Towards a Domestication Strategy for Indigenous Fruit Trees in the Tropics - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 30

● The need to combine many desirable traits for simultaneous selection and

improvement.

● A requirement for high product uniformity to ensure profitability and to

meet market specifications. This contrasts with the genetic heterogeneity
that is a characteristic of seedling progenies of outbreeding trees.

● The products are highly valuable and can thus justify the extra expense

and care required to ensure quality and productivity, especially when the
risks of market saturation are minimal.

● The species to be propagated is a shy seeder (i.e. does not flower and fruit

every year or produces only a very small seed crop).

● The propagation material is limited, as for example in: (i) the progeny of a

specific controlled pollination made in a breeding programme; (ii) the
products of a biotechnological manipulation such as the transmission of
genetic material; or (iii) the result of hybridization where segregation would
occur in the F 2 generation and beyond (hybrid progenies are also often
sterile, so further propagation has to be done vegetatively).

● The timescale in which results are required is insufficient to allow progress

through the slower process of breeding. This is particularly relevant in fruit
trees with a long juvenile period prior to the attainment of identifiable
superiority and sexual maturity, as vegetative propagation can be applied
to shoots from trees that have already shown their superiority, and that
have already acquired sexual maturity. Such shoots will retain both this
superiority and their maturity when propagated vegetatively.

● The seeds of the chosen species have a short period of viability (i.e. they are

recalcitrant) or very low viability, and hence cannot be stored for later use.

● Knowledge of proven traits is acquired through either the indigenous

knowledge of farmers or a long-term experiment. This situation is plagued
by the problems of propagating mature tissues vegetatively. Currently, the
usual procedure is to use grafting/budding if the mature traits are required
(i.e. fruiting ability) and to coppice the tree if rejuvenation is required.

● A participatory tree domestication programme is planned. This is because

farmers do not generally have the time or genetic knowledge to implement
a breeding programme.

The antithesis of these situations is that sexual propagation is preferable when
the requirements are for large quantities of genetically diverse, low-value plants
with unlimited seed supplies.

2.2 Developing a Strategy for Creating New 'Cultivars' Vegetatively

The increased interest in vegetative propagation has arisen from the desire to
rapidly acquire higher yields, early fruiting and better quality fruit products in
agroforestry trees. The development of cultivars through cloning also results in
the uniformity of the products, as all the trees of a given clone are genetically
identical. This is beneficial in meeting the market demand for uniform products.
A range of vegetative propagation techniques can be utilized to achieve this