Ideotype is a combination of traits to be sought in a breeding program, supporting the selection process. However, there must be sufficient genetic variability to be explored to ensure success in this process. Thus, this study aimed to evaluate the genetic diversity of a population of Formosa papaya from the cultivar Rubi Incaper 511, maintained by farmers, and the use of an index based on the genotype-ideotype distance for preserving the original traits of the cultivar. A population of 250 individuals, maintained for approximately 10 years, was evaluated for 13 quantitative morpho-agronomic descriptors. Genetic divergence was estimated from the dissimilarity matrix using the mean Euclidean distance, and the dendrogram was formed using the hierarchical method of unweighted pair groups method with arithmetic averages (UPGMA). The index based on the genotype-ideotype distance was used for plant selection, with the cultivar Rubi Incaper 511 being the desired ideotype. The new means of the selected individuals and the selection differential were obtained after this selection. The individuals had fruit mass ranging from 0.73 to 1.99 kg, soluble solids content between 9.63 and 12.68 °Brix, and number of commercial fruits per plant ranging from 23 to 90. The dendrogram divided the genotypes into five groups. The selected individuals exhibited favorable selection differentials for ten traits and were closer to the selected ideotype. The management of this population by the farmers proved to be efficient in maintaining the genetic variability of the cultivar, and the selection through the index based on the genotypeideotype distance can be used to restore the phenotypic pattern of open-pollinated cultivars
