ARTICLE
Auteur(s) :, Jean-Pierre
LABOUISSE1, Tiata SILEYE2, Jean-Paul
MORIN3, Chantal HAMELIN4, Luc
BAUDOUIN3, Roland BOURDEIX3, André
ROUZIÈRE4
1CIRAD, c/o VARTC, BP 231, Santo, Vanuatu
2VARTC, BP 231, Santo, Vanuatu
3CIRAD, c/o INRA Phytopharmacie et médiateurs chimiques,
route de Saint-Cyr, 78026 Versailles
4CIRAD, TA 80/03, Avenue Agropolis, 34398 Montpellier,
Cedex 05
Located in the Pacific northeast of New Caledonia, Vanuatu is an
archipelago of around 80 islands and islets of volcanic origin
straddling the 13th and 22nd parallels, over a distance of about
850 kilometres. Coconut is a traditional crop used by rural
populations for highly varied purposes (nutritional, medical,
ritual) and for making domestic articles and constructing
dwellings. Since 1870, coconut has become a cash crop through
exports of a single product, copra, obtained by drying the kernel
of the coconut fruit. Throughout the twentieth century, this
commodity was the main source of income for the Condominium of the
New Hebrides, which became the Republic of Vanuatu after the
proclamation of independence in 1980. The latter years of the last
century were marked by a slow but steady decline in copra
production, though it still reached 29,500 tonnes in 2001,
despite record low prices and damage by two cyclones that year.
Ninety percent of production is ensured by smallholders farming a
few hectares, the rest being supplied by ageing estates. Around
half this production is processed locally into oil. These two
products, copra and oil, still account for 26% of the country’s
total export earnings [1].Agricultural research on coconut is
relatively recent in Vanuatu. The Saraoutou research station was
founded in 1962 on the island of Santo and placed under the
authority of the Institut de recherches pour les huiles et
oléagineux (IRHO), then of the Centre de coopération internationale
en recherche agronomique pour le développement (CIRAD), a French
State-run research establishment, in 1985. In 2002, the coconut
research station was integrated into the Vanuatu agricultural
research and technical centre (VARTC).The first research work
involved coconut breeding and agronomy, along with the improvement
of livestock grazing under coconut [2]. In the context of the
1960s, the aim of research was to increase productivity in coconut
plantings, expressed in tonnes of copra per hectare, by improving
the yield potential of planting material and developing modern and
cost-effective management techniques.The geographical dispersion of
Vanuatu and the diversity of its soils and climates would suggest
substantial genetic diversity but, until recently, all the Tall
coconut populations in the country were grouped under the generic
name New Hebrides Tall, then Vanuatu Tall (VTT) after independence.
The common trait of these populations is the large number of small
nuts, as reported by several observers and scientists as early as
the 1960s [3, 4]. The Vanuatu Tall should be classed among coconut
palms with high phenotypic variability. Manciot [5] gave the
following average values for the different production parameters:
- – Number of nuts/palm/year = 88
(c.v. = 44.2 %)
- – Copra weight/nut = 148 g
(c.v. = 17.9 %)
- – Number of flowers/bunch = 43
(c.v. = 55.1 %)
- – Number of bunches/year = 11
(c.v. = 30.5 %)
- – Number of nuts/bunch = 8
(c.v. = 34.5 %)
The high coefficients of variation (c.v.) suggested possibilities
for improving both the number of nuts and the copra content. The
latter trait in particular is highly heritable [6] and the cost of
extracting fresh meat, a labour-intensive operation that is
difficult to mechanize, can be reduced by increasing the copra
content of the nut.Consequently, in 1963, surveys were launched in
two coconut estates near the research station, Surunda Plantation
and Leroux Plantation (( figure 1 )) and led to the
selection of the two Vanuatu Tall populations that were to become
the basis for future genetic improvement: Vanuatu Tall Surunda
(VTT1) and Vanuatu Tall Leroux (VTT2). Based on this nascent
collection, the breeding programme at the Saraoutou station
proceeded along two parallel and complementary lines. Firstly,
improvement of the Vanuatu Tall continued with several mass
selection cycles and crosses within and between populations, and
secondly the hybridization pathway was explored by testing numerous
combinations between local and introduced cultivars.After forty
years of work and data gathering at the Saraoutou station, it seems
now appropriate to describe here the breeding methods applied and
the main results obtained. The first part of this article focuses
on the improvement of Vanuatu Tall production potential by mass
selection.
The mass selection improvement programme of the Vanuatu
Tall
Initial selection work in the estates (initial generation G0) led
to the creation of populations VTT1 and VTT2 (generation G1) by
mass selection with open pollination.
We have data available making it possible to evaluate the gain
obtained with population VTT2, which descended directly from palms
selected in the Leroux estate. Selection focused first of all on
copra weight per nut, which had to be over 160 g, and on
overall yields, which had to be over 10 kg of copra per palm.
Twenty-five palms were chosen and the nuts collected then underwent
strict culling in the nursery. For instance, nuts that germinated
late and the least vigorous seedlings were eliminated in appliance
with protocols drawn up by IRHO [7, 8]. The Leroux estate, and the
collection plot in which population VTT2 was planted, were very
close to each other and were both located on coral soil.
Table 1( Table 1 ) shows
that the production components of population VTT2 were largely
improved when compared to the original population. Nut copra
content (C/N) was improved by 26%, the number of nuts (NN) by 37%
and total yields by 71%. The coefficients of variation for these
parameters decreased. For lack of a "non-selected" control to
compare with VTT2 in the same collection plot, it was not possible
to determine the share attributable to the environment, management
methods, palm age or the effect of culling (in the field and at the
nursery stage) in the improvement of these components. However, the
production potential of the Vanuatu Tall had already been revealed,
along with the possibility of substantially increasing copra weight
per nut.
However, several authors [6, 9, 10] showed that mass selection
with open pollination, when compared to hybridization, was not
particularly efficient in terms of genetic progress and also
entailed major risks:
- • Given the high negative correlation existing between
the "number of nuts" and "copra weight per nut" traits, selection
limited to a search for larger nuts could work against an increase
in copra yields.
- • During strong periods of growth in the hot season, the
bunch emission rate accelerates, and high-yielding mother palms
could adopt an autogamous reproduction system. As coconut palms
have a heterozygous genome, their progenies would display a
depressive inbreeding effect, which would be reflected in their
lower average performance when compared to the parental
population.
Thus, right from the second generation, mass selection was used
with intercrossing. After a period of yield observations, the best
palms in a population were crossed with each other. This required
the hand pollination technique, which is much more labour-intensive
than selection with open pollination, but more efficient in terms
of the expected genetic progress. At Saraoutou, the risk of
inbreeding was reduced by taking parents from two distinct
populations, VTT1 and VTT2, though they are genetically close. The
progenies obtained were tested in two comparative trials (GC2 and
GC9), and formed generation G2.
A new selection cycle was undertaken, leading to the creation of
the Elite A seed garden using seednuts from palms in trial GC9.
Initially, culling was based on the germination rate and seedling
vigour in the nursery. Then, at the adult stage, the least
productive palms in the seed garden were eliminated to promote more
favourable combinations. The seednuts produced in Elite A seed
garden (generation G4) are currently distributed to growers in
Vanuatu.
More recently, index-based pre-selection [11] was carried out,
in order to more effectively assess the genetic value of individual
palms. All the coconut palms in trial GC9 were classed according to
an index based on the estimated copra yield per palm. Trial GC9
compared 24 half-sib families. The best 60 palms chosen
from the best 5 families were intercrossed by hand
pollination, avoiding within-family combinations. The progenies
were planted in seed gardens in 1997 to supply future Elite B
seednuts (generation G4).
A diagrammatic representation of the programme for VTT
improvement by mass selection is given in ( figure 2 ).
Table 1 Annual production means for palms in the
Leroux plantation and its progeny.
|
Leroux Plantation
|
VTT2
|
|
Generation G0
|
Generation G1
|
|
205 palms observed during 3 years
|
290 palms observed during 4 years
|
|
(1963-1965)
|
(1973-1976)
|
|
NN
|
C/N
|
C/A
|
C/ha
|
NN
|
C/N
|
C/A
|
C/ha
|
|
Means(Min-Max)
|
68.5
|
139.2 g (62-223)
|
9432 g
|
1.35 t
|
93.7
|
175.2 g (123-235)
|
16114 g
|
2.3 t
|
|
Standard deviation
|
31.2
|
25.8
|
3962
|
|
36.2
|
22.8
|
5874
|
|
|
C.V. (%)
|
45.6
|
18.5
|
42.0
|
|
38.6
|
13.0
|
36.5
|
|
On-station trials: methods and results
Trial site
The Saraoutou station (longitude 167°12′E, latitude 15°27′S) is
located 11 kilometres north of Luganville on the east coast of
the island of Santo. Its current domain extends over around
500 ha, on a low terrace along the coast, comprising shallow
humus-bearing coral soils, and a limestone plateau enriched with
volcanic ash, with deep, fertile soils rich in clay and organic
matter [12, 13]. ( Figure 3 ) shows that it
benefits from abundant rainfall with 2,815 mm on average
between 1984 and 2002, and temperatures between 21.4°C (mean of
monthly minimums from 1986 to 2002) and 28.6°C (mean of monthly
maximums). July and August are the coldest and driest months of the
year.
The country is periodically subject to cyclones. For its part,
the Saraoutou station was particularly affected by cyclones Wendy
(1972), Gordon (1979), Nigel (1985) Dani and Ella (1999) and Paul
and Sose (2001).
Experimental design
The performance of the different Vanuatu Tall populations was
assessed at different periods, in several collection and trial
plots at the research station. This involved 28 plots
containing VTT1 and VTT2 progenies planted between 1964 and 2000.
Table 2( Table 2 ) gives the
main characteristics of the trials and collections, for which data
will be examined in the following sections.
Under these conditions, and in the absence of a constant
control, it needs to be borne in mind that numerous environmental
factors introduced bias when assessing the genetic value of the
different generations arising from the selection cycles, such
as:
- – soil: some trials at the station are conducted on
coral soil, others on plateau soil. It may involve planting after
forest clearance, or a replanting;
- – trial management: this embraces such diverse aspects
as the development and age of the seedlings on leaving the nursery,
the planting period, the care taken of seedlings and the
fertilization applied, which are rarely identical for all
trials;
- – adverse conditions: the effect of cyclones is
considerable and can seriously reduce the performance of a palm
[14]. A prolonged period of drought (rare event on Santo) can also
disrupt growth and yields. Lastly, insect attacks or diseases may
also play a role.
Table 2 Simplified description of the trials and
collections observed.
|
Generation (Accession)
|
Type
|
Field number
|
Origin
|
Planting date
|
Experimental design
|
Sol
|
|
G1 (VTT1)
|
Collection
|
P02
|
Surunda Plant.
|
1964
|
–
|
Coral
|
|
G1 (VTT1)
|
Collection
|
P00
|
Surunda Plant.
|
1967
|
–
|
Coral
|
|
G1 (VTT2)
|
Collection
|
P00
|
Leroux Plant.
|
1967
|
–
|
Coral
|
|
G1 (VTT2)
|
Trial GC1
|
P43
|
Leroux Plant.
|
1969
|
Rows
|
Plateau
|
|
G2
|
Trial GC2
|
P51
|
VTT1 (P02) x VTT2 (P00)
|
1969
|
2 blocks
|
Plateau
|
|
G2
|
Trial GC9
|
P44/54
|
VTT1 (P02) x VTT2 (P00)
|
1969
|
Lattice 5x5, 6 replications
|
Plateau
|
|
G3
|
Trial GC14
|
P63
|
Trial GC2
|
1982
|
5 blocks
|
Plateau
|
|
G3
|
Elite A seed garden
|
P106/116/117
|
Trial GC9
|
1987
|
–
|
Plateau
|
|
G3
|
Elite B seed garden
|
P84
|
Trial GC9
|
1997
|
–
|
Plateau
|
|
G4
|
Trial GC29
|
P50
|
Elite A seed garden
|
1998
|
5 blocks
|
Plateau
|
Observation methods
The main characteristics of the populations were recorded using
methods developed by IRHO and standardized by IPGRI [15].
Harvesting was carried out by hand with hooked knives, taking
bunches with partially dry nuts. The nuts were placed in the shade
in a dry place for between 10 and 15 days to ensure a
uniform degree of ripeness. After sorting to eliminate abnormal
nuts, they were notched and placed in a seedbed with supplementary
watering. New germinations were recorded each week. After
cumulation, a germination-versus-time curve was plotted.
Once the first flower appeared in a plot, an inspection round
was organized to record newly flowered palms every two months. A
cumulated flowering curve gave the percentage of palms bearing
flowers in relation to time.
At Saraoutou, the yields of the Tall populations were estimated
by recording the number of bunches and the number of ripe nuts,
palm by palm, at a rate of 6 harvesting rounds per year. Meat
weight was then determined either by individual weighing in the
case of collections, or by sampling the elementary plots in the
case of trials, in order to make up a sample of 20 to
30 nuts per treatment. Nut copra content was calculated from
the fresh meat weight and the moisture content of the meat obtained
after drying in an oven at 105°C. By definition, copra weight was
equivalent to that of meat with 6% moisture. The copra yield per
palm was thus equal to the number of nuts multiplied by the weight
of copra per nut. Lastly, the theoretical yield of a plantation was
determined on the basis of 143 palms per hectare corresponding
to a planting design in 9 meters equilateral triangles.
Results
Germination rate
The Vanuatu Tall is a Tall ecotype displaying very rapid
germination [16], beating the Rennell Tall for this trait, which is
itself reputed to be rapid. The germination curves were plotted for
a few of the generations obtained (( figure 4 )). Under good
nursery conditions, with supplementary watering, the first
germinations were obtained between 30 or 50 days after sowing,
depending on the generation. The maximum rate was achieved more
quickly for the last generation, G4, probably due to lower
variability in that population. In this last case, 50% of
germinated nuts were obtained after 60 days and the maximum
germination rate was achieved around the 90th days and exceeded
90%.
Flowering precocity
The Vanuatu Tall is also reputed for its very early flowering [16,
17]. Flowering palms were recorded for the different Vanuatu Tall
generations (( figure
5 )). Generation G1 (VTT1 and VTT2) planted on coral soil
(plot P00) had 50% of flowering palms after 54 months as
opposed to only 44 months for the same type of material
planted on plateau soil (P43). For generations G2, G3 and G4, which
were all planted on plateau soil, the first flowers appeared after
29 to 33 months, which is remarkable for a Tall. For
generation G2, 50% of the palms had flowered after 50 months,
as opposed to 44 months for generation G3 and 36 months
for G4. The performance of generation G4 ( Elite VTT) was quite
exceptional, with a much less staggered start to the flowering
period than for the earlier generations, which may have been due to
a less variable planting material from a genetic viewpoint, but
also to planting with material displaying more uniform development
on leaving the nursery. The seedlings of this generation also
benefited from favourable climatic conditions in 1999 and 2000,
which were warmer and wetter years than average.
Precocity therefore seems to depend on the environment, as
already reported by de Nucé [16], who indicated that the VTT1 flowered 12 to 18 months
earlier in Vanuatu than at the Marc Delorme station in Ivory Coast,
where the soil and climate are less suitable for its development.
This trait is also improved through culling in the nursery.
The Vanuatu Tall has confirmed its very precocious Tall trait.
The Elite T seeds currently distributed give an improved population
which, under good nursery and field growth conditions, starts to
flower after 30 to 36 months, with 50% of flowering palms
between 40 and 45 months after planting. The first
harvest can therefore take place 4 years after planting
out.
Description of the palm
The VTT has along and thin stem, and a rather large bole ( (figure 6) ). The
fruits are of medium size with various shapes but most of them are
oblong and green, greenish brown, or reddish brown in colour (
(figure 7) ).
Yield characteristics
Improvement of copra content
The Vanuatu Tall populations on which the breeding programme is
based had an average copra/nut weight (C/N) of under 150 g. At
each stage of selection, an attempt was made to eliminate parents
with a C/N of less than 160 g.
In addition, to obtain the palms in trial GC9, use was made of
VTT1 parents from plot P02 whose individual C/N was equal to or
greater than 189 g on average over 5 seasons (overall
mean of the C/N for all these palms = 210 g), and
VTT2 parents from plot P00 with an individual C/N equal to or
greater than 183 g over 3 seasons (overall mean of the
C/N for all these palms = 201 g).
The results obtained (( figure 8 )) shows this
selection to be efficient, as reflected in a 46% increase in C/N
between G0 and G42, and even reaching
50% in the case of GC9 palms with almost 210 g of copra per
nut (minimum 200g – maximum 226 g).
The environmental effect seems to be not decisive. No notable
difference was found between palms of the same origin depending on
soil type (coral or plateau). Moreover, de Nucé [16] did not report
any significant difference for this character between the VTT
population at Saraoutou and the one at Marc Delorme in Ivory
Coast.
Number of nuts per palm and copra per palm
In the long term, these two parameters were closely dependent upon
the environment (soil, growing conditions), but were also highly
sensitive over shorter periods to cyclone effects in the case of
mature palms. The yield curves (( figure 9 )) clearly
illustrate the fluctuating nature of production and its
susceptibility to cyclones.
Table 3( Table 3 ) gives a
recap of average annual yields calculated from 5 to
10 years after planting. This made it possible to integrate
the precocity factor in yield expression.
Table 3 Yield characteristics for 3 VTT
generations. Annual averages calculated from 5 to
10 years after planting.
|
G1 (VTT2)
|
G1(VTT2)
|
G2 (GC2)
|
G2 (GC9)
|
G3 (GC14)
|
|
Field number
|
P00
|
P43
|
P51
|
P44-54
|
P63
|
|
Soil
|
Coral (a)
|
Plateau (b)
|
Plateau (c)
|
Plateau (d)
|
Plateau
|
|
Number of nuts/palm/year
|
71.6
|
81.4
|
74.5
|
75.1
|
83.1
|
|
Copra/nut (g)
|
172.7
|
173.9
|
194.7
|
209.8
|
197.0
|
|
Production copra/palm/year (kg)
|
12.4
|
14.1
|
14.5
|
15.8
|
16.4
|
|
Production copra/ha/year (tonnes)
|
1.77
|
2.02
|
2.07
|
2.25
|
2.34
|
|
Cumulated number of nuts 9 years after planting
|
342
|
414
|
372
|
352
|
448
|
(a)Effect of cyclone Wendy in year 5 and year 6.
(b)Effect of cyclone Wendy in year 4, of cyclone
Gordon in year 9 and year 10, drought in year 11.
(c)Drought in year 4.
(d)Effect of cyclone Nigel in year 5 et year
6.
Discussion
In the absence of a constant control, and given the growing
conditions, climatic adversities and planting dates, which differ
depending on the trials, comparing the performance of the different
generations is tricky. Nonetheless, these data provide some
information:
- • Yields per palm are mainly determined by the
environment (soil type, growing conditions), which affects both
flowering precocity and the number of nuts.
- • There is no increase in the number of nuts per palm
over the different generations, but rather a slight decrease. The
progenies of GC9, whose parents were subject to severe selection
for C/N, had a mediocre number of nuts. It should be noted that the
control in GC9 was obtained by mass selection of VTT2 (plot P00)
with open pollination (based on unknown selection criteria, though
it was doubtless copra/nut). This control also produced very large
nuts (C/N of 224 g) and came second out of 25 for this
trait. For the number of nuts, it was within the trial mean. This
shows that C/N is highly heritable and that the intensity of mass
selection with open pollination is decisive. Consequently, in this
precise case, controlled intercrossing was no more effective than
mass selection with open pollination, since it was based too
exclusively on the copra per nut criterion and involved two
populations that are genetically very close.
- • Selection is highly effective in increasing copra
content, a trait which participates significantly, though in a
limited way, in increasing the production potential of coconut
palms.
- • The gain, expressed as copra per ha, obtained between
generation G1 (VTT2-P43) and G3 is modest (+15.8%), especially when
bearing in mind that generation G1 was subjected to numerous
climatic adversities (cyclone, drought).
- • The performance of the latest generation G4 has yet to
be completely assessed at the station3 However, the production potential of the
Elite seednuts (mean of years 5 to 10) can be estimated from
that of generations G2 and G3 when established in good soil
conditions:
- – Number of nuts = 75 to 85;
- – Copra per nut = 195 g to
205 g;
- – Copra per palm = 15 to 17 kg;
- – Copra per hectare = 2.1 to
2.4 tonnes (at a density of 143 palms per ha).
Seednut supplies to growers, and recorded performances
Dissemination of improved planting material primarily took place
during the Coconut development project (Kokonas Devlopmen Projek or
KDP) funded by the European development fund between October 1982
and March 1993. Over that period, around 2800 hectares were
planted with improved planting materials produced by the research
station, a majority of which were Vanuatu Tall palms. The origin of
the seednuts varied over time. From 1982 to 1985, they were
produced in a seed garden located at Matevulu (planted after
2 mass selection cycles with open pollination based on the
Leroux population), then open pollinated seednuts from trial GC9
were distributed from 1985 to 1991 and, lastly, for the final phase
of the project, seednuts from the Elite A seed garden were used
[18].
Several demonstration plots were set up in Vanuatu [18, 19].
Some of them were observed during the KDP project, then from 1995
to 1997 in connection with a project of the International coconut
genetic resources network (COGENT). By 3 1/2 years, 36% of the
palms had flowered, and 93% by 4 1/2 years. The average copra
weight recorded was 200.2 g, the number of nuts produced was
68.7 and annual production was estimated at 1.9 tonnes
per hectare [20].
Achievements and limitations of VTT improvement by mass
selection
The main purpose of the first genetic improvement work carried out
on the Vanuatu Tall was to increase its production potential in a
monoculture context, where it was often combined with cattle
grazing, and exclusively geared towards copra production.
Mass selection with open pollination proved to be effective in
improving nut copra content, right from the first generation. It
led to populations that are more uniform, a trait that is also
promoted by culling in the nursery. However, it revealed its
limitations for increasing production potential. Flowering
precocity, the number of nuts, and consequently copra production
per plot remain highly dependent upon growing conditions and the
care taken with seedlings in the nursery.
The breeding programme was based on using two Vanuatu Tall
populations VTT1 and VTT2, which are probably very close in genetic
terms, as they were surveyed in two estates next to the Saraoutou
station. Mass selection with intercrossing thereby lost efficiency
and the adaptation of progenies to ecological conditions different
from those at Saraoutou – such as those found on soils developed on
volcanic ash, or in a dryer or colder climate – could not be
guaranteed. The demonstration plots set up during the KDP project
were intended to assess such adaptation but, for lack of human and
financial resources once the project ended, observations could not
be satisfactorily completed. However, in order to widen the genetic
base of the Vanuatu Tall, two surveys were carried out of local
coconut populations between 1983 and 1986, then more recently
between 1998 and 2000 on several islands in Vanuatu [21]. Samples
of populations were collected and have been conserved ex situ at
the Saraoutou station. These populations have been partially
described and have yet to be used in a selection programme.
Compared to other types of higher-yielding planting material,
such as hybrids, the Vanuatu Tall offers two major assets: total
tolerance of Coconut Foliar Decay (CFD), a viral disease endemic in
Vanuatu, and the possibility of being reproduced very cheaply by
growers from seednuts harvested from under their palms.
Conclusion and prospects
In order to compensate for low efficiency in mass selection of the
Vanuatu Tall, hybridization of distinct cultivars was launched at
the beginning of the 1970s, for which the main constraint was the
search for CFD tolerance. However, such a programme meant setting
up and maintaining living collections of exotic cultivars (all of
them susceptible to CFD), setting up seed gardens and implementing
costly hybridization techniques.
Apart from its cost, the centralized production of improved
planting material (hybrids or Elite VTT seednuts) in a scattered
structure like the Vanuatu archipelago, was a major hindrance to
widescale dissemination of this planting material [22]. In order to
derive maximum benefit from the results obtained at the station,
decentralized Vanuatu Tall seed gardens could be created on islands
with a similar ecology to that at Saraoutou, using seednuts
harvested from the Elite seed gardens. This would lead to a
reduction in seednut costs and rapid access for growers to already
improved material.
In the longer term, the efficiency of the first mass selection
cycle demonstrated at the station in terms of copra content means
that a similar selection scheme could be considered for setting up
seed gardens based on smallholdings on the different islands in the
archipelago. There are numerous advantages expected from such seed
gardens, in different ways: better adaptation to the ecology of
each island, maintenance of biodiversity, upgrading of the role
played by growers, and stimulation of exchange networks.
Selection could be based on criteria specific to the growers,
subject to their being highly heritable. The prerequisite for
implementing such a production system is an in−depth study of
current coconut seednut exchange and conservation systems in
village communities. It also relies on growers having good
knowledge of the individual traits of the mother palms that will
supply seednuts for setting up the seed garden. Such research on
the in situ management of local genetic resources is under way
[23].
Research and development organizations will have a major role to
play in helping growers to define selection methods and in
providing training in nursery techniques and plantation management
which, as we have seen, are decisive if the genetically improved
Vanuatu Tall is to express its production potential.
Acknowledgement
We thank Peter Biggins (CIRAD) for the translation.
Références
1 VANUATU STATISTICS OFFICE. Copra and cocoa annual report 2001.
Port-Vila, Vanuatu : Vanuatu Statistics Office, 2002.
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conditions écologiques, étude régionale des cocoteraies existantes.
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1 The origin of the VTT population at the
Marc Delorme station is not formally known but, in view of the
introduction date (1969), it can be imagined that it involves a
selection from the Leroux estate (VTT2, generation G1). All the VTT
populations worldwide (Tanzania, Ghana, Jamaica, Philippines,
Brazil) are derived from this African collection.2 C/N for generation G4 was calculated from the data
collected during one year in GC29 trial.3
In trial GC29, the first harvest took place 4 years after planting.
In this trial, the yield of Elite VTT reached 2.0 tons for the
fifth year after planting.
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