The future of the world cocoa economy depends on the availability of genetic diversity and the sustainable use of this broad genetic base to breed improved varieties. Decreasing cacao genetic diversity (in situ, on-farm and conserved in collections) is a serious problem, and all its many causes need to be urgently addressed: the destruction of the Amazonian rainforests, changing patterns of land use, the spread of pests and diseases, sudden changes in climate and threats from natural disasters and extreme weather. These factors are resulting in an irreversible loss of the cacao genetic diversity so essential for farmers, breeders and consumers. A Global Strategy was published in 2012 to optimize the conservation and maximize the use of cacao genetic resources as the foundation of a sustainable cocoa economy. The chapter describes the key challenges, how they are being addressed and the priorities for further research and actions.
Cocoa, Theobroma cacao, is an important tropical perennial crop grown widely in the humid tropics. The exchange of cocoa germplasm between germplasm collections and breeding centres is vital for varietal development. Intermediate quarantine facilities, such as the International Cocoa Quarantine Centre, Reading UK (ICQC-R) play a vital role in ensuring the transfer of germplasm whilst minimising the risk of spreading pests and diseases. Current screening procedures combine visual inspection and molecular techniques, which are effective in detecting Cocoa swollen shoot virus (CSSV), a badnavirus, which causes severe losses but are restricted to West Africa. However, the detection of latent or mild virus infections that produce no visual symptoms has been a challenge. Recently two badnavirus species of cocoa producing mild symptoms, cacao mild mosaic virus (CaMMV) and cacao yellow vein-banding virus (CYVBV), have been sequenced. Here, we report new assays for the detection of these two species, for the first time in non-symptomatic accessions. Evolutionary and bioinformatic analyses of the viruses suggest their most recent source was from Trinidad, though there is historic evidence that these viruses may have their origin in South America and then become widespread globally over the last century. We also report a novel colorimetric Loop-mediated isothermal amplification (LAMP) assay for the detection of CYVBV. This simple and accurate method could be employed in field virus testing.
The availability of high-performance planting materials to cocoa farmers is an important part of a package of measures to improve the productivity of cocoa farms and thus the sustainability of the cocoa economy. This chapter reviews the methods, advantages and challenges of techniques of mass propagation, with a focus on seed and conventional vegetative propagation (since tissue culture techniques are covered in a separate chapter). The chapter discusses cross-cutting issues to be taken into account when developing a strategy to supply farmers with planting materials. These include availability of source materials, requirements for human resources and facilities, phytosanitary considerations, costs and demand. Finally, the chapter looks ahead to potential future research trends in this area.
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