Fanglun JIN, Ming LI, Chengmin HAN, Fawei ZHANG, Xuexi AO

Guizhou Institute of Sericulture and Pepper, Zunyi 563006, China

Cherry (Prunus spp.), belonging to the subfamily Prunoideae of the family Rosaceae, is a popular fruit with bright red color,delicious taste,pleasant appearance,rich nutrition, high medical value and health care function, which has the earliest maturity stage among various deciduous fruit trees. Cherry exhibits relatively strong adaptability, early fruit bearing, high yielding ability and rapid Economic returns,thereby being popular with the majority of growers.Moreover, cherry is one of the preferred tree species for eco-tourism development and conversion of cropland to forest with high comprehensive benefits in agricultural planting industry[1].Currently, Cerasus avium L., Cerasus ceraus L., Cerasus pseudocerasus and Cerasus tomentosa have become commonly cultivated cherry varieties in the world.

Cherry is one of the major fruit species cultivated in Guizhou Province. Cherry production occupies a certain position in the fruit industry in Guizhou Province. Guizhou Plateau is located in the south of the Yangtze River, belonging to the subtropical monsoon humid climate, with abundant rainfall,long frost-free period,apparent stereo climate,complex terrain,numerous small climatic zones, largearea mountains and hills, and slightly acidic soils. Therefore, Guizhou Province has become a paradise for survival and reproduction of animals and plants due to superior location,varied and complex topography,abundant water resources and pleasant climate without severe cold in winder or intense heat in summer[2].The special geographical location andunique geographical conditions provide good conditions for the growth of cherry and other deciduous fruit trees.In the late 1990s,with the optimization and adjustment of agricultural industrial structure, cherry fruit industry in Guizhou Province has been developing rapidly. However, the irrational variety structure and ununiform, poor management levels lead to the production of low-grade, uncompetitive fruit,which seriously hindering the development of cherry industry in Guizhou Province. A large number of studies have been conducted on the comparative evaluation of excellent traits and biological traits in different cherry varieties[3-7], which still can not meet the demand for cherry production in Guizhou Province. In this study,phenological response, botanical characteristics, economic traits and stress resistance of two new introduced cherry varieties were investigated and compared, aiming at screening excellent cherry varieties suitable for cultivation in Guizhou Province.

Materials and Methods

Materials

An overview of the experimental garden The experiment was carried out in Guizhou Institute of Sericulture and Pepper, 27°43′ E, 106°55′ W, at an altitude of 880 m, with an annual average temperature of 14.9 ℃, maximum temperature in summer of 38.4℃, average temperature in the hottest month(July)of 25.8 ℃,minimum temperature in winter of -3.0 ℃, average temperature in the coldest month(January) of 3.0 ℃, effective accumulated temperature above 10 ℃of 4 938℃, annual rainfall of 1 040 mm, and the precipitation mainly occurred in summer; the experimental soil belonged to typical yellow loam in southern region, pH 6.2, containing 93.0 mg/kg alkali-hydrolyzable nitrogen,67.9 mg/kg available phosphorus,165.0 mg/kg available potassium and 6.2% organic matter, with the depth of above 1.0 m generally, which was mainly irrigated with rainwater.

Experimental varieties Black Pearl(introduced by Guiyang City, Guizhou Province), Pitch-Black-skinned Cherry(introduced by Guiyang City, Guizhou Province) and a local variety were used as experimental materials.

Experimental cherry trees at the age of 9-11 years were transplanted in the spring of 2003, with a planting density of 825 plants/hm2, plant spacing and row spacing of 3.0 m × 4.0 m.According to high-standard garden construction method, cherry trees were planted reasonably using highlevel cultivation management techniques, focusing on strengthening fertilizer and water management and tree management.Cherry trees bore fruit in 2004 and were put into production successively since 2005.

Methods

Various indicators were investigated for four consecutive years from 2011 to 2014. Representative plants were selected. Five fruit-bearing branches in the middle and upper part of each plant were randomly selected and marked From late February to early March,the flowering amount was surveyed. Ten flowers were randomly selected to investigate the morphological characteristics. In addition, the growth status of plants and fruit-bearing branches was investigated. In early-mid May,biological traits of each variety were investigated, including plant growth, morphological characteristics of middle leaves and 1-yearold branches, fruit-bearing rate, and fruit economic traits. Sugar content in fruit juice was measured using with a portable sugar meter.

Table 1 The growth status of 7-10 years old plants of three cherry varieties

Results and Analysis

Plant growth

As shown in Table 1,after rectangular transplanting and natural opencentered training in the spring of 2003,the average growth of 7-10 years old plants of three cherry varieties during four consecutive years was as follows:Black Pearl and Pitch-Black-skinned Cherry exhibited strong tree vigor; local variety exhibited relatively strong tree vigor. Tree shape of Pitch-Blackskinned Cherry was opening and that of other two cherry varieties was semiopening. Plant height of three cherry varieties demonstrated a descending order of local variety ＞Black Pearl ＞Pitch-Black-skinned Cherry. Crown size of three cherry varieties demonstrated a descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety. Trunk height of three cherry varieties demonstrated a descending order of local variety ＞Black Pearl ＞ Pitch-Black-skinned Cherry.Trunk girth of three cherry varieties demonstrated a descending order of Black Pearl ＞local variety ＞Pitch-Black-skinned Cherry. Annual spring shoot growth of three cherry varieties demonstrated a descending order of local variety ＞Black Pearl ＞Pitch-Black-skinned Cherry.

Botanical characteristics

Branch characteristics As shown in Table 2, dense branches were sprouted by Black Pearl; Pitch-Blackskinned Cherry exhibited moderate branch density; sparse branches were sprouted by local variety. Branch germination rate of three cherry varieties demonstrated a descending order of local variety ＞Black Pearl ＞Pitch-Black-skinned Cherry. Branching rate of three cherry varieties demonstrated a descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞ local variety. New shoots of three cherry varieties were light green. Plants ofthree cherry varieties had no dense pubescence. Spring shoots of three cherry varieties were light greenbrown. Spring shoot length, internode length and diameter of three cherry varieties demonstrated a descending order of Black Pearl ＞ Pitch-Blackskinned Cherry ＞local variety. Spring shoot number per plant of three cherry varieties demonstrated a descending order of local variety ＞ Pitch-Blackskinned Cherry ＞Black Pearl.Number of leaves per plant of three cherry varieties demonstrated a descending order of Black Pearl ＞ Pitch-Blackskinned Cherry ＞local variety.

Table 2 Branch characteristics of three cherry varieties

Table 3 Leaf characteristics of three cherry varieties

Table 4 Flower characteristics of three cherry varieties

Leaf characteristics As shown in Table 3, according to the leaf characteristics of three cherry varieties,leaves of Black Pearl were oblong and dark green; leaves of other two cherry varieties were oval and dark green.Leaf size of three cherry varieties demonstrated a descending order ofBlack Pearl ＞ Pitch-Black-skinned Cherry ＞ local variety. Leaf tips of Black Pearl were acute and warped;leaf tips of Pitch-Black-skinned Cherry were acuminate and warped; leaf tips of local variety were acuminate and dropped. Leaf base of Pitch-Blackskinned Cherry was wedge-shaped,while that of other two cherry varieties was circular. Petiole length of three cherry varieties demonstrated a descending order of Black Pearl ＞local variety ＞Pitch-Black-skinned Cherry.Petiole diameter of three cherry varieties demonstrated a descending order of Black Pearl ＞ Pitch-Blackskinned Cherry = local variety. All these three cherry varieties had multiple and blunt serratures on leaf margins. Moreover, moderate-maturing local variety had moderately deep and large serratures on leaf margins, while other two cherry varieties had deep and large serratures on leaf margins.Leaves of three cherry varieties were plagiotropous, curled reversely towards the front and formed acute angles with smooth surface.

Table 5 Fruit economic traits of three cherry varieties

Flower characteristics As shown in Table 4, flower characteristics of three cherry varieties were significantly different. To be specific, corolla size of three cherry varieties demonstrated a descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞ local variety. Stalk length of three cherry varieties demonstrated a descending order of Black Pearl ＞ Pitch-Blackskinned Cherry=local variety.Nectariferous disks of three cherry varieties were light green. Flowers of three cherry varieties had five separated,opening, slightly overlapped, whitepurple, circular petals with circular apexes.Stamens of three cherry varieties were golden. Stamen length of three cherry varieties was generally in the descending order of Black Pearl ＞Pitch-Black-skinned Cherry = local variety.Stamen number of three cherry varieties was generally in the descending order of Pitch-Black-skinned Cherry ＞Black Pearl ＞local variety.The tallest stamens of three cherry varieties were taller than stigmas and the height difference between the tallest stamen and stigma of three cherry varieties demonstrated a descending order of Black Pearl = Pitch-Black-skinned Cherry ＞local variety.In addition, stamens of three cherry varieties were ununiform. Stigma number of three cherry varieties was 1.0. Ovaries of three cherry varieties were lageniform. Stigma length of three cherry varieties was generally in the descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety. From the perspective of sepalnumber, sepal tip shape, uniformity and combination type, all these three cherry varieties exhibited five uniformly distributed, separated sepals; moreover, sepals of Pitch-Black-skinned Cherry had round tips, and sepals of other two cherry varieties had acuminate tips. Sepal size of three cherry varieties was generally in the descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety.Sepals of local variety were triangular and light purple;sepals of Pitch-Blackskinned Cherry were nearly triangular and purple;sepals of Black Pearl were nearly triangular and light purple. Furthermore, sepals of three cherry varieties were extended horizontally, upright and separated.

Table 6 Phenological response of three cherry varieties

Table 7 Fruit-bearing traits and yield of three cherry varieties

Fruit economic traits

As shown in Table 5, fruit economic traits of three cherry varieties were significantly different. To be specific, fruit shape of three cherry varieties was nearly circular; average single fruit weight, maximum fruit weight and fruit diameter of three cherry varieties demonstrated a descending order of Black Pearl ＞ Pitch-Blackskinned Cherry ＞local variety.Ground color of three cherry varieties was yellow-green; peel color of three cherry varieties was purple. Carpopodium length and diameter of three cherry varieties were generally in the descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety.Stalk cavities of Pitch-Black-skinned Cherry were deep and nearly circular without rusty spots; stalk cavities of other two cherry varieties were moderately deep and nearly circular without rusty spots. Calyx cavities of three cherry varieties were flat and nearly circular without rusty spots. Fleshes of three cherry varieties were orange,juicy, tender and crisp with strong aroma;in addition, fleshes of local variety were sour, while fleshes of other two cherry varieties were sweet and sour.Sugar content in fruit juice of three cherry varieties demonstrated a descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety.Fruit edible rate of three cherry varieties demonstrated a descending order of Pitch-Black-skinned Cherry ＞Black Pearl ＞local variety. Fruits of Black Pearl and Pitch-Black-skinned Cherry exhibited superior quality, and fruits of local variety exhibited moderate quality. Seed weight, length, width and diameter of three cherry varieties were generally in the descending order of Black Pearl ＞local variety ＞Pitch-Black-skinned Cherry. In addition,seeds of three cherry varieties were circular, light yellowish-brown and plump with cuspate-lobate tips.

Phenological response

As shown in Table 6,the squaring stage of local variety was in late January - early February, and that of other two cherry varieties was both in mid-late January; the flowering stage of Black Pearl was in late February -early March, and that of other two cherry varieties was both in early-mid March; the maturity stage of Black Pearl was in late April-early May, and that of Pitch-Black-skinned Cherry and local variety was in early-mid May and mid-late May, respectively; the defoliation stage of Black Pearl and Pitch-Black-skinned Cherry was in mid-late November, and that of local variety was in late November-early December. All these three cherry varieties started bearing fruits at two years old.

Fruit-bearing traits

As shown in Table 7, fruits of three cherry varieties were distributed throughout the trees with rare physiological fruit-dropping and preharvest fruit-dropping. Fruit-bearing rate of three cherry varieties demonstrated a descending order of Pitch-Blackskinned Cherry ＞Black Pearl ＞local variety.Yield per plant,maximum yield per plant and yield per unit area of three cherry varieties were generally in the descending order of Black Pearl ＞Pitch-Black-skinned Cherry ＞local variety. In addition, Pitch-Black-skinned Cherry exhibited relatively strong stress resistance, while other two cherry varieties had strong stress resistance.

Conclusion and Discussion

Black Pearl and Pitch -Blackskinned Cherry introduced by Guiyang City of Guizhou Province and a local variety were transplanted in Guizhou Institute of Sericulture and Pepper in the spring of 2003. After rectangular transplanting and natural open-centered training, under scientific management conditions, some plants started bearing fruits in the second year, and all the plants in the experimental garden bore fruits in the third year. During four consecutive years from 2011 to 2014,plant growth,characteristics of branches, leaves and flowers, fruit economic traits, phenological response,yield traits and stress resistance of three cherry varieties were investigated and compared. According to the experimental results,Black Pearl exhibited the best performance, followed by Pitch -Blackskinned Cherry. These two new introduced cherry varieties were superior to the local variety. Therefore, Black Pearl and Pitch-Black-skinned Cherry could be developed appropriately with supporting cultivation techniques in Northern Guizhou region.

Black Pearl has strong tree vigor and opening tree shape with the plant height of 272.8-335.8 cm, crown size of 284.4 cm×418.3 cm,branch generation rate of 85.42%,branching rate of 18.75%, spring shoot length of 35.5 cm, annual spring shoot growth of 6 223.2 cm.Leaves of Black Pearl are 14.9 cm × 7.6 cm; flowers of Black Pearl are 2.5 cm × 2.6 cm; fruits of Black Pearl have superior quality,which are matured in late April-mid May, with an average single fruit weight of 3.85 g,maximum fruit weight of 4.7 g, sugar content of 14.5%, and edible rate of 76.47%.Black Pearl has strong resistance to stresses with the fruit-bearing rate of 28.48%, average yield per plant of 15.6 kg, maximum yield per plant of 23.9 kg,and yield per unit area of 12 882 kg/hm2.

Pitch -Black cmskinned Cherry has strong tree vigor and opening tree shape with the plant height of 288.5 cm - 328.0 cm, crown size of 278.4 cm×407.2 cm,branch generation rate of 80.89%, branching rate of 15.87%,spring shoot length of 31.6 cm,annual spring shoot growth of 5 956.6 cm.Leaves of Pitch-Black-skinned Cherry are 13.8 cm × 8.1 cm; flowers of Pitch-Black-skinned Cherry are 2.3 cm × 2.4 cm; fruits of Pitch-Blackskinned Cherry have superior quality,which are matured in early-mid May,with an average single fruit weight of 3.68 g, maximum fruit weight of 4.5 g,sugar content of 14.2%, and edible rate of 77.23%. Pitch-Black-skinned Cherry has relatively strong resistance to stresses with the fruit-bearing rate of 29.81% , average yield per plant of 11.9 kg, maximum yield per plant of 18.4 kg, and yield per unit area of 9 814.5 kg/hm2.

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