Three hybrid populations (F1) of Coffea arabica were evaluated under field and laboratory conditions, derived from sources carrying the SH1 coffee leaf rust (CLR) resistance gene and the CX.2385 line, obtained from the Caturra × Timor Hybrid CIFC-1343. The results obtained under controlled conditions and analyzed using survival curves allowed to estimate the probable times (p < 0.05) for the development of symptoms associated with CLR in the plants of populations evaluated. Phenotypic variation was observed as a defense response to Hemileia vastatrix infection, and plants with incomplete resistance to CLR were identified via an evaluation using the increasing lesions scale. The plants with incomplete resistance exhibited a delay in the development of the incubation period and an absence of the development of the dormancy period. Data suggest that when resistance genes in the sources are defeated by compatible strains, their recombination can give rise to new levels of resistance in the progeny. Additionally, the detached leaf methodology is recommended as an alternative to preselect genotypes with resistance to CLR, thus reducing the number of plants that are finally planted for field evaluations.

The development and evaluation of techniques that increase the efficiency of selection for planta plant resistance to pathogens is a challenge in all breeding programmes for disease resistance. Under field and laboratory conditions, hybrid populations (F1) of Coffea arabica derived from sources that carry the rust resistance gene SH1 and the CX.2385 line obtained from the Caturra variety × Timor Hybrid CIFC-1343 were evaluated. By means of survival curves, under controlled conditions, the probable times (P<0.05) for the development of symptoms associated with coffee rust were found to be highly variable. Similarly, phenotypic variation in resistance reactions was detected, and plants with incomplete resistance to rust, late development of the incubation period (PI), and no development of a latency period (PL) were identified. The results suggest the use of the detached leaf method as an alternative for the preselection of genotypes for resistance to coffee rust, which could reduce the number of plants used for field evaluations.