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SUMMARYThe effective pollination periods (EPP) for 'Manzanillo' and 'Picual' olive trees have been determined in two consecutive years in irrigated orchards in California and Spain. The duration of the EPP was variable between year and cultivar. Fruit set declined gradually in response to sequential cross-pollination. Consistent differences with respect to the maximum levels of initial fruit set occurred between 4 -6 d after anthesis (DAA) in 'Manzanillo', and between 8 -14 DAA in 'Picual'. Fertilisation was first observed on day-2 after cross-pollination in both cultivars. Ovule longevity, determined by fluorescence microscopy, appeared to last > 14 d in both cultivars. The stigmas remained receptive for > 8 d. Estimates of the duration of the EPP, based on analyses of its components, were longer than those indicated by the declines observed in fruit set, suggesting that other factors such as the suitability of the style to support pollen tube growth may limit the duration of the EPP. These results suggest that self-incompatibility may be a more important factor than a short EPP in limiting fruit set in 'Picual', as well as in 'Manzanillo' olive trees.

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The fluorochromatic reaction that viable pollen grains exhibit when exposed to fluorescein diacetate (FDA) is an easy, quick and accurate tool for assessing pollen viability in many plants. Despite its widespread use, the method as initially proposed by Heslop-Harrison and Heslop-Harrison lacks specificity in some respects that are essential for comparing simultaneously the viability of different pollen sources. We have determined the time needed for the fluorochromatic reaction to take place and fade, and the lifetime and most effective concentration of the FDA working solution. Our results show that consistent records of pollen viability in samples of olive (bicellular pollen grains) and cherimoya (tricellular pollen grains) can be obtained within minutes, but that measurement must be completed in the first hour after pollen exposure to FDA. The lifespan of the FDA working solution is 1 h, whereas concentrations between 1.5x10(-5) M and 1.8x10(-3) M are equally valid. Pollen grains of both species responded similarly, although some differences were observed in the persistence of fluorochromasia.