Resistance to Meloidogyne incognita in Ethiopian Coffea arabica accessions

The Meloidogyne incognita nematode is a destructive, widespread pathogen of Coffea arabica varieties in Guatemala and in other coffee production countries. Nematode resistant Robusta (Coffea canephora) is frequently used as a rootstock; however, as it is not adapted to high altitudes, this is an inadequate solution. Arabica varieties resistant to the nematode would avoid the need for grafting at altitudes of more than 800-1000 m. Trials were carried out to test the response to an M. incognita isolate from Guatemala on; 50 semi-wild Ethiopian and Sudanese accessions, 20 F1 hybrid families obtained by crossing eight accessions with three susceptible varieties and five F2 populations. An additional trial was conducted to compare resistance to the Guatemalan nematode isolate with a M. incognita isolate from Brazil. The inoculum doses was 1000 ± 200 eggs for each 2-3 month old coffee seedling, and the number of egg masses per plant was observed. Resistance to M. incognita observed in the Ethiopian accessions was important, as 40% of the accessions tested were totally resistant. Resistance was dominant in F1 and transmitted to the F2 generations. Segregation in the F2 populations indicated the presence of a single dominant gene for some crosses and two complementary dominant genes for others. The reactions of the Ethiopian accessions to the Brazilian isolate of M. incognita were similar to those of the Guatemalan isolate. These results confirm the necessity of widening the genetic base of C. arabica breeding populations using semi-wild Ethiopian trees as a source of resistance to M. incognita. (Résumé d'auteur