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Laura Soler and Julián Cuevas

This paper describes a novel technique to produce cherimoya (Annona cherimola) fruit during the winter season. In a controlled experiment the trees were encouraged to flower out of season by pruning them back severely in January, followed by tipping the newly emerged shoots together with the removal of apical leaves on either 1 or 15 June. Both dates were highly successful because all tipped shoots produce a second bloom in July. On average, four flowers per shoot were produced in the new growth in response to defoliation treatments. The second blooming lasted no more than 2 weeks. Late-forming flowers were hand pollinated and gave rise to fruit of high quality about 50 d later than an ordinary crop. A yield of 13 t·ha−1 was produced, with no significant differences between treatments. Postponing hand defoliation by 15 days delayed the harvest period 15 to 20 days, but no other effects on fruit set and quality were noted. Fruit harvested in December and January did not show chilling injury and reached full flavor. Number of seed per fruit, and consequently fruit size, was often increased in out-of-season cherimoyas. Late fruit suffered less preharvest drop than an ordinary crop. This work shows the possibility of producing high-quality cherimoyas during winter when the cherimoya fruit is in great demand.

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Virginia Pinillos and Julián Cuevas

Most Spanish olive orchards are monovarietal as a result of the farmer's belief that the species does not require cross-pollination. Paradoxically, accumulated evidence from controlled experiments demonstrates that olive is partially self-incompatible and that cross-pollination increases yield and fruit quality in this wind-pollinated crop. With the aim of assessing cross-pollination deficit in large plots of the most widespread olive oil cultivar in Spain, fruit set was compared in two solid orchards of ‘Picual’ in response to self-, open-, and artificial cross-pollination. In both orchards, ‘Picual’ behaved as a self-incompatible cultivar with reduced fruit set under self-pollination (index of self-incompatibility = 0.21). However, cross-pollination rarely increased fruit set in comparison with open-pollination. Bagging experiments demonstrated that open-pollination provided enough cross-pollen to induce high levels of fruit set. The increase in fruit set in response to mechanical application of cross-pollen was limited to the trees directly receiving the pollen flow and only in one orchard. Consistently, airborne pollen concentration after a single terrestrial application significantly fits a decay curve with a short dispersal. In contrast with the limited dispersal of single mechanical applications, open-pollination results suggest that trees from plantations at least 250 to 500 m away are acting as unsuspected pollenizers. This is probably taking place to some extent in most traditional olive districts in Spain, and it explains why farmers have never demanded pollination designs in this crop. Modern homogeneous plantations can, however, change this situation dramatically and give rise to pollination deficits.

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Julián Cuevas and Vito S. Polito

We investigated pollination and fruit set parameters in `Manzanillo' olive (Olea europaea L.) following self-pollination and pollination with `Sevillano', `Ascolano', and `Mission' pollen. Results of analyses and experiments conducted over 2 years in central California indicated that `Manzanillo' behaves as a self-incompatible cultivar (index of self-incompatibility = 0.22 to 0.24). Pollination with `Sevillano' resulted in a more than 4-fold increase in fruit set over self-pollination. When `Mission' or `Ascolano' pollen was used, there was no increase over self-pollinated samples. Analyses of pollen tube growth, fertilization, initial fruit set, and final fruit set were consistent with `Manzanillo' being considered as a self-incompatible cultivar cross-incompatible with `Mission' and `Ascolano'. Our results indicate that `Manzanillo' is likely to be more productive when interplanted with `Sevillano' rather than when planted without a pollinizer or with `Mission' or `Ascolano'.

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Alberto Sánchez-Estrada and Julián Cuevas

In countries new to producing ‘Manzanillo’ olive trees (Olea europaea), free cross-pollination is often insufficient to obtain high levels of fruit set. An appropriate pollination design is therefore essential to ensure a timely, abundant, and compatible pollen supply. With a view to determining whether a pollination deficit exists in a nontraditional olive area such as the northern Mexico, pollination experiments were carried out in two consecutive seasons in both a monovarietal and a multivarietal Manzanillo orchard, where Sevillano, Barouni, Picual, Pendolino, Mission, Nevadillo, and Frantoio trees were growing nearby. The pollination treatments were self-, open, and cross-pollination with ‘Barouni’ and ‘Sevillano’ pollen, the latter only in the multivarietal orchard. The results confirmed the full self-incompatible condition of ‘Manzanillo’. Open-pollination did not improve fruit set in the monovarietal orchard, but it did so significantly in the multivarietal plot, where fruit set levels under open-pollination matched those of cross-pollination. Lower pollen adhesion, as well as occasional decreased germination, and reduced and delayed pollen tube growth were observed under self-pollination, highlighting self-incompatibility reactions. The reduction in fertilization rates led to low fruit set under self-pollination. Positive effects of open- and cross-pollination treatments were also noted on fruit weight (despite higher crop loads) and pulp-to-pit ratios. A strategic plantation design, including appropriate pollinizers in the right number and position, is therefore suggested for increasing ‘Manzanillo’ fruit quality and yield in Mexico. Both ‘Barouni’ and ‘Sevillano’ served as efficient pollinizers for ‘Manzanillo’, although we recommend ‘Barouni’ as a more efficient because the bloom periods of them matched that of ‘Manzanillo’