**7. Conclusion**

206 Genetic Diversity in Plants

b)

Plate 4. a. Sites of cacao germplasm collection(red dots) in cocoa producing region of

in Nigeria; d. Population structure indicating cacao types grown on farmers fields in

Nigeria.

c)

Nigeria; b. Relationships showing spatial differentiation among cacao accessions collected in farmers' fields in ideal climate (yellow), ideal soil (blue) and marginal climate (white) conditions in Nigeria; c. Relationships between farmers and field genebank cacao accessions

Amenolado 24%

Trinitario 6%

Others 4%

Upper Amazon Forastero Amenolado Trinitario Others

Upper Amazon Forastero 66%

d)

Cocoa beans either as export commodity or processed into cocoa products remain a significant revenue earner for the government and a veritable means for livelihood sustenance for the people of West and Central Africa. It was therefore pertinent to determine the extent of genetic diversity in this crop in order to safeguard, not only the livelihood of the people and revenue base of the government, but also the multi-billion dollars industry of processing and consuming countries. From results obtained in recent studies, the presence of appreciable genetic diversity in farmer-grown cacao indicated that there is enough resilience in the cacao types now grown in West and Central African countries to withstand any major disease outbreak, which may constitute a serious threat to the cocoa industry. This is in contrast to the situation in the 1930s and 1940s, when, due to a small range of genetic variability in materials grown in farms, the Cocoa Swollen Shoot Virus almost ruined the industry. At that time, more than 20 million trees were cut down as a control measure. The outbreak of Witches' Broom disease in the late 1980s in Brazil provides a recent example of how disease attack can affect farmers' livelihoods and the cocoa industry. The outbreak led to a drop in cocoa production from 380,000 tons per year (at that time Brazil was the world's second largest cocoa producer) to 90,000 tons in the late 1990s, when cocoa actually had to be imported. The presence of some private alleles in farmers' population also gives an opportunity to select useful recombinants on the field that have shown greater adaptation and possibly accumulated genes for resistance to prevalent diseases such as *Phytophthora* pod rot, mirid attack (*Sahlbergella singularis* and *Distantiella theobromae*), and abiotic stress (e.g., drought). Restricted gene flow and spatial differentiation as observed in Cameroon, Cote d'Ivoire, Ghana and Nigeria indicated the existence of inefficient seed delivery systems in some cases, which are not extending the benefits of improved varieties developed by researchers to farmers. There is a need, therefore, for the establishment of a functional and efficient seed delivery system to facilitate farmers' easy access to improved planting materials.

These studies revealed that research efforts to develop improved varieties over the years have been limited to a narrow range of diversity present in germplasm collections. This, in turn, has limited the gains that would have been made from utilizing useful attributes, such as resistance genes against *Phytophthora* pod rot disease in the Scavina variety and the large bean size of the Iquitos Mixed Calabacillo variety. This information is useful for future cocoa breeding efforts and a guide for future germplasm introduction. This knowledge is also important to enable the development of appropriate breeding strategies to improve planting materials, with particular attention to the integration of available genetic diversity into future cocoa improvement programmes. However, the discontinued use of the Amelonado cocoa by farmers have significant implication for the conservation of this stock, some of which are completely homozygous at all loci used in this study. It is hereby suggested that conservation strategies should be developed to preserve the local Amelonado landraces in order to exploit their useful values in future breeding programs.

Although useful information have now been obtained on genetic diversity in the major cocoa producing (Cameroon, Cote d'Ivoire, Ghana and Nigeria) West and Central African countries, much information is still needed on the genetic diversity situation in other countries in the region and others such as Eastern and Southern African countries. For instance, information on genetic diversity in Sao Tome & Principe island and Fernando Po (Bioko) in Equatorial Guinea, the earliest places of cocoa introduction in Africa will be useful to determine the sources of many private alleles that were found in farmers accessions but absent in field genebanks. It is also very important to capture the diversity that might be present in order to exploit these for benefits of the ever increasing sophistication of the cocoa market including 'origin' and 'specialty' emphasis of the consumers. It will be very useful if funding could be made available to determine the genetic diversity of cacao types in Madagascar, Malawi, East African countries such as Tanzania and Uganda in addition to the rest West and Central African countries. This is because a thorough knowledge of genetic diversity in on-farm and field genebanks, particularly in an introduced crop species as cacao is crucial to the utilization of the genetic resources available. This will also be important for the sustainability of the global cocoa industry.
