Molecular physiology and genetics of coffee resistance to parasites :

Coffea arabica cultivars usually display a high-yielding and good coffee quality, but exhibit a high susceptibility to many pests and diseases. Enhancing their resistance to parasites have become a crucial priority toward an economic and sustainablecoffee production. Research activities were therefore developed to identify and clone genes involved in the specific resistance of coffee to nematodes (Meloidogyne spp.) and rust (Hemileia vastatrix). A positional cloning project was started to isolate aresistance gene derived from C. canephora, that confers resistance against M. exigua. Based on the analysis of progenies obtained from resistant introgressed arabica lines, 15 AFLP markers tightly linked to the resistance gene were identified. Further linkage investigations allowed the construction of a localized genetic map of the chromosome segment carrying the M. exigua resistance. The low rate of recombination indicated these markers could be useful landmarks for map-based cloning of the resistance gene. With this purpose, a bacterial artificial chromosome library is being constructed. In addition, disease resistance gene analogues (RGA) were cloned in coffee (C. arabica and C. canephora) using DNA primers designed from conserved motifs (NBS) of known plant resistance (R) genes. Analysis of PCR-derived coffee NBS sequences revealed nine distinct families of RGAs, belonging to the non-TIR class type of R-genes, in both species. Sequence variation observed among coffee RGAs suggested point mutations asthe primary source of diversity within RGAs families. Efforts are being pursued to explore the possibility of implication of isolated coffee RGA families in the identified nematode resistance. In parallel, genes expressed early during the specific resistance reaction of coffee (C. arabica) to the fungus H. vastatrix were isolated from cDNA libraries constructed using the suppression subtractive hybridization method (Diatchenko et al., 1996). cDNA clones showing specific expression in the early stages of the resistance reaction were selected and characterized. Similarities were found with plant sequences involved in plant defence reactions such as chitinases, heat shock proteins, cytochrome P-450, metallothioneins and ionic channels. Further work will aimat understanding the role of selected clones in the mechanism of specific coffee resistance to parasites.

Bibliographic Details

Main Authors:	67112 Fernández, D., 99612 Noir, S., 40279 Agostini, C., 49833 Bon, M.C., 58486 Combes, M.C., 118926 Silva, M.C., 74218 Guerra Guimaraes, L., 43095 Anthony, F., 48644 Bertrand, B., 85180 Lashermes, P., 3180 Association Scientifique Internationale du Cafe, París (Francia), 32308 19. International Scientific Colloquium on Coffee Trieste (Italia) 14-18 May 2001
Format:	biblioteca
Language:	eng
Published:	Trieste (Italia) ASIC 2001
Subjects:	COFFEA, COFFEA ARABICA, COFFEA CANEPHORA, HEMILEIA VASTATRIX, MELOIDOGYNE, NEMATODA, RESISTENCIA A LA ENFERMEDAD, ENZIMAS, ENFERMEDADES FUNGOSAS, EXPRESION GENICA, GENES, PROTEINAS DE SHOCK TERMICO, LOCI, GENETICA MOLECULAR, MUTACION, SECUENCIA NUCLEOTIDICA, ENFERMEDADES DE LAS PLANTAS, NEMATODOS DE LAS PLANTAS, ORGANISMOS PATOGENOS, PLAGAS DE PLANTAS, FISIOLOGIA VEGETAL,
Online Access:	http://orton.catie.ac.cr/repdoc/
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