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Carica papaya L. and Vasconcellea monoica, cultivated and wild forms, respectively, belong to Caricaceae family and have 2n = 18 chromosomes. The objectives of the present work were to evaluate the meiosis and the pollen viability in both species. Floral buds in different development stages were collected in 3:1 ethanol/acetic acid and put into the freezer until their utilization. Anthers were squashed on slides, stained with 1% acetic carmine and covered with cover glasses. The slides were sealed and observed under optical microscope. The meiotic analyses confirmed that both species are diploids, with 2n = 2x = 18 chromosomes and 9 bivalents at diakinesis. Abnormalities were observed in different meiotic stages, in both species although they were higher in V. monoica. This fact could be explained by the presence of sticky chromosomes in V. monoica, which resulted in an irregular segregation during the anaphase I and contributed to produce unbalanced cells and consequently, irregular meiotic products. In C. papaya and V. monoica lag chromosomes were observed. The meiotic index and pollen viability were higher in C. papaya than in V. monoica: 94.84 and 96.0% against 77.57 and 70.93%, respectively. These data suggest that V. monoica is a meiotic unstable species with low pollen viability. Therefore, this species can be problematic when involved in hybridization methodologies. No unpaired chromosomes were observed in Carica papaya. Thus, there is no evidence of sexual heteromorphic chromosomes.

Meiotic behavior of Carica papaya and Vasconcellea monoica