Genetic analysis of partial resistance to coffee leaf rust (Hemileia vastatrix Berk & Br.) introgressed into the cultivated Coffea arabica L. from the diploid C-canephora species

The objective of this study was to identify polymorphic molecular markers associated with partial resistance to coffee leaf rust, Hemileia vastarix. A segregating F (2) population derived from a cross between the susceptible Coffea arabica cv. Caturra and a C. canephora-introgressed Arabica line exhibiting high partial resistance was analyzed. Rust resistance measured as rust incidence (RI) and defoliation (DEF) was evaluated in field conditions in three consecutive years (2003-2005). During the 2003 season, which was characterized by favorable conditions for a rust epidemic, the F (2) plants exhibited different levels of resistance ranging from very susceptible (50.1% for DEF and 49.5% for RI) to highly partial resistance (9.1% for DEF and 3.7% for RI). Molecular analysis enabled identification of seven polymorphic markers (5 AFLP and 2 SSR) exhibiting significant association with partial resistance. Coexistence of resistance homozygous alleles (RR) at codominant SSR loci was correlated with high resistance. This study is the first attempt to develop PCR-based sequence specific markers linked to partial rust resistance in coffee.