Beyond vegetative propagation of indigenous fruit trees: case of Dacryodes edulis (G. Don) H. J. Lam and Allanblackia floribunda Oliv.

Abstract

Indigenous fruits/nuts of Africa's humid tropics are increasingly being recognized for their contribution to food security, health (nutrition/medicine), income generation, employment and environmental benefits. However, cultivation of the trees yielding these fruits/nuts is constrained by lack of improved planting materials that are true-to-type and have a short enough juvenile phase to fruit production. In addition, information on both above and belowground growth attributes of these species is scarce. This paper presents an overview of the results of a doctoral research focused on two African indigenous fruit tree species, i.e. Dacryodes edulis (G. Don) H. J. Lam (Burseraceae) and Allanblackia floribunda Oliv. (Clusiaceae), which are currently under domestication. For D. edulis, the objective was to assess and compare the structural and fine rooting systems together with the above ground growth attributes of fruiting trees propagated either sexually or vegetatively. The research aim for A. floribunda was to shorten the long juvenile phase before first fruiting through grafting techniques. In summary, the results from the studies on D. edulis suggest that vegetative propagation of the species, reduces the long juvenile phase to fruiting and maintains trueness in the transfer of desirable traits over generations, it also results in trees that are apparently less competitive for below ground resources, have more stable root system, and are bigger in stature and higher in carbon sinks compared to trees of seed origin. In parallel, A. floribunda was shown to be amenable to grafting both under nursery and field (in situ) conditions. Furthermore, a grafted A. floribunda tree transplanted in the field in 2007, flowered and carried a single fruit to maturity after 4 years, thereby reducing the long juvenile period to first fruit production from about 10-12 years reported in literature to less than 5 years. The findings of this doctoral research are therefore pertinent to efforts towards indigenous fruit/nut tree domestication. However, research should be confirmed as it can be considered a pilot study, one that aims to obtain insights into the effect of vegetative propagation methods on above and below ground growth and development of improved planting materials of D. edulis and A. floribunda under domestication. Simon and Leakey (2004), domestication of agroforestry trees encompasses both the socio-economic and biophysical processes involved in the identification and characterization of germplasm resources; the capture, selection and management of genetic resources; and the regeneration and sustainable cultivation of the species in managed ecosystems. The importance of domesticating and integrating these high-value fruit trees in agricultural landscapes by farmers is increasingly being recognized in Africa's humid tropics. However, in an agroforestry context, there has been scant research into the above and below ground growth attributes of intercropped trees that determine whether the association will be complementa...

Domesticating and Commercialisation of Indigenous Fruit and Nut Tree Crops for Food Security and Income Generation in the Kingdom of Eswatini

“…These techniques can help clone elite specimens and avoid the long juvenile periods from seeds [81]. Under domestication, and in response to purposeful man-led selection, species like D. edulis have reduced juvenile phase, larger fruit size, extended fruiting season, more complementary rooting system if intercropped in agroforestry context with companion crops and are significant carbon sinks within the production system [83]. Farmers in southern Africa deliberately maintain indigenous fruit trees on their farms mainly for their fruits and nuts [84].…”

“…Most African native fruit species have not been brought up to their full potential in terms of quality breeding and selection, scale of production and distribution, value addition and availability [80,83]. The potentials in recurrent selection programmes for breeding of indigenous fruit trees are limited by the relatively long expected time until first fruiting for many of the species [80].…”

“…Indigenous people have good knowledge of how and when to utilise the fruits around them for their benefit [5, 97,98]. This approach conforms to the aims of the Convention on Biological Diversity, which seeks to protect the rights of local people to their indigenous knowledge and germplasm [83,85] and the land property rights [99][100][101]. A project that engages and empowers the local people at the beginning is likely to succeed, as rural communities have strong social and economic attachment to indigenous fruit trees [102].…”

Vegetative propagation of Garcinia lucida Vesque (Clusiaceae) using leafy stem cuttings and grafting

“…All these factors may in one way or the other play a part in the success rate of grafting and further studies are needed to determine which are the most important. For instance, Asaah et al (2012) found side tongue grafting to be the most appropriate grafting method for Allanblackia floribunda.…”

Propagation and seedling establishment of selected multipurpose woody species of Uganda

“…However, dependence on seed may not be the best solution from the farmer's point of view as seed progeny can be highly variable and also have long emergence periods so there is significant time delay before being able to harvest useful products. Vegetative propagation, on the other hand, may lead to low genetic variability but yield offspring that are highly precocious and enable farmers to access products within a short timescale (Akinnifesi et al 2008;Hartmann et al 2011;Asaah et al 2012).…”