Experimental Research on Pomegranate Varieties

Lianjun WANG

Shanghai Chenshan Botanical Garden, Shanghai 201602

Abstract [Objectives] To study the introduction performance of pomegranate (Punica granatum) varieties in Shanghai area. [Methods] In this experiment, five pomegranate varieties were introduced, namely ‘American 002’ pomegranate, ‘Huohulu’ pomegranate, ‘Wanli No.1’ pomegranate, ‘Yicheng Hongpitian’ pomegranate, and ‘American Qingpisuan’ pomegranate. Then, using these five varieties, various biological traits such as phenology and fruit quality of pomegranate, as well as stress resistance such as heat resistance and cold resistance were studied. [Results] Five varieties of pomegranates began to mature in succession in early September; the smallest single fruit weight was 90 g, and the largest was 110 g; the plants grew fast, the plants were strong, the flowers were single petal, and plants bore fruits which were ornamental and edible. In addition, the pomegranates of these five varieties had good water tolerance and heat resistance, and good cold resistance. [Conclusions] This study is intended to provide a certain reference for the introduction of pomegranate varieties, and also provide a practical basis for the large-scale planting of pomegranate.

Key words Pomegranate, Varieties, Fruit, Stress resistance

1 Introduction

Pomegranate (Punicagranatum) is a deciduous shrub or small arbor belonging to the genus Punica Linn. in family Lythraceae. Pomegranate is an important fruit tree for human beings. It is generally believed that pomegranate originated in West Asian countries such as Afghanistan and Iran. At present, pomegranates are widely distributed, and are distributed in Asia, Europe, the United States and many other areas. In China, Pomegranate cultivation was first seen in the Han Dynasty. According to records, pomegranates were introduced by Zhang Qian when he was accredited to the Western Regions. Currently, it is distributed in many regions of China, including Shaanxi Province, Shandong Province, Anhui Province, Sichuan Province, Shanghai Municipality,etc.According to the purposes of use, pomegranate can be divided into flower pomegranate and fruit pomegranate. Flower pomegranate is mainly ornamental pomegranate and has important ornamental value. Flower pomegranates are mostly double-petal pomegranates with bright colors and long flowering periods, and generally have no fruits. Common flower pomegranate varieties include double-petal red flower pomegranate, double-petal white-flower pomegranate, agate pomegranate, double-petal orange flower pomegranate, double-petal rose pomegranate,etc.Fruit pomegranate is a kind of pomegranate mainly for eating. It can bear fruit and also has flower. The flower is single petal and easy to bear fruit.

At present, there are many studies on pomegranate at home and abroad, mainly focusing on cultivation techniques[1-12]. In addition, there are some studies about the breeding of new and excellent varieties[13]and some studies are concentrated on pomegranate pests and diseases[14-15]. The results of this study can not only provide a reference for the introduction of pomegranate, but also provide a practical basis for the large area planting of pomegranate.

2 Materials and methods

2.1 Overview of the experimental siteWe selected the pomegranate area in Shanghai Chenshan Botanical Garden as the experimental site. It is located on the east side of Chenshan Botanical Garden in Songjiang District, Shanghai, with an annual average temperature of 15-16 ℃; the soil fertility is medium, the soil is clay, and the soil is slightly alkaline.

2.2 Selection and collection of materialsWe the ground-planted pomegranate as the experimental material, and various methods were used to collect pomegranate resources. In addition to traditional purchase methods, collection methods also included peer exchange and wild introduction. The introduction places included Zhejiang, Anhui, and Shanghai and other places, specifically including Zhejiang Hongyue Flower Co., Ltd. and Lu’an Luyu Fruit Tree and Flower Research Center.

2.3 Experimental design and methodsA total of 5 groups were set up in the experiment, one group for each pomegranate variety, and ‘American 002’ pomegranate was taken as the control. When planting, the pomegranates of 5 varieties were randomly arranged without repeated treatment, with ridge width of 200 cm, ditch width of 50 cm, plant spacing of 250 cm. Through the field observations in 2019-2022, various methods such as photographic records and measuring tapes were used to judge the phenological records, cold resistance, heat resistance, diameter at breast height (DBH), and crown width of pomegranates. The DBH, height and other traits of pomegranate were measured by measuring tape.

3 Results and analysis

3.1 Phenological records of pomegranate treesAs indicated in Table 1, five varieties of pomegranate (‘American 002’ pomegranate, ’Huohulu’ pomegranate, ‘Wanli No.1’ pomegranate, ‘Yicheng Hongpitian’ pomegranate, ‘American Qingpisuan’ pomegranate) started to germinate in mid-March and entered the full flowering period around mid-May. In terms of fruit ripening, ‘American 002’ pomegranate and ‘Huohulu’ pomegranate, ‘American Qingpisuan’ pomegranate began to ripen in mid-September; ‘Wanli No.1’ pomegranate began to ripen in early September, and ‘Yicheng Hongpitian’ pomegranate started to ripen in the late September. In terms of leaf defoliation period, the pomegranates of all these five varieties began to shed their leaves in mid-to-late November.

Table 1 Phenological records of pomegranate varieties

3.2 Traits of pomegranate varietiesAs indicated in Table 2, in terms of plant height, the plant height of ‘Wanli No.1’ pomegranate was 180 cm, and the height of the other four pomegranates was in the range of 200-220 cm. In terms of crown width, the crown widths of the four pomegranate varieties ‘Huohulu’, ‘Wanli No.1’, and ‘American Qingpisuan’ pomegranate were in the range of 170-180 cm, while the crown width of ‘Yicheng Hongpitian’ pomegranate was 200 cm. In terms of plant DBH, the DBH of these five pomegranates was in the range of 7-10 cm. In terms of fruit size, ‘American Qingpisuan’ pomegranate was 5 cm×4 cm, ‘American 002’ pomegranate was 6.0 cm×5.5 cm, Huohulu’ pomegranate was 7 cm×6 cm, ‘Wanli No.1’ pomegranate was 6.0 cm×5.5 cm, and ‘Yicheng Hongpitian’ pomegranate was 6 cm×6 cm. In terms of fruit surface color, after the pomegranates were ripe, ‘American 002’ pomegranates, ‘Huohulu’ pomegranates, and ‘Yicheng Hongpitian’ pomegranates were red peel pomegranates; ‘Wanli No.1’ pomegranates were black peel pomegranate, and ‘American Qingpisuan’ pomegranates were green peel pomegranates. In terms of pulp taste, ‘Yicheng Hongpitian’ pomegranates had a sweeter taste, while the other four pomegranate varieties were sweet and sour. In terms of fruit weight, the single weight of these five varieties of pomegranate was in the range of 90-110 g.

Table 2 Traits of pomegranate varieties

3.3 Adaptability of pomegranate varietiesThrough 3 years of experimental research, we found that the growth potential of 5 varieties of pomegranate was good, the plants grew fast, and the plants were strong. In terms of cold resistance, the lowest temperature in Shanghai was -9 ℃. At this temperature, pomegranates had no obvious frost damage, indicating that the introduced pomegranates had good cold resistance in Shanghai. In terms of heat resistance, Shanghai will experience high temperature weather every summer, and there will be extremely high temperature weather in July and August, with the highest temperature reaching 41 ℃. However, the pomegranates of each variety did not show obvious high-temperature burns, indicating that they had good heat resistance. In terms of water tolerance, there is Huangmei weather (rainy season) in Shanghai every year. There is continuous rainfall from June to July. It rains almost every day during the rainy season. However, the pomegranates of these five varieties did not have obvious rotten roots or even death, indicating good water tolerance (Table 3).

Table 3 Adaptability of pomegranate varieties

3.4 Utilization of pomegranate germplasm resourcesAt present, there are a total of 150 pomegranates of various varieties in the pomegranate planting area of Chenshan Botanical Garden, and the pomegranate resources are rich. There are two main applications: one is scientific research on pomegranate cultivation techniques, and the other is to carry out popular science picking activities. At present, Chenshan Botanical Garden has successfully carried out a number of pomegranate picking activities, including the picking activities of the garden union and bureau union, and the picking activities of primary school students in summer camp activities. Picking activities made different groups of people experience the fun of picking. Especially for children, experiencing picking activities in person would be of great help to their physical and mental growth.

4 Discussion and conclusions

In addition to the variety, there are many factors that affect the fruit yield of pomegranate and it is also closely related to the cultivation technology. For example, pomegranate is a sun-loving plant. When planting, it should be planted in a sunny place. If pomegranate is planted in a shady environment, there will be less or no flowering, and there will be more unfavorable phenomena such as excessive growth of branches.

In terms of fertilization, it is necessary to apply fertilizer reasonably. After the leaves fall in winter, it is necessary to apply the base fertilizer one time. The base fertilizer generally adopts cow dung as organic fertilizer, and bean dregs can also be added appropriately. Because bean dregs have strong fertility, it is easy to burn seedlings, so they should be soaked in water first, and each plant should not exceed 1 kg. In addition to the base fertilizer, a certain amount of compound fertilizer can be applied before flowering. Flowering needs to consume a lot of energy and nutrients, and topdressing must be carried out after flowering. Generally, compound fertilizer can be used, because compound fertilizers have fast fertilizer effect and can be quickly used for fruit setting and fruit expansion. During the flowering period, fertilizer is generally not applied, and at the same time, it is necessary to avoid frequent and excessive fertilization, so as to avoid excessive growth of branches and leaves or few flowers.

Furthermore, pruning is very important for fruit trees. If pomegranate tree is not pruned and allowed to grow, the pomegranate will have a lot of elongated branches, and it will grow very fast, and there will be very few flowering and fruiting, which will have a great impact on the yield. In general, after the pomegranate leaves fall, pruning can be carried out to remove the elongated branches and tillering branches. Besides, it is necessary to thin out the branches that are too dense, and top the branches that are too long. At the same time, pay attention to the shape of the tree after pruning.

Moreover, in terms of the maintenance and management of fruit at the flowering stage, due to the low self-pollination efficiency of pomegranate, the high cross-pollination efficiency, coupled with the presence of female septic breeding of pomegranate, it may lead to physiological flower and fruit drop, so artificial pollination can be used to improve the fruit setting rate.

Finally, in terms of pests and diseases, pomegranates will have some common pests and diseases, such as: Fusarium wilt, brown spot, aphids, fruit flies and so on. It is necessary to prevent and control such diseases and insect pests in time, otherwise the leaves and fruits will be greatly affected.

In conclusion, from the perspective of introduction performance, ‘American 002’ pomegranate, ‘Huohulu’ pomegranate, ‘Wanli No.1’ pomegranate, ‘Yicheng Hongpitian’ pomegranate, and ‘American Qingpisuan’ pomegranate have good planting adaptability in Shanghai area, the plants grow fast, the plants are strong, the flowering period is May to June, and the fruit period is September to October. Their heat resistance, cold resistance and water tolerance are good, without frost damage, and rare death of plants.