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

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). INTRODUCTION Cactus (Opuntia ficus-indica (L.) Mill. ), commonly known as cactus pear, belongs to Cactaceae family, subfamily Opuntioideae which is reported to contain about 130 genera and nearly 1500 species and that were originally native to the New World (Singh, 2003). This species, the most worldwide cultivated, is characterized by its edible fruits that contain viable seeds (100-250 per fruit). The pulp of the fruit develops from the funicular envelopes of the seeds which contribute also to the development of the seed coat (Mejía and Cantwell, 2003). The viable seeds are morphologically large and their presence greatly restricts the commercial quality and limits fruits acceptability in many markets because of the hard seed coat. The three main cultivars of Opuntia characterizing the Sicilian cultivation area are clone’s populations of the same genetic origin known as ‘Gialla’ (yellow), ‘Rossa’ (red) and ‘Bianca’ (white) (Barbera et al., 1992; Mondragon-Jacobo and Bordelon, 1996). Their fruits present various colours due to the combination of two pigments present in different concentrations in fruit pulp and skin (Butera et al., 2002). The yellow cultivar or ‘Gialla’ is the most abundant; it represents 80 and 90% of Sicilian orchards (Butera et al., 2002). Presumably, it is the most productive, able to be handled and well-liked by consumers (Barbera et al., 1992). ‘Rossa’ cultivar is less Proc. VIII IC on Cactus Pear and Cochineal Eds.: Inglese et al. Acta Hort. 1067, ISHS 2015