Diploid hybrid potato breeding requires the development of novel inbred lines. However, few diploid wild potatoes are self-compatible. Solanum malmeanum (1EBN, 2n=2x=24, tertiary genepool) is a Southern South American species sister of S. commersonii. This less-known wild relative bears valuable traits to prevent pests, adapt to abiotic stresses and could provide novel quality traits. Previous studies suggested that some genotypes of S. malmeanum that set fruit and seeds when self-pollinated could be self-compatible if apomixis is rejected and self-fertilization confirmed. Thus, five diploid accessions from Embrapa potato genebank were screened to evaluate their reproductive behavior and check if the production of viable seeds when self-pollination is performed results from successful fertilizations or apomixis. Five treatments based on controlled crosses assessed viability of gametes; self-pollination; parthenocarpy and/or apomixis; autogamy and allogamy. Pistils from all treatments were stained with LACMOID to evidence pollen tube development observed with an optical microscope (6,3 x). Cross-pollinations confirmed that all accessions produced viable gametes and are allogamous, since pollen tube growth confirmed fertilization in treatments where seeds were set, also corroborating the accuracy of the technique applied. No accession produced parthenocarpic fruit. Four self-pollinated accessions were self-incompatible with no fruit and seed set and self-incompatibility was due to a pre-zygotic barrier confirmed by inhibited pollen tube growth at 2/3 style length. One self-pollinated accession produced 3 fruits totalizing 51 seeds. This genotype self-compatibility was confirmed based on the image record of pollen tubes reaching the ovules, thus rejecting apomixis, which also did not occur in non-manipulated and emasculated flowers. The seeds were sown and 17 seedlings germinated, from which 16 tuberized. These first-generation endogamous plants will be self-pollinated towards developing inbred lines. Still, further investigations are needed to elucidate the mechanism responsible for the self-compatibility, such as S-locus inhibitor (Sli), S-RNase or presence of HT genes.