Elementos do sistema reprodutivo de etnovariedades de batata-doce, provenientes do Vale do Ribeira, SP, Brasil / Elements of the reproductive system of sweet potato landraces from the Vale do Ribeira, SP, Brazil
Lucielio Manoel da Silva
DATA DE PUBLICAÇÃO
The objective of this work was to study the reproductive system of sweet potato landraces - specifically, to determine which genotypes are either self-compatible or selfincompatible and which are either compatible or incompatible among themselves. The reproductive system was studied in 13 landraces of sweet potato, by means of the fruit production and in situ observation of the pollen tubes in the pistil with the epifluorescence technique with aniline blue in hand-pollinated flowers. A viability test was performed using the dyes acetic carmine and tetrazolium chloride in fou different collecting times (6:00; 8:00; 10:00 and 12:00 h). In order to detect a possible association between incompatibility and flower morphology, several flower parts were measured. Fruit production occurred only in those flowers subjected to cross-pollination. Among 78 crosses performed between 13 landraces, 46.15% produced fruit. Pollen tubes were observed in the pistils of the self-pollinated flowers of 38.46% of the landraces and of the cross-pollinated flowers of 85.90% of the crosses. These results show that sweet potato has a complex sexual reproductive system. Most landraces had a pollen viability rate over 80% when dyed with carmine, but below 70% when dyed with tetrazolium. However, the variation in pollen viability among the four collecting times was insignificant with either dye. All the flower variables measured showed significant differences at 5% of probability, revealing floral polymorphism. Even within-plant morphological pollen polymorphism, which is rather rare, was found. Four well-defined patterns of the relative position of stigma and highest anther were established: stigma well above the anther; stigma slightly above the anther; stigma at the same level as the anther; and stigma below the anther. However, no association was found between floral morphology and incompatibility patterns. There were successful crosses between all morphotypes.
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