The former Coffea subgenus is a species complex showing qualitative gene flow and reproductive barriers between species. Such qualitative gene flow allowed its evolution over time, particularly during the successive forest expansion-regression cycles in relation with glaciation periods.

Arabica coffees (60 % of current world coffee production) 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 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 in several other coffee producing countries. Many of the resulting CLR- and CBD + CLR-resistant cultivars (true-breeding lines and F1 hybrids) meet the required standards of profitable and sustainable crop production. Challenges of more recent date include limited access to additional genetic resources of Coffea arabica, breakdown of host resistance to CLR, aggravating insect pest problems and the increasingly negative impact of climate change on arabica coffee production worldwide. This review discusses prospects of breeding and disseminating next generation (hybrid) cultivars of arabica coffee for sustainable coffee production under changing conditions of diseases, pests and climate. International networking on coffee breeding will facilitate sharing of resources (financial, genetic) and scientific information, application of genomics-assisted selection technologies, and pre-breeding for specific characters. Breeding and multiplication of new cultivars well adapted to the local environment will continue to be carried out at national or regional levels. A tree crop like arabica coffee does not lend itself to centralized variety development and dissemination on a global scale.

Knowledge on heritability is essential for selecting varieties resistant against coffee wilt disease caused by Fusarium xylarioides, which is currently devastating coffee in East and Central Africa. Variability of the resistance against coffee wilt disease in Coffea canephora and its inheritance were investigated in three experiments corresponding to a clonal trial involving 20 clones, a 10-parent partial diallel progeny, and a half-sib progeny test. There were significant quantitative genetic variations among the clones and progenies, suggesting polygenic control of the resistance. Around 50–65 % tree mortality was the optimal disease level for calculating heritability and genetic gains. General and specific combining abilities calculated within the optimal disease range for partial diallel analysis were significant. Broad-sense heritability for the same analysis and same disease range was moderate (0.329), and corresponding narrow-sense heritability was low (0.112). Broad-sense heritability from clones in the field at the same disease range was also moderate (0.333). Narrow-sense heritability from regression of half-sib progeny means onto parent means in the field and screen house was 0.183 and 0.369, respectively. Selecting tolerant clones for improvement against the disease is possible, and genetic gains are possible by using tolerant parents in breeding programs.

agr.2012.0560 Auteur(s) : Andre Charrier hacharrier@orange.fr Theme choisi pour ce numero : Numero thematique : Cafes et cafeicultures •. Association for Science and Information on Coffee (ASIC) www.asic-cafe.org L’Association pour la science et l’information sur le cafe (ASIC) a ete fondee en 1966 avec le soutien de l’Institut francais du cafe et du cacao (IFCC), sous la forme juridique des associations de loi francaise (1901). Cette organisation permanente reunit [...]

agr.2012.0558 Auteur(s) : Andre Charrier1 hacharrier@orange.fr, Benoit Bertrand2 benoit.bertrand@cirad.fr, Philippe Lashermes3 philippe.lashermes@ird.fr 1 Montpellier SupAgro 2, place Pierre Viala 34060 Montpellier cedex 2 France 2 Cirad UMR RPB (Cirad, IRD, universite Montpellier II) IRD 911, avenue Agropolis BP 64501 34394 Montpellier cedex 5 France 3 IRD UMR RPB (Cirad, IRD, universite Montpellier II) IRD 911, avenue Agropolis BP 64501 34394 Montpellier cedex 5 France Tires [...]

A quantitative trait locus (QTL) analysis designed for a multi-parent population was carried out and tested in oil palm ( Elaeis guineensis Jacq.), which is a diploid cross-fertilising perennial species. A new extension of the MCQTL package was especially designed for crosses between heterozygous parents. The algorithm, which is now available for any allogamous species, was used to perform and compare two types of QTL search for small size families, within-family analysis and across-family analysis, using data from a 2 × 2 complete factorial mating experiment involving four parents from three selected gene pools. A consensus genetic map of the factorial design was produced using 251 microsatellite loci, the locus of the Sh major gene controlling fruit shell presence, and an AFLP marker of that gene. A set of 76 QTLs involved in 24 quantitative phenotypic traits was identified. A comparison of the QTL detection results showed that the across-family analysis proved to be efficient due to the interconnected families, but the family size issue is just partially solved. The identification of QTL markers for small progeny numbers and for marker-assisted selection strategies is discussed.

Coffea canephora Pierre ex Frohener is a perennial plant originated from Africa. Two main groups, Guinean and Congolese, have already been identified within this species. They correspond to main refugia in western and central Africa. In this paper we present the analysis of a region that has not yet been studied, Uganda. Two wild, one feral (once cultivated but abandoned for many years), and two cultivated populations of C. canephora from Uganda were evaluated using 24 microsatellite markers. Basic diversity, dissimilarity and genetic distances between individuals, genetic differentiation between populations, and structure within populations were analysed. Expected heterozygosity was high for wild compartments (0.48 to 0.54) and for cultivated and feral ones (0.57 to 0.59), with the number of private alleles ranging from 12 for cultivated genotypes to 37 for a wild compartment. The Ugandan samples show significant population structuring. We compared the Ugandan populations with a representative sample of known genetic diversity groups within the species using 18 markers. Coffea canephora of Ugandan origin was found to be genetically different from previously identified diversity groups, implying that it forms another diversity group within the species. Given its large distribution and extremely recent domestication, C. canephora can be used to understand the effect of refugia colonization on genetic diversity.

Coffee wilt disease (CWD), which is caused by Fusarium xylaroides Steyaert, the conidial stage of Gibberella xylarioides Hem. & Saccas, is the most serious problem of Robusta coffee (Coffea canephora) production in Uganda, the Democratic Republic of Congo (DRC) and Tanzania. It is also affects Arabica coffee (Coffea arabica) production in Ethiopia. CWD spreads quickly and widely, thus it is a threat to coffee production in all continents. It can be controlled effectively by planting resistant varieties. In Uganda CWD was first observed on C. canephora in 1993, in areas bordering the DRC and by 2002 it had spread to many parts of the country, where it had destroyed 44.5% of the crop (Oduor, 2005). This reduced Uganda?s coffee exports by nearly 50% and led to economic loss of US dollars 80-270 million annually between 1996 and 2007. Consequently, a search for CWD resistant C. canephora varieties was initiated at the Coffee Research Centre (COREC) in 1997. This involved screening C. canephora germplasm in naturally infected fields and in artificial inoculations carried out in the screen house for resistance. The C. canephora genotypes both in field and screen house studies, responded quantitatively to the disease, implying that CWD resistance in C. canephora is controlled by many genes. 1519 completely resistant genotypes were identified through large scale germplasm screening in artificial inoculations at COREC and these were planted in mother gardens and thereafter they were cloned and planted in field evaluation trials. 167 of the clones underwent preliminary evaluation and four (4) were selected for being resistant to leaf rust and red blister disease and having good cup and bean qualities. The four selected clones were planted in on-farm multi location evaluation trials, en route to being recommended for commercial cultivation. Similarly, four (4) CWD resistant clones were selected from among many genotypes screened in naturally infected fields at COREC and were also planted on-farm multi location trials, en route for recommendation for farmer cultivation. (Resume d'auteur)

Coffee is one of the main products on the international markets, in association with oil, corn, sugar, and paper pulp. The history of coffee-tree cultivation is incompletely documented, both regarding its domestication in Africa, and its assisted dispersal throughout the world. This review focuses on the coffee mutant, Coffea arabica ‘Laurina’ (Chevalier A in Encyclopedie Biologique. Vol 28, 1947), also named ‘Bourbon pointu’. This plant is generally acknowledged to have been selected in the island of ‘Bourbon’ (La Réunion) from a field at the beginning of the 19th century. Compared with the common ‘Bourbon’ variety, ‘Bourbon pointu’ trees are dwarf, with a characteristic Christmas-tree shape and the beans have an excellent cup quality. Although cited many times in literature, the origin of this variety is ambiguous and is largely discussed even today with increasing confusion, particularly in books and local newsletters. This article provides a thorough historical and bibliographical review of coffee cultivation in La Réunion, which leads to an understanding of the bottleneck responsible for the low genetic diversity of the ‘Bourbon’-type modern varieties. Complemented by a review of the scientific studies conducted on this subject, confirmation of the veracity of the various historical accounts becomes possible, and appropriate conclusions on the origin of the ‘Bourbon pointu’ are derived. Although historical texts provide important information and represent priceless resources that give direction to scientific research, it is clear that this same research makes it possible, in turn, to clarify and to interpret historical texts.

Coffee wilt disease (CWD) caused by Fusarium xylarioides, considered to be a soil-inhabiting fungus, is endemic in several African countries, affecting commercially important coffee species and causing serious economic losses. Coffee wilt disease development in naturally infected Coffea canephora fields at the Coffee Research Institute in Uganda was assessed from April 2001 to March 2006 to generate information about temporal and spatial spread of the disease. Maps of diseased trees were also generated from the data. Semi-variance analysis was performed on the data to show the spatio-temporal structure of disease. Host influence on the spatio-temporal structure was deduced from the distribution pattern of diseased and healthy trees and analysis of variance. Results show that the temporal disease epidemic progress was slow. The disease was found to spread from initial infections to healthy neighbouring trees, resulting in an aggregated pattern. An infected tree could infect up to three healthy trees away, in any direction. Disease foci formed and expanded with time, coalescing but punctuated in spots planted with resistant hosts. There were varying levels of susceptibility among host genotypes, affecting the rates and levels of epidemic development. The implications of the findings to the control of CWD are discussed.