A large germplasm prospecting expedition was carried out in different ecoregions in ten Brazilian States in order collect and characterize Psidium guajava L. and another Psidium species, known as araçá. Ecogeographic sampling areas were defined based on eco-geographical zoning and vegetation maps. The accessions were characterized for 40 descriptors, according to the International Union for the Protection of New Varieties of Plants guidelines. One hundred and nineteen guava accessions and 40 araçá accessions araçá were sampled and characterized in 35 different Brazilian ecoregions. The most invariable descriptors for both guava and araçá were color of young shoots, leaf pubescence on lower side, leaf blade length and width, leaf variegation, fruit surface relief, fruit longitudinal ridges and grooves and evenness of fruit flesh color. The large majority of araçá accessions presented widely spaced leaf veins, contrasting with the guava accessions that presented medium to close spacing. Most fruits of araçá accessions were classified as small, while most fruits of guava accessions were grouped into the class of medium size. For the fruit flesh color, 91% araçá were grouped as cream and white, while 58% guava accessions presented pale pink, pink and dark pink coloring. These fruit differences among wild Psidium species and guava suggested that the fruit traits have been the most altered trait by artificial selection.

Relationships between eco-geographic origin and phenotypic variation were established for 143 Psidium accessions, including "araçá" (a general term for wildgrowing Psidium spp. in Brazil) and guava (P. guajava) species, sampled in 31 different eco-geographic regions of ten Brazilian States. The accessions were characterized for 35 categorical traits according to the International Union for the Protection of New Varieties of Plants (UPOV) descriptors for P. guajava. The correlation between the cophenetic values and the simple matching matrices was 0.55, and the badness-of-fit of the multidimensional scaling was 0.30. Eighty-eight percent of the araçá accessions were grouped together and they clustered according to ecogeographic regions. Clusters of guava accessions were verified only in collections from four Brazilian States, and did not present clustering by specific ecogeographic regions. It was expected that the capturing of rare alleles and the enhancement of the genetic variability of Psidium germplasm could be achieved by sampling accessions according to predefined geographical areas, even for guava germplasm.