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The durability of resistance to a disease of high economic impact such as coffee rust (H.vastatrix) is a key element for the sustainability of Coffea arabica L. To achieve it, genetic diversity was proposed as a strategy. The objective of this research was to validate, using evaluations between 1995 and 2017 in two populations, the effect of mixtures and genotype area unit (GAU) on the progress of H.vastatrix in derivatives of Caturra x Timor Hybrid 1343/I.574. Population one (P1) was formed by a diverse mixture of genotypes randomly established in 1977, vs. population two (P2) established in 1991, formed by a mixture of genotypes arranged in furrows of four plants. The results obtained indicate a rapid presence of races compatible with all genotypes, which increased their level over time. However, in P1 it stabilized in the lower and middle strata of the tree, while in P2 it continued its advance until it affected all strata. The Wilcoxon rank sum test showed highly significant differences (p=0.001) in 55% of the evaluations performed, where highly favorable periods for the disease temporarily reduced the effect of the mixture of genotypes. The observations confirm the stabilizing effect of this strategy and the unfavorable implications when GAU is high. These are in agreement with those recorded in commercial fields and it is expected that the chosen strategy will allow a lasting resistance, given the current increase in Colombia of the area cultivated with these varieties.