Résumé
Arabica coffees make up about 60% of current world coffee production and are generally sold at considerably better prices than Robustas on account of superior beverage quality. However, costs of production are much higher, mainly due to more stringent demands for soil and climatic conditions, crop management, primary processing and control of several pests and diseases including the potentially very destructive Arabica-specific coffee leaf rust (CLR) and berry disease (CBD). Breeding for disease resistance in combination with vigour, productivity and quality started in the early 1920s in India, but especially in the second half of the 20th century comprehensive breeding programmes have been implemented also by research centres in several other coffee producing countries, particularly in Brazil, Colombia, Costa Rica, Kenya, Tanzania, Ethiopia and Angola/Portugal. Many of the resulting CLR- and CBD+CLR-resistant cultivars (true- breeding lines and F1 hybrids) meet the required standards of profitable and environmentally sustainable crop production. Nevertheless, in many countries the speed of replanting the traditional, disease-susceptible, varieties with these modern Arabica cultivars has been slow. Reasons for the disappointing impact of innovative variety development on Arabica coffee production include: inadequate coffee extension services, limited access to credit facilities for financing costs of replanting and inputs, inefficient systems of multiplication and distribution of the new cultivars to the growers, and last but not least the persistent scepticism among coffee traders about the cup quality of disease-resistant cultivars. Challenges of more recent date are the conservation of and access to additional gene tic resources of Coffea arabica, breakdown of host resistance to CLR in some countries and the increasingly negative impact of climate change on Arabica coffee production worldwide. The durability of CLR resistance can be improv ed by strategic management of the available SH genes, through marker-assisted gene pyramiding or multilines, and by a continued search for new R genes in the Coffea gene pool. A novel approach to achieving durable host resistance in obligate biotrophic pathogens like CLR could be selection for “loss of susceptibility” within the host-pathogen relationship. However, the host resistance to CBD has proved to be very durable so far. Chance s of detecting and successfully introgressing effective host resistances to important coffee pests, other than nematodes, from different Coffea species appear to be low, especially when genetic modification is not an option. Searching for heat- and drought-tolerant genotypes within the Coffea gene pool seems to be the preferred approach to countering the negative effects of climate change, but success under field conditions is as yet unconfirmed. On the other hand, there is ample room for improving crop water productivity in Arabica coffee, by selection and innovative crop management, without decreasing cup quality. Functional-genomic methods of analysis open perspectives of effectively selecting genotypes combining high yields with superior beverages, e.g. identifying metabolic pathways of the aroma/flavour precursors of intrinsic cup quality. This review discusses ways to improve the development and dissemination of new Arabica coffee cultivars, by seeds or clones, with or without growers' participation, by the public or private sector, with the objectives of contributing to sustainable, climate-change tolerant and diversified coffee production. Advanced coffee variety development could benefit tremendously from networks of collaborating research institutes to facilitate the sharing of resources (financial, genetic and genomic), technologies and scientific information. (Résumé d'auteur)