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G. Steven Sibbett, Mark Freeman, Louise Ferguson and Vito S. Polite

The `Manzanillo' olive (Olea europaea L.) is widely grown in California, because olive processors prefer its uniform size and quality for their canned product. Although it is self-compatible, 10% of a planting should be committed to a pollinizer cultivar to promote optimal production of seeded `Manzanillo' fruit and minimal occurrence of worthless parthenocarpic “shotberries.” As fruits of pollinizer cultivars are of substantially less value and more difficult to manage within a `Manzanillo' planting, less commitment of land for pollination purposes would be desirable. Here we show that topical applications of supplemental olive pollen can be a feasible alternative to commitment of land to olive pollinizer cultivars within a `Manzanillo' planting.

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A. Delgado, M. Benlloch and R. Fernández-Escobar

Change in B content of olive (Olea europaea L.) leaves during anthesis reveals the appearance of a potent B sink. This phenomenon was more marked in young leaves of bearing trees with a high degree of flowering than in nonbearing trees with a low degree of flowering. Applying B to the leaves at the time of anthesis increased the B concentrations in leaf blades, petioles, bark of the bearing shoot, and flowers and fruit 3 days after treatment. The results suggest that B is mobilized from young leaves during anthesis to supply the requirements of flowers and young fruit.

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Isabel Trujillo, Luis Rallo and Pere Arús

Pollen samples of 155 olive (Olea europaea L.) cultivars from different origins were analyzed to study isoenzymatic variability in five enzyme systems: alcohol dehydrogenase (ADH), esterase (EST), glucose phosphate isomerase (GPI), leucine aminopeptidase (LAP), and malic enzyme (ME) using starch gel electrophoresis. Polymorphism was observed in all of the isozyme systems. ME, GPI, EST, and LAP were the most useful systems for identification of cultivars. Different combinations of banding patterns of these systems allowed us to identify 85% of the cultivars. The remainder were separated into groups of two or three cultivars that could be identified using morphological characteristics. No intracultivar polymorphisms were observed.

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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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Octavio Arquero, Diego Barranco and Manuel Benlloch

The effects of potassium (K) status and water availability in the growth medium on growth, water content, water-use efficiency and stomatal conductance was studied in mist-rooted `Chemlali de Sfax' olive (Olea europaea L.) cuttings grown in a perlite substrate. Potassium starvation produced dehydration of all parts of the plant, reduced shoot growth and water-use efficiency. By contrast, K starvation enhanced stomatal conductance in well-irrigated plants and, even more, in water-stressed plants. These results suggest that moderate K deficiency in olives may impair the plant's ability to regulate stomatal closure; this may account for the dehydration observed in K-starved plants, particularly in situations of water stress. This result is of great importance for agricultural practices of this crop, because K status, which may not be considered deficient, can cause disorders in olive trees.

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Susanna Marchi, Luca Sebastiani, Riccardo Gucci and Roberto Tognetti

Net photosynthesis, dark respiration, chlorophyll and carbohydrate content, and leaf and shoot growth in plants of evergreen olive (Olea europaea L.) grown under controlled conditions were measured to assess changes in carbon balance during leaf development of the 6th, 12th, and 16th node (from the base, first flush) through expansion to maturity. Shoot and leaves expanded in a sigmoid pattern with differences among nodes. Photosynthesis varied with leaf development; young leaves had low CO2 assimilation rates that were reflected in their chlorophyll concentration. Net daily CO2 assimilation was negative in young expanding leaves. The sink-source transition, defined to be the time when the increase in daily carbohydrate exchange rate exceeds the daily increase in leaf carbohydrate content, occurred before full leaf expansion, between 10% and 30% expansion depending on the node.

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Louise Ferguson, Hesham Gawad, G. Steven Sibbett, Mark Freeman and James J. Hatakeda

A stepwise multiple regression analysis, using payment by processors as the dependent variable (Y) and numerous physical and chemical characteristics as the independent variables (X), demonstrated that the primary factor determining `Manzanillo' olive (Olea europaea L.) value at harvest was size. Optimal crop value correlated strongly with the combined percentage of standard, medium, large, and extra-large olives; R' values were 0.93***, 0.93***, and 0.42 (ns) in 1984, 1985, and 1986, respectively. As the harvest season progressed, increased percentages of olives within these size classifications, not weight increases of individual olives within the size categories, produced the increase in value. Individual olives within size categories maintained the same weight through the harvest season, regardless of tree crop load. The best criterion for predicting optimal harvest time “is the total percentage of standard, medium, large, and extra-large olives.

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R. Fernández-Escobar, D. Barranco and M. Benlloch

Chlorotic `Manzanillo' olive (Olea europaea L.) trees and `Maycrest' peach [Prunus persica (L.) Batsch] trees were injected with Fe solutions using an apparatus that consisted of a plastic injector and a pressurized latex tube containing the solution to be injected. Injections were made on various dates from Sept. 1987 to July 1988. All treatments increased chlorophyll content compared to that of the control. Ferrous sulfate was the most effective Fe compound in alleviating chlorosis; its effect lasted for two seasons in peach and for at least three seasons in olive. Also, ferrous sulfate increased vegetative growth and affected cropping the year following injections. Ferrous sulfate at 0.5% to 1% is recommended to reduce the risk of foliar burning. The injection method effectively introduced Fe compounds into olive and peach trees.

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M. Benlloch, F. Arboleda, D. Barranco and R. Fernández-Escobar

The influence of sodium and boron excess in the irrigation water on shoot growth and on the distribution of these elements within various leaf types was studied on rooted olive cuttings (Olea europaea L.). `Lechín de Granada' was more tolerant than `Manzanillo' to sodium excess, as indicated by greater shoot growth and lower accumulation of sodium, especially in the young leaves. `Picual' was more tolerant to boron than `Manzanillo', with less accumulation in adult leaves. The results suggest the avoidance of toxicity by an ionic exclusion mechanism that is more effective in some cultivars than others. Also, the results reveal cultivar differences in the tolerance of olive to sodium and boron excess in the culture medium.

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A.R. Alcalá and D. Barranco

The date of full bloom for olive (Olea europaea L.) tree varieties planted in the World Collection in Córdoba, Spain, has been determined from 10 years of data. The full bloom dates were analyzed using three methods to develop a model predicting flowering time. The method of heat units accumulated before flowering was the most accurate. The heat accumulation periods were determined from phenological and temperature data. Prediction methods were evaluated for the earliest-flowering variety, a model variety representing the mean values for the collection, and the latest-flowering variety. The most appropriate threshold temperature for heat accumulation has been confirmed to be 12.5C; it can be used to predict the flowering time in olive.