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1. Institute of Olive, Longnan Academy of Non-Wood Forest, Wudu 746000, China; 2. Longnan Academy of Non-Wood Forest, Wudu 746000, China; 3. Bijie Institute of Animal Husbandry and Veterinary Science, Bijie 551700, China

Abstract With the local major cultivar Leccino as the control, the fruit quality, yield and early maturing property of introduced olive cultivars (Koroneiki, Arbequina, Hojiblanca) from Spain were studied. The results showed that there were differences in fruit traits such as single fruit weight, ratio of flesh content, moisture content and oil content between different cultivars. The yield of early maturing property of the introduce cultivars were better than those of Leccino. The introduced varieties can fruit after 1-2 a, showing early maturity and high yield. This can provide a theoretical reference for the cultivation of olive in Longnan.

Key words Olive, Fruit traits, Oil content, Yield

1 Introduction

Olive (Oleaceae:Olea)[1]is a subtropical evergreen tree species. It is one of the world’s four largest woody oil plants[2]. The low mountain valley of Bailong River in Longnan was identified as the first-level suitable area for olive cultivation in China[3]. However, some studies have reported that about 70% of the olive groves have problems such as late fruiting, low and unstable yield, poor fruit quality and low fruit oil content[4]. In this study, with the local major cultivar Leccino as the control, the fruit traits, oil content, early maturing property and yield of introduced olive cultivars (Koroneiki, Arbequina, Hojiblanca) from Spain were studied to provide a theoretical basis for the selection of olive varieties in Longnan.

2 Materials and methods

2.1OverviewofthetestsiteThe test was conducted in Dabao Village (104°53′32″ E, 33°24′3″ N; 1 055 m asl) of Chengjiao Township in Wudu District, which is located in the Bailong River Basin and belongs to highland. It has a semi-arid climate of the northern margin of the northern subtropical zone, with annual average temperature of 15.3℃, average temperature in July of 24.7℃, average temperature in January of 2.7℃, the extreme minimum temperature of -7℃, the extreme maximum temperature of 38.2℃, ≥10℃ annual effective accumulated temperature of 4 893.6℃, average annual sunshine duration of 1 871 h, frost-free period of 270 d or more, and average annual precipitation of 468 mm. The precipitation is mainly concentrated in June-September of each year, with an annual average relative humidity of 56.6%, and dryness of 0.49. The soil is sandy loam (pH 7.9), with good drainage. The contents of nitrogen, phosphorus and potassium in the soil are 0.584, 0.005 and 5.397 g/kg, respectively. The test site has very convenient irrigation and traffic conditions.

2.2TestmaterialsThe test olive cultivars included Leccino (local), Koroneiki, Arbequina and Hojiblanca (introduced from Spain). The four cultivars were transplanted simultaneously in the spring of 2011 at a plant and row spacing of 4 m × 4 m. and the fertilizer and water management measures were consistent.

The used instruments and equipment included fat extractor, water bath, cooling water machine, electronic balance (accuracy 0.001 g), micro grinder, electric blast drying oven, dryer, qualitative filter paper, cotton wool, 100-mL graduated cylinder, tweezers, plastic sealing pockets, ethanol, ether,etc.

2.3Testmethods

2.3.1Fruit shape and fruit quality. The measurement contents included fruit longitudinal diameter, fruit transverse diameter, fruit shape index, single fruit weight, and sing fruit volume.

A total of ten fruit were randomly selected. Their longitudinal diameters (L1,L2, …,L10) and transverse diameters (W1,W2, …,W10) were measured with a vernier caliper. The mass of each of the ten fruit was weighed three times repeatedly (M1,M2andM3) with an electronic balance at an accuracy of 0.000 1 g. The volume of each of the ten fruit was measured three times repeatedly (V1,V2andV3) using graduated cylinder drainage method[5].

Average longitudinal diameterL= (L1+L2+ … +L10)/10

Average transverse diameterW= (W1+W2+ …+W10)/10

Fruit shape index =L/W

Average single fruit weightM= (M1+M2+M3) /30

Average single fruit volumeV= (V1+V2+V3)/30

Average fruit densityP=M/V

2.3.2Determination of ratio of flesh content. A total of ten medium-sized and normal fresh fruit were randomly selected for each cultivar, and their mass (F) was weighed accurately. The pulp of the fruit was completely peeled off with a knife. The cores were fully washed and dried, and their mass (H) was weighed. The above process was repeated three times[6].

Ratio of flesh content = (F-H)/F×100%

2.3.3Determination of fruit moisture content. One fresh fruit was sampled for each cultivar, and its mass (F) was weighed. Then, the fruit was placed into the electric blast drying oven, dried at 105℃ for 36 h. After cooled, the mass of the fruit (D) was weighed again. The dried fruit was placed in a desiccator for use. The above process was repeated three times[6].

Moisture content of fresh fruit = (F-D)/F×100%

2.3.4Determination of fruit oil content. The washed and dried fruit sample (M) and extraction bottle (M1) were weighed, respectively. The fruit sample was ground fully in a micro-grinder, and placed into a filter paper tuber folded with a qualitative filter paper. The oil residue in the grinder was wiped off with absorbent cotton dipped with ether, and then the absorbent cotton was also placed into the filter paper tube. Then, the filter paper tube was wrapped two layers and sealed with cotton thread. Finally, the filter paper was put into the fat extractor. Three replicates were arranged for each olive cultivar[7].

An appropriate amount of anhydrous ether was poured into the extraction bottle, which was then put into a 65℃ water bath. After starting the cooling water machine, extraction was performed for 8 h. The extractor was replaced, and the ether was recovered 2-3 times using a recovery tube. The extraction bottle (filled with the oil extracted) was taken off, dried in an oven to constant weight at 60℃, cooled and weighed again (M2).

Oil content of dried fruit (%)= (M2-M1)/M×100

whereMrepresents the mass of the sample;M1represents the mass of the extraction bottle; andM2represents the mass of the extracted oil and the extraction bottle.

Oil content of fresh fruit = Oil content of dried fruit × (1-Moisture content of fresh fruit)

2.3.5Determination of yield. A total of five plants were sampled for each olive cultivar, and their annual yield was measured.

2.4StatisticsandanalysisCalculation was performed using Excel, and significance test of differences was conducted using Duncan’s Multiple Range of SPSS19.0.

3 Results and analysis

3.1Comparisonoffruittraitsamongthefourolivecultivars

As shown in Fig.1, there were differences in the fruit shape index among the four olive cultivars. The fruit shape index of Leccino was different significantly from those of Hojiblanca and Arbequina, and was different insignificantly from that of Koroneiki. The fruit shape indexes of Hojiblanca and Arbequina were low, and the appearance of their fruit was relatively round; and the fruit of Koroneiki and Leccino were slender, and their fruit shape indexes were high.

There were differences in the single fruit weight among the four olive cultivars. The single fruit weight of Leccino was different insignificantly from those of Koroneiki and Arbequina, and was different significantly from that of Hojiblanca. Among the four olive cultivars, the single fruit weight of Hojiblanca was largest, which was 1.7 times that of Leccino. The single fruit weights of the four olive cultivars ranked as Hojiblanca > Leccino > Arbequina > Koroneiki.

There were differences in the single fruit volume among the four olive cultivars. The single fruit volume of Leccino was different significantly from those of Hojiblanca and Koroneiki, and was different insignificantly from that of Arbequina. The single fruit volume of Hojiblanca was the largest, which was 1.7 times that of Leccino. The single fruit volume of Koroneiki was 47.4% smaller than that of Leccino. The single fruit volumes of the four olive cultivars ranked as Hojiblanca > Leccino > Arbequina > Koroneiki, which was consistent with the rank of single fruit weights of the four olive cultivars.

The fruit densities of the four olive cultivars were different. The fruit density of Leccino was different insignificantly from those of Hojiblanca and Arbequina, and was different significantly from that of Koroneiki. The fruit density of Koroneiki was largest. The fruit densities of the four olive cultivars were in the order as Koroneiki > Arbequina > Leccino > Hojiblanca, which was just opposite from the ranks of single fruit weights and single fruit volumes of the four olive cultivars.

In terms of ratio of flesh content, the ratio of flesh content of Leccino was different significantly from that of Hojiblanca, and was different insignificantly from those of Koroneiki and Arbequina. Among them, the ratio of flesh content of Hojiblanca was the largest, 5.6% higher than that of Leccino. The olive cultivar of Hojiblanca has large fruit volume and high ratio of flesh content, and it is suitable for the processing of fruit. The flesh content ratios of the four olive cultivars were in the order as Hojiblanca > Koroneiki > Leccino > Arbequina.

Note: Vertical line indicates the standard error (± SE); and different lowercase letters on the top of the columns indicate significant differences at the 0.05 level. The same as below.

Fig.1Comparisonsoffruittraitsamongdifferentolivecultivars

3.2ComparisonoffruitmoisturecontentandfruitoilcontentamongthefourolivecultivarsAs shown in Fig.2, there were differences in the moisture content of fresh fruit among the four olive cultivars. The moisture content of fresh fruit of Leccino was different significantly from that of Koroneiki and was different insignificantly from those of Hojiblanca and Arbequina. The moisture content of fresh fruit of Koroneiki was 8.1% lower than that of Leccino. The fresh fruit moisture contents of the four olive cultivars ranked as Arbequina > Leccino > Hojiblanca > Koroneiki.

Fig.2Comparisonsoffreshfruitmoisturecontentanddried(fresh)fruitoilcontentamongdifferentolivecultivars

The oil content of dried fruit differed among the four olive cultivars. The oil content of dried fruit of Leccino was different significantly from those of Hojiblanca and Arbequina, and was different insignificantly from that of Koroneiki. The oil content of dried fruit of Leccino was highest; the oil content of dried fruit of Arbequina was 17.9% lower than that of Leccino; and the oil content of dried fruit of Hojiblanca was lowest, which was 30.8% lower than that of Leccino. The oil content of dried fruit is an absolute content, which indicates the basic content of the oil. The dried fruit oil contents of the four olive cultivars ranked as Leccino > Koroneiki > Arbequina > Hojiblanca.

The oil content of fresh fruit also differed among the four olive cultivars. The oil content of fresh fruit of Leccino was different insignificantly from that of Koroneiki, and was different significantly from those of Hojiblanca and Arbequina. The oil content of fresh fruit of Arbequina was 21.9% lower than that of Leccino; and the oil content of fresh fruit of Hojiblanca was the lowest, which was 27.6% lower than that of Leccino. The oil content of fresh fruit is a relative content, and it varies with the change of fruit moisture content. The fresh fruit oil contents of the four olive cultivars were in the order as Koroneiki > Leccino > Arbequina > Hojiblanca.

3.3Comparisonoffruityieldamongthefourolivecultivars

After the test trees were planted in May 2011, comprehensive conservation and management measures such as uniform fertilization, irrigation and pruning were carried out. They began to bear fruit in success, and the time of fruiting of different olive cultivars was different. Hojiblanca and Koroneiki began to bear fruit after one year; Arbequina began to bear fruit after two years; and Leccino began to bear fruit sporadically after three years. Due to olive cultivars usually fruit densely and sporadically successively, the fruiting volume of the test olive cultivars fluctuated among the years.

As shown in Table 1, there were differences in the fruiting time and yield among the four olive cultivars. Leccino began to bear fruit four years after the planting, and the average annual yield of single plants was 621 g. However, Hojiblanca and Koroneiki began to bear fruit after one year, and Arbequina began to bear fruit after two years, showing early maturing property. The average annual yield of single plants of Arbequina was highest, which was four times that of Leccino. The average annual yield of single plants of Koroneiki was three times that of Leccino. The average annual yield of single plants of Hojiblanca was 83.9% higher than that of Leccino. Among the four olive cultivars, the average single plant annual yields ranked as Arbequina > Koroneiki > Hojiblanca > Leccino.

Table1Comparisonofsingleplantyieldamongdifferentolivecultivars

CultivarPlanting timeYield∥g2012201320142015TotalAverage annual yield of single plantLeccinoMay 201100260.0012 160.0012 420.00 621.00Hojiblanca4.43135.0010 282.0012 420.0022 841.43 1 142.07 Koroneiki722.30029 459.009 080.0039 261.30 1 963.07 Arbequina 0285.0033 309.0017 360.0050 954.00 2 547.70

4 Conclusions and discussions

The fruit traits of olive mainly depend on the interaction between growth conditions and genetic potential of the cultivar. The fruit traits such as single fruit weight and ratio of flesh content, moisture content of fresh fruit and oil content of fresh fruit differed between Leccino and the three introduced cultivars. These differences were the results of the combination of genetic and environmental factors. Xue Yimin[8]considered the economic characteristics of the olive fruit should be mastered, and the appropriate use of the fruit should be clarified, and the fruit should be processed reasonably (oil use or meal use), thereby increasing the economics of growing olive. Koroneiki and Leccino are excellent oil cultivars, and Arbequina is good oil cultivar, which can be processed into olive oil. Hojiblanca has low oil content but large single fruit weight, large single fruit volume and high ratio of flesh content, and it can be used for production of meal fruit.

The yield and quality of olive are the result of the combined effects of light, temperature and water. Due to different variety characteristics and climatic conditions, the yield differs greatly among different varieties and different regions[9]. The fruiting time and yield of the three introduced cultivars were different from those of Leccino. The introduced cultivars began to bear fruit 1-2 years after the planting, showing early maturing property and high yielding capacity.

When selecting the variety in the construction of olive groves, the early maturing property and high yielding capacity must be taken into account. The fruiting time and yield of the variety affect the economic benefits of the olive grove. This study found that Koroneiki and Arbequina have early fruiting and high yield, so they can be vigorously promoted in the olive-producing areas.

In this study, the fruit traits such as single fruit weight and flesh ratio, moisture content of fresh fruit, and oil content of fresh fruit were compared preliminarily among different olive cultivars. In order to more comprehensively reflect the differences in the traits of different cultivars, experimental research on the quality of oil of olive pulp and the active ingredients of single-varietal olive oil needs to be carried out. Hu Qiongetal.[10]concluded that fruit shape index, total soluble sugar, vitamin C and mineral element content are important indicators for evaluating the quality of fresh jujube fruit, which is very referenceable for future research. This is also the direction of next research.