Nghiên cứu chọn tạo giống dâu lai f1 lưỡng bội trồng hạt cho cách tỉnh phía bắc việt nam LA TT EN

MINISTRY OF EDUCATION
AND TRAINING

MINISTRY OF AGRICULTURE AND
RURAL DEVELOPMENT

VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
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NGUYEN THI MIN

RESEARCH ON THE BREEDING OF DIPLOID HYBRID MULBERRY
VARIETY F1 FOR THE NORTHERN PROVINCES OF VIETNAM

Major: Plant genetics and breeding
Code: 9.62.01.11

DOCTORAL THESIS SUMMARY OF AGRICULTURE

Hanoi, 2018


The doctoral thesis was completed in:
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES

Supervisors:
1. PGS.TS. Ha Van Phuc
2. TS. Nguyen Tat Khang

Objection 1:

Objection 2:

Objection 3:

The Doctoral thesis is defended at Institute Committee of PhD
Dissertation Examination:
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
At .............day ............. month ...................2018

PhD thesis can be found at:
- National Library of Vietnam
- Library of vietnam academy of agricultural sciences


INTRODUCTION
1. Rationale
Silk is a natural fiber made from mulberry silkworm (Bombyx Mori L.) that feeds
on mulberry leaves and synthesizes the proteins in mulberry leaves to form cocoons of
silk length of 700-800 meters (multi-ploid varieties), or more than 1000 meters (diploid
varieties). Silk yarns and silk products have very precious properties such as nonconductive, moisture-draining, spongy, glossy and soft. Wearing silk clothes feels cool
in the summer but feels warmer than other fabrics in the winter. Since silk has such
precious properties, since ancient times, man has given silk yarn "the queen of textile".
At the 18th International Silk Conference, Silvio Silva, president of the
International Silk Association, assessed the value of silk: "After more than 4,000 years
of existence, silk has been the only fiber of intermittent length. Since the beginning of
time, silk does not depend on any artificial energy industry, nor does it produce any
pollutants. Silk is a jewelry of weave industry. With its historical and literature values,
silk will still be loved for a long time" (Vietnam Silkworm Corporation, 1993).
Silk yarns, beside being used to make garments, also produces some of the byproducts that are processed into many valuable commodities for human life, such as
extracts of chlorophyll from silkworm to produce medicine, production of Lingzhi

mushrooms, silkworms to produce carnations...
In our country, mulberry has many favorable conditions to develop the mulberry
industry such as an abundant source of secondary labor in rural areas and mulberry leafpicking is suitable for both children and the elders. The land available for growing
mulberries in the Northern Delta is currently about 19,000 ha. That land area is currently
planting crops that are not highly economic such as maize, sweet potato and cassava.
The climate in our country is favorable for mulberry growing year-round, so in a year 810 silkworm crops can be harvested. Meanwhile, in some temperate countries, only 4-5
silkworms are harvested in a year. Moreover, the cost of investing in mulberry
production is not expensive but the return of capital is fast. On average, silkworms can
be harvested every 20-25 days to sell cocoons. Compared with rice cultivation, silkworm
mulberry grows 3.5 times more profit. But if the incubation is taken into account, the
profit is 5 times higher than that of rice (Ha Van Phuc, 2013).
Beside various advantageous potentials, the mulberry industry in Vietnam still has
low cocoon productivity per hectare, so the total income is only 80 million (Le Hong
Van, 2013) while the average income per hectare in Guangdong, Guangxi (China) with
the same climatic conditions as the Red River Delta is 150 million VND (Zhu Fang
Rong, 2010). Furthermore, the labor used in harvesting mulberry and silkworm is
growing, so the value is getting lower.
Over the past years, Vietnamese scientists have chosen to crossbreed and plant
some new mulberry varieties such as the triploid variety (3n = 42), the cloned varieties
7, 11, 12, 28 (Ha Van Phuc, 1994) and the triploid varieties VH9, VH13, VH15 (Ha Van
Phuc et al., 2002, 2003, 2009). These new mulberry varieties have changed the structure
of mulberry varieties and contribute to improve the economic efficiency of production.
However, the new mulberry varieties mentioned above are multi-merino varieties,
in addition to the advantages of yield and leaf quality, they have spongy trunks and
branches, resulting in severe borer damage caused by worms, and the ability to
regenerate after cutting the branches is not so good that it hinders harvesting by cutting.
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Moreover, in order to breed a triploid mulberry variety, it is necessary to use the

tetraploid variety (4n = 56) as the starting materials. However, currently there is only
one tetraploid mulberry variety, which is DB86, so the crossbreeding to create new
varieties to select is limited.
Originated from that fact, we have chosen the topic: "Research on the breeding
of diploid hybrid mulberry variety F1 for the Northern provinces of Vietnam".
2. Objectives and requirements of the dissertation
To create the diploid hybrid mulberry variety with higher leaf yield and better leaf
quality than or equivalent to VH13 mulberry varieties, suitable for the climate and land
conditions in northern provinces of Vietnam.
3. The scientific and practical significance of the topic
3.1. The scientific significance of the topic
- Along with a number of results of the research on the selection of VH9, VH13
and VH15 seedlings, the results of this research will be the scientific basis to confirm
that creating new mulberry varieties by natural crossbreeding is superior to cloned
crossbreeding.
- To open new research direction, which is to use hybrid advantage to select
diploid mulberry variety planted by seeds.
- To asset the great value in the use of imported mulberry varieties as starting
materials for breeding, especially the imported mulberry varieties from Guangdong,
Guangxi (China).
- Initially, to determine the effect of leaf harvesting method by cutting branches,
so that the new research direction is to select the mulberry varieties suitable with cutting
branches to reduce labor costs in harvesting mulberry and silkworm growing.
3.2. The practical significance of the topic
- To select some mulberry varieties as starting materials.
- The results of the dissertation will create new varieties of mulberry for
production, contributing to the increase in productivity of silkworm cocoons.
- To identify suitable ecological zones for new mulberry varieties to promote the
superiority of varieties.
- To evaluate the regeneration capacity of new varieties and the direction of

branch cutting.
4. New findings of the dissertation
The new mulberry varieties in our country since 1996 are produced by the hybrid
method between diploid and tetraploid mulberry varieties to create triploid varieties.
However, this research was carried out in the direction of selecting diploid seeds using
the natural hybrid method.
This study wants to select new varieties for the Northern provinces to meet the
requirements of the topic.
5. Structure of the dissertation
The dissertation consists of 143 A4 -size pages including 64 tables, 9 figures. The
dissertation includes the Introduction (5 pages); Overview (38 pages); Materials,
contents, methodology (10 pages); Results and discussion (88 pages); Conclusions and
recommendations (2 pages). This study cites 110 documents in total, including 32
Vietnamese, 62 English and 16 Chinese papers.
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CHAPTER I: OVERVIEW OF THE MATERIALS AND SCIENTIFIC BASIS OF
THE DISSERTATION
1.1. The scientific basis of the topic
Bombyx Mori L only eats mulberry leaves. Therefore, yield and quality of
mulberry leaves are closely related to yield and quality of cocoons (Ha Van Phuc, 2003).
Moreover, over 60% of the cost of producing cocoons is used to grow, care for and
harvest mulberry leaves (Deng Wen et al., 2010). Thus, mulberry leaves also
significantly affect the cost of cocoon production.
The yield and quality of mulberry leaves depend on many factors such as soil
condition, climate, cultivation methods, harvesting, etc., but mulberry is a very
influential factor. Today mulberry is considered as a means of production.
1.2. Study on breeding new mulberry varieties
1.2.1. Studies in the world

1.2.1.1. Study on the breeding of cloned multiplication varieties
Mulberry is a wood-getting tree, which has strong rooting characteristics when
planting by branches in suitable crop. Cloned varieties always keep the genetic traits of
the breed through generations.
Natural hybridization is the hybridization of genes between father and mother
breeds, from which hybrid mulberry trees inherit good genes. Good individuals selected
through cloned hybridization will maintain these traits.
In 1967, the silkworm experiments of the Ministry of Agriculture, Forestry and
Fisheries of Japan (Zheng Mong Xia, 1987) crossbred two local mulberry varieties,
Ichinoxe and Cailieunemi to create the new variety Xinichinocar. This new mulberry
variety has overcome the drawback of the Ichinoxe, so it is suitable for harvesting
mulberry leaves by cutting branches. The mulberry grows well, yielding 12% higher
yield than the parent mulberry varieties. However, through planting in the production
areas, the new mulberry variety has the disadvantage of being susceptible to viral
diseases and dry black bacteria.
To overcome this disadvantage of the new mulberry variety, in 1976 the Japanese
breeders have hybridized the Xinichinocar with the Kokyco 21 variety and chose the
"Nan Mery" variety. This new variety retains the good characteristics of the
Xinchinocar, but it has the potential to overcome the bacterial and viral susceptibility.
Indian breeders Das et al. (2006) selected a number of promising hybrids from
hybrid combinations of Morus India, Morus Latifolia and Morus Multicaulis with
M.Alba, Morus Rotundiloba. He said that the parent varieties participating in the hybrids
are far from each other in terms of geographical conditions and traits, so hybrid F1
generations exhibit manifold traits. Therefore, it is necessary to select individuals to find
the mulberry trees to meet the target selection.
Yang Fing Hoa et al. (2012) at the Chinese Mulberry Research Institute has
combined the Lake 39 mulberry planted in the Zhejiang province with a temperate
climate with Guangdong subterranean mercury having a subtropical climate. The result
was that seedlings No. 2 had spring germination properties similar to Lake 39. Straight
and multi-branch shoots were suitable for cutting method, good resistance to bacterial

and viral diseases but feasible. However, cold tolerance of this variety is less than that of
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the Lake 39 one. This new mulberry variety has grown widely in Zhejiang and Fujian
provinces.
Since 1994, scientists from the Guangdong Chinese Silkworm Research Institute
(Sun Xiao-Xia et al., 2013) have crossbred the line between the 408th Chineseoriginated Bulgarian mussel variety with early spring germ inability, high germination
rate, big and thick leaves, healthy growth of mulberry trees. Lake No. 7 sprouts late
spring, has large and thick leaves, and is resistant to viral and bacterial diseases. The
result was selected new breed called "72 - 1" has the advantage of spring germination
earlier than Lake one. The mulberry grows strong, has short internode, big and thick
leaves. Leaf yields were 23-41% higher than control varieties. The quality of the leaves
should be increased by 15% compared to the control varieties.
According to Wang Hong-Chi (1987) and Malli Krafunappa (1992), from the 1950s
through the use of crossbreeding between mulberry varieties with geographic origins,
Chinese researchers has selected many high yielding varieties such as No. 2, Chinese
Variety 5801, 6031 original Chinese Variety, Lake Seed No. 4 and Seed No. 11, etc.
1.2.1.2. Use of natural hybrid production to create seedlings
Cloned varieties besides various advantages described above, there are some
disadvantages such as the rate of plants are low because it depends on the ability of the
seed, planting time and some other techniques. The root system of the mulberry grows
poorly, so it is resistant to external conditions, especially in drought conditions. From
this fact, the breeders have turned to breeding for mulberry seed.
From the 1930s, some researchers from the Soviet Union such as Dien Ren Co,
Bytenko, Kytro-Ka-Rop (Ha Van Phuc, 2003) selected F1 hybrid dipterocarp seeds due
to the hybrid combination of local mulberry varieties with Japanese imported varieties,
the results have selected a number of suitable varieties grown in the north such as San
Nhit17 hybrid with Pionhski, the Lixi 5 hybrid with Pionhski, Bobetda hybrid with
Pionhski... For the southern climate is the San-nhit 15 hybrid with Pionhski (Ha Van

Phuc, 2003). Leaf productivity of hybrid mulberry varieties was higher than that of local
mulberry varieties from 28 to 54.20%. From 12 diploid F1 hybrids, Bulgarian breeder
Bulgarian PenKob and their colleagues selected the hybrid varieties No. 117 with No.
118 and No. 117 with No. 120 for leaf growth of 12.2 - 24.5 % compared with old
mulberry varieties (According to Ha Van Phuc, 2003).
Multi-seed F1 hybrid multiplication was also investigated later than diploid variety.
Zhen Fu- Zhao et al. (1999) have chosen to produce the second seed of the Guangdong
seedlings, which yields higher leaf yields than the dipterocarp cultivar. Better leaf
quality, the silkworms fed on this mulberry leaves have 9.22% more cocoon yield, the
number of eggs increased by 26.4%. In 1999, scientists from the Guangxi Mushroom
Research Institute (Zhu Fang Rong 2012, Luy fu Sheng 2011) created 10 pairs of
triploid varieties and two tetraploid hybrid varieties (4n = 56).
1.2.1.3. Use of mutagenic agents to produce mulberry varieties
Mutations in mulberry plants can also occur in natural conditions, but at a very low
rate. In the field of modern breeding, humans have used a number of physical and
chemical agents to generate genetic variations in many different crops.
In the field of breeding mutant mulberry, Japan and India have done earlier and
achieved some meaningful achievements, created some mutant varieties such as
IRB240-1, IRB240-5, S54 (Sugiyama T.1962, Katagiri and CS 1990). China has started
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to research in this direction since 1960s. Sichuan Mulberry Research Institute has used
the γ emitter from Co60 to harvest mulberry, which obtained broad adaptive mutation
7681, healthy mulberry plant (Lin Tai-Kang, 1987). Zhejin Research Institute for
Radiation Oncology has shown radiation on the Xinjiang iris tree and created the
tetraploid mutant (4n = 56) R81-1 and R81-2. This mutation is resistant to bacterial
disease and has good leaf quality. (Loguoshi et al., 2011).
Materials used to irradiate γ in mulberry trees are pollen, mulberry seed, strawberry
sprout and strawberry branch. The research shows that the use of cuttings and mulberry

plants are more effective mutation. According to Lin Tai-Kang and CS (2011), the
appropriate dose of x-ray irradiation in the mulberry tree was 10,000-11,000 R, the
strawberry variety was 10,000 R, the dried mulberry seed was 40,000 R, and the pollen
was 4,000 R
1.2.2. Research on the breeding of mulberry in Vietnam
1.2.2.1. Causing mutation
Mulberry growing in our country has a long history, but research on silkworm
breeding has only started in 1964 and we have been breeding mulberry since 1970. In
this period, they used a number of chemical agents such as Colchicines and irradiated γ
radiation on the seeds of the local mulberry breed of Ha Bac with doses ranging from
2,000 to 10,000 have received the mutation in the dose of 7,000 to 10,000 R. The
authors named these mutations 2R7, 1R10 and 2R10 (Ha Van Phuc et al., 1994). In the
2R10 form of mosaic, the variety had two types of leaves in the tree.
Nguyen Van Vinh (1996, 1997) also treated γ rays into cuttings of the Indian
variety VA186 and Bao Loc’s variety Bau Den with a dosage of 1 Krad to 10 Krad. The
author also invitro mulberry plants with a dose of 0.5 to 4.5 Krad. The result of this
study was the selection of 6 mutant lines from Bau Den mulberry variety namely B93-1,
B93-2, B93-3, B-16, B-17, B-18 and 5 lines from VA186 mulberry VA93- 5; VA93-8;
VA-12; VA-15 and VA-18 from VA-186. Just like the results above, these mutations are
only different from primitive varieties of leaf morphology, branch shoots, etc.
From the above results, the direction of selection of mutant mulch by irradiation
method γ was not oriented to the result of breeding for human purpose.
1.2.2.2. Creating the multi-harvest varieties of mulberry
From the combination of C71A mutation caused by colchicines treatment, in 1972,
author Ha Van Phuc and his colleagues have hybridized some local mulberry varieties
such as Chan Vit, Quang Bieu and Ngai to create new mulberry triploid varieties 7, 11
and 12 (Ha Van Phuc et al., 1994). The results of field trials in some localities in the
Northern Delta show that all three new mulberry varieties have the advantage that those
mulberry varieties grow stronger than the C71A tetraploid, the large leaf size and thicker
than the diploid varieties that are involved in the hybrids, Chan Vit, Quang Bieu and

Ngai. Leaf productivity of new varieties No. 7, No. 11 and No. 12 were 10-15% higher
than those of control. Due to the leafy foliage, leaf quality through silkworm rising gave
higher cocoon productivity (Ha Van Phuc, Nguyen Thi Tam, 1986). These new
mulberry varieties are well rooted so clonally propagation rate is over 90%. Results of
the trial showed that the variety No. 11 suitable for saline soils in the coastal areas, No.
12 varieties can grow in the mulberry growing areas of the Northern Delta. Only No. 7
varieties are resistant to Brassica and are well adapted to the Central Highlands such as
Lam Dong. According to the report of Lam Dong Son Lam Agricultural Experiment
5


Center (Phan Dinh Son et al., 1995), (Le Quy Tuyen - PhD in agriculture, Hanoi 2013),
No. 7 mulberry varietiy are being expanded in the Central Highlands such as Lam Dong,
Dak Nong, ..
In 2013, the Bao Loc-Lam Dong Agricultural Research Center conducted a trial of
hybrid mulberry TBL03 and TBL05 in some production areas in Dak Nong and Lam
Dong. Both breeds were formed by hybridization between local Lam Dong mulberry
varieties and imported varieties from Guangdong province, China. The results showed
that leaf yield of these new mulberry varieties was higher than that of control variety
VA201 from 13.7 to 22.4%, leaf quality was equivalent to that of Bau Den variety in
Bao Loc.
1.2.2.3. Creation of hybrid mulatto varieties (seeds)
Due to the disadvantage of cloned varieties (seed cuttings), since 1996, author Ha
Van Phuc has shifted to the direction of crossbreeding varieties by natural hybridization.
From 20 combinations of mulberry, Ha Van Phuc et al. (2002) selected three varieties of
mulberry hybrids: VH9 and VH13 both yielded higher leaf yields than those of mulberry
variety No. 12 12.5%, and 6% higher than that of Chinese imported mulberry seed (Ha
Van Phuc, 2003). In 2012, the seedlings of VH15 seedlings have high leaf yield, high
leaf yields are added to production (Vu Duc Ban, Ha Van Phuc et al.). Application to the
production of seed mulberry varieties have changed the farming practices in the planting

season. In the past, when growing varieties of cloned breeds, the planting season is only
in the mid-November to the end of December. But for the varieties of mulatto seed
multiplication, the planting season lasts from January to November. In addition,
mulberry varieties grown from seeds are very adaptable to climate and land conditions.
In summary, nearly half a century ago, the work of researching new mulberry
varieties in our country has been in the direction of breeding mulberry seedlings, diploid
multiplication clones with sexual duplication. In this thesis we will present the results of
selection of hybrid breeding mulberry
CHAPTER II. MATERIALS, CONTENTS AND METHODOLOGY
2.1 Study Materials
Research materials include: 12 imported varieties of mulberry, as follow:
- 9 varieties of Chinese origin are: K9, K10, K11, Q1, Q2, No. 2, No. 3, DB1, DB2.
- 1 mulberry varieties of Indian origin: IA.
- 2 varieties of Vietnamese origin: Ngai, Ha Bac.
- 10 combinations of F1 mulberry made by crossbreeding including VH18, VH19,
VH20, VH24, VH25, GQ1, GQ2.
- The reference variety mulberry VH13 is a new mulberry variety, approved by
the Ministry of Agriculture in 2006, which is made up of the hybrid variety IA
originating in India with the cultivar DB84 of Vietnamese origin.
- GQ2218 double-glazed silkworms and hybrid yellow silkworms (ĐSK × TQ).
2.2. Research content
2.2.1. Study on assessment of some mulberry varieties used as starting materials and
crossbreeding to create new hybrid combinations
2.2.2. Comparison and selection of new hybrid breeding
2.1.2.1 Study on the growth, composition and leaf productivity of hybrid combinations
2.2.2.2 Degree of infection of some major diseases
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2.2.3. Selected comparisons of some promising hybrid combinations

2.2.3.1. The study identified several factors that contributed to yield, leaf productivity
and levels of some key pests and diseases
2.2.3.2. Quality inspection of mulberry leaves through silkworm rising
2.2.4. Study the effect of cuttings on composition and leaf yield of GQ2
2.2.5. Adaptation of GQ2 in some ecological areas of Northern provinces
2.2.5.1. Experiment on some components of yield and leaf productivity of GQ2
2.2.5.2. Adaptive and stable assessment of the GQ2 variety
2.3. Methodologies
2.3.1. Evaluation of some mulberry varieties used as starting materials
- Implementation time: 2006 - 2008.
- Study location: Ngoc Thuy, Gia Lam, Hanoi on alluvial soil not accreted.
- Methodology: The mulberry seedlings were grown in the seed group at the
planting distance of 1.5m x 0.3m. Each variety planted 20 plants, not repeated. Planted
in 2006.
2.3.2. Natural hybrid combinations
- Time for implementation in January - March 2009
- Hybridization method:
+ The mulberry varieties selected to participate in crossbreeding are grown in the
group of mulberry varieties in Ngoc Thuy, Long Bien, Hanoi and Viet Hung, Vu Thu,
Thai Binh. The distance is 1.5m x 0.3m. Each variety planted 20 plants, not repeated.
Planting time is in 2006
- Regarding organic fertilizer: 25 tons/ha/year, once in December, NPK ratio is
16.5:7:7, 2000 kg NPK/ha/year, which is fertilized in January, April, July and
September.
+ In the winter of 2008, all the mulberries are not cut, only cut the tops from 1015cm, marked and hang the sign of the name.
+ In the spring of 2009, when the mulberry trees sprout the flower buds, using
paper bags cover the strong branches of the breed to isolate the intersection. After
observing that female and male flowers of hatching parent breeds reached more than
70%, cut the branches of the male flowers in isolation bags of the female flowers and tie
them to the branches. After 2-3 days of pollination, the flower stamens from white to

light yellow, then pocketed isolate, cut off a few female flowers due to late bloom so not
pollinated. Use the pollen wrap to wrap mulberry pollen and protect the berries. When
ripe berries are dark purple, take fruit, split strawberries and sow in the pot. The regime
of mulberry tree care in the pots of hybrid combinations is uniform. When the mulberry
tree grows in the height of 20-25cm, it will be planted in the field at each replication of
the hybrid.
2.3.3. Composite selection for hybrid combinations
- Implementation time: July 2009 to December 2011. Mulberry is planted since
May 2009. In 2010, mulberry trees were cut in winter crop, in 2011, cut in the summer.
- Study location: Ngoc Thuy, Gia Lam, Hanoi.
- Hybrids selection method: based on population selection, based on some
indicators of productivity, productivity and level of infection of some major diseases to
select the promising hybrid combinations.
- Experimental methods:
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The experiment was arranged in a randomized complete block of 3 replicates,
each repeating the planting of 40 trees on the same row. The planting distance is
1.20x0.3 m. The regimes of care for mulberry trees are uniform among varieties and
repeated.
2.3.4. Study on comparison of some promising hybrid varieties
After two years of research on 10 combinations of mulberry, it is based on the
results obtained on the criteria of composition, yield, leaf..., to select four most
promising hybrid combinations for basic testing.
2.3.4.1. Field experiment method
- Implementation time: July 2011 to December 2014.
- Location: Ngoc Thuy, Long Bien, Hanoi.
+ The experiment was arranged by the method of random block complete repeated
3 times, each time planted 30m2. The planting distance is 1.20x0.3 m. The regimes of

care for mulberry trees are uniform among varieties, repeated. Planted since May 2011.
2.3.4.2. Laboratory methods:
+ Silkworm evaluation of leaf hybrids of all spring, summer and autumn crops
was carried out. Spring and the second silkworm growing GQ2218, the summer
breeding of multi-hybrid silkworm (WK × China)
- Methods: 4 combinations of mulberry and control mulberry varieties were 5
treatments. Each formula feeds 3 silkworms aged 4, each with 300 silkworms.
Silkworms from 1 to 3 years old gave silkworms the same leaves of mulberry varieties
not in the experiment (mulberry No28). Silk worms from the age of 4 to the ripe
silkworm fed the leaves of hybrid combinations with the number of mulberry leaves are
weighed each meal to ensure the formula has the same amount of mulberry leaves. Fecal
work, silkworm care, sleep,... ensure uniformity in formulas. When the silkworm is ripe,
the silkweed will be shuffled into each replicate of the experiment.
2.3.5. Study on the effect of cuttings on composition and leaf yield of GQ2
Implementation time: 2015-2016, strawberry plantation in 2013.
Location: Ngoc Thuy, Long Bien, Hanoi.
Research Methods:
- The experiment was arranged by complete block method. Area of each cell is
2
30m , 3 times to lift. The experiment consists of 4 formulas:
1: Cut branches once on April 4 - 2015. Then pick leaves on 2/6, 18/6, 14/8 and
9/10.
2: Cut branches twice, the first time on 4 April 2015, the second on 18/6, then the
next on 14/8 and 9/10.
3: Cut branch 3 times, first on April 4, 2015, the second on June 18 th, the third on
August 14th, then picked the leaves on October 9th.
4: Foliage control (control).
2.3.6. Study on the adaptation of GQ2 variety in some parts of northern Vietnam
2.3.6.1. Leaf yield test
Implementation period: from 2012-2014.

- Materials: GQ2 mulberry variety, VH13 mulberry variety.
- Trial location:
+ Silkworm silkworm mills (Son La).
+ Tinh Cuong Cooperative, Cam Khe, Phu Tho.
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+ Co-operative Thieu Do, Thieu Hoa, Thanh Hoa.
- Methodology: According to the regulations of the Department of cultivation,
each place to grow two varieties of berries next to each other. Area of each variety is
1000, plant density is 40,000 trees / ha. The trial was planted in May 2012.
Care regime: organic fertilizer 25 tons / ha / year application once in December,
NPK ratio 16.5: 7: 7, quantity 2000 kg NPK / ha / year, application 4 times in months 1,
4, 7 and 9
2.3.6.2. Evaluation of leaf yield stability of GQ2
To evaluate the stability of new mulberry varieties, we used the preliminary data
processing method in the statistical software Excel 2013, and then processed according
to stable software by Nguyen Dinh Hien (2001).
2.4. Laboratory criteria and monitoring methods
- The method of monitoring the experiment criteria in the field is applied
according to branch standard (10TN 328-98) and TCVN 9485: 2013/Department of
Plantation and Rural Development and QCVN 01-147: 2013/BNNPTNT
CHAPTER III. RESULTS AND DISCUSSION
3.1. Study on evaluation of some mulberry varieties as starting materials and
natural hybrid multiplication
3.1.1. Morphological characteristics of some parts of the mulberry tree
Among mulberry varieties used as starting materials, there are differences in leaf
shape, head and leaf bottom, seed shape and peak state of the germ.
3.1.2. Some biological characteristics
- The time of spring germination among mulberry varieties in the experiment was

very different. Chinese imported mulberry varieties have a longer germination period
than the local varieties from 4-12 days, and Indian mulberry varieties are only two days
earlier.
- The number of germination sprouts on the plants of Chinese mulberry varieties
is 6-18% higher, the number of sprouts is 7-54% higher. Indian mulberry varieties in
both indices are lower than Ha Bac varieties of 5-9% and mulberry varieties do not
differ much from Ha Bac varieties.
- The time to blossom in the Chinese mulberry varieties is also 3 to 12 days earlier
than the Ha Bac variety. Two varieties IA and Ngai are the same as Ha Bac varieties.
3.1.3. Leaf productivity of mulberry varieties
- Mulberry varieties originated from China due to the advantage of high number
of sprout and useful sprout, high leaf size and mulberry tree, the leaf productivity was
higher than that of Ha Bac varieties -26%, imported Indian mulberry varieties higher
than 5%, mulberry varieties did not differ from the control varieties in Ha Bac (Figure 1
shows this result)

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Figure 3.1. Leaf productivity of mulberry varieties compared to control varieties
3.2. Natural hybrid combinations
Based on the characteristics and components of productivity and leaf yield of the
hybrid varieties, we have crossbreed between mulberry varieties to form hybrid
combinations
No.
Mother mulberry
Father mulberry
Hybrid complex
1
K10

Q2
VH18
2
K9
Q2
VH19
3
IA
Q2
VH20
4
ĐB1
Q2
VH21
5
Q1
K11
VH22
6
Q1
Ngai
VH23
7
Q1
ĐB2
VH24
8
IA
Ngai
VH25

9
No. 3
Q2
GQ1
10
Q1
No2
GQ2
Seeds obtained from hybrid combinations were sown in pots, when plants taller
than 20 cm were planted in comparative experiments for selection.
3.3. Selected comparison of new hybrid combinations
3.3.1. Characteristics of germination
3.3.1.1. Germination in the spring
- Germination time: Determine the time of spring germination to determine the
spring time of spring silkworm. The spring and autumn seasons in the Red River Delta
are two seasons appropriate for the production of high-yield cocoon productivity and
high quality cocoon. The results of two-year follow-up showed that hybrid combinations
of Guangxi and Guangdong, China had higher incidence of early spring emergence than
the control variety VH13 for 3-5 days. Thus, the early germination characteristics of the
mulberry tree were dominant.
- The effective number of hybrid combinations ranged from 33.05 to 57.54
germination, and the control variety VH13 had 37.8 germination. Thus compared with
10


the control varieties hybrid VH25 hybrid exceeds 52%, VH18-27%. GQ2- 16% and
VH19-12%.
3.3.1.2. Germination in the autumn
In the autumn season, the number of germination germs of hybrid combinations
ranged from 30.60 to 53.70 germination and effective germination was 11.67 to 16.02

germination. The control variety VH13 has the number of germination germs of 35.30
germination, the effective germination number is 14.25 germ. Compared to the hybrid
variety VH13, crossbreds had higher yields than the control varieties including GQ2 12.42%, VH21-8.98%, GQ1 - 7.09%, VH19-6, 74%. The remaining combinations are
equal to or lower than the control varieties.
3.3.1.3. Some indicators on leaves
- Leaf size includes leaf length and width. Leaf size is related to the yield of
mulberry leaves, while also affecting labor productivity when harvesting leaves.
Table 3.1. Average size of mulberry leaves in 3 crops of hybrid combinations
(Unit of account: cm, %)
% compared to control varieties
Hybrid
Leaf length (cm) Leaf width (cm)
complex
Length
Width
VH18
VH19
VH20
VH21
VH22
VH23
VH24
VH25
GQ1
GQ2
VH13 (đ/c)

17,14±0,21
16,85±0,16
15,25±0,19

16,49±0,18
17,46±0,20
17,78±0,26
16,49±0,23
15,45±0,15
17,96±0,18
17,94±0,20
15,25±0,15

14,60±0,12
14,±0,12
13,73±0,11
14,50±0,13
14,97±0,17
14,90±0,16
14,54±0,14
13,63±0,12
15,36±0,17
15,84±0,14
14,00±0,13

104
104
98
104
106
106
103
97
110

113
100
(Data in 2010)
The data in Table 1 shows that except that the VH20 and VH25 hybrid
combinations have the same leaf size as the control mulch VH13, the remaining hybrid
combinations have a larger leaf size than the control. In which the GQ1 and GQ2
hybrids had the largest leaf size, the leaf length was 18% higher than the control variety,
the leaf width increased by 10-13%, followed by the VH22 and VH23 hybrid leaf
lengths increased from 14-17%, width increased by 6%.
- Number of leaves per meter of branch:
The number of leaves per meter depends on the length of internode on the branch,
the longer the internode, the fewer the number of leaves per meter. The data obtained in
the experiments show that hybrid combinations of VH20, VH25 and VH24 have more
leaf numbers than the control varieties of 3.26-8.28%, GQ1, GQ2, VH21, VH18 all had
3-14.6% fewer leaves, indicating that these hybrid combinations have long internodes.
- Leaf mass per meter:
The leaf mass per meter of sprouts reflects the branching length, leaf size and
thickness and is closely related to leaf productivity. In 10 hybrid combinations, VH25
11

112
110
100
108
114
117
108
101
118
118

100


had lower leaf volume than the control sample of 6%. The remaining hybrid
combinations have leaf mass per meter increase from 6-12% compared to control
varieties, of which hybrid GQ2 increased 20%, followed by GQ1, VH19 and VH20
increased from 13-17% The remaining hybrid combinations increased from 4-7%. The
hybrid combinations have higher leaf weights per meter than control varieties due to
their large leaf size as shown in the table above.
3.3.3. Leaf yield
Leaf yield is the composite indicator of the components of leaf productivity, to
increase the total income per unit of area that has to improve cocoon production. The
most important factor affecting cocoon production is the yield of mulberry leaves.
Table 3.2. Yield of hybrid mulberry leaves of
Unit of Account: kg/100m2, %
Name of
Spring harvest Summer harvest Fall harvest
Total
CSSS
hybrid species
VH18
88.94
213.68
73.29
375.91
118.42
VH19
68.60
222.35
58.40

349.35
110.06
VH20
76.26
199.83
55.90
331.99
104.57
VH21
56.43
214.84
41.93
313.20
98.67
VH22
59.68
196.94
48.48
305.10
96.12
VH23
57.83
184.98
52.47
295.28
93.02
VH24
60.91
207.28
46.28

314.47
99.07
VH25
70.64
195.68
48.36
314.68
99.13
GQ1
76.78
213.63
51.80
348.47
109.78
GQ2
79.78
210.00
74.28
364.69
114.89
VH13
69.51
189.35
58.57
317.43
100.00
CV(%)
9.77
7.29
9.57

LSD(0,05)
8.69
10.06
6.78
Data in 2010
Total annual yield of hybrid combinations ranges from 295.28 kg to 375.91 kg over
100m2. Among them, the highest yield was VH18 and GQ2, which are 375.91 kg and
364.69 kg respectively, followed by hybrid VH19 and GQ1 with 349.35 kg and 348.69
kg respectively.
Productivity of Mulberry leaf
(% compared to control variety)

Name of cross
combinations

Figure 3.2. % leaf yield compared to the control of cross combinations
12


3.3.4. Infection degree of dangerous diseases
- Phyllactinia moricola usually occurs in low temperature and high humidity period.
Diseases cause the leaf quality to decrease and the consumption ratio of mulberry leaves
increases for cocoon. The results show that all cross combinations and mulberry
varieties are infected with Phyllactinia moricola but differed in severity. On average of
spring and autumn crops, the infection of Phyllactinia moricola disease in cross
combinations ranges from 13.80% to 19.43%, the disease index is 4.85-8.64%, and the
control variety VH13 has the corresponding figures 12.99% and 4.02%, respectively.
Thus, the control variety VH13 is less susceptible than cross combinations.
- Level of virus infection
Virus is the most dangerous disease for mulberry plants since there is no

medication or treatment available, but the main measure to limit the disease is the
selection of mulberry varieties and cultivation methods. The results of the spring and
autumn crops show that all cross combinations and the control variety are infected, of
which VH20 and VH25 have the highest rates of disease which are 13.48% and
13%.87% respectively, VH22 and VH23 have the same disease rate as the control
varieties, the remaining cross combinations have lower rate.
Degree of Virus infection
((% compared to control variety)

Name of cross
combinations

Figure 3.3. Percentage of mulberry plants infected with Virus disease in cross
combinations compared to the control variety
Based on the synthetic results of productivity and leaf yield indexes, we selected
four promising cross combinations, VH19, VH20, GQ1 and GQ2 to conduct a basis and
detailed evaluation of advantages and disadvantages of each variety.
3.4. Comparison and selection of promising cross combinations
3.4.1. Factors contributing to the yield of mulberry leaves
- Germination time in Spring crop
In the spring of 2013, from January 8 to 13, the mulberry trees of the cross
combinations began to germinate. According to calculations, it was not until January 22
that GQ1 and GQ2 cross combinations reached over 50% germination, which is the time
of germination of these two cross combinations. VH19 and VH20 have their germination
on January 28. As for the control variety VH13, the germination time is on February 4.
Thus, GQ1 and GQ2 have their germination time 12 days earlier compared to the control
variety and 6 days compared to VH19 and VH20. This result reaffirms that the early
germination characteristics of the dominant mulberry varieties in hybrid mulberry trees.
13

- Size of leaf blade
Our collected data show that in all three crops including spring, summer and
autumn, leaf length and width of hybrid combinations were significantly higher than that
of the control variety VH13. The average leaf length and width in 3 crops of cross
combinations in comparison with the control variety are shown in Figure 3.4.

% width
compared to
control variety
% length compared
to control variety

Figure 3.4. Average leaf length and width in 3 crops of cross combinations in
comparison with the control variety
The data in Figure 4 shows that GQ2 has the largest leaf size; its length and width
exceed the control variety with 13% and 8% and VH19 with 13% and 9% respectively,
followed by VH20 with 11% and 4%, and GQ1 with 7%.
- The number of leaves in 500g
Table 3.3. The number of leaves in 500g
(Unit: leaf, %)
The number of leaves in 500g in 3
%
crops
compared
Cross
Average of
No.
to the
combination

3 crops
control
Spring
Summer
Autumn
variety
1
VH19
239.33
174.00
366.00
259.78
93
2
VH20
235.33
1.67
415.00
268.67
96
3
GQ1
232.00
140.30
359.67
244.00
87
4
GQ2
243.00

142.00
294.00
226.30
81
5
VH13
251.00
241.33
345.67
279.33
100
CV (%)
7.71
7.29
7.02
LSD 0,05
2.88
16.69
33.52
The data in the table clearly indicate that leaves of cross combinations are large, so
the number of leaves in 500g in 3 crops spring, summer and autumn is less than the
control variety. GQ2 has fewer leaves than the control variety at 19% and less than GQ1
at 13%. The remaining two cross combinations are less than 4-7%
- Stem growth
Stem growth is the most influential factor in the yield of mulberry leaves. This
indicator impacts on some factors such as soil fertility, care regime, rainfall,
temperature, etc. in which mulberry varieties are significantly affected. The stem growth
is shown in tree height, stem diameter and total length of stem.

14

Table 3.4. Some indicators of stem
(Unit: cm, stem, %)
Tree
Cross
No.
height
combination
(cm)

1
2
3
4
5

VH19
VH20
GQ1
GQ2
VH13

264.67
258.40
274.62
272.27
250.73

Total length of stems

Number
on a tree (cm)
Number
Average
of
Diameter
of firstTotal stem
%
height of
second- of firstlevel
length / compared
stem
level level stem
stem
tree
to the
(cm)
stem
(cm)
(stem)
control
(stem)
variety
1940.73
108
102.30
7.47
11.60
1.85
1836.50

103
90.02
7.80
12.60
1.96
1907.45
107
92.19
8.15
12.54
1.95
1996.83
112
104.53
7.30
12.80
1.98
1782.97
100
106.76
5.90
10.80
1.70

Data in table 3.4 shows that the growth rate of germ in 3 crops of cross
combinations is higher than that of the control variety. Trees of the four cross
combinations are higher than those of the control variety. The number of stems and the
stem length of the cross combinations are higher, so the total length of stems in all four
cross combinations is higher than that of the control variety at 2-12%. The total length of
the biggest stem is 1996.13cm, exceeding the control variety with 12%, followed by

VH19 and GQ1 increasing 8% and 7% respectively.
3.4.2. Leaf yield and quality of promising cross combinations
The data in the table indicate that in the spring and summer crops, the yield of cross
combinations is higher than that of the control variety, but only GQ2 and VH20 cross
combinations are higher in the autumn crop. It is most noticeable that the yield of cross
combinations is high in spring crop, in which GQ2 reaches the highest with 89.41 kg /
100m, followed by GQ2 - 79.52kg / 100 m, the control variety only reaches 65. 80kg.
Spring and autumn crops have weather that is most suitable for bivoltine silkworm race
that produce high-quality cocoon. Thus, mulberry has high yield in spring and autumn
crops, which is significant for improving the economic efficiency of mulberry
production. The comparison of annual yield of cross combinations with the control
variety is shown in Figure 3.6.
Figure 3.5. Leaf yield in crops of cross combinations in 2014
(Unit: kg, %)
2
Amount of leaves in kg/100 m
Cross
Total amount
No.
combination
per year (kg)
Spring
Summer
Autumn
1
VH19
74.16
236.11
44.69
354.96

2
VH20
68.07
242.22
59.77
370.06
3
GQ1
79.52
224.68
50.83
354.68
4
GQ2
89.41
234.44
65.90
389.75
5
VH13
65.80
208.51
55.44
329.75
CV (%)
11.70
6.90
8.40
LSD 0,05
10.54

12.49
8.75
-

15


Leaf yield
% compared to the control variety

Cross combinations

Figure 3.6. Comparison of four-year average yield of cross combinations
GQ2 has the highest leaf yield, exceeds the control variety with 18%, followed by
VH19 with 8%, and GQ2 with 6%. VH20 is only 3% higher.
Table 3.6. Leaf yield of cross combinations in 2012-2015 in Ngoc Thuy-Long Bien Hanoi
(Unit: Kg/100m2)
%
Name of
compared
Average
Cross
2012
2013
2014
2015
to the
of 4 years
combinations
control

variety
VH19
347.70
322.91
354.96
408.81
358.60
110.61
VH20
311.92
318.00
370.06
384.06
336.01
103.64
GQ1
305.94
347.70
354.68
441.05
354.84
109.45
GQ2
331.00
369.90
389.75
409.85
375.24
115.74
VH13(control) 310.23

307.00
329.95
349.63
324.20
100
CV (%)
6.60
5.50
4.10
6.80
LSD 0,05
20.01
24.60
17.85
31.36
Data of leaf yield over 4 years followed up show that only GQ2 and VH19 have
higher yield than VH13 with the reliability level of 95% in 2012; GQ1 and VH20
show no significant difference from the control variety. In 2013, only two GQ1 and
GQ2 have yield reliable differences compared to control variety. But in 2014 and
2015, the yield of all four cross combinations is higher than the control variety with
the reliability level of 95%. On average, GQ2 has the highest leaf yield, 16% higher
than the control variety, and 11% higher than VH19. The remaining two cross
combinations are lower than GQ2 4-9%.
- Leaf quality is a reflection of chemical compositions of mulberry leaves, which
gives silkworms producing high-quality cocoon. In order to evaluate the quality of
leaves, researchers often use biochemical method which analyze leaf nutrient and
biological method which is based on the results of silkworm rearing. In these two
methods, biological method is more common and accurate (Ha Van Phuc, 2003). We
have been raising silkworms in 3 crops a year, bivoltine silkworm race is raised in
spring and autumn crops, and multivoltine silkworm race is raised in summer crop .

16


Table 3.7. Cocoon productivity of cross combinations
(Unit: gram, %)
Spring crop
Summer crop
Autumn crop
%
%
%
Cross
Net
Net
Net
No.
combination amount compared amount compared amount compared
to the
to the
to the
(gram)
(gram)
(gram)
control
control
control
1
VH19
491.68
106.78

245.44
100.01
367.29
96.07
2
VH20
460.32
99.97
256.77
104.12
371.48
97.17
3
GQ1
483.14
104.93
248.22
100.65
393.41
102.91
4
GQ2
471.53
102.41
252.95
102.81
386.62
101.13
5
VH13

460.45
100.00
246.62
100.00
382.30
100.00
CV (%)
3.90
1.20
1.00
LSD 0,05
35.16
5.56
7.31
Data in Table 3.7 show that cocoon productivity obtained in cross combinations in
three crops is different from that of the control variety VH13, but this difference is not
significant.
The evaluation of cocoon quality by indicator of cocoon rate and some
technological parameters of silk yarn also have similar results as cocoon productivity.
The difference in cocoon quality between cross combinations with VH13 is not
significant at 95% reliability level.
3.4.3. Infection level of major pests
3.4.3.1. Phyllactinia moricola disease in mulberry leaves
North Delta has high humidity, so phyllacdinia moricola usually develops in spring
and autumn seasons. This disease reduces the quality of mulberry leaves, increasing the
consumption of mulberry leaves for cocoon weight.
Table 3.8. Infection degree of phyllactinia moricola in spring crop of cross
combinations
Spring crop 2013
Spring crop 2014 2-year average

Cross
No.
combination
Rate
Indicator Rate Indicator Rate Indicator
1
VH19
16.65
6.70
9.12
4.50
12.88
5.60
2
VH20
14.24
7.25
7.40
3.70
10.82
5.44
3
GQ1
14.85
6.15
10.18
5.49
12.51
5.82
4

GQ2
12.35
5.70
8.20
4.05
10.27
4.87
5 VH13(control)
6.12
2.87
5.70
3.40
5.91
3.13
The results show that in the spring crop of the two years, the disease rate and
indicator in the four cross combinations are higher than that of VH13, indicating that
cross combinations are hypersensitive to the disease..
3.4.3.2. Level of Virus infection
Production reality shows that all local varieties of mulberry, new and imported
varieties are infected with virus disease with various level.

17


Table 3.9. Degree of virus infection in cross combinations
(Unit: tree, %)
No.

Cross
combination

Number
of
inspected
trees

Summer crop
Number
%
of
infected
infected
trees
trees

Autumn crop
Number
%
of
infected
infected
trees
trees

Annual average
Number
%
of
infected
infected

trees
trees

1
2
3
4
5

VH19
120
15
12.50
11
9.16
10.80
72
VH20
108
12
11.11
9
8.83
9.70
64
GQ1
99
10
10.10
11

11.11
10.60
70
GQ2
108
11
10.18
13
12.73
11.45
76
VH13(control)
96
13
13.54
16
16.66
15.10
100
Average data obtained during the summer and autumn crops show that the
percentage of mulberry plants infected with virus disease in the four cross combinations
is 24-36% lower than the control variety. We predict that this difference derives from the
damage extent due to stem-eaten pests which we will present below.
3.4.3.3. Damage level due to stem-eaten pests
There are many kinds of stem-eaten pests but we observe that the northern type is
Apriona Germany Hope. The mulberry tree eaten by pests at the top of the tree, stem and
stump are hollowed out so mulberry trees age quickly.
Table 3.10. Damage level due to stem-eaten pests
(Unit: trees, %)
Number of damaged trees

Number
Cross
of
Number of
% damaged tree
No.
% damaged
combination inspected damaged
compared to control
tree
tree
tree
variety
1
VH19
120
47
39.16
62
2
VH20
108
51
47.22
74
3
GQ1
99
40
40.40

64
4
GQ2
108
37
34.25
54
5
VH13(control)
96
61
63.54
100
The data in Table 3.10 show that all four cross combinations have a lower
percentage of mulberry trees damaged by stem-eaten pests compared to the control
variety with 28-46%. This difference is due to VH15 mulberry trees of triploid type (3n
= 42), while the four cross combinations are diploid (2n = 24). According to author Ha
Van Phuc (1994), the thickness of the wood in the stem, branches of multiplied mulberry
varieties are much thinner than the diploid variety, but the heartwood is thicker.
Therefore, the stem-eaten pests love eating multiplied mulberry trees.
Based on the results of the comparison of the four promising cross combinations
described above, we have identified that GQ2 has more advantages and has been
recognized by the Scientific Council of the Ministry of Agriculture and Rural
Development and allowed for trial production in mulberry fields of the Northern Delta.
18


3.5. Study on the effect of branch pruning on factors contributing to productivity
and yield of GQ2 mulberry leaves
Based on the results of the experiments mentioned above, the regeneration

characteristics of the new diploid cross combinations, including GQ2 are better than
those of VH13, displayed in the number of germination, effective germs after pruning in
years, all crops with higher productivity. This characteristic of GQ2 is favorable for the
application of pruning methods instead of leaf picking and is also applied to silkworm
rearing to reduce labor.
3.5.1. Impact of branch pruning on leaf growth rate and budding
Table 3.11. Impact of pruning 3 times to grow mulberry trees

Date-Month
Formula

Pruning 1
time
Pruning 2
times

Pruning 3
times

Leaf
picking
(control)

Indicator
Length of
germ (cm)
Number of
leaves (leaf)
Length of
germ (cm)

Number of
leaves (leaf)
Length of
germ (cm)
Number of
leaves (leaf)
Length of
germ (cm)
Number of
leaves (leaf)

24-9

(Unit: cm,leaf, %)
Compared
BQ/
to control
date
variety

4-9

9-9

14-9

19-9

0.00

2.15

8.05

13.73 16.94

0.85

185

0.00

2.00

3.50

4.70

6.10

0.31

207

0.00

2.05

9.22

12.74 15.93

0.80

174

0.00

1.93

3.40

4.27

5.07

0.25

167

0.00

3.66

15.93

26.71 36.13

1.81

393

0.00

1.93

4.27

6.33

7.93

0.40

270

0.00

1.79

5.99

8.67

9.11

0.46

100

0.00

1.60

2.73

3.13

3.13

0.15

100

Our data obtained upon pruning one time and two times are similar to pruning three
times, if the increase in germ length, the number of leaves increases are relied on the
number of branch pruning, the number of branch pruning increases the rate of growing
germ length and the number of leaves increasing compared with the leaf picking as
shown in Figure 3.7

19


Process of increasing germ length after 3 times of pruning

Germ length

Leaf picking
Pruning 1 time

Pruning 2 times
Pruning 3 times

Time
(date/month)

h)

Figure 3.7. Process of increasing germ length after 3 times of pruning
The difference in growth rate and emergence of leaf between cuttings and leaf
picking is due to the distance from the resin path from leaf to root and from root to leaf.
This distance is shorter in mulberry trees having branch pruning, allowing the germs and
leaves to receive nutrients faster, so the growth rate is faster.
3.5.2. Effect of branch pruning to size and thickness of leaf blade
The bigger number of branch pruning is, the smaller the leaf length and width are;
the formulas of branch pruning 1 time and 2 times have no difference, only reducing leaf
length 3%, and leaf width 6%. For formula of 3-time branch pruning, this indicator
decreases by 11% and 15% respectively.
Table 3.12. Amount of 100cm2 leaves of the experimental formulas
Indicator
Amount of 100 cm2 leaves
Time
Formula

After the 1st After the After the 3rd
Average
pruning
2nd pruning
pruning

Compared to
control
variety (%)
96
88
84
100

1st pruning
2.30
2.22
1.95
2.16
nd
2 pruning
2.36
1.66
1.82
1.94
rd
3 pruning
2.32
1.63
1.60
1.85
Leaf picking
2.75
2.10
1.78
2.21

(control)
The thickness of leaf blade is determined by amount of 100cm2 leaf area, the larger
the amount of leaf blade is, the thicker it is. Data shown in Table 12 indicate that the
bigger the number of branch pruning is, the smaller the amount of leaf blade is in
comparison with control leaf picking formula. Thus the method of harvesting mulberry
leaves by branch pruning reduces the size and thickness of leaf blade because branch
pruning causes mulberry trees to lose an amount of nutrients accumulated in branches.
Moreover, according to Lin Shou Kang (1999), roots, hairs of mulberry trees
temporarily die after branch pruning, then recover after a while. Hence, the function of
20


nutrient in taking of roots is interrupted. Whether roots' recovery time is fast or slow
depends on pruning time and number of leaves left on stems.
3.5.3 Effect of branch pruning on leaf yield
Table 3.13. Productivity of experimental formulas
Indicator
Leaf yield (kg/100m2)
Converted
ha (ton)
Time (date - month) 4 - 4 2 - 6 18 - 6 21 - 7 1 4- 8 9 - 10
Total
ab
Pruning 1 time
30.70 28.90 20.70 71.7 134.1 86.1 372.23
37.22
ab
Pruning 2 times
32.50
136.2

101.5 75.6 345.47
34.58
b
Pruning 3 times
31.90
128.3
114.4 57.4 332.03
33.20
a
Leaf picking (control) 11.20 61.70 42.0 66.7 132.1 81.3 395.17
39.52
CV (%)
6.86
LSD0,05
49.52
Branch pruning thus reduces leaf yield by 6% to 16% compared to leaf picking,
depending on the number of pruning time. Based on the results of statistical analysis,
leaf yield in single and double pruning formulas compared to leaf-picking are not
significant, while double and triple punning formulas are significantly different in leaf
yield with 95% reliability level.
The most effective method of harvesting mulberry leaves by branch pruning is to
reduce labor in leaf picking and silkworm rearing stages. To overcome the disadvantages
of this technique, the density of mulberry plantation, cutting method and appropriate
care need to be studyed.
3.6. Study on the adaptation of GQ2 in some areas of Northern provinces of Vietnam
3.6.1. Testing on leaf yield
We have planted GQ2 mulberry varieties in three localities: Moc Chau (Son La),
located in the northern mountainous area, Thieu Do commune (Thanh Hoa Province),
located in the northern central region and Tinh Cuong Commune, Cam Khe District
(Phu Tho) belonging to the Red River Delta.

GQ2 has the number of leaves per meter of branch in 3 trial locations smaller than
the control variety, is it has longer node, while its leaf length and width are bigger.
Therefore, the leaf amount per meter of branch is also higher than the control variety.
This result is consistent with the comments in the comparative experiments above.
Table 3.14. Some indicators on leaves
(Average in 2015)
Unit: leaf, gam, cm
Number of P leaves/m
Leaf dimensions (cm)
leaves/m
Variety
Location
branch
Length
Width
branch
Thanh Hoa
24.80
60.70
18,40±0,70
15,40±0,40
Phu Tho
25.60
65.59
21,10±0,60
18,70±0,25
GQ2
Moc Chau
26.870
63.20

20,30±0,40
16,80±0,30
Average
25.70
63.20
19,93±0,50
16,60±0,30
Thanh Hoa
26.70
54.70
16,50±0,40
14,30±0,40
Phu Tho
26.90
57.80
18,70±0,30
15,60±0,60
VH13(control)
Moc Chau
28.20
58.40
17,80±0,20
15,80±0,30
Average
27.30
56.96
17,60±0,30
15,10±0,40

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Table 3.15. Leaf yield of GQ2 in testing locations
Leaf yield (tons/ha)
Location

Variety

2014

2015

Average

Unit: ton/ha
%
compared
to breed
113,60

GQ2
37,06
38,20
37,60
VH13(control)
32,40
33,87
33,10
GQ2
39,74

40,80
40,30
119,20
Phu Tho
VH13(control)
33,23
34,40
33,80
GQ2
33,80
35,90
34,80
112,90
Moc Chau
VH13(control)
30,20
32,10
31,10
Although the three localities conducted variety testing have different soil fertility
and climatic conditions, the leaf yield of GQ2 is higher than that of VH13. In Thanh
Hoa, the average number of GQ2 variety exceeds 13%, Phu Tho with 19.20% and Moc
Chau (Son La) with 12.90%. On average, the yield of mulberry leaves GQ2 is 15%
higher than that of the control variety.
Table 3.16. Infection degree of phyllactinia moricola, rust and virus
Unit: %
Phyllactinia
Rust
moricola
Variety
Characteristics

Virus
Rate
Indicator
Rate
Indicator
Thanh Hoa
20.40
4.85
6.10
3.10
10.77
Phu Tho
24.90
6.80
7.70
3.50
9.32
GQ2
Moc Chau
40.10
8.40
8.90
4.30
11.20
Average
28.46
6.70
7.60
3.63
9.08

Thanh Hoa
26.30
3.10
4.70
2.40
14.32
Phu Tho
18.90
4.20
5.30
2.50
10.22
VH13(control)
Moc Chau
27.80
5.40
6.40
3.20
12.21
Average
21.00
4.20
5.46
2.70
12.25
Data obtained on infection level in the three locations show that the GQ2 has higher
rate and indicator of disease in all three localities than VH13 in terms of Phyllactinia
moricola. Particularly in Moc Chau, the rate of disease is really high (40.10%) since the
climate here has suitable temperature and humidity for the development of fungal
diseases from May to September. This data show that if the extension of GQ2 growing is

conducted in Moc Chau, the application of measures to prevent Phyllactinia moricola
disease is needed. For rust disease, the difference between the two varieties is not large.
For viral disease, VH13 has higher disease rate than GQ2.
3.6.2 Evaluation of leaf yield's stability of GQ2
The new high-yield mulberry varieties are a target of breeding, but at the same
time new varieties need to be stabilized in terms of leaf yield during different crops and
ecological regions. Mulberry is a perennial crop that lasts 20-30 years, so the stability of
leaf yield will contribute to the high economic efficiency of the mulberry industry.
Based on the results obtained on leaf yield of the new mulberry variety- GQ2, in each
Thanh Hoa

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crop of the year, in each year and in three trial locations, we affirm that the adaptability
and stability of leaf yield are as follows:
Table 3.17. Indicators of adaptation and stability of leaf yield of GQ2 through 3
crops in Thanh Hoa, Phu Tho, Moc Chau
Indicators
Average Regression
Indicator Reliability
of
Crop
Variety
productivity coefficient Ttn
of
level S2di
stability
(ton/ha)
(bi)

adaptation
(P)
(S2di)
11.11
0.523
0.915
0.007
1.066
0.617
GQ2
Spring
VH13(control)
10.387
1.477
0.915
0.007
1.066
0.617
16.761
0.829
0.783
0.178
1.807
0.919
GQ2
Summer
VH13(control)
14.471
1.171
0.783

0.178
1.807
0.919
9.76
0.989
0.057 -0.028
0.820
0.428
GQ2
Autumn
VH13(control)
9.153
1.011
0.057 -0.028
0.820
0.428
The variety has a stable regression coefficient (bi), the indicator of adaptation is 1
and the stability indicator S2di is 0. The data in table 3.64 show that GQ2 has the
regression coefficients (bi)  1 and the stability indicator (S2di)  0 but they are not
significant. Thus, GQ2 variety is determined to have high leaf yield, stable in spring,
summer and autumn crops in the Red River Delta.
CONCLUSION AND PROPOSALS
1. Conclusion
1.1 Results of the evaluation research on some mulberry varieties used as starting
materials
In the beginning of the crossbreeding, imported mulberry varieties from
Guangdong and Guangxi China all had outstanding advantages such as early spring
germination, number of germs and number of effective germs. The size of leaf blade is
large, the average leaf length and width of the varieties are higher than the local variety
Ha Bac, with an increase of 8-32% and 5-27% respectively. The IA variety of India is

equivalent to Ha Bac mulberry variety.
The average leaf yield of varieties imported from Guangdong, Guangxi, China is
12-20% higher than that of Ha Bac variety, and only 5% higher than the IA variety of
India.
Based on the results of the study, we have combined parent breeds for
crossbreeding to create 10 cross combinations.
1.2. Using crossbreeding to combine hydrid pairs between seven mulberry
varieties of female flowers and six mulberry varieties of male flowers to create 10 cross
combinations of VH18, VH19, VH20, VH21, VH22, VH23, VH24, VH25, GQ1 and
GQ2.

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