Pollen Morphology and Reproductive Performances in Opuntia ficus-indica (L.) Mill.

The fruits of Opuntia ficus-indica (L.) Mill., the most worldwide cultivated species of Cactaceae family, contain viable seeds (100-250) of large size. This characteristic influences the commercial quality of the fruit. The study of floral biology in Opuntia allows to understand the behaviour of the plant during reproductive phase and perhaps to distinguish clones with different fruits behaviour (with seed and seedless). The study resulted in a palynological characterization by optical and scanning microscopy (SEM), followed by a qualitative analysis on the male line with pollen viability and in vitro germination tests, in addition to a pollenpistil interaction survey. The plant material collected, during June-July 2010, consisted of clonal samples of the same genetic origin collected from populations characterizing the Sicilian cultivation area and distinguished in seedly cultivar ‘Gialla’ (yellow) and ‘Rossa’ (red) and seedless cultivar ‘Bianca’ (white). The palynological characterization revealed that Opuntia pollen has a radio-symmetric shape with a reticulated surface, poly-panto-porate with a perimeter from circular to polygonal. Moreover, the membrane of the pore appears finely granulated. Scanning microscopy reveals that the pollen has an intectated, reticulated and hetero-brochated exine with about 20-24 pores with a thin membrane. The average viability of the pollen was 91.2% (± 4.6) in ‘Bianca’ cultivar, 82.40% (± 9.88) for both seedly cultivars. In vitro germination rate was 28.76% (± 6.59) in the white cultivar, 27.85% (± 5.15) as overall average in ‘Gialla’ and ‘Rossa’ cultivar. In vivo germination rate in the seedless cultivar (75.77% ± 5.32) was higher than what was that recorded in the other two (53.5% ± 6.5).