Báo cáo nghiên cứu khoa học " Strengthening Capacity in Forest Tree Seed Technologies Serving Research and Development Activities and ex-situ Conservation " pptx

A greater emphasis is placed on the breeding, testing and selection of the Elite Population each generation, because the clones derived from the Elite Population serve as the clones for

Ministry of Agriculture & Rural Development

Collaboration for Agriculture and Rural Development

Strengthening Capacity in Forest Tree Seed Technologies Serving Research and Development Activities and ex-situ Conservation

TABLE OF CONTENTS

GENETIC IMPROVEMENT PLAN FOR 1

EUCALYPTS IN VIETNAM 1

EXECUTIVE SUMMARY 4

1 Introduction and Background 6

1.1 Species-Provenance Trial in the Lowlands of Central Vietnam 6

1.2 Species-Provenance Trials in the Southern Highlands 8

1.3 Current Eucalypt Species in Reforestation Programs 8

2 Genetic Improvement of Eucalyptus species in Vietnam 9

2.1 Candidate Plus Tree Selection and Clonal Testing 9

2.2 Development of Eucalypt Hybrids 9

2.3 Open Pollinated Progeny Trials Developed into Seedling Seed Orchards 10

2.4 The Need for a Genetic Improvement Strategy and Plan 10

3 Basic Elements of Planning Tree Improvement 11

3.1 Need for a Well Defined Strategy and Plan 11

3.2 Clear Objectives 11

3.4 Selection and Mating 12

3.5 Personnel and Funding 13

3.6 Hybrid breeding 13

4 Determinants of a Breeding Strategy 15

4.1 Breeding Objective 15

4.2 Economic Weights 15

4.3 Deployment Objective 15

4.4 Selection Criteria and Traits for Selection 16

4.5 Genetic Resources 16

5 Breeding Strategy 20

5.1 Outline of Breeding Strategy 20

5.2 Expected Genetic Gains 21

5.3 Breeding Population 22

5.3.1 Structure of the Main Population 22

5.3.2 Structure of the Elite Population 22

6 Outlines of Improvement Plan 23

6.1 Eucalyptus urophylla 23

6.1.1 Main breeding population and seedling seed orchard 23

6.1.2 Elite population and clone bank/clonal seed orchard 23

6.1.3 Selection of candidate trees for the second generation 28

6.1.4 Conversion of trials to seed orchards 29

6.2 Eucalyptus pellita 29

6.2.1 Main breeding population and seedling seed orchard (optional) 30

6.2.2 Elite population and clone bank/clonal seed orchard 30

6.2.3 Selection of candidate trees for the second generation 32

6.2.4 Conversion of trials to seed orchards 33

6.3.1 Main breeding population and seedling seed orchard 34

6.3.2 Elite population and clone bank/clonal seed orchard (optional) 34

6.3.3 Selection of candidate trees for the second generation 36

6.2.4 Conversion of trials to seed orchard 36

6.4 Eucalyptus grandis 37

6.4.1 Main breeding population and seedling seed orchard 37

6.4.2 Elite population and clone bank/clonal seed orchard (optional) 37

6.4.4 Conversion of trials to seed orchard 39

6.5 Eucalyptus camaldulensis 40

6.5.1 Main breeding population and seedling seed orchard 40

6.5.2 Cloning of the progeny trial 40

6.5.3 Establishment of clonal trials 41

6.5.4 Conversion to clonal seed orchard 41

7 Program Review 42

References 43

EXECUTIVE SUMMARY

The Government of Vietnam (GoV) has embarked on a massive tree plantation program By

2010 it plans to establish an additional 5 million hectares of plantations on bare hills and degraded forest lands, over and above the current plantation estate of one million ha, plus the equivalent of more than 50,000 hectares of community forests in scattered plantings This dramatic expansion requires equally dramatic increases in the amounts of genetically-superior seed suitable for the different ecological zones in Vietnam The GoV is committed

to improving the amounts and qualities of tree seed produced from its own seed orchards, which is a more sustainable strategy than depending on imported seed Exotic species such as acacias and eucalypts are important species included in the planting programs

In order to enhance the productivity of the plantations in Vietnam, genetic improvement programs have been carried out for many tree species mainly by the Research Centre for Forest Tree Improvement of the Forest Science Institute of Vietnam However, these works have been conducted without a written plan that follows a clearly defined genetic improvement strategy As part of AusAID-supported CARD project (No 058/04VIE)

“Strengthening Capacity in Forest Tree Seed Technologies Serving Research and Development Activities and ex-situ Conservation” a genetic improvement plan has been

developed focusing on priority Eucalyptus species A separate CARD project (No

032/05VIE) “Sustainable and profitable development of acacia plantations for sawlog production in Vietnam” will soon develop a genetic improvement plan for acacias It should also be stressed that the approaches discussed in this breeding strategy are applicable for most tree species

Breeding populations of five Eucalyptus species (E camaldulensis, E grandis, E pellita, E

tereticornis and E urophylla) already set up by the Research Centre for Forest Tree

Improvement provide the basis for genetic improvement framework being addressed by this

improvement plan However, greater effort and input are put into E urophylla as the highest priority Eucalyptus species for pure and interspecific hybrid breeding Other species have

been managed less extensively with an aim to use them as pollen sources for interspecific hybridisation

The proposed breeding strategy is based on a structured breeding population that is divided into two levels based on genetic quality That is the breeding population is subdivided into two parts, a ‘Main (large) Population’ and an ‘Elite (small) Population’ The populations have several distinct functions in the breeding program, and a large part of the breeding strategy in each generation deals with the plan that specifies the selection, breeding and management of these two components of the breeding populations As interspecific hybridisation is receiving increasing interest, the ‘Elite Population’ is the source of genetic material used for interspecific hybrid crossing, in addition to it being one of the sources of pure-species clones for operation deployment Therefore, the strategy places maximum emphasis on this population to ensure maximum genetic progress The ‘Main Population’ provides for gene conservation and long-term, sustained genetic progress, by providing new selection to the ‘Elite Population’ each generation

For the ‘Main Population’ there is only a single type of genetic test (open-pollinated progeny test) for each generation The families and individual trees within families are ranked using the test data, and selection are made to move up to enrich the gene pool of the ‘Elite

Population’ and to regenerate the next generation’s Main Population The overall strategy in the Main Population can be defined as recurrent selection for general combining ability

A greater emphasis is placed on the breeding, testing and selection of the Elite Population each generation, because the clones derived from the Elite Population serve as the clones for use in operational plantations and for intra- and interspecific hybridisation Controlled crosses are made between selections of the same species and of other species Vegetative propagation of the progeny and clonal testing is used for forward selection of the best clones for operational use The very top ranking clones only are used for interspecific hybridisation

A time plan for operation is provided for each species It should be treated as a general guide only A more detailed work program providing month-by-month activity schedules should be prepared by the Research Centre for Forest Tree Improvement taking into consideration both administrative possibilities and technical limitations

It is common for every genetic improvement plan to be reviewed and may be revised after some period of operation This genetic improvement plan is no exception and should be subject to an independent review after 2 years into the program

1 Introduction and Background

Eucalypts are one of the most important groups of plantation species for the supply of industrial raw materials in Vietnam Their wood is used for pulp and paper, particleboard, construction and furniture There are substantial block plantations of eucalypts in many parts

of Vietnam They are widely planted along canal banks in the Mekong Delta, and along dams, rice paddy boundaries and roadsides and as wind breaks in the Red River Delta They are also widely planted in many places throughout the country as scattered trees Moreover, eucalypts provide much of the fuel wood for most of rural areas of Vietnam Together with acacias, eucalypts have significantly contributed to the improvement of income and living standards of rural people in lowland areas, particularly in central and central-northern Vietnam The area of eucalypt plantations Vietnam at the end of 2001 was estimated as 348

000 ha (Le Dinh Kha et al 2003a) The current planted area is believed to be around 500,000

ha This figure does not include millions of row plantings and scattered trees equivalent to 50,000 ha in routine plantation form

Eucalypts have been introduced into Vietnam since 1930 Eucalyptus camaldulensis and E

robusta were the first Eucalyptus species introduced into Vietnam in 1930 by the French

More species were introduced during 1950-1958 in Da Lat (central highlands), and among

these E microcorys was found to be very promising In 1960 E exserta was introduced and

became an important species for re-greening bare land and denuded hills Up to 50,000 ha of

E exserta plantations were planted during the 1960s However, the popularity of E exserta

has since declined because of its slower growth rate than other species

It was not until the 1980s that systematic species and provenance trials were established at different ecological zones of Vietnam However, lack of comprehensive representations of provenances in some species in those early trials led to premature conclusions An example

was the case of the Petford provenance of Eucalyptus camaldulensis which was identified as

an outstanding seed source in the early 1990s (FSIV 1990, Hoang Chuong 1992) Results of later species-provenance trials revealed that growth of Petford provenance was only mid-ranked and it was very susceptible to die back diseases in the south-eastern part of Vietnam and Thua Thien Hue (Sharma 1994, Pham Quang Thu 1999) The most promising

provenances of E camaldulensis in Vietnam are Laura River, Kennedy River and Morehead

River (northern Queensland) and Katherine (Northern Territory) (Le Dinh Kha and Doan Thi

Bich 1991) while the best provenance of E tereticornis tested during the 1990s was Sirinumu

Sogeri (Papua New Guinea) (Hoang Chuong 1996)

1.1 Species-Provenance Trial in the Lowlands of Central Vietnam

Provenance seedlots of six species were planted at Dong Ha, Quang Tri province in 1991

(Table 1) Eight-year growth data show that many provenances of E cloeziana (e.g Queensland provenances of Herberton, Helenvale, Woondum and Cardwell), E pellita (Queensland provenances of Kuranda and Helenvale) and E urophylla (Indonesian provenance of Lembata) performed well above overall trial mean In general, E

camaldulensis, E grandis and E tereticornis were slower in growth rate than the other three

species with most provenances ranking below the overall trial mean However, it should be

noted that some of the best performing provenances of E camaldulensis (i.e Laura River, Kennedy River and Morehead River) were not included in this trial and E grandis was not suitable for low land areas (Le Dinh Kha et al 2003b)

Table 1 Growth of eucalypt species and provenances tested at Dong Ha

(Quang Tri province) (1/1991-7/1999)

1.2 Species-Provenance Trials in the Southern Highlands

Twenty four provenances of 9 Eucalyptus species were tested in Da Lat at Lang Hanh

(altitude 900 m) and Mang Linh (altitude 1500 m) in 1992 Available growth data at 18

months of age at Mang Linh shows that the fastest growing provenance was E urophylla, Mt Egon, Flores, Indonesia It was followed by E grandis Lam Dong land race and Paluma, Qld, and E saligna Blackdown and Barrington, Qld E camaldulensis from GibbRiver, Katherine and Morehead River also grew well Slower growing provenances were E brassiana Jackey Jackey, Qld; E camaldulensis Emu Creek Petford, Qld; E tereticornis Mt Garnet, Qld; E

grandis Mt Lewis and Tinaroo, Qld All E pellita provenances grew slower than overall trial

mean The high altitude of 1500 m appeared to be too high for many Eucalyptus species such

as E brassiana, E camaldulensis, E pellita and E tereticornis

No further detailed information from these 1992 trials was available except a brief reference

in Le Dinh Kha et al (2003a) that some 11-year-old trees of Da Lat land races of E saligna and E microcorys were growing well at Lang Hanh, mean height 25.1 and 22.5 m

respectively

Based on the results of past species and provenance trials, many species are considered promising for planting in different regions of Vietnam:

Lowlands, central to southern provinces: E brassiana, E camaldulensis, E cloeziana, E

exserta, E pellita, E tereticornis, E urophylla

Lowlands, northern provinces: E exserta, E pellita, E urophylla (on deeper soils (canal

banks, roadsides etc) E camaldulensis is an excellent performer and widely planted in the

north, although it is no good on the shallow hillside soils I don’t know that there is much

evidence that E pellita is good in the north (it may be) You probably need a paragraph

describing the different types of planting sites available – small planting areas on flat land with deep soil, and much larger areas (bare hill type site) of sloping land with generally rocky shallow soil especially in north and central-north In the south and parts of the central highlands there are larger areas of better soil and reasonably level ground although these are mostly being planted to acacia hybrid now The species rankings and performance of hybrids change according to these soil types

Central highlands: E grandis, E microcorys, E saligna,E urophylla and E pellita can also

be planted up to altitudes of around 900 m asl in the Central Highlands

1.3 Current Eucalypt Species in Reforestation Programs

Vietnam has embarked on a massive tree planting program as part of the national 5-million hectare Reforestation Program (2000-2010) In general, the type of planting sites available for tree planting differs between regions In the north and central north, there are small areas

on flat land with deep soil, and much larger areas (bare hill type site) of sloping land with generally rocky shallow soil In the south and parts of the Central Highlands there are large areas of better soil and reasonably level ground although these are now mostly being planted

There are also quite large plantings of E camaldulensis and E tereticornis in central

Vietnam e.g in Hue province but these seem to be being progressively replaced with acacia hybrid plantations

The total annual planting in Vietnam is about 200,000 ha of which 70,000-80,000 ha are of eucalypt species The planting material of eucalypts can be divided into 70% from seed and 30% from vegetative propagation means especially rooted cuttings There are also large areas

of eucalypt plantations, especially E camaldulensis and E tereticornis, regenerated by

coppicing after harvesting

2 Genetic Improvement of Eucalyptus species in Vietnam

The Forest Science Institute of Vietnam (FSIV) through the Research Centre for Forest Tree Improvement (RCFTI) is the leading government agency conducting genetic improvement of eucalypts in Vietnam A great deal of this work is in cooperation with FSIV regional centres such as those in central and southern Vietnam Other agencies conducting or involving in tree improvement work include Phu Tho Forestry Research Centre and some of the Provincial forest departments The work program is described in the following sections

2.1 Candidate Plus Tree Selection and Clonal Testing

Prior to mid 1990s, the focus of genetic improvement was on selection of locally grown

superior trees of E camaldulensis and E urophylla, followed by clonal testing for high productivity and adaptability Some highly productive eucalypt clones of E urophylla and its

interspecific hybrids were also imported for planting, e.g from China

In 1993, a clonal trial testing 38 clones of E camaldulensis selected from a 4-year-old

plantation was established at Cam Qui, Ha Tay province Diameter and height of all selected trees exceeded the plantation mean by more than 1.5 standard deviations Eight clones were

found to perform better than commercial seed of E camaldulensis (C), E exserta (E), E

urophylla (U) and a natural hybrid E exserta x E camaldulensis (EC) Results at 7 years

showed that 26 clones grew faster than E camaldulensis control and 12 were poorer The stem volumes of the two fastest clones C22 and C7 were two times greater than the E

urophylla seedling control and three times greater than the E camaldulensis clones The trial

provided a good lesson to local forest research institutes the essential need to field-test clonal selections

Candidate plus trees of E urophylla were also clonally tested The Forestry Research Centre

in Phu Tho has selected many superior individuals of E urophylla from plantations and

provenance trials and tested them in clone trials Some of these are now listed as commercial clones: PN2, PN3d, PN10, PN14, PN24, PN46, PN47 and PN108 These clones performed better than two imported clones, U6 (urophylla) and GU8 (grandis x urophylla), from China

However, PN2 was later found to be very susceptible to leaf blight disease caused by

Phaephleospora destructans (Nguyen Hoang Nghia 2003)

2.2 Development of Eucalypt Hybrids

From the early 1990s, very positive results have been gained by integration of plus tree

selection of three parental species: E camaldulensis (C), E exserta (E) and E urophylla (U),

followed by controlled pollination to produce pure-species and interspecific hybrid crosses and field testing to develop superior clones Studies on flowering biology, pollen collection

and storage and controlled pollination techniques were carried out for all three species By controlled pollination, reciprocal hybridisation between the three species has been conducted and more than 70 inter- and intraspecific hybrid combinations have been made Some of the interspecific hybrid families created by RCFTI have out-performed their parental species in terms of volume growth by 100-300% Results from this work were reported in Le Dinh Kha

et al (2003a)

In general, the hybrid combination UC grows well on the deep soils of the Red River delta and seasonally waterlogged, acid sulphate soils in Kien Giang province Hybrid combinations

UE and EU are usually fast-growing on hill sites Intraspecific crosses within E urophylla

also perform well in these environments Hybrid combinations EC and CE are the slowest among the hybrid combination created Their growth is only slightly better than the open-pollinated offspring of their parent trees The performance of individual hybrid and pure-species families can be classified into the following groups (suffixes refer to parent tree numbers):

(i) Fast growing hybrid combinations for hill sites, deep and fertile soils in Red River delta and acid sulphate soils in Kien Giang (Mekong Delta): U15C4, U29E1, U29E2 and

progeny trials integrated with seedling seed orchards of key species including E

camaldulensis, E grandis, E pellita, E tereticornis and E urophylla These plantings were

initially established as provenance-progeny trials, and are assessed and selectively thinned as they develop They are very important not only to supply seed, but also for selecting the most promising provenances, families and superior individuals for further genetic improvement Together, these plantings now provide most of the breeding populations for genetic improvement programs in Vietnam Details of these plantings are discussed in Section 4.5

2.4 The Need for a Genetic Improvement Strategy and Plan

To date the RCFTI has done an excellent job of conducting genetic improvement of key

Eucalyptus species Many genetic trials have been established and superior trees selected for

inter- and intraspecific hybrid crossing programs Many individual hybrid trees from different combinations have been recognised by the Ministry of Agriculture and Rural Development as

Technological-Advanced Germplasm However, all these works have been conducted

without a written breeding plan that follows a clearly defined genetic improvement strategy

As part of an AusAID CARD project (058/04VIE), Strengthening Capacity in Forest Tree

Seed Technologies Serving Research and Development Activities and ex-situ Conservation,

we define the breeding strategy for the selected Eucalyptus species and put together a written

plan so that it can be used as a practical guide for long-term management of eucalypt improvement in Vietnam

It is noted that genetic improvement encompasses two main activities, namely breeding

which involves selection of superior trees and crossing them in some way to produce new

offspring, and propagation, that is to say the mass-production of genetically improved

planting stock, either from seeds (typically produced in seed orchards) or by vegetative propagation of superior clones or known superior seedling families Many scientists use the term breeding more generally to cover both breeding and propagation

3 Basic Elements of Planning Tree Improvement

3.1 Need for a Well Defined Strategy and Plan

Tree improvement programs aim to develop new plantations superior to their predecessors in one or several key economic traits The modus operandi of most contemporary programs is to start with a carefully chosen breeding strategy implemented through a dependent breeding plan These key components of tree breeding are defined as follows –

Genetic improvement strategy (a conceptual plan) – the framework of ideas, the conceptual

overviews, or philosophy of the management of genetic improvement of a tree species used

in plantations Its essential elements are:

(a) population improvement by a combination of a particular type of selection and a particular type of mating, starting with a well adapted broad genetic base; and

(b) an efficient system for mass propagation of outstanding selected individuals either as seed or cuttings

Breeding plan – having decided which Breeding Strategy (particular combination of selection

and mating) will provide the greatest gain per generation at an acceptable cost for a particular plantation program, the tree breeder can write a detailed Breeding Plan to implement the Strategy Typically the plan includes a set of objectives and a flow chart of what is to be done each month or year for several years ahead and is subject to regular revision, every 2-5 years

(Eldridge et al 1993)

3.2 Clear Objectives

Tree breeding projects should have a clear set of objectives defining the improvements required and identifying the traits to select These traits and the economic weights given to the different traits for improvement should aim to improve the economic performance

(profitability) of the tree growing and processing industries (Greaves et al 1997)

3.3 Hierarchy of Four Populations in a Breeding Strategy

As an ongoing recurrent process, a breeding strategy accumulates benefits over successive generations through a cycle of testing, selection and mating (Figure 1) Every effective breeding strategy for an individual tree species involves the maintenance of a hierarchy of three major types of population which can continue to meet the demand for genetically improved planting stock for a fourth population, the commercial plantations These four populations are:

Base population – The base or gene resource population consists of millions of trees in the

natural forests of a particular tree species and some plantations in which selection can be

carried out These broadly-based reserves will continue to be a source of a wide range of genetic variation to meet future needs

Breeding population – The selected trees and their progeny (up to 300 to 400 families of 100

trees each) in a series of progeny trials and clonal archives in which the breeding cycle of selection and mating will be repeated over many generations This is the tree breeder’s main area of work

Propagation population – The intensively selected trees (commonly fewer than 100 selected

trees) propagated in seed orchards or cuttings multiplication areas where the combinations of genes selected in the breeding population are mass produced as genetically improved planting stock

Production population – The major plantation areas established using the improved

Propagation population

Production population

select trees

tests

seed orchards/

clone banks

plantations

selection

mass propagation mating

In some programs two other types of populations are also employed One is an ‘infusion population’ which comprises additional material from the base population or elsewhere It is brought into the breeding population in the second or later cycles of breeding to maintain or increase genetic diversity and provide additional superior genetic material (Harwood and Mazanec 2001) The other is a ‘nucleus population’ or ‘elite population’, which is a small subpopulation of the breeding population Elite populations typically comprise less than 50 genotypes which are the focus of the most intensive breeding (Erikson and Ekberg 2001) In the shorter term, larger gains can be provided by the smaller elite population Gene conservation and long-term gains are provided by the larger or main subpopulation of the breeding population

3.4 Selection and Mating

Selection and mating are key activities in breeding They accumulate genes which influence yield and adaptation, increasing over successive generations the frequency of superior trees Every successful breeding strategy, therefore, requires efficient methods of selecting superior material including the progeny tests in which the selection is carried out, appropriate measurement techniques and selection technology (e.g selection indices) Mating can be

done by open pollination or controlled pollination, carefully minimising the potential of inbreeding and allowing for material from other sources to be incorporated

In pursuing its principal functions of efficient selection and mating, a strategy should aim to assess the variation within a species, generate genetic information about it and see that genetic resources for future selection are conserved (Matheson 1990)

3.5 Personnel and Funding

Availability of technical expertise and institutional support as well as an appropriate level of funding over a longer term are key elements in determining the type of breeding strategy adopted RCFTI has a cadre of scientists and technical staff who have a proven record of success in carrying out the basic operations of eucalypt improvement Some RCFTI scientists are now developing skills in high-level quantitative genetics that will be valuable in the management of advanced-generation breeding programs An area that has been identified

as requiring greater expertise is the development of breeding objectives and multi-trait selection indices tailored to the requirements of particular wood-using industries

3.6 Hybrid breeding

Interspecific hybrids are already important in Vietnam (see section 2.2 above), so it is important to consider efficient strategies for hybrid breeding and propagation The main issues have been comprehensively reviewed recently by Potts and Dungey (2004) Some of the main features are as follows:

Not all interspecific combinations yield productive hybrid clones An understanding of

breeding barriers within Eucalyptus is essential to avoid wasted effort However, it is already

known from work in Vietnam and elsewhere that good interspecific hybrid combinations can

be made among the following species of the subgenus Symphyomyrtus, all of which are established in Vietnam: E camaldulensis, E exserta, E grandis, E pellita, E saligna, E

tereticornis and E urophylla None of these species can be crossed with Corymbia citriodora, which is in a different subgenus

Most successful hybrid clones are derived from crosses between pure-species parents, but this is not always the case Outstanding advanced-generation hybrid clones have been produced in southern Brazil by crossing among superior hybrid individuals (T.F Assis, pers comm 2001), but inviability is frequently encountered

The degree to which the breeding value1 of an individual for pure species breeding correlates with its hybrid breeding value is not yet fully understood However, hybrid breeders generally select superior pure-species individuals for hybrid breeding, and this approach is sensible in the absence of detailed information obtainable from complex breeding schemes such as reciprocal recurrent selection

In general, interspecific eucalypt hybrids must be mass-propagated for plantations by vegetative propagation of selected hybrid clones This is because open-pollinated seed collected from F1 hybrid individuals displays segregation or hybrid breakdown, with high variability and poor vigour F2 progeny, making them unsuitable for plantations It would be

1

Breeding value is defined as twice the general combining ability (GCA of the individual, for the trait in

question GCA can be estimated from progeny tests as the deviation of the individual’s progeny from the trial mean, when an individual has been crossed with a representative set of other individuals

possible to plant out known outstanding F1 family crosses such as those described in Section 2.2 above, but the cost of mass-producing seed by controlled crossing would be too high Because of the requirements for controlled pollination and vegetative propagation of individual clones, hybrid breeders need to pay attention to the use of technological advances that make these operations easier RCFTI has recently moved to develop a clone bank of flowering potted grafts to make controlled pollination easier and safer, and advanced eucalypt propagation systems (hydroponic mini-cuttings systems: Assis 2001) to improve the rooting obtained from clonal selections, but these systems are not yet fully operational

Graft of selected E urophylla individual at Ba Vi clone bank

which has flowered and set seed

4 Determinants of a Breeding Strategy

4.1 Breeding Objective

The aim of tree breeding is to select and propagate superior trees with characteristics that satisfy the needs of growers, processors and end-users of forest products, and which also suit the specific conditions of the planting sites The breeding objective may vary to some extent with species but all should have a similar goal, to maximise the profitability of the grower enterprise, or the grower-processer enterprise for vertically integrated producers who use the wood products produced in the plantations To put it another way, genetically improved planting stock enables production of high-value products, fetching a high price from users, at

a lower cost, through faster growth and improved product quality In Vietnam, the main wood products from eucalypt plantations are pulpwood, small to medium sawlogs, and poles for scaffolding and informal construction Small-diameter log ends, branches and offcuts are usually used for fuelwood

4.2 Economic Weights

“Economic weights are defined as the additional profit that may be expected from a one unit increase in a trait X (say a cm2 increase in sectional area of stem) relative to that from a one unit increase in trait Y (say a 1 kg m-3 increase in wood density)” (Cotterill and Dean 1990) There are several approaches to determining appropriate economic weights (Cotterill and Dean 1990) They can be derived from detailed financial analyses of the processing industries, but this can become quite a major undertaking Alternatively, production functions can be used to describe the economic relationship between biological traits, as factors of production in the case of a breeding objective and final profit of an integrated plantation and

wood processing industry (Greaves et al 1997) Several published studies provide instructive examples (see Ponzoni 1986, Fonseca et al.1995, and Greaves et al 1997)

There is a need to undertake detailed analyses and studies necessary to derive the appropriate economic weights for use in the eucalypt breeding program in the near future These economic weights can then be used to identify the value of each trait to the breeding program (which can be defined as the relative improvement toward the breeding objective for a given

selection intensity when selecting for each trait individually (Greaves et al 1997) It is no use

aiming to improve traits that are of no value! The main objective traits for kraft pulpwood are well known – they are wood volume at rotation age, wood density and percentage pulp yield The relative economic weights among these three traits are not known exactly for Vietnam but they will be quite similar to those already calculated in other tropical countries

4.3 Deployment Objective

The deployment objective of eucalypt breeding program in Vietnam is to produce sufficient quantity of genetically improved planting material to meet the required planting rates The planting material is orchard seed as well as rooted cuttings of superior tested clones of pure species and interspecific hybrids

There may be some difficulties in achieving more widespread diffusion and adoption of genetically improved germplasm produced in Vietnam There is still a perception from local growers that the quality of planting material produced in Vietnam is inferior to that of imported material, especially seed from Australia A concerted effort is needed on improving the diffusion pathways and adoption of genetically improved material produced from within Vietnam

4.4 Selection Criteria and Traits for Selection

The selection objective describes the target ideal superior tree to be identified by the selection process In general, most initial selection usually concentrates on adaptation together with growth and stem form, i.e the objective is ‘big, healthy and straight trees’ In Vietnam, selection for pulpwood plantations must also include other traits such as wood density and percentage pulp yield (or cellulose content which is closely related to this) The following traits are considered important for eucalypts in Vietnam:

i) survival

ii) freedom from major disease and pest damage

iii) rapid growth

iv) high wood density

v) high percentage pulp yield

vi) a single straight stem

vii) thin branches that shed easily (more important for solid-wood products such as

sawlogs)

It should be noted that when a large number of traits is selected simultaneously, genetic gain

in individual traits generally tends to diminish as the number of traits under selection increases In practice, therefore, breeders must try to minimise the number of traits under selection

The most important traits under selection for increased pulpwood production are volume and

basic density (Borralho et al 1993) At present for most growers, valuable wood is that

which has high density as wood is sold on a weight basis (wood is often still sold on a stacked volume basis in the field, but by green weight at the pulp or chipmill) Thus the target for the growers is big, healthy, straight trees with higher density wood Ideally, an average wood basic density of between 500 and 550 kg m-3 is considered desirable for pulpwood

plantations Older trees of some high-density species (E camaldulensis and E tereticornis)

will actually be too dense for pulping, the upper end of the optimum range is 600 kg m-3 Efficiency of selection may be improved by utilising a multi-trait selection index Smith-Hazel indices are often used and incorporate information on heritabilities, genetic correlations and phenotypic correlations, but the calculations are complex (Cotterill and Dean 1990) If the key traits in the index are not strongly correlated, then simple indices such as the primary index can work just as well for selection in first-generation breeding populations and are far easier to calculate At present, it is relatively easy to predict multivariate breeding values and do multi-trait selection using multivariate ASReml However, this is mainly relevant to pure-species breeding, not hybrid breeding and deployment which will probably

be more important in the long run in Vietnam

Multi-trait selection for clonal forestry is easier in some respects because specific individual clones with outstanding growth, optimum density and high pulp yield can be selected and deployed in clonal plantations to meet the genetic improvement objective as has been done in Brazil

4.5 Genetic Resources

The principal genetic resources used in the breeding programs of E camaldulensis, E

grandis, E pellita, E tereticornis and E urophylla mainly came from the species’ natural

distribution in Australia, Papua New Guinea and Indonesia In addition seed-orchard seedlots

were included for E pellita and E tereticornis Details of the provenances and number of

families representing in each breeding population are given in Tables 2-6

At present greater effort and resources are put into E urophylla as the highest priority species for pure species and interspecific hybrid breeding Breeding populations of E camaldulensis,

E grandis, E pellita and E tereticornis have been managed less extensively with an aim to

use them as pollen sources for interspecific hybridisation However, there are good seed

orchards of E camaldulensis and E pellita in Vietnam that can be developed to

mass-produce pure-species seed

CSIRO

Seedlot No Provenance location

Latitude (S)

Longtitude (E)

Altitude (m)

Van Xuan Phu Tho

Ba Vi Ha Tay

Table 2 Seedlots of E urophylla from Indonesia and number of families represented in the

main breeding population in Vietnam

Table 3 Seedlots of E pellita and number of families represented in the main breeding

Longtitude (E)

Altitude (m)

Bau Bang

Gia Lai

19718 SSO Melville ex PNG & Indonesia NT 11 34 130 34 50 13 14

population in Vietnam Indo = Indonesia, PNG = Papua New Guinea, Qld = Queensland, NT = Northern Territory

Ham Thuan Nam Phu Yen

12965 SW of Mt Garnet Qld 18 30 144 45 800 1

13398 East of Kupiano PNG 10 04 148 15 25 17 10 10

13418 Sirinumu Sogeri Plateau PNG 09 30 147 26 580 20 17 13

20553 Little Mulgrave Deeral Qld 17 09 145 52 40 5 5

Table 4 Seedlots of E tereticornis and number of families represented in the main

breeding population in Vietnam Qld = Queensland, PNG = Papua New Guinea

Table 5 Seedlots of E grandis from Australia and number of families represented in the

CSIRO

Seedlot No. Provenance location State Latitude (S)

Longitude (E)

Altitude (m)

No of families

main breeding population planted at Lang Hang, Lam Dong, Vietnam

Qld = Queensland, Vic = Victoria

Table 6 Seedlots of E camaldulensis from Australia and number of families represented in the

CSIRO

Seedlot No. Provenance location State

Latitude (S)

Longitude (E)

Altitude (m)

No of families

main breeding population planted at Lang Hanh, Lam Dong, Vietnam.

Qld = Queensland, Nt = Northern Territory

5 Breeding Strategy

5.1 Outline of Breeding Strategy

The breeding strategy of selected priority eucalypt species in Vietnam is based on a structured breeding population that is divided into two levels based on genetic quality

(Cotterill et al 1989) The breeding population is subdivided into two parts, a ‘Main (large)

Population’ and an ‘Elite (small) Population’ These populations have several distinct functions in the breeding program, and a large part of the breeding strategy each generation deals with the plan that specifies the selection, breeding and management of these two components of the breeding population

In Vietnam, interspecific hybridisation is receiving increasing interest The ‘Elite Population’

is the source of genetic material used for interspecific hybrid crossing, in addition to it being one of the sources of pure-species clones for operational deployment Therefore, the strategy needs to place maximum emphasis on this population to ensure maximum genetic progress The ‘Main Population’ provides a broad genetic base that is managed less intensively to provide for gene conservation and long-term, sustained genetic progress, by providing new selection to the ‘Elite Population’ each generation A diagrammatic form of the strategy is presented in Figure 2

Therefore, the strategy for eucalypt improvement program in Vietnam necessitates pollinated management of the Main Population each generation This is a simple, low cost option that

open-(i) obviates the need for any controlled pollination among selections,

(ii) allows rapid turnover of generations, and

(iii) provides for substantial genetic progress

For the Main Population, there is only a single type of genetic test (i.e open-pollinated progeny test) each generation The families and individual trees within families are ranked using the test data, and selections are made in these open-pollinated progeny tests both to move up to enrich the gene pool of the Elite Population and to regenerate the next generation’s Main Population Thus, the overall strategy in the Main Population can be defined as recurrent selection for general combining ability with open pollination in a

breeding population keeping family identity (Namgoong et al 1989, Eldridge et al 1993)

A greater emphasis is placed on the breeding, testing and selection of the Elite Population each generation, because the clones derived from the Elite Population serve as the clones deployed for use in operational plantations and for intra- and interspecific hybridisation Controlled crosses are made between selections of the same species and of other species Vegetative propagation of the progeny and clonal testing with combined index selection is used for forward selection of the best clones for operational use, as well as to increase the genetic quality of the Elite Populations which ensures still larger gains in the operational clones identified in future generations The very top ranking clones are used for interspecific hybridisation programs on the assumption, as yet unproven, that general hybridizing ability correlates well with pure-species general combining ability

Main Population Elite Population

Establish progeny trial for first

Controlled crossing (intra & interspecific)

Progeny trials

Clone trials

Plantation establishment

Figure 2 A general schematic diagram representing the basic breeding strategy.

Next gen breeding population

5.2 Expected Genetic Gains

A significant proportion of the gains to be achieved in the first cycle is generally due to releases from ‘neighbourhood inbreeding’ Natural stand eucalypt seed has a degree of

inbreeding due to neighbourhood inbreeding effects (Eldridge et al 1993) Experience from

other eucalypt breeding programs indicates that usable volume gains of up to 20% per generation can be anticipated from seed produced by the seedling seed orchards, over and above those from provenance selection, with substantial improvement in form traits as well (Meskimen 1983) Gains from deployment of tested clones are expected to be greater than those from improved seed (Shelbourne 1991) Similarly, gains from tested interspecific hybrid clones are expected to be greater than those from breeding within parental species in environments where hybrids outperform pure species

The actual magnitudes of gains to be achieved will depend on heritabilities and genetic variances of the traits of interest Substantial improvements in wood properties and stem form, as well as volume, are anticipated from this breeding program

5.3 Breeding Population

Systematic genetic improvement programs of eucalypts in Vietnam are in place for five species which can be divided into three subgroups according to their priority levels

Group 1 comprises the top two priority species E urophylla and E pellita

Group 2 comprises the second priority species E camaldulensis and E tereticornis

Group 3 comprises E grandis (to be used for interspecific hybridisation)

First generation breeding populations (open-progeny trials integrated with seedling seed orchards) have already been established for all the species in the three groups They are the basis of breeding material within which selection and mating have been carried out

5.3.1 Structure of the Main Population

The Main Population each generation is basically the open-pollinated progeny trials The functions of the Main Population are:

(i) to become a seedling seed orchard after selective thinning to remove undesirable trees and families;

(ii) to provide new selections each generation to form and maintain the broad genetic base of the next generation’s breeding population;

(iii) to provide selection of the best individuals of the best families to move up and broaden the genetic base of the smaller Elite Population;

(iv) to provide the best individuals of the best families to establish clonal seed orchards

if that is required; and

(v) to provide a broad genetic base for gene conservation and flexibility in case of unexpected changes in product goals or emergence of challenges such as new pests and diseases or change in climate

RCFTI’s main populations of Eucalyptus species (see Tables 2-6) were established as

open-pollinated progeny trials using latinised row-column designs Each trial was established using

6 -10 replicates of 4-trees plots planted at 4m x 1.5m or 2m x 3m spacing with These designs are still considered appropriate for any main breeding populations to be established in future The main breeding population of most species was established on two to three locations to provide against catastrophic loss, increase the precision of the parental rankings, and increase the intensity of within-family selection

5.3.2 Structure of the Elite Population

For each of E urophylla, E camaldulensis, E pellita ? The Elite Population each generation

will be created by cloning (grafting) 30 trees of the best 15 families (i.e 2 trees per family) screened from the Main Population after detailed assessment of growth traits The functions

of the Elite Population are:

(i) to accelerate genetic improvement by providing the best trees each generation for

controlled crosses and development of the very best possible clones for deployment;