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Traditional cultivars of arabica coffee (Coffea arabica) are susceptible to coffee leaf rust (CLR, Hemileia vastatrix) and coffee berry disease (CBD, Colletotrichum kahawae). CLR is of worldwide importance, while CBD is still restricted to Africa. Host resistances present in C. canephora to both destructive diseases have been successfully introgressed into C. arabica, after several decades of breeding and selection notably in Brazil, Colombia, India and for CBD resistance in East Africa. CLR resistant cultivars have since been grown on hundreds of thousands of hectares in Latin America and elsewhere, while CBD (and CLR) resistant cultivars are now increasingly being planted in East and South Eastern Africa. They contribute to ecologically sustainable coffee production and to considerable socio-economic benefits for the coffee growers. Nevertheless, some representatives of the international coffee trade continue to be sceptical about the cup quality of these modern cultivars. This paper presents an overview of the considerable amount of scientific evidence accumulated over the years showing that, with all environmental factors at optimum level, disease-resistant cultivars can produce quality coffees as good as those from the best traditional varieties. [ABSTRACT FROM AUTHOR]

Breeding for host resistance to coffee berry disease (CBD) in arabica coffee ( Coffea arabica) was initiated some 35–40 years ago in Kenya, Ethiopia and Tanzania in response to severe CBD epidemics. The release of CBD resistant cultivars to the coffee growers has been in progress since 1985. The resistance of cultivars like Ruiru 11 (Kenya) and Ababuna (and other cvs in Ethiopia) appears to be of a durable nature, since confirmed cases of a breakdown of host resistance under field conditions have not been reported over the past 20 years. Host resistance to the hemibiotrophic fungus Colletotrichum kahawae is of a quantitative nature, but nevertheless can be practically complete in some genotypes of arabica coffee. There is still no consensus on the genetics of CBD resistance, some claiming convincing evidence for oligogenes (1–3 major genes) and others for polygenes determining CBD resistance. Results from genetic studies with germplasm from the centre of genetic diversity for C. arabica in Ethiopia are presented here. These together with the recent identification of molecular markers associated with and the mapping of one major gene, provides additional evidence for oligogenic inheritance of CBD resistance. The development of cultivars combining yield and quality with durable host resistance to CBD has contributed greatly to increased sustainability of arabica coffee production in Africa. It has also considerable relevance to arabica coffee in Latin America and Asia, where CBD is still a quarantine disease but with a risk of becoming endemic one day, just as has happened earlier with coffee leaf rust ( Hemileia vastatrix). [ABSTRACT FROM AUTHOR]