African Humid Tropics Regional Programme – World Agroforestry Centre 1 Vegetative Propagation methods - theory Ebenezar Asaah ICRAF-WCA/HT BP 16317 Yaounde,

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African Humid Tropics Regional Programme – World Agroforestry CentreAfrican Humid Tropics Regional Programme – World Agroforestry Centre

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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Topics for discussion

Definition of vegetative propagationVegetative propagation methodsRationale for vegetative propagationApplication of vegetative propagation

in the domestication of Agroforestry trees: case of Allanblackia

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Definition of Propagation

What is propagation? 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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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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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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Allanblackia propagation by cuttings

Coppice shootsCuttings in propagator

Weaned cuttingsCS of propagator

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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 wildingYaounde, Cameroon

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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

Grafting terminologies

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Grafting of Allanblackia

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Effect of grafting techniques on survival of A. floribunda grafts

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Time (weeks)

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side tongue whip and tongue side veneer graft

Grafting experiments registered 80 % survival rate in A. gabonensis and flowering while still in the nursery.

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In situ grafting of A. floribunda wildings and coppiced shoots under shade open light registered 45% vs 35% survival rate respectively.

Effect of shade & light on survival of A. floribunda in situ grafts

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3 5 7 9 11

Time (week)

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Shade Light

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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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Air layering Allanblackia trees

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Noel cultivar

Capture of traits by air layering

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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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When is it appropriate to use vegetative propagation

When the species in question: 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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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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Creation of a cultivar

Anticipated earlier fruiting, smaller trees and uniform quality Allanblackia fruits

Variation in Allanblackia fruits

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Problematic seed germination and storage 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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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

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Combining more than one genotype in one plant 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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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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Application of vegetative propagation in Tree domestication

Selection and Capture of desirable traits Suitable techniques include layering (marcotting) and

grafting

Mass propagation 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

Documents

African Humid Tropics Regional Programme – World Agroforestry Centre 1 Vegetative Propagation methods - theory Ebenezar Asaah ICRAF-WCA/HT BP 16317 Yaounde,