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I. Baktir, S. Ulger, L. Kaynak and David G. Himelrick

Changes in hormone concentrations in leaf, node, shoot tip, and fruit samples of three Turkish olive (Olea europaea L.) cultivars (`Gemlik', `Memecik', and `Tavsan Yuregi') were monitored at monthly intervals over two successive years of the alternate-bearing cycle. Concentrations of abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid-like substances (GA), and kinetin-like cytokinin were determined and their relationship to flower bud formation were examined during “on” and “off” years. Results showed significant differences in IAA, ABA, GA3-like, and kinetin-like cytokinins between “on” and “off” cropping years in various tissues of olive trees. Relative balances between GA3-like and ABA concentrations of tissues appears to exhibit evidence of being a key regulator of floral development and alternate bearing.

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L. León, L.M. Martín and L. Rallo

Fatty acid composition has been studied in seedlings from a diallel cross (nine families) among `Arbequina', `Frantoio', and `Picual' olive (Olea europaea L.). Variance among samples within genotype, genetic and environmental (yearly) variances, and year-to-year consistency of data were estimated. A correlation analysis of the standardized data for fatty acid composition between first and second year data was also carried out to select the most interesting genotypes as early as possible. The results showed that fatty acid composition exhibit significant differences between genotypes and years. The variance component attributable to differences between genotypes represented >60% of total variance for all the fatty acids evaluated. High correlation coefficients between the first and second year data were found for oleic and linoleic acid percentage; these correlations were slightly poorer for the other fatty acids analyzed. These results may be useful for improving the efficiency of olive breeding programs in first-stage selection on whole progeny populations.

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Saïda Sghir, Philippe Chatelet, Noureddine Ouazzani, Françoise Dosba and Ilham Belkoura

The responses of several Moroccan and French olive (Olea europaea L.) cultivars to various strategies for in vitro establishment and culture were compared. A cultivar effect was clearly observed with `Haouzia' cultivar being more readily multiplied. ZR produced the best response in all the cultivars studied, in particular when considering the time elapsed between explant inoculation and budbreak for 50% of the explants (lag phase), growth of the primary shoot and the multiplication rate. Treatments with BA alone or combined with NAA increased the number of axillary buds and internodes without improving their growth. Root induction with IBA in the dark using a two-phase scheme resulted in the best rooting rate in shoots obtained in vitro, and this for all cultivars. Chemical names used: 6-benzyladenine (BA), indole-3-butyric acid (IBA), alpha-naphthalene acetic acid (NAA), zeatin riboside (ZR).

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Fabio Orlandi, Bruno Romano and Marco Fornaciari

The relationship between heat units trends and reproductive development in olive (Olea europaea, L.) was studied over a 3-year period (1999-2001) in 15 areas in the southern Italian regions of Campania, Calabria, Puglia, and Sicily. Heat units were calculated using GDH and GDD formulas and the flowering phases in the olive groves were studied using volumetric pollen traps that aspirate fixed quantities of air. With this method, the olive pollen release and flowering trends were determined. The main objective of the study was to correlate the spring heat unit amounts and the phases of maximum pollen emission with the date of flowering. Moreover, the ranges of GDH and GDD in the different study areas were calculated to identify maps of olive pollen release.

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Slavko Perica, Patrick H. Brown, Joseph H. Connell, Agnes M.S. Nyomora, Christos Dordas, Hening Hu and James Stangoulis

A 2-year field study was conducted to determine if foliar B applications prior to flowering increased fruit set in olive (Olea europaea L.) cv. Manzanillo. Boron solutions were applied (935 L·ha-1) at four concentrations (0, 246, 491, and 737 mg·L-1) to trees exhibiting no vegetative symptoms of B deficiency. Foliar B application increased both the percentage of perfect flowers and fruit set, but no effect on pollen germination was observed in either year. The increase in fruit set was not accompanied by a reduction in fruit size. The beneficial effects of foliar B application varied between years and were greater when fruit set was low. The results obtained here are in agreement with those observed in other tree species, in which foliar B applications made immediately prior to flowering or during the period of floral bud initiation significantly increased fruit set and yield. The physiological basis for this effect, however, remains unclear.

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Guillaume Besnard, Catherine Breton, Philippe Baradat, Bouchaib Khadari and André Bervillé

One hundred and thirteen olive (Olea europaea L.) accessions were characterized using randomly amplified polymorphic DNA (RAPD) markers. Forty-five polymorphic RAPD markers were obtained enabling us to distinguish 102 different RAPD profiles. The approximate estimation of the probability of obtaining the same RAPD profile for two different trees was between 6.75 × 10-5 and 4.82 × 10-14. A dendrogram was constructed using Ward's minimum variance algorithm based on chi-square distances. This led to a more clear-cut classification of profiles than the classical approach of unweighted pair group method with arithmetic average. Twenty-four clusters of RAPD profiles were shown in Ward's dendrogram. Reliability of the dendrogram structure was checked using variance analysis. RAPD data exhibited an acceptable resolving power for cultivar identification. A combination of three primers was proposed for rapid molecular identification of cultivars in collections and in nurseries.

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Victoria Estaún, Amelia Camprubí, Cinta Calvet and Jorge Pinochet

This paper reports the effects of inoculation with arbuscular mycorrhizal fungi on early plant development, field establishment, and crop yield of the olive (Olea europaea L.) cultivar Arbequina. The response of olive plants to the fungi Glomus intraradices (Schenck and Smith) and G. mosseae (Nicol.& Gerd.) Gerdemann & Trappe in different potting mixes was studied in two different nursery experiments. Pre-inoculation with selected arbuscular mycorrhizal fungi prior to transplanting in the field improved plant growth and crop yield up to three years after inoculation. G. intraradices was more efficient at promoting plant growth than both G. mosseae and the native endophytes present in the orchard soil. Inoculation at the time of transplanting enhanced early plant growth in all the field situations studied. Diminishing mycorrhizal effects over time resulted from natural colonization of noninoculated seedlings and related to the native arbuscular mycorrhizal (AM) fungal population of the field soil. Early inoculation of olive seedlings enhances early plant development and crop productivity of olive trees.

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Lorenzo León, Luis M. Martín and Luis Rallo

Thirteen characters were evaluated over four years in progenies from a diallel cross among the olive (Olea europaea L.) cultivars `Arbequina', `Frantoio', and `Picual' to determine if phenotypic correlations existed between these characters. Yield per tree, ripening date, oil yield components and fatty acid composition were recorded annually once seedlings began to flower and produce fruit. Significant correlations were found between several characters including oil yield components and fatty acids composition. Lower correlation coefficients were obtained between ripening date and oil and oleic acid content. Generally, yield was not correlated with the other characters evaluated. Principal components analysis confirmed the main correlations among characters and showed them to be independent of the parents used.

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F. Sanz-Cortés, M.L. Badenes, S. Paz, A. Íñiguez and G. Llácer

Forty olive (Olea europaea L.) cultivars from Valencia, Spain, were screened using random amplified-polymorphic DNA (RAPD) markers. Eighteen selected decamer primers produced 34 reproducible amplification fragments that were then used as polymorphic markers. The resulting combinations of these RAPD markers were used to discriminate 40 cultivars. Results were analyzed for similarity among cultivars and the relatedness of polymorphisms obtained between cultivars agreed with previous results using isozymes. Unweighted pair group method cluster analysis of their similarity values revealed two main groups divided according to geographic origin within Valencia. A third group, which included two Spanish cultivars from regions outside of Valencia, was clustered separately from the Valencian cultivars. RAPD technology proved useful in discriminating closely related cultivars. There was no apparent clustering of cultivars by fruit size or other morphological traits.

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Raphael Goren, Moshe Huberman and George C. Martin

Previous studies have demonstrated that phosphorus, which stimulates ethylene biosynthesis, induces abscission of olive leaves directly without the involvement of ethylene. In the present study this possibility was further explored by comparing the effects of an ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), and an ethylene action inhibitor, 2,5-norbornadiene (NBD), in olive [Olea europaea (L.) `Manzanillo'] and citrus [Citrus sinensis (L.) Osbeck `Shamouti']. In olive, leaf abscission was always induced in the presence of KH2PO4 with or without AVG and NBD (alone or in combination), but it was much more pronounced when KH2PO4 was applied alone. In citrus, KH2PO4 did not induce leaf abscission in the presence of NBD during the first 48 (detached shoots) or 60 hours (leaf explants) despite the high levels of ethylene production by the tissues. Our results demonstrate that phosphorus can, at least partly, act independently of ethylene action in inducing leaf abscission in olive but not in citrus.