MINISTRY OF EDUCATION
MINISTRY OF AGRICULTURE
AND TRAINING
AND RURAL DEVELOPMENT
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
HOANG MANH CUONG
STUDY ON SELECTION OF AVOCADO VARIETIES (persea
americana miller) SUITABLE FOR SOME PROVINCES IN THE
WESTERN HIGHLANDS
Major Field: GENETICS AND PLANT BREEDING
Code: 62.62.01.11
DOCTORAL THESIS SUMMARY
HA NOI - 2015
The Doctoral thesis was completed in
2
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
Scientific Supervisors: 1. Prof. Dr. Do Nang Vinh
2. Dr. Le Ngoc Bau
Reviewer 1:
Reviewer 2:
Reviewer 3:
Dissertation will be defended before committee in charge for doctoral
dissertation in academy level, meeting place ……… on …………, 2015
The PhD thesis may be fount at:
- Ha Noi National Library
- Library in Vietnam Academy of Agricultural Sciences
HA NOI - 2015
1
INTRODUCTION
1. Urgency of research
According to FAO’s statistics, avocado trees were grown in 63 countries with a
total area of 417 thousand hectares, yield of 3,078 thousand tons per year, the average
yield of 7.4 tons/ha, with annual exports of 491.5 thousand tons and exports of 606.6
million USD (Gazit and Degani, 2002; John and Gary, 2012; Pliego et al., 2002).
Also according to FAO’s statistics, 2011, countries with major world avocado
production were mainly distributed in tropical climates in Central and South
America. The country, which had the world's largest avocado productivity, was
Mexico (1,264,141 tons), followed by subsequent countries such as Chile (368,568
tons), the Republic of Dominique (295,080 tons), Indonesia (275,953 tons), Canada
(238,544 tons), Colombia (215,595 tons), Peru (212,857 tons), Kenya (201,478 tons),
Brazil (160,376 tons), China (108,500 tons) and (Bruce et al, 2013). France and the
Netherlands were the two countries which imported the world's largest avocado with
average amount about 94 thousand tons per year mostly from Mexico, Chile, Israel,
Spain and South Africa (Bruce et al, 2013). Avocado yield variations were high from
1.3 tons/ha (Portugal) to 28.6 tons/ha (Samoa), mainly depending on the variety,
ability of intensive cultivation and climate conditions (Gazit and Degani, 2002). The
goal of the world avocado industry sector is to improve yield up 30 tons/ha in terms
of intensive industry conditions with measures such as variety, good grafting, thick
growing with adjustable density and shaping, watering and nutritious control for
reducing fruit losses, plant protection, etc.
In Asia, the avocado trees were quite extensively grown in Southeast Asian
countries such as Indonesia, the Philippines, Thailand, Vietnam and China. Indonesia
is the country ranked the fourth in the world and the head of the Southeast Asian
countries to produce avocado. Our country is on the same latitude line as Mexico and
between the two countries growing large avocado in Asia including Indonesia and
China (ranked 11th in the world), and there is the ecological conditions very suitable
to growth of avocado trees in both Southern and Northern (Bruce et al, 2013).
Reality of avocado cultivation over 70 years in the central Western Highlands
showed that good growths, quite yields, some good qualities considered as special
tree varieties of area were found in avocado trees at altitude over 500 m. However,
development of avocado production is still limited by some of the following causes:
First, the study of avocado variety selection has remained a lot of limitations,
has not specified avocado variety sets suitable for various ecological regions and has
not selected to create the avocado varieties spread with harvest time soon, main and
late crop.
Second, some of the world's commercial avocado varieties have been
introduced, however not yet evaluated trials to select good varieties and high
adaptation to the ecological conditions in the Western Highlands.
Third, no systematic studies on the techniques of cultivation, post-harvest,
storage, processing and improving the fruit quality of different avocado varieties.
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To contribute in overcoming some limitations mentioned above, the
implementation of the dissertation "Study on selection of avocado varieties (Persea
americana Miller) suitable for some provinces in the Western Highlands" is essential
as a basis of the science and practice in order to promote sustainable development of
avocado tree on areas of provinces in the Western Highlands.
2. Research objectives
2.1. General objectives
To construct the scientific and practical base for selection of avocado varieties
with high yield, good quality, different harvest time in the year and good adaptability
to the ecological conditions of some major growing regions in the Western Highlands.
2.2. Specific objectives
- To identify bio-agricultural characteristics of different avocado varieties
selected in the domestic country and abroad in conditions of production in the
Western Highlands.
- To select some avocado varieties with yield above 50 kg/tree/year, dry matter
content over 23%, lipid over 13%, different harvest times in the year and good
tolerance to some pests and diseases in the Western Highlands.
3. Object and scope of dissertation
3.1. Object of research
- Avocado varieties are grown in the provinces Dak Lak, Gia Lai and Lam
Dong in the Western Highlands.
- 10 most promising variety materials collected in domestic: TA1, TA2, TA3,
TA4, TA5, TA31, TA44, TA47, TA50, TA54, and 2 imported varieties: Booth 7 and
Hass.
3.2. Scope of research
Comparative and evaluative experiments on 12 promising avocado varieties
were conducted in three major growing regions in Dak Lak, Gia Lai and Lam Dong
provinces.
4. Novelty of dissertation
- The first times in our country, the dissertation had conducted to test, evaluate
and compare different avocado varieties in a systematic way in the regions with
diverse ecological conditions in the Western Highlands.
- The dissertation already examined and evaluated bio-agricultural
characteristics of 38 avocado strains and varieties selected in domestic country and
import.
- The research results of the dissertation selected eight new avocado varieties
with high yield and good quality adapting for export standards, in which there were 4
avocado varieties (TA1, TA3, TA5 and Booth 7) recognized by Ministry of
Agriculture and Rural Development for trial production in 2011.
5. Contributions of the dissertation
5.1. Scientific significance
- For the first times in our country, the dissertation determined important bioagricultural characteristics of many different avocado varieties as well as imported
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varities planted in different ecological regions of the Western Highlands. The
dissertation provided the information, scientific data about breeding, cultivation and
biological characteristics, yield, fruit quality of the strains and varieties selected in
domestic country and import. New selected avocado strains and varieties could be
used as material sources for scientific research on variety improvement in the future
in order to enhance the competitiveness of Vietnam avocado varieties.
- Deep studies on avocado variety selection are still very few in Vietnam. So,
research results of the dissertation can make valuable reference material for pupils,
students and faculty at Universities and Research Institutes. The dissertation also
provides the scientific arguments for researchers in variety selection and avocado
development in Vietnam.
5.2. Realistic significance
- Research dissertation of PhD cadidate significantly contributed in selection of
new avocado varieties for regions in the Western Highlands. We selected 9 promising
avocado varieties including 4 new avocado varieties TA1, TA3, TA5 and Booth 7
with high yield, good quality and suitability for production reality of Western
Highlands regions, which were regconized by Ministry of Agriculture and Rural
Development for trial production in 2011.
- Avocado varieties selected with high yield, good quality and export standards
have been propagated quickly to replace the avocado varieties with low yield and
poor quality in production. New avocado varieties have been transferred to 5
enterprises, 3 farmer cooperatives in Dak Lak, Dak Nong, Gia Lai, Lam Dong and
Dong Nai provinces in the Western Highlands.
CHAPTER 1
OVERVIEW
1.1. STUDIES IN ABROAD
1.1.1. Origination and plant classification
Avocado trees were originated from Mexico and Central America. The scientific
name of the avocado tree is Persea americana Miller., the family Lauraceae, the genus
Persea and species P. americana. The avocado is in class of 2 cotyledons, chromosome
number 2n = 24; however the species remains in the triploids 3n = 36 and tetraploid 4n
= 48 chromosomes. Species of Persea americana Miller are classified into 3 different
ecological strains as Mexico, Guatemala and West India (Gary, 2012; Popenoe, 1952).
Botanical characteristics of these three ecological strains were described in table 1.1.
These three avocado strains could be cross-bred with each other as easily as they are
planted close together (Bergh, 1969; Crowley and Arpaia, 2002; Popenoe, 1952).
Mexican strain: originated from the Mexican plateau and are resistant to cold,
and the leaves smell of anise. However, the disadvantages of this strain are the small
fruits, soft skin and relatively large seeds. Hybridization selected from this strain is
valuable variety. For example, varieties Fuerte and Zutano are 2 hybridizations
between Mexico and Guatemala, having the medium fruit size and smooth skin.
4
Guatemala strain: the varieties of this strain as Hayes, Hopkins and Hass were
originated from the Western Highlands; however they are less tolerant than Mexican
strain. The varieties of this strain usually have large fruit, thick skin, rough shell
structure, and shell color changes from green to black when the fruit is mature. Seeds
are small and are held in the fruit.
West India strain: this strain is suitable in hot areas with low altitude and
humidity. The varieties of this strain are not resistant to cold, big fruits with tough
shell, nice design and not thickness as the fruits of Guatemala strain. The popular
varieties of this strain are Pollock, Booth 7 and Simmonds.
1.1.2. Development history and distribution in the world
Avocado tree development history has proven its good adaptation to the
ecological conditions in many countries. Avocado trees were introduced and brought to
plant in Indonesia and Philippines in 1750, and Southern Western of Indian Ocean, East
of Madagascar in Republic of Mauritius in 1780 and Hawaiian Islands in 1825, and they
were grown in Florida in 1833, California in 1871 and India in 1982 (A Profile of the
South African avocado market value chain, 2012). However, most of the varieties were
planted by seeds, they had been recently started growing in grafted avocado trees since
1890 in the U.S. After that avocado trees have been grown widespread in the tropical
regions of Central America and Caribbean in the countries such as islands in Central and
the South Pacific including Hawaii, Samoa and Cook islands.
To date, commercial varieties have developed very strongly throughout the
continents. The largest avocado producing countries in the world are shown in table
1.2, and 1.3. Starting from the 20th century, avocado trees are well developed but are
still primarily grown in regions of tropical climates and tropical Asia, and located in
between 40 degrees North and South of the equator. Statistics showed that, avocado
amounts were produced for 76% in the regions of America, 11% in Africa, 9% in
Asian, 2% in the countries of Europe and the South Pacific (Gary, 2012).
Statistics of Global Agricultural Information Network in November, 2012 said
that commercial avocado was grown with a total area over 150,000 hectares in Mexico
with amounts about 85% of the varieties belonging to the Mexican strain. Varieties
Hass and Fuerte were 2 commercial varieties grown mainly and accounted for 95%,
and also States of Mexico had grown more commercial varieties as Criollo, Bacon,
Gwen, Pinkerton, Nabal and Reed but with small areas. Avocado varieties produced
under American APHIS's certificates with a total area of 75,000 hectares (Dan Berman,
2012). Mexico is a country with the largest area and productivity in the world today,
and it has an altitude between 800-2,500 m above sea level. Most avocado varieties are
grown in the strains resistant to cold, high adaptability, average yield (10.1 tons/ha),
and ranked fourth in the world behind only the Dominican Republic (19.3 tons/ha);
Colombia (16.5 tons/ha); Brazil (12.9 tons/ha); before America and Indonesia (9.8
tons/ha) (Bruce et al, 2013; Ministry of Economy, 2011).
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1.1.3. Ecological requirement and tolerance
1.1.3.1. Ecological requirement
Rainfall: avocado trees have wide adaptability, growth and development in the
range from 30 degrees of North to 30 degrees of South, this wide distribution created
differences of 3 strains. Avocado trees are very sensitive to humidity, but not
drought. During the formation of immature fruit, if weather conditions are too dry,
the fruits will be felled very much. Most avocado varieties are sensitive to excess
water conditions, high soil moisture and poor drainage. In Hawaii, the avocado tree
grows quite with 3,125 mm in annual rainfall on well-drained soils. Requirement of
regular rainfall are from 1,250-1,750 mm. In 3 avocado strains, West India strain
adapted the high rainfall in the summer, while the Mexican strain was tolerant to
conditions of water lackage and low humidity (Douhan, 2009).
Temperature: avocado tree's response to temperature conditions depending on
the type of genes, the Mexican strain is the highest tolerant to cold, followed by
Guatemala, and the West India strain is suitable in the hot region and less cold
tolerance. Growth of seedlings: the flowers and fruit bud development of avocado
tree will be badly affected when temperature is 00C. Night and day temperature
amplitude may also clearly impact to growth and development of plants, especially in
the development of the flower. 150C – 200C in night temperature and 200C during the
day were suitable for the growth of flowers, pollen tube growth and the periods of the
embryo growth (Gazit and Degani, 2002).
Land: Many previous recommendations of French and American experts said
that we should choose the land for avocado cultivation in moderate slope. Also it is
necessary to pay close attention to the depth of the groundwater veins (depth of
underground water levels above 1 m). In Puerto Rico, the avocado tree grew better in
neutral or alkaline soil in comparison with medium or very acidic soil. In Israel, the
varieties belonging to Mexico and Guatemala strains became yellow leaves when
grown on the land containing much calcium; also in the Rio Gran Valley belonging to
the State of Texas, the Mexico strain must be grafted onto stumps belonging to West
India and resistant to salt (Lahav et al, 1989).
1.1.3.2. Tolerant ability
The highest salt tolerance was in West India strain, and the lowest one was in
Mexican strain. However, each of the 3 salty tolerant strains was also highly variable
(Kadman and Ben-Ya'acov, 1976), including real trees borned from the same mother
plant (Kadman, 1968). Although yellow leaf tolerance properties due to the high
content of lime in the soil can be seen in the varieties belonging to West India strain,
this tolerance also has considerable variability between varieties in the strain.
West India stumps reacted very poorly in heavy soil and flood conditions; there
were reports of selection of salty tolerant stumps and yellow leaves due to the high
content of lime (Ben-Ya'acov et al, 1974; Sánchez and Barrientos, 1987). Selected
stumps from South Africa's Dusa proved to endure highly with alkaline water in
California (Crowley and Arpaia, 2002). West India purebred stumps did not respond
well to cold soil conditions in California, but the special hybridizations of Mexico
6
strain seemed very good adaptations. In frost prone areas, it is necessary to have
stumps enhancing tolerance of grafting shoots, but these cold tolerant graft-stumps
belonging to Mexico strain brought into the research program genetically did not
transfer tolerance to grafting shoots (Ben-Ya'acov, 1987, 1998).
Cold tolerance: most of the world's avocado cultivation regions occasionally
suffer from damages of salt fog, and cold tolerance is a great advantage for the fruit
as well as for all plants in general. Cold tolerance is only limited on Mexico strain,
meanwhile the temperature over 00C can still be harmful to varieties belonging to the
West India strain. Hass, considered the variety belonging to Guatemala strain, has
special strength of cold tolerance, but children survey of Hass has about 1/5 of this
variety's gene numbers originated from the Mexico strain and supplied evidences that
Hass was originated between the two strains (Ben-Ya'acov et al, 1974; Mhameed et
al, 1997). This may be explained for the cold tolerance as well as the ripe fruits
earlier than those of Hass compared to purebred Guatemala. Cold tolerant ability in
the same strain as well as among the strains is different. For example, among the
varieties regarded as purebred ones, Nahal and Reed are highly tolerant to cold, but
Anaheim is very susceptible to cold. Yama, regarded as the coldest tolerant variety of
the Mexico strain, was tolerant to - 80C without any serious harm, which is a proper
parent in selecting cold tolerant varieties. In Florida, the varieties of Mexico strain
were selected for promising commercial varieties with the high cold tolerant
characteristic in conditions to occur in cycles (Knight, 1971).
Hot tolerance: hot tolerant ability of the varieties is very high variation.
However, the average hot tolerant ability of Mexico strain is higher than other strains,
typically in the Mexicola strains: Mayo and Indio. Moreover, because the varieties of
Mexico strains make earlier blooms and sooner old fruit, they are little to bear the
impacts of hot stages in the spring. Among the varieties belonging to Guatemala
strain, Frey and Hass are more sensitization with hot temperatures. Irving
hybridization between Mexico and Guatemala showed good tolerance to high
temperature and low humidity in California (Bergh and Lahav, 1996).
1.2. STUDIES IN VIETNAM
1.2.1. History, distribution, and actual state of avocado development in Vietnam
From the stored documents of the USDA/ARS, the avocado variety of Florida
(U.S.A.) was brought to Vietnam before 1933 in Quang Tri, the name of this variety
was Pollock, but there were not any documents confirming this event in Vietnam.
According to some documents in Vietnam, avocado trees were planted by French and
showed abilities to grow well in the Di Linh (Lam Dong) from 1940s. In 1958, an aid
delegation of United States brought around 60,000 avocado seeds belonging to 3
strains of Mexico, Guatemala and West India, and planted in Lam Dong – Bao Loc
Experimental Center, Hung Loc – Dong Nai Experimental Center and Eakmat-Dak
Lak Experimental Center.
From these variety corporations, there were comments, initial assessments of
growth and yield, as well as a description of fruit characteristics. After the complete
liberation of the South in 1976, Fruit-tree variety station in Cao Loc - Lang Son
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planted for tests of the avocado variety corporation imported from Cuba. The results
showed that the avocado trees grew well, yielded quite and had year by year fruiting
phenomenon (Phan Quoc Sung, 1986; Trinh Duc Minh and et al., 2005). For the
areas with an elevation over 500 m in the Western Highlands, this is an advantage of
avocado tree for good growth, quite yield and some trees with the quite tasty quality,
which are considered as the region's special crop. Avocado trees, however, have not
been developed by a number of limitations. In addition to obstacles such as avocado
trees planted by seeds, no selection, strong separation or poor cultivation techniques,
which leaded to low yield and poor quality, one of the important elements was the
market price affecting products. With the characteristics of the sudden respiratory
avocado fruits, fresh consumption and hard storage, so if the ripe time focuses on a
given time, it will make the problems of difficult consumptions and low prices.
CHAPTER 2
MATERIAL, CONTENT AND RESEARCH METHODOLOGY
2.1. RESEARCH MATERIAL
- 26 avocado varieties were locally selected, and 12 avocado varieties were
imported from America, which were grown in the corporative garden and the
experiments in Dak Lak, Gia Lai, Lam Dong, 2002.
- 12 promising avocado varieties TA1, TA2, TA3, TA4, TA5, TA31, TA44,
TA47, TA50, TA54, Booth 7 and Hass were planted in Dak Lak, Gia Lai, Lam Dong
provinces, 2007.
- Variety material: Varieties were grown in the experiments and the corporative
garden by grafting them on the stumps of variety TA44.
2.2. RESEARCH CONTENT
2.2.1. Study on some bio-agricultural characteristics of local selected avocado
varieties and new imported varieties in Dak Lak
- Location: Corporative garden and the comparative experiments of avocado
varieties at Western Highlands Agriculturure and Forestry Science Institute.
- Scale and planting years: a total of 4 ha, of which 2 ha for corporative garden
grown in 2003 and 2 ha for the experimental garden of promising avocado variety
comparison, 2007.
- Study period: from 2011-2014.
2.2.2 Comparative and evaluative studies on some promising avocado varieties
at the ecological regions in the Western Highlands
- Location: Comparative and evaluative experiments of avocado varieties at 3
major growing regions in Dak Lak, Gia Lai and Lam Dong provinces.
- Scale and planting year: 6 hectares grown in 2008, in which 2 ha for each
province.
- Study period: from 2010-2014.
- Experimental varieties: composed of 12 varieties: TA1, TA2, TA3, TA4,
TA5, TA31, TA44, TA47, TA50, TA54, Booth 7 and Hass.
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2.2.3. Study on determination of harvest time of some promising avocado
varieties in Dak Lak
- Location: Corporative garden and the comparative experiments of avocado
varieties at Western Highlands Agriculturure and Forestry Science Institute.
- Scale and planting years: a total of 4 ha, of which 2 ha for corporative garden
grown in 2003 and 2 ha for the experimental garden of promising avocado variety
comparison in 2007.
- Study period: from 2011-2014.
- Experimental varieties: 9 avocado varieties: TA1, TA4, TA5, TA17, TA21,
TA40, Booth 7, Fuerte and Reed.
2.3. RESEARCH METHODOLOGY
2.3.1. Study on some bio-agricultural characteristics of local selected avocado
varieties and new imported varieties in Dak Lak
- Analysis of genetic characteristics of autosomal phenotype according to
IPGRI's methods, 1995. Polymorphic properties (Polymorphous) of avocado
varieties, including canopy shape, canopy size, number of branches at levels 1, 2 and
3, the ability to branch, dwarf, high and medium canopy forms, etc.).
- Study on the flowering and fruiting characteristics of varieties according to the
method for comparing the phase differences between groups A and B (Bergh, 1969).
- Total number of experiment plants: 38 varieties x 10 plants/variety = 380
plants.
2.3.2. Comparative and evaluative studies on some promising avocado varieties
at the ecological regions in the Western Highlands
- Designed experiments to compare varieties based on biology characteristics of
avocado trees by the method of Razeto et al., 1994.
- Planting density was 210 plants/ha, and planting distance was 7 m x 7 m
- Experimental design according to RCBD (Randomized Complete Block
Design), 1 element and 3 replications.
-Total experiment area: 6 ha (in Dak Lak, Gia Lai and Lam Dong provinces, 2 ha
for each province). Total experiment plants: 12 varieties x 3 locations x 3 replications
x 12 plants/variety = 1,296 plants.
- Determination of fruit weight and yield of avocado varieties: Each variety was
collected for 10 fruits and calculated for average fruit weight; Assessment of yield by
counting the number of fruit/plant and multiplying it by the average fruit weight.
- Selection criteria: builded on the basis of summarized references of standards
in the market, UNECE STANDARD FFV-42 trade and the Codex standard for
Avocado-Codex stan 197-1995 of the world and Europe CX/FFV 11/16/5. For plants:
plant age is 7 years, yield is 50 kg of fruits/plant/year, good growth and
development, less pests and serious diseases. For fruits: fruit weight is 300 g, the
fruit is round to oval and is easy to pack. The thick shell is 1 mm and is easy to peel.
The dry matter content is 19%, meat ratio is 65%, color is yellow to dark yellow,
flesh is little or no fiber, and fat content is 13%. Beads are snugly closed into the
flesh of the fruit, but husk are not attached into flesh and easily split when ripe.
9
- Determination of some main pest and disease species on the promising
avocado varieties in the Western Highlands. For pests: collect mature pest and bring
them to the room to describe colors and measure the size of the pests. Combination
with some documents is used for describing the morphological characteristics of pests
to determine pest species. For diseases: collect disease samples and bring them to the
lab to isolate and identify pathogens.
2.3.3. Study on determination of harvest time of some promising avocado
varieties in Dak Lak
- Subject was conducted by experiments on the determination of the harvest
time on 6 promising avocado varieties selected in our country: TA1, TA4, TA5,
TA17, TA21, TA40 and 3 imported varieties: Booth 7, Fuerte and Reed.
- Experimental methods: mark plants, braches and fruits to observe, hang tags
and note flowering and fruiting dates on each variety. The fruiting time was
determined when the fruits had a diameter from 0.5-1 cm.
- Harvest time observation: after flowering and fruiting for 4 months, we
observed the dry matter percentage in the fruits as following: 20 days for each sample
collection times, 5 fruits for each times (four fruits at 4 directions outside and 1 fruit
inside the plant canopy) then proceeded to determine the rate of dry matter in the fruit.
DIAGRAM OF AVOCADO VARIETY SELECTION IN THE WESTERN
HIGHLANDS
Evaluate 26 strains and varieties
collected in the Western
Highlands and 12 imported
varieties in the corperative garden
in Dak Lak (2002-2014)
Test, compare and evaluate 12
promising avocado varieties in the
different ecological regions in the
Western Highlands (2006-2014)
Select 8 promising avocado varieties TA1, TA3, TA5 TA6 TA17,
TA40, Booth 7 and Reed (2010)
Recognize 4 varieties TA1, TA3, TA5 and Booth 7 (2011)
CHAPTER 3
RESULTS AND DISSCUSIONS
3.1. STUDY ON SOME BIO-AGRICULTURAL CHARACTERISTICS OF
LOCAL SELECTED AVOCADO VARIETIES AND NEW IMPORTED
VARIETIES IN DAK LAK
3.1.1. Morphological characteristics of avocado varieties at the 10th age (2013)
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Table 3.1. Canopy shape, thickness and diameter of avocado varieties (2013)
Canopy
Order Variety
Canopy shape and thickness
diameter (m)
1
TA1
5.00
Medium canopy, flattened circular, weak tree
2
TA2
5.80
Thin canopy, cylinder, weak tree
3
TA3
5.40
Thin canopy, flattened circular, weak tree
4
TA4
6.50
Medium canopy, flattened circular, healthy tree
5
TA5
8.00
Thick canopy, cylinder, healthy tree
6
TA6
9.00
Thin canopy, pyramid, healthy tree
7
TA7
5.50
Medium canopy, flattened circular
8
TA8
7.30
Thin canopy, flattened circular, healthy tree
9
TA9
4.00
Thick canopy, pyramid, health
10
TA16
5.50
Thin canopy, cylinder, weak tree
11
TA17
7.30
Thick canopy, flattened circular
12
TA19
6.20
Medium canopy, pyramid, healthy tree
13
TA20
8.00
Thick canopy, pyramid, healthy tree
14
TA21
8.00
Thin canopy, pyramid, weak tree
15
TA26
6.30
Thick canopy, flattened circular, weak tree
16
TA31
5.90
Medium canopy, flattened circular, cây khỏe
17
TA36
7.30
Thin canopy, flattened circular, weak tree
18
TA37
6.70
Thin canopy, flattened circular, weak tree
19
TA39
6.50
Thick canopy, pyramid, healthy tree
20
TA40
6.40
Thin canopy, pyramid, weak tree
21
TA44
5.00
Thick canopy, flattened circular, healthy tree
22
TA45
6.30
Thin canopy, flattened circular, weak tree
23
TA47
5.50
Thick canopy, pyramid, healthy tree
24
TA48
5.60
Thick canopy, pyramid, healthy tree
25
TA50
7.10
Thick canopy, flattened circular, healthy tree
26
TA54
5.90
Thick canopy, flattened circular, healthy tree
27
Số 5
5.50
Thin canopy, pyramid, weak tree
28
Booth 7
8.00
Medium canopy, cylinder
29
Hass
6.00
Thick canopy, flattened circular, weak tree
30
Tiger
9.00
Thick canopy, pyramid, weak tree
31
Ardith
6.20
Thin canopy, pyramid, weak tree
32
Reed
5.50
Thin canopy, cylinder, healthy tree
33
Edtinger
6.30
Thin canopy, cylinder, healthy tree
34
Fuerte
6.00
Thin canopy, cylinder, weak tree
35
Sharwill
6.30
Thick canopy, flattened circular, healthy tree
36
GA
4.20
Thin canopy, cylinder, weak tree
37
GB
5.20
Thin canopy, pyramid, healthy tree
38
GC
5.60
Thick canopy, flat, healthy tree
Trung bình
6.31
CV(%)
18.44
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The process of monitoring and evaluation of avocado varieties in the garden
showed that the largest canopy diameter reached 9 m, and the smallest one reached 4
m. Overall, the varieties could develope good canopy with 6.31 m in average;
however, there were big differences among varieties in statistic analysis for very high
coefficient of variation around 18%, which proved these differences.
In experimental conditions at some provinces in the Western Highlands, the
varieties are planted on fertile bazan red soil areas having high fertile levels above
4.5%, the average rainfall for years over 1,800 mm and the average temperature
around 220C, which are suitable for development of avocado varieties, particularly
the varieties imported from American had very strong growth around double times
compared to places planting the native varieties. However, most varieties which
developed too strongly will result in low yield due to the ability to take in pollens
limited by the too thick canopy. Commonly in many regions belonging to the
tropical monsoon climate countries because of high temperatures and heavy rain,
avocado varieties strongly developed on the branches and twigs longer than the
countries that carry the characteristics of tropical Asia and cold climate.
3.1.2. Growth and development of avocado varieties at the 10th age (2013)
Table 3.4. Growth and development of avocado varieties
Order
Variety
Stem diameter (m)
Plant height (m) Flower group
1
TA1
0.29
5.80
A
B
2
TA2
0.24
5.50
A
3
TA3
0.20
4.50
4
TA4
0.27
4.70
A
5
TA5
0.36
7.20
B
6
TA6
0.34
5.50
B
7
TA7
0.25
4.00
A
8
TA8
0.39
5.70
B
9
TA9
0.29
4.80
A
10
TA16
0.23
5.30
A
11
TA17
0.27
6.40
A
12
TA19
0.28
5.60
A
13
TA20
0.32
6.20
B
14
TA21
0.33
5.80
B
15
TA26
0.33
5.10
B
16
TA31
0.39
5.90
A
17
TA36
0.27
5.70
B
18
TA37
0.30
6.00
B
19
TA39
0.25
4.60
A
20
TA40
0.24
5.80
B
21
TA44
0.20
5.50
A
22
TA45
0.38
5.60
A
23
TA47
0.23
4.40
A
24
TA48
0.34
6.00
A
25
TA50
0.28
6.54
B
12
Order
26
27
28
29
30
31
32
33
34
35
36
37
38
Variety
Stem diameter (m)
Plant height (m) Flower group
TA54
0.25
6.78
B
So 5
0.24
5.10
B
Booth 7
0.30
6.20
B
Hass
0.28
5.80
A
Tiger
0.40
5.80
B
Ardith
0.26
6.00
A
Reed
0.33
6.00
A
Ettinger
0.29
5.60
B
Fuerte
0.25
5.70
B
Sharwill
0.30
4.00
B
GA
0.38
4.60
A
GB
0.33
4.00
B
GC
0.24
3.40
A
Mean
0.29
5.45
CV (%)
18.44
15.25
For the stem diameter growth, the varieties had an average diameter of 0.29 m,
and the tree had the largest stem diameter of 0.40 m and the smallest one of 0.20 m.
Statistical analysis showed the quite high coefficient of variation around 18%. This
proved that there was a great difference in terms of the level of growth in the
diameter and the uneven growth. Similarly, the ability to grow in the plant height also
showed that there were huge differences among varieties in the garden with a rather
large fluctuation about 15%.
The greatest plant height of the varieties reached over 7 m, reflecting the
advantage of height, and the lowest plant height was 3.40 m. In terms of cultivation,
the characteristic of the plant height could decide to intensive forms or different
intercropping. The TA1, TA20, TA21, TA17, TA5, TA31, TA40, TA48, TA50,
TA54, Booth 7, Reed and GA with strong growth speeds proved advantages of these
varieties in terms of ecological conditions of Dak Lak. However, variety selection
responding for export goals depends on a lot of the more important factors such as
yield and quality of the variety.
Botanical characteristics of 2 flower groups A and B have been very
thoroughly studied by many scientists around the world and proven in both groups on
all avocado varieties carrying hermaphrodite without separation of male and female
flowers. There are parallel stamens and pistils formed in the same flower; however
the structure of these 2 flower groups is very different, and there is only a single
flower group A or B.
Observation of the structure of 2 flower groups showed that flower group A
had 6 stamens surrounding high and vertical distribution equal to the top of pistils,
and the anthers cluster inside. Varieties having this flower group can pollinate
themselves, but the average rate was very low only 0.47%; in contrast, the flower
group B have 6 stamens dumped about two parties outside the pistils, for what
varieties having this flower group cannot pollinate. This proved that the avocado trees
are species required by the cross pollen exchanges. The exchange of pollen between
13
two flower groups is especially meaningful in improving varieties, reducing the
ability to variety degeneration due to pollination in the same flower group.
Structure of flower group A and B of avocado tree
Flower group A
Flower group B
3.2. COMPARATIVE AND EVALUATIVE STUDIES ON SOME PROMISING
AVOCADO VARIETIES AT THE ECOLOGICAL REGIONS IN THE
WESTERN HIGHLANDS
Comparative experiments were conducted to evaluate 12 avocado varieties
grown from 2007 in 3 ecological regions of Dak Lak, Gia Lai and Lam Dong. The
subject had been conductive in observating and evaluating for many years, and the
updated data were collected in the dissertation in the years from 2010-2013.
However, in this report, the data were only analyzed focusing on the nearest year
2013, and the data of the previous years were put into the annexes at the tables and
3.18.1, 3.18.2 and 3.18.3 in this report. The data analyzed here will prove the
adaptability of each variety at three experimental places in Buon Ma Thuot- Dak Lak,
PleiKu - Gia Lai and Bao Loc - Lam Dong.
3.2.1. Growth and development of the avocado varieties at the 7th age in some
ecological areas in the Western Highlands (2013)
Table 3.20. Growth and development of avocado varieties at the seventh age
Province
Dak Lak
Gia Lai
Lam Dong
SD
PH
CD
SD
PH
CD
SD
PH
CD
Variety
(m)
(m)
(m)
(m)
(m)
(m)
(m)
(m)
(m)
TA1
0.25 6.18 5.05 0.16 4.99 3.43 0.17 3.60 4.83
TA2
0.24 6.14 6.16 0.17 5.03 4.62 0.24 3.72 4.49
TA3
0.26 5.50 6.11 0.11 3.20 3.39 0.26 3.89 4.84
TA4
0.21 5.49 5.61 0.14 4.38 4.39 0.19 3.58 4.72
TA5
0.29 6.68 7.21 0.15 4.11 4.00 0.18 3.93 4.74
TA31
0.24 5.25 5.64 0.13 4.13 3.86 0.04 1.82 1.51
TA44
0.24 5.71 6.86 0.15 4.25 4.27 0.06 2.17 2.03
TA47
0.21 5.62 5.77 0.14 4.27 4.15 0.07 2.71 2.34
14
TA50
0.28 6.54 7.12 0.16 5.18 4.48 0.07 2.58 1.51
TA54
0.25 6.77 5.88 0.16 5.19 3.67 0.07 2.58 1.83
Booth 7
0.26 5.40 5.60 0.13 3.72 3.67 0.25 3.69 4.93
Hass
0.26 5.62 5.31 0.13 3.41 2.80 0.22 3.52 3.61
Mean
0.25 5.91 6.03 0.14 4.32 3.89 0.15 3.15 3.45
CV (%)
9.60 8.99 11.60 12.00 15.57 13.64 55.30 23.20 42.67
LSD0,05
0.51 0.74 0.85 0.32 0.56 0.55 0.47 0.90 0.98
Note SD: Stem diameter; PH: Plant height; CD: Canopy diameter
Avocado varieties at the 7th age in ecological condition in the Dak Lak showed
that 2 monitored targets of stem diameter and plant height had very small coefficient
of variances only about 8-9% and demonstrated that the varieties could grow and
develop quite evenly, and also clearly showed relative adaptability of the varieties
with the ecological conditions in Dak Lak. The varieties reached 0.25 m in the
average stem diameter and 5.91 m in average plant height, and varieties selected in
the domestic country had growth speeds and development quite evenly. Similarly, 2
imported varieties equally grew and developed over 0.26 m in stem diameter and 5.40
m in plant height.
Another very important norm that influences elements to constitute yield is the
canopy diameter. Overall, the varieties had rather good development levels of canopy
with an average canopy diameter of 6.03 m; variety TA5 had the strongest canopy
development for 7.21 m and variety TA1 had a weaker canopy development just 5.04
m. Coefficient of variation around 11% showed that developments of canopies were
fairly uniforms among varieties. To the ecological conditions in the Gia Lai, in overall,
growth and development speeds of varieties were in good levels, manifesting
themselves in the growth of stem diameter at 0.15 m. Booth 7 and TA3 had the
smallest stem diameter at 0.12 m, and TA1 and TA2 had the greatest stem diameters
over 0.18 m. Average plant height was 4.33 m in which variety Hass had the lowest
plant height at 3.38 m, and variety TA54 had the biggest plant height at 5.24 m.
Likewise the average canopy diameter of varieties was 3.94 m, Hass had the weakest
level of canopy development at 2.83 m, and TA2 developed the strongest canopy at
4.81 m.
Statistical analysis showed; in all monitored targets, stem diameter, tree height
and canopy diameter within low coefficient of variation below 15% demonstrated
differences but not significant in the monitored targets. To the ecological conditions
in Bao Loc - Lam Dong, the varieties grew and developed at an average rate
somewhat demonstrated that most of the varieties had good adaptabilities. The
varieties had 0.15 m in the average stem diameter, 3.15 m in the plant height, and
3.45 m in the canopy diameter. For statistical analysis, all monitored targets within
very high levels of coefficient of variation over 23% and other different values were
greater than the theory, showing significant differences among varieties on their
ability to grow, develop and adapt to the ecological conditions among regions.
3.2.2. Flowering and fruiting characteristics and harvest time of avocado varieties
15
Table 3.19. Flowering and fruiting characteristics and harvest time
Flower Flowering and fruiting
Order Variety
Harvest time
group
period
1
TA1
A
January - March
July - September
2
TA2
B
December - February
July - August
3
TA3
A
January - March
August - September
4
TA4
A
January - February
June - August
5
TA5
B
March - April
September - October
6
TA31
A
February - April
September - October
7
TA44
A
February - April
September - October
8
TA47
A
January - February
July - August
9
TA50
B
December - January
June - August
10
TA54
A
January - March
June - August
11
Booth 7
B
January - March
October - November
12
Hass
A
January - March
August - October
Observation process showed that there are 8 varieties belonging to group A:
TA1, TA3, TA4, TA31, TA44, TA47, TA54 and Hass, and the rest varieties belong
to group B. Harvest time lasts from 2 to 3 months. 7 late harvest varieties are TA1,
TA3, TA5, TA31, TA44, Booth 7 and Hass in August to November, and the rest
varieties have the main crop harvest time around June to August. For all three
experimental areas, there are cool air temperature ranged from 22-230C and the
changes of the high night-day temperatures, which are very suitable for uniform
flower sprouts in bulks. Particularly during the period from December to February,
most avocado varieties began the sexual releasing period.
3.2.3. Yields of avocado varieties at the 7th age in the ecological regions in the
Western Highlands (2013)
Table 3.20. Yields of avocado varieties at the seventh age (kg/tree)
Province
Order
Variety
Dak Lak
Gia Lai
Lam Dong
1
TA1
17.33
18.60
21.90
2
TA2
107.97
31.70
21.10
3
TA3
12.31
9.00
57.70
4
TA4
56.53
27.30
57.90
5
TA5
32.44
0.00
78.10
6
TA31
40.95
0.00
0.00
7
TA44
25.97
6.80
0.00
8
TA47
85.80
18.00
0.00
9
TA50
25.60
20.60
0.00
10
TA54
67.00
0.00
0.00
11
Booth 7
66.69
0.00
88.40
12
Hass
16.28
6.60
20.20
Mean
46.24
17.33
49.33
CV (%)
66.08
54.06
57.91
LSD0,05
26.81
10.02
26.74
16
In experimental areas, most of the 7th age varieties only reached yields in
average levels. In ecological conditions in Buon Ma Thuot - Dak Lak, all varieties
showing uniform fruits with superior yield compared to other regions with an average
yield of 46.24 kg/tree demonstrated good adaptability of the varieties with ecological
condition in Buon Ma Thuot - Dak Lak. Meanwhile, 7 varieties gave an average yield
of 49.33 kg/tree in Lam Dong, and the remaining varieties TA31, TA44, TA47, TA54
and TA50 had not fruits due to the ability to receive the very poor pollen of those
varieties in the climatic conditions of Bao Loc - Lam Dong where extremely low air
temperatures under 150C during flowering periods from December to March each
year. Similarly varieties TA5, TA31, TA54 and Booth 7 grown in the ecological
condition in PleiKu - Gia Lai had not any fruit, the remaining varieties had the lowest
average yield of 17.33 kg/tree, and 8 varieties had fruits. In all three research areas, 4
varieties TA2, TA47, TA54 and Booth 7 gave the highest yields and relative stability,
and initially showed the potential yield of those varieties. In particular, variety TA2
had very high average yield over 100 kg/tree in ecological conditions in Buon Ma
Thuot - Dak Lak. Differences in ability to fruit in different varieties are very crisp
and significant due to the coefficient of variation and the great different values
compared to theory, which proved this element.
Table 3.21. Yield of avocado varieties through the years from 2010-2013 in Buon
Ma Thuot - Dak Lak (kg/tree)
Yield
Variety
Mean
CV (%)
2010
2011
2012
2013
TA1
26.30
6.05
17.33
21.50
17.80
48.58
TA2
35.00
66.56
107.97
78.60
72.03
41.92
TA3
25.50
27.35
12.31
21.70
21.72
30.84
TA4
58.60
41.11
56.53
60.00
54.06
16.19
TA5
31.70
78.26
32.44
20.00
40.60
63.41
TA31
40.70
13.18
40.95
30.00
31.21
41.84
TA44
55.20
16.38
25.97
5.00
25.64
83.83
TA47
55.80
60.28
85.80
120.00
80.47
36.64
TA50
33.40
25.60
25.60
0.00
21.15
68.90
TA54
9.10
67.00
67.00
4.60
36.93
94.18
Booth 7
91.00
87.53
66.69
86.30
82.88
13.24
Hass
1.40
11.86
16.28
10.00
9.89
63.12
LSD0,05
2.22
2.85
3.61
6.01
Table 3.22. Yield of avocado varieties through the years from 2010-2013 in
Pleiku - Gia Lai (kg/tree)
In Buon Ma Thuot - Dak Lak, continuous yield statistics for 4 years showed
that the year by year flowering status occured in most varieties and was partly
influenced by erratic changes of the climatic conditions in recent years in Daklak.
Especially during flowering and fruiting period, the humidity under 50% made
deformitied pollens, strong winds and drought causing low fruiting rates as well as
high fruit falling rates due to lack of water. Out of 12 variety experiments, there were
4 varieties TA2, TA4, TA47 and Booth 7 tending to increase yield over the age of the
17
tree, and the fluctuations below 15% showed stability in yields of those varieties. In
particular, varieties TA47 and Booth 7 had high and stable yield about 80
kg/tree/year. Varieties TA3, TA4, Booth 7 and Hass had low yield changes from ± 6
to ± 10 kg/tree/year. The value from statistical analysis was more different than the
theory, showing the significant differences in the yields of the cultivated varieties in
Dak Lak. Those were the source of the promising materials serving effectively in
further practice and research.
Yield
Năng suất
(kg/tree)
(kg/cây)
Picture 3.2. Yield change of avocado varieties over the years in Dak Lak
Figure 3.2. Pronounced fluctuations in the yield of the varieties taking part in
experiments.
Year
Variety
Mean
CV (%)
2010
2011
2012
2013
TA1
12.20
10.00
18.60
4.50
11.33
51.49
TA2
0.00
26.50
31.70
5.00
15.80
98.97
TA3
15.60
0.00
9.00
3.30
6.98
98.17
TA4
34.90
20.00
27.30
6.88
22.27
53.56
TA5
11.70
0.00
0.00
0.00
2.93
0.00
TA31
5.80
0.00
0.00
1.35
1.79
153.83
TA44
19.10
12.50
6.80
0.00
9.60
84.77
TA47
4.30
21.90
18.00
3.30
11.88
79.73
TA50
0.00
3.50
20.60
10.00
8.53
106.20
TA54
0.00
0.00
0.00
19.00
4.75
200.00
Booth 7
12.00
10.00
30.00
8.20
15.05
67.02
Hass
0.00
0.00
6.60
0.00
1.65
200.00
LSD0,05
1.86
1.64
3.34
1.82
18
At Pleiku - Gia Lai, generally the yields of the varieties were much lower than
those in Buon Ma Thuot - Dak Lak. Varieties TA5, TA31, TA54 and Hass did not
give yield in several years, particularly low average yield in 2013 from 2-22
kg/tree/year, and showed their poor adaptations to the climatic conditions in the
region. Explanation for this cause can see on variety Hass belonging to Guatemalan
strain originated from the regions of tropical Asia with more cold temperatures than
all other experiments on research places. According to many studies in the world,
variety Hass could split flower sprouts at 170C at night and about 250C during the
daytime, while Gia Lai had a higher temperature than that of requirements of the
variety. In contrast, varieties TA1, TA2, as TA4, TA47 and Booth 7 tended to the
highest and stable average yield over 11 kg/tree/year clearly showed ability to adapt
well to ecological conditions in the region. The yield fluctuations of the varieties for
many years were very high over 80%, showing the instability of the observed targets.
The value from statistical analysis was more different than the theory, proving the
differences in the yields of varieties grown in Gia Lai. Figure 3.3 will demonstrate
those fluctuations.
Varieties
Yield
(kg/tree)
Picture 3.3. Yield change of avocado varieties by years in Gia Lai
Table 3.23. Yield of Avocado varieties through the years from 2010-2013 in Bao
Loc - Lam Dong (kg/tree)
Year
Variety
Mean
CV (%)
2010
2011
2012
2013
TA1
24.00
31.20
21.90
14.10
22.80
30.86
TA2
30.00
25.50
21.10
15.60
23.05
26.70
TA3
39.20
48.50
57.70
12.20
39.40
49.86
TA4
30.50
30.50
57.90
18.60
34.38
48.45
TA5
22.90
44.50
78.10
6.70
38.05
0.00
TA31
0.00
0.00
0.00
0.00
0.00
0.00
TA44
0.00
0.00
0.00
0.00
0.00
0.00
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