Unveil the new techniques of winter fruit pruning and flowering promotion of Sunshine Rose grapes in northwest Guangxi
Wei Yuanke et al
Sunshine Rose grape is a mid-to-late maturing grape variety bred by the Japan Plant Grape Research Institute with Azuki 21 (Steuben×Muscat of Alexandria) × KattaKourgan (KattaKourgan × Kai Road), which is a European and American hybrid. Sunshine Rose grape has the advantages of vigorous growth, strong disease resistance, crisp and hard flesh, rose fragrance, good quality, long fruit-bearing period, no fruit cracking, storage and transportation, as well as yellow-green fruit and no high temperature veraison obstacle in summer, and the planting economic benefits are high. The late ripening period of the secondary fruit just fills the gap of fresh fruits in the winter market, and the economic benefits are good. "Two generations of different halls" cultivation mode of the first and second fruits are not hung on the tree at the same time to grow, so the growth of the first and second fruits does not interfere with each other, which can not only ensure that the first fruit is very early ripe and marketed, but also can make the second fruit extremely late ripening (around New Year's Day) on the market, and the cultivation management is convenient, and it is the preferred mode of viticulture in Guangxi for two harvests a year. How to ensure the high yield and good quality of secondary fruits, pruning and flowering time are the key. Grape cultivation is to break the dormancy of winter buds by pruning and germination, so as to promote their second flowering and fruiting, so the appropriate pruning time should be selected. If the pruning and germination are too early, the recovery time of the tree is not enough, the flower bud differentiation is incomplete, and the flowering rate is low. Therefore, the pruning time has a direct impact on the flowering rate and fruit quality of the grapes. The cultivation of grapes with two harvests a year has high requirements for water and fertilizer conditions and cultivation management. If the tree is poor, or the amount of fruit in summer is too large, the nutrient consumption is too much, the nutrient accumulation is insufficient, and it is difficult to form a secondary flower. In this paper, the effects of different pruning times on the flowering rate and fruit quality of winter fruit (secondary fruit) of Sunshine Rose were discussed, in order to clarify the best pruning time suitable for secondary fruiting in Hechi area, and to provide a reference for the cultivation of Sunshine Rose grapes in Northwest Guangxi Province with two harvests a year.
1 Materials and methods
1.1 Test Materials
The test grape variety was Sunshine Rose, planted with detoxified seedlings in 2018, planting row spacing of 2.2 m×3.0 m, using "V" shaped trellises, arch type simple rain-sheltered cultivation, normal management, large summer fruiting, weak tree strength, average tree nutrients, summer fruits were harvested on July 28.
1.2 Overview of the test site
The test was conducted in 2022 in the vineyard of Miaodiao Village, Luoxi Town, Yizhou District (108°48′45" E, 24°29′19" N, 109 m above sea level), with low soil organic matter content, average fertility, yellow loam soil, and slightly acidic. The average daily temperature is 18 °C, the annual rainfall is 1 617.8 mm, and the rainfall from July to December is only 398.8 mm.
1.3 Experimental design
The experiment was carried out from August 9 to September 4, and the treatment was done once every 5 days, and a total of 5 pruning and flowering promotion times were set, which were August 9, August 15, August 19, August 24, and September 4, and the weather conditions on the day of pruning and flowering promotion are shown in Table 1. Plants with relatively consistent growth were randomly selected in the same plot, 6 plants per treatment, and 3 replicates.
Table 1 Weather conditions on different pruning promotion days
1.4 Test implementation
Select the fully lignified fruit mother branch for pruning, leave 5~7 buds for pruning, depending on the fullness of the bud eye, before 10:00 or after 16:00 on the day of pruning, it is best to choose a cloudy day with 50% monocyanamide 20 times liquid to coat the cut buds and cut the edge. After pruning, drip irrigation is used to maintain the water holding capacity of the soil, and the branches are sprayed with water in dry weather. Combined with fertilization (mainly available nitrogen fertilizer) to loosen the soil, the depth is about 20 cm, increase the soil permeability, conducive to root growth, remove all the old leaves after germination, and prevent and control gray mold, downy mildew and other diseases and insect pests in a timely manner during the flowering and pollination period, especially during the flowering and pollination period, in case of high temperature weather above 30 °C, strengthen the water spray in the shed to cool down, ensure the success of pollination, and improve the fruit setting rate.
1.5 Survey Items and Methods
During the experiment, the results of different treatments, the number of flowering branches and the flowering rate of the mother branches were investigated. After the fruit ripened, 3 panicles were randomly determined for each treatment, and the single grain weight and soluble solids content of the fruit in the upper, middle and lower three parts of each panicle's backlight and light were randomly determined, and the single grain weight was weighed with an electronic scale (QZ-157A), and the soluble solids content was determined by refractometer (Brix 0.0%~33.0%). The calculation method is as follows: flowering rate (%) = total number of flowering spikes / number of pruning fruit mother branches × 100.
1.6 Data analysis
The trial data were analyzed using Excel 2020.
2 Results and Analysis
2.1 Flowering rate of fruiting mother branches
It can be seen from Table 2 that different pruning and flowering promotion time have different effects on the secondary flowering of the fruiting mother branches of Sunshine Rose grapes, and there are significant differences. The flowering rate was > on August 24 (58.97%)> August 19 (50.45%)> September 4 (36.36%)> August 15 (36.00%) On August 9 (12.59%), the flowering rate of the mother branch was the lowest on August 9 (12.59%), the highest was 58.97% on August 24, 36.36% on September 4, and 36.00% on August 15. On August 9 and July 28, the interval between the harvesting time of summer fruit was the shortest, only 12 days, and the tree body had not yet recovered, and the nutrients were insufficient, and the interval between August 15, August 19, August 24, and September 4 was 18, 22, 27, and 38 days, respectively, and the recovery time of the tree body was relatively sufficient after the interval of more than 22 days, and the flowering rate of the mother branch was also relatively increased, but the flowering rate of the pruning decreased to 36.36% on September 4, indicating that the longer the interval, the higher the flowering rate.
Table 2 Effects of different pruning and flowering promotion time on the secondary flowering of Sunshine Rose grapes
Note: Different lowercase letters in the same column indicate significant differences (P<0.05). The same applies hereinafter.
According to the experimental data, the recovery time of the tree body in about 25 days can basically make the tree nutrients sufficient. Although the flowering rate is affected by many factors, the appropriate pruning and flowering time is one of the key factors to improve the flowering rate.
2.2 Fruit quality
It can be seen from Table 3 that different pruning and flowering promotion time had little effect on the average grain weight of fruits, and there was no significant difference, but there was a significant difference in the content of soluble solids. If the pruning and flowering time is too late, the light and temperature are insufficient, the fruit growth cycle is short and immature, which directly affects the fruit quality. In this experiment, pruning was carried out on September 4 to promote flowering, but the time was too late and the fruit could not ripen. In the northwest region of Guangxi, the latest pruning and flowering promotion time should not exceed August 25, because the light and temperature after mid to late October are difficult to meet the needs of late fruit growth. The soluble solids content of the other four pruning and flowering promotion treatments from high to low were August 15, August 19, August 24 and August 9, and the soluble solids content was 15.82%, 15.52%, 15.39% and 14.21%, respectively, and the soluble solids content of the other four pruning and flowering promotion treatments reached the highest on August 15, August 9 and August 24, respectively Daily pruning and flowering promotion treatment was low. Pruning too early or too late was not conducive to increasing the soluble solids content of secondary fruits.
Table 3 Effects of different pruning and flowering periods on the secondary fruit quality of Sunshine Rose grapes
3 Conclusion and Discussion
Grape cultivation mode can fill the gap in the fruit market, but the cultivation of two crops a year has relatively high requirements for climatic conditions and cultivation management level, and the growth cycle of winter fruit is about 120 days, which is shorter than that of summer fruit, and the quality is slightly worse than that of summer fruit. The amount of fruit in summer in this experimental garden is large, the nutrient consumption is excessive, the nutrient accumulation of the tree is insufficient, and the grape flowering rate is low and the particles are small, which cannot achieve the expected effect. Reasonable control of the amount of summer fruit and strengthening field cultivation management are the prerequisites to ensure that Sunshine Rose grapes are harvested twice a year. Climate is a direct factor in the flowering of grapes. The right pruning time is the key to increasing the flowering rate of the grapes, and the flowering rate and fruit quality vary from region to region due to different climatic conditions. In this study, different pruning and flowering time had an effect on the secondary flowering rate and fruit quality of Sunshine Rose grapes. Grape cultivation can only be pruned and flowering after the end of summer fruit harvest and tree recovery, and the interval between pruning time and summer fruit harvest time is about 25 days to ensure winter fruit yield and quality. The interval should not be too long, as the temperature and light begin to decrease gradually around November, which is not conducive to fruit production and sugar accumulation. The results of this experiment showed that pruning and flowering promotion from August 19 to 24 in Northwest Guangxi were more suitable, with sufficient sunlight and suitable temperature during this period, and the temperature and light required for grape flowering and pollination, fruit development and growth, and fruit expansion were basically satisfied, and the flowering rate and fruit soluble solids content were relatively better than those of other pruning and flowering time treatments, and there were significant differences. There were differences in the ecological factors and nutritional status of secondary fruits at different flowering stages, so there were also differences in the growth period and fruit quality of secondary fruits. The secondary flowering rate and winter fruit quality of Sunshine Rose grapes are affected by various factors such as cultivation conditions and climate, and this experiment was only carried out for one year, so further experimental studies are needed to determine the best pruning and flowering time for winter fruits.