view, "Sunshine No. 1" orange grapefruit is large and full, highly recognizable, crisp and tender in taste, unique flavor, strong pomelo fragrance, sweet and sour, soluble solids (TSS) content in 13% ~ 17%, total acid of 0.6%, with a golden sugar-acid ratio, thin peel, high edible rate (more than 88%), easy to peel, not dirty hands, and the quality is better than most citrus varieties on the market in the same period. It should be noted that Bijiang District has a humid mid-subtropical monsoon climate with abundant rainfall, and its climatic characteristics also mean that pomelo may face delays in ripening caused by continuous rainy weather, so it is necessary to combine weather forecasts and historical data when predicting the ripening period.
4.2 Harvesting techniques
Harvesting is a key part of the process that affects the quality and storage life of Sunshine 1 orange grapefruit, so it should be harvested with great care. Specifically, harvesting should be done early in the morning or in the afternoon to avoid stress during the daytime heat, and picking tools should be disinfected frequently to prevent infection after fruit injury. When picking the fruit, it is necessary to leave a 2 ~ 3 cm fruit stalk, which helps to reduce wounds and prolong the storage time. In order to ensure the quality of post-harvest and reduce the exposure time of the field as much as possible, from the actual situation, Bijiang District is rich in heat, high rainfall, and the humid and hot environment provides suitable conditions for the breeding of spoilage bacteria, and the fruit is easy to breed mold after harvest, so pre-cooling and drying treatment are particularly important, and the fruit should be pre-cooled or transferred to a cool and ventilated place as soon as possible after picking.
During the picking process, the fruits are preliminarily sorted, and the diseased and insect fruits, injured fruits and deformed fruits are eliminated to ensure the uniformity and aesthetics of the marketed fruits. In addition, fruits with different ripeness are picked in stages to ensure that the ripeness of each batch is relatively consistent. In practice, the professionalism of the picking team is also crucial, as experienced pickers can accurately judge the ripeness of the fruit and reduce damage to the fruit during the picking process, thus ensuring the quality of the fruit. Due to the mountainous terrain of Bijiang District, special attention should be paid to the safety of picking operations, and safety belts, safety nets and other equipment need to be used to ensure the safety of pickers. At the same time, depending on the slope of the hill, ropes or long pole tools may be required to assist in the harvesting. During the whole harvesting process, attention should be paid to reducing the damage to the branches, protecting the tree body, and laying a good foundation for the next year's growth.
5 Conclusion
"Sunshine No. 1" orange grapefruit is very popular with consumers because of its superior variety characteristics. After the detailed exploration of the project team of Wuling Mountain Fruit and Vegetable Flower Plantation in Guizhou Province, the cultivation technology has been clarified: apply organic fertilizer in winter, select a suitable planting period, apply organic and inorganic fertilizer in a balanced manner, and focus on biological control of pests and diseases. In terms of ripening management, the best harvest time is determined through a comprehensive evaluation of physiological and chemical indicators, and appropriate harvesting methods and pre-cooling treatment are adopted to maintain fruit quality. The implementation of these technologies not only improves the yield and quality of "Sunshine No. 1", but also has a significant impact on improving market competitiveness and satisfying consumers' pursuit of high-quality fruits. Therefore, the promotion and application of "Sunshine No. 1" is of great practical significance for promoting the high-quality development of the mainland pomelo industry and breaking the existing development bottleneck.