Download Propagation of Agroforestry Trees

Vegetative Propagation
methods - theory
Ebenezar Asaah
ICRAF-WCA/HT
BP 16317 Yaounde, Cameroon
Tel: (+237) 223 75 60
Fax: (+237) 223 74 40
Email: [email protected]
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African Humid Tropics Regional Programme – World Agroforestry Centre
Topics for discussion
Definition of vegetative propagation
 Vegetative propagation methods
 Rationale for vegetative propagation
 Application of vegetative propagation
in the domestication of Agroforestry
trees: case of Allanblackia
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African Humid Tropics Regional Programme – World Agroforestry Centre
Definition of Propagation

What is propagation?

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Propagation is the natural mechanism
by which plants regenerate.
Propagation is most often by seeds
produced by a plant
or by plant parts like vines, roots,
tubers, stem cuttings etc..
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African Humid Tropics Regional Programme – World Agroforestry Centre
Vegetative Propagation

Asexual propagation (vegetative propagation)
= reproduction of plant material from
vegetative organs (leaf, stem, root, bud) so
that the offspring will contain the exact
characteristics of the parent plant with
regards to genotypes and health status.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Vegetative Propagation method…1
Cuttings: severed uninodal
leafy shoot or root fragments
usually place into a suitable
rooting substrate and kept
under high humidity in
propagators until adventitious
roots and shoots are formed
respectively.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Allanblackia propagation by cuttings
Coppice shoots
Weaned cuttings
Cuttings in propagator
CS of propagator
African Humid Tropics Regional Programme – World Agroforestry Centre
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Vegetative Propagation method…2

Grafting is a technique
used to untie ‘parts’ of
different plants by bring
the cambium of each
into contact and then
creating a situation
under which the cut
surfaces can unite and
grow away together.
Field grafted AB wilding
Yaounde, Cameroon
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African Humid Tropics Regional Programme – World Agroforestry Centre
Grafting terminologies

Scion -The part of the graft
that will provide the new
system. The scion maybe
united either at the apex or
side of the rootstock.

Rootstock – the lower part
of the graft. It normally posses
a root system that will support
the subsequent shoot
development from the scion
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African Humid Tropics Regional Programme – World Agroforestry Centre
Grafting of Allanblackia
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African Humid Tropics Regional Programme – World Agroforestry Centre
Grafting of Allanblackia
side tongue
whip and tongue
side veneer graft
% survival
100
80

Grafting
experiments
registered 80
% survival rate
in A.
gabonensis
60
40
20
0
3
4
5
6
7
8
9
10
11
Time (weeks)
12
and flowering
while still in
the nursery.
Effect of grafting techniques on survival of A.
floribunda grafts
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African Humid Tropics Regional Programme – World Agroforestry Centre
Grafting of Allanblackia
Shade
Light
100
90
80
% survival
70
60
50
40
30
20
10
0
3
5
7
9
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Time (week)
Effect of shade & light on survival of A. floribunda in situ grafts

In situ grafting of A. floribunda wildings and
coppiced shoots under shade open light
registered 45% vs 35% survival rate respectively.
African Humid Tropics Regional Programme – World Agroforestry Centre
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Vegetative Propagation method…3
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Air layering (marcotting) technique
is similar to cuttings with the
advantage that the propagule is
detached from the parent tree only
after development of roots.
Its multiplication rate is lower than that
of cuttings
Used in capturing the attributes of elite
trees within genetically diverse wild
populations, so avoiding the long, slow
process of tree breeding.
Rooted Marcot
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African Humid Tropics Regional Programme – World Agroforestry Centre
Air layering Allanblackia trees
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African Humid Tropics Regional Programme – World Agroforestry Centre
Capture of traits by air layering
Noel cultivar
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African Humid Tropics Regional Programme – World Agroforestry Centre
Vegetative Propagation method…5
Micropropagation specialized propagation with small
pieces of plant tissues on artificial media under
sterile conditions.
It embraces the regeneration from:
shoot & root tips,
callus tissue,
 leaves,
seed embryo,
anthers and even single cells.
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African Humid Tropics Regional Programme – World Agroforestry Centre
When is it appropriate to use
vegetative propagation
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When the species in question:
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is an out breeder;
is dioecious;
has recalcitrant seeds;
has low germination rates;
flowers and fruits erratically and;
to capture their genetic diversity.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Rationale for vegetative propagation.…1

Maintaining superior genotypes

Most tropical tree species are outbreeders
implying that through the recombination of genes
during sexual reproduction, many important
characteristics might disappear. If a superior
individual tree has been identified by farmers or
researchers, its genetic information can be 'fixed'
through vegetative propagation, thus allowing the
reproduction of the same superior individual in the
next generation
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African Humid Tropics Regional Programme – World Agroforestry Centre
Creation of a cultivar
Variation in Allanblackia fruits
Anticipated earlier fruiting, smaller trees
and uniform quality Allanblackia fruits
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African Humid Tropics Regional Programme – World Agroforestry Centre
Rationale for vegetative propagation.…2

Problematic seed germination and
storage

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Some tree species produce seedless
fruits (e.g. off-season Dacryodes edulis,)
and need to be propagated vegetatively,
others bear fruit very scarcely or
erratically (Prunus africana) or seeds
difficult to gereminate (Allanblackia spp).
In these cases, vegetative propagation
might be a suitable and cheaper
alternative to seedling production.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Rationale for vegetative propagation.…3
Shortening time to flower and fruit

Most vegetative progaules
originate from scions or
cuttings from mature trees, and
maintain the characteristics of
maturity after grafting or
rooting.
Flowering Allanblackia graft
African Humid Tropics Regional Programme – World Agroforestry Centre
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Rationale for vegetative propagation.…4

Combining more than one genotype in one plant
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Grafting is a unique way of combining desired
characteristics from two or more plants into a single one.
Graft scions with particular fruit characteristics onto
rootstocks with other desirable characteristics:
 disease resistance and adaptability to environmental
constraints.
Another possibility is the grafting of more than one cultivar
or species onto the same stem, for example Irvingia
gabonensis (sweet fruits) grafted to an Irvingia wombolu
(bitter fruits) rootstocks and a male AB pollinator branch
grafted to a female tree.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Rationale for vegetative propagation.…5

Uniformity of plantations

For many commercially
grown species, Irvingia spp,
Dacryodes edulis, Cola spp,
Allanblackia spp. etc.
uniformity of growth form or
fruiting season is important
economically.
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African Humid Tropics Regional Programme – World Agroforestry Centre
Application of vegetative
propagation in Tree domestication

Selection and Capture of desirable traits


Mass propagation
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Suitable techniques include layering (marcotting) and
grafting
Suitable techniques include propagation by cuttings and to
a lesser extent grafting. Micropropagation is most suitable
but expensive and skill demanding.
Tree Improvement

Vegetative propagation techniques can provide an exact
copy of the mother tree from which the seed was harvested
and retain the desired fruit quality in the following
generation if the traits are heritable
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African Humid Tropics Regional Programme – World Agroforestry Centre