Analysis on Factors Related with Slender Spindle Shaped Apple Trees

Jie HAO Xiange WANG Xueying LI Xiangmin SUO Liang WEI Xinmin YAN Jianzhong FENG

Abstract［Objectives］ This study was to determine the correlations of stem taperingness with small central shaft total roughness, average roughness, total length, and average length by slender spindle pruning mode on different apple cultivars.

［Methods］ A total of 2 tree structures were selected, namely, the slender spindleshaped Zhongqiuwang from Shen County of Hebei Province and slender spindleshaped short shoot Fuji from Xingtang County of Hebei Province, to investigate the growth indicators of the small central shafts. SPSS analysis was used to compare the correlations between the taperingness with the growth factors of the small central shafts.

［Results］ The stem taperingness on slender spindleshaped Zhongqiuwang was positively correlated with the various growth factors of the small central shaft, and the difference in the positive correlation with average roughness reached the extremely significant level. The stem taperingness of slender spindleshaped short shoot Fuji was negatively correlated with the total roughness of small central shaft, but was positively correlated with the average roughness, total length and average length.

［Conclusions］ The results provided scientific and theoretical basis for guiding the dense planting of dwarfing apple tree pruning technology.

Key wordsApple; Slender spindle pruning; Related factors analysis

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Received: September 6, 2018Accepted: September 26, 2018

Jie HAO (1979-), female, P. R. China, master, associate researcher, devoted to research about breeding and pest and disease control of fruit trees, Email: haohao_822@163.com.

** Cocorresponding author. Email: guoshusuofjz@126.com.

At present, apple production is mostly carried out by close planting cultivation of the dwarfing selfrooted rootstocks or the dwarfing interstocks［1-2］. According to the culture characteristics of the dwarfing apple tree structure and the characteristics of canopy formation, the pruning of young trees should be completed in 3 years, and the pruning from the second to the third year is the key. The mostly adopted tree shapes are slender spindle and free spindle［3-4］. The difference between the upper and lower diameters of tree stem within the unit length is called the taperingness［4］. How to carry out appropriate pruning according to the characteristics of saplings of different varieties is the key technology to ensure the shaping of young trees. At present, the shaping and pruning indexes of young dwarfing apple trees in close planting is determined mainly based on some cultivation experience［5-6］, but there is no related indepth research, lacking in relevant data support. In this paper, the relationship of the taperingness of the central stem with each central shafts was studied in the pruning of dwarfing apple trees, and the techniques related with the pruning of different cultivars of young dwarfing apple trees were explored systematically, with the aim to provide scientific bases for the development of dwarfing apples trees in close planting.

Materials and Methods

Materials

The test was carried out in 2014 in the apple demonstration parks of Jialuoying Village, Xingtang County, Hebei Province and Qinghuitou Village, Shen County, Hebei Province (the central and southern apple producing areas of Hebei Province). The selected regions were planted with different varieties of apples trees with healthy growth vigor, similar tree ages, and the regions had superior cultivation conditions with the planting locations adjacent to each other.

The test varieties were the 6-8yearold slender spindle Zhongqiuwang and slender spindle short shoot Fuji (Tianhong No.2) of the fruitbearing period, a total of 2 tree shapes with the row spacing of 2 m × 3 m.

Test methods

Test treatment

The apple trees for the test were selected randomly and marked. An individual tree was a treatment, and there were a total of 30 treatments in random arrangement.

Test survey

The survey was carried out after the leaves fallen from the trees in the winter of 2014, when the tree growth of the year had totally completed and entered a period of suspension. For each tree shape structure, 6 apple trees were randomly selected from the directions of east, south, west, north and center, and a total of 30 trees were selected for the test.

Calculation method of stem taperingness

The trees of the 2 apple varieties with the slender spindle shapes were measured according to the following method, and the taperingness of the trees of different varieties with slender spindle pruning structure were calculated. The calculation formula of the taperingness was as follows:

Taperingness (%) = (Base diameter-Tip diameter)/Length from the cutting to the tip×100% (cm).

Survey method of small central shaft

Each small central shaft along the central stem was measured separately for the roughness and length (cm).

Correlation analysis

SPSS13.0 statistical software was used for the correlation and significance (2tailed) analysis on the taperingness of the central stem with the related factors of small central shafts from the slender spindleshaped apple trees of different varieties［6-7］, and the test repeated for N=30 times.

Results and Analysis

Analysis on factors related with central stem taperingness of slender spindleshaped Zhongqiuwang apple tree

The obtained taperingness of the central stem and the roughness and length of the small central shafts of the slender spindleshaped Zhongqiuwang apple trees were processed using SPSS13.0 to analyze their correlations and significant differences (Table 1). As shown in Table 1, the taperingness of the central stem showed positive correlations with the total roughness, average roughness, total length and average length of the small central shaft with the correlation coefficients of 0.275, 0.581, 0.340 and 0.443, respectively. The difference in the positive correlation between the taperingness of the central stem and the average roughness of the small main shaft reached the extremely significant level (P<0.01). At the same time, according to the SPSS analysis, the internal factors of the small central shafts also showed positive correlations with each other. There was no significant difference between the total roughness and average roughness of the small central shaft (P>0.05). The difference between the total thickness and the total length and the average length reached the extremely significant level (P<0.01), and the difference between average thickness and total length, average length was not significant (P>0.05), while the difference between total length and average length reached the extremely very significant level (P<0.01).

Table 1Related factors analysis on central stem taperingness and small central shaft of slender spindleshaped Zhongqiuwang apple tree

StemtaperinggradeCentralshaft totalroughness∥cmCentral shaftaverageroughness∥cmCentralshaft totallength∥cmCentral shaftaveragelength∥cm

Stem tapering gradePerson correlation analysis1

Significant difference analysis

Central shaft total roughness∥cmPerson correlation analysis0.2751

Significant difference analysis0.241

Central shaft average roughness∥cmPerson correlation analysis0.581**0.1371

Significant difference analysis0.0070.564

Central shaft total length∥cmPerson correlation analysis0.3400.700**0.1981

Significant difference analysis0.1430.0010.402

Central shaft average length∥cmPerson correlation analysis0.4430.697**0.0410.755**1

Significant difference analysis0.0500.0010.8650

** Correlation is significant at the 0.01 level (2tailed).

Table 2Related factors analysis on central stem taperingness and small central shaft of slender spindleshaped short shoot Fuji apple tree

StemtaperinggradeCentralshaft totalroughness∥cmCentral shaftaverageroughness∥cmCentralshaft totallength∥cmCentral shaftaveragelength∥cm

Stem tapering gradePerson correlation analysis1

Significant difference analysis

Central shaft total roughness∥cmPerson correlation analysis-0.3481

Significant difference analysis0.324

Central shaft average roughness∥cmPerson correlation analysis0.2640.3371

Significant difference analysis0.9420.341

Central shaft total length∥cmPerson correlation analysis0.3030.745*0.2541

Significant difference analysis0.3950.0130.478

Central shaft average length∥cmPerson correlation analysis0.705*0.2690.4840.780**1

Significant difference analysis0.0230.4530.1560.008

* Correlation is significant at the 0.05 level (2tailed); ** Correlation is significant at the 0.01 level (2tailed).

Analysis on factors related with central stem taperingness of slender spindleshaped short shoot Fuji apple tree

The obtained taperingness of the central stem and the roughness and length of the small central shafts of the slender spindleshaped short shoot Fuji apple trees were processed using SPSS13.0 to analyze their correlations and significant differences (Table 2), and the results showed some differences from those of Zhongqiuwang apple trees in Table 1. As shown in Table 2, the taperingness of the central stem was negatively correlated with the total roughness of the small central shaft (correlation coefficient of -0.348), but it showed positive correlations with average roughness, total length and average length of the small central shaft with the correlation coefficients of 0.264, 0.303 and 0.705, respectively. The difference between the taperingness of the central stem and the average roughness of the small main shaft reached the significant level (P<0.05). At the same time, according to the SPSS analysis, the internal factors (total roughness, average roughness, total length and average length) of the small central shaft also showed positive correlations with each other. The results of significant difference analysis in Table 2 were different from those in Table 1. The difference between the total roughness and total length of the central shaft was at the significant level (P<0.05), and the difference between the total length and average length of the central shaft was at the extremely very significant level (P<0.01).

Agricultural Biotechnology2019

Discussion

As for the research on tree shapes, studies at home and abroad lay the focus on the research aiming at achieving quality production by making full use of the light energy, put the emphasis on suitable planting density, reasonable community structure and individual spatial distribution, and good light system, which are the key to achieve high quality and high yield production. As for the dwarfing trees, emphases are given to the advantages of the central stems. It must keep the tree shape to achieve high quality and high yield production, and the lateral branches must be controlled in time to maintain the advantages of the central stem. The lateral branches must have the basal roughness below 1/3 of the central stem, with 1/4-1/5 the optimum. In addition, the tree height must be controlled strictly. The elevation angle from the extension of the canopies from 2 adjacent rows with the crowns must be smaller than 49°, and there should be operation lanes with the width over 1.5 m between the rows［7-8, 11］.

At present, the close planting of dwarfing selfrooted rootstocks or dwarfing interstocks has been widely used in apple production. In China, dwarfing interstocks are more widely used, and the commonly used tree shapes are slender spindle and main stem shape［9-10］. These tree shapes are characterized for the strong central stems, which can bear multiple small central shafts, wide opening angle, even distribution, no lateral branches on stems and single shaft extension. The fruitbearing branches and the fruitbearing branch groups are grown on the central stems and small central shafts with long and narrow crowns of big downside and small upside.

As for the cultivation of tree structure, the pruning from the second to the third year is the key［10］. The test results show that first, for the slender spindleshaped Zhongqiuwang apple tree, the taperingness of the central stem showed positive correlations with the total roughness, average roughness, total length and average length of the small central shaft with the correlation coefficients of 0.275, 0.581, 0.340, and 0.443, respectively. The difference in the positive correlation between the taperingness of the central stem and the average roughness of the small main shaft reached the extremely significant level (P<0.01). The results indicate that the suitable tree structure for the slender spindleshaped Zhongqiuwang apple tree should increase the average roughness of the small central shafts, which can be achieved by properly reducing the number of small central shafts to make the average roughness of the growing branch thicker, and by properly increasing the branch length of the small central shafts, which can achieve the reasonable structure characteristics of slender spindle. Second, as for the slender spindleshaped short shoot Fuji apple tree, the taperingness of the central stem was negatively correlated with the total roughness of the small central shaft (correlation coefficient of -0.348), but it showed positive correlations with average roughness, total length and average length of the small central shaft with the correlation coefficients of 0.264, 0.303 and 0.705, respectively. The difference between the taperingness of the central stem and the average roughness of the small main shaft reached the significant level (P<0.05). Therefore, in order to get the ideal slender spindle shape with high yield for short shoot Fuji, it should increase the number of small central shafts to thin the total roughness of the growing branches. In view of the slender spindle shape, it can properly increase the lengths of the small central shafts to get high taperingness, thereby obtaining high yield.

In all, the transformation of different tree structures is to meet the best lighting conditions required to produce highquality fruit. It has proved that the tree with good light conditions can produce high quality fruit, and the germinated flower buds are also significantly increased［11］. Therefore, for the dense planting garden of dwarfing apple trees, it is required that the crown light should be optimal［11］, which can be achieved by the pruning measures like budnotching, enlarging branch bending angel at the early growth stage, adjusting branch bending time, and raising the stem height［10, 12-14］.

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