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Carmen del Río and Abdeslam Proubi

An experiment was carried out to determine when to initiate training potted rooted cuttings of olive (Olea europaea L.), so that tall and well developed nursery trees could be produced in an 8-month growing season. Initiating training to single shoot when average height of tallest shoots was 38 cm (15.0 inches) produced 1-m (3.28-ft) tall nursery trees in 7.5 months, with training restricted to the last 2.5 months. Taller plants [1.17 m (3.84 ft)] and some lateral shoots growing above 1 m were produced following another 0.5 month of growth. Five training months were needed to produce 1.43-m (4.69-ft) trees if training was initiated when main shoots were only 16 cm (6.3 inches). Initiating training at the beginning of the growing season did not produce significantly taller trees. Untrained plants only reached a height of 69 cm (27.2 inches) at the end of the test period.

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Carmen del Río and Ana M Romero

Several experiments showed that whole, unmilled olives (Olea europaea L.) could be dehydrated in 42 hours in a forced-air oven at 105 °C (221 °F), so that they could be used in determining their oil content in a nuclear magnetic resonance (NMR) analyzer. After confirming that the NMR and the official Soxhlet methods estimate the same oil percentages in milled olives, linear regression analysis also showed that NMR provides the same oil percentage results with milled and unmilled fruit. This new method avoids sample manipulation before dehydrating the fruit, making it possible to work with olive samples weighing as little as 70 g (2.47 oz). It allows for processing a large number of samples in a short period of time and may be also used with unmilled fruit flesh. The method is also very useful for screening genotypes, either from germplasm banks or progenies from olive breeding programs, and for evaluating cultivars in comparative trials.

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J.C. Melgar, J. Dunlop, J.P. Syvertsen* and F. García-Sánchez

Physiological responses of olive cuttings of `Koroneiki' and `Picual' (Olea europaea L.) to zero or high salinity (NaCl 100 mmol·L-1) and to ambient CO2 (380 ppm) or elevated (700 ppm) CO2 concentration were studied in sand culture in greenhouses. Growth parameters, net gas exchange of leaves and leaf chloride concentration were measured after two months of treatment. `Koroneiki' had significantly greater shoot growth and net assimilation of CO2 (Ac) at elevated CO2 than at ambient CO2 but this difference disappeared under salt stress. Growth and Ac of `Picual' did not respond to elevated CO2 regardless of salinity treatment. Stomatal conductance and leaf transpiration were lower at elevated CO2 such that leaf water use efficiency increased at elevated CO2 in both cultivars regardless of saline treatment. The saline treatment increased leaf chloride (Cl) concentration and reduced growth and net gas exchange responses in both cultivars. There was no difference in leaf Cl accumulation between the two varieties. At high salinity, elevated CO2 had little effect on leaf Cl implying that at least in `Koroneiki', Cl accumulation was not closely linked to water uptake.

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Raphael Goren, Moshe Huberman and George C. Martin

Previous studies, in which the role of phosphorus in abscission of olive leaves was examined in the presence of ethylene biosynthesis inhibitors, have suggested that phosphorus induces abscission directly, without 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) cv. Manzanillo] and citrus [Citrus sinensis (L.) Osbeck cv. Shamouti]. In olive, leaf abscission was always induced in the presence of KH2PO4, with or without AVG and NBD (alone or in combination), but was more pronounced when KH2PO4 was applied alone. In citrus, the effect of KH2PO4 alone on the induction of leaf abscission and ethylene production was much stronger than that observed in olive. However, in the presence of NBD, KH2PO4 did not induce leaf abscission in citrus during the first 60 hr. Similar results were obtained when NBD was replaced by AVG, but, in this case, abscission was inhibited for only 48 hr. In both cases, ethylene was detected after the inhibitory period had ended. The results obtained with citrus indicate that the observed effect of KH2PO4 on the ethylene-independent induction of leaf abscission in olive is not a general phenomenon and may differ in different species.

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E.W. Pavel and E. Fereres

Responses to low soil temperatures at winter days of high evaporative demand were studied in 20-year-old (fi eld) and 1-year-old potted (controlled conditions) olive (Olea europaea L. cv. Picual) trees in 1996 and 1997. Low soil temperatures apparently affected tree water status as evidenced by low water potentials and stomatal conductance. Low night (2 and 5°C) but ambient day (above 10°C) temperatures did not affect stomatal conductance (gl), leaf (ψl), and xylem (ψx) water potentials of potted olive trees. Tree ψl and ψx decreased when exposed to low night and day temperatures (8°C), but gl was not affected. Water potential of those trees recovered very rapidly when the soil temperature was raised above 10°C at midday. When the trees were exposed to soil temperatures below 8°C for 3 days, ψl, ψx, and gl immediately decreased. After the first day, gl and ψx started to recover while gl was maintained at low levels, thus allowing for tree rehydration. Root hydraulic resistance (rroot)—a major part of whole plant resistance—increased immediately in response to soil temperatures below 10°C relative to that of control trees. The relationship between ψx and rroot indicated that the root system apparently plays a mayor role in the control of tree water status in response to low soil temperatures. During the winter months, olive tree water uptake seems to be primarily limited by low soil temperatures, even though soil water content is normally adequate due to high seasonal rainfall.

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Aurora Díaz, Antonio Martín, Pilar Rallo, Diego Barranco and Raúl De la Rosa

We studied the self-incompatibility of two main Spanish olive (Olea europaea L.) cultivars, `Picual' and `Arbequina', by testing the selfing of the seeds with microsatellites. For this purpose, we used a rapid single-seed DNA extraction method and four highly polymorphic microsatellites. We analyzed seeds produced in branches bagged for selfing from mono- and multi-cultivar orchards in 2002 and 2003. We did not find any seed coming from selfing in the bagged branches, for either cultivar, in the two types of orchards. Additionally, we tested seeds coming from free pollination in mono-cultivar orchards from different locations. In the case of `Picual' olive, only three seeds out of the 70 collected were the product of selfing, although they came from mono-cultivar orchards located in areas where the cultivar used as the female parent was predominant. From the 20 seeds of `Arbequina' olive harvested in the middle of two high-density plantations, not one was a product of selfing. According to this, olive would behave as an allogamous species in mono-cultivar growing conditions and the pollen coming from long distances would be able to produce a normal bearing. Therefore, there is strong evidence to support the idea that the cultivars studied could be self-incompatible. Future experiments in self-compatibility should include a paternity check of the possible self seeds obtained.

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Innocenzo Muzzalupo, Nicola Lombardo, Aldo Musacchio, Maria Elena Noce, Giuseppe Pellegrino, Enzo Perri and Ashif Sajjad

Genetic diversity studies using microsatelite analysis were carried out in a set of 39 accessions of Olea europaea L., corresponding to the majority of the regional autochthon germplasm in Apulia. Samples of olive leaves were harvested from plants growing in the olive germplasm collection of the Consiglio per la Ricerca e Sperimentazione in Agricoltura (C.R.A.) - Istituto Sperimentale per l'Olivicoltura at Rende in Cosenza Italy. Herein, we evaluated the extent to which microsatellite analysis using electrophoresis was capable of identifying traditional olive cultivars. In addition, the DNA sequence of all amplicons was determined and the number of repeat units was established for each sample. Using five loci, electrophoretic analysis identified 24 genotype profiles, while DNA sequence analysis detected 28 different genotype profiles, identifying 54% of cultivars. The remaining 46% were composed of seven different accession groups containing genetically indistinguishable cultivars, which are presumably synonyms. This study demonstrates the utility of microsatellite markers for management of olive germplasm and points out the high level of polymorphisms in microsatellite repeats when coupled with DNA sequence analysis. The establishment of genetic relationships among cultivars in the Apulian germplasm collection allows for the construction of a molecular database that can be used to establish the genetic relationships between known and unknown cultivars.

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M. Nieves Criado, M. José Motilva, Tomás Ramo and M. Paz Romero

The aim of this study was to monitor the pigment profile and chlorophyllase (Chlase) and lipoxygenase (Lox) activities of olive (Olea europaea L.) drupes during the development of the fruit from `Arbequina' and `Farga' in order to find better ways to characterize cultivars such as `Arbequina' that produce virgin olive oils that are highly appreciated in international markets. `Farga' was included as a comparative reference. The total pigment content in olive drupes from the two cultivars studied suffered a decrease when the maturation process began, the rate of chlorophyll degradation being more marked than that of the carotenoid pigment. Chlorophyllides a and b, cis-α-carotene, β-cryptoxanthin, and esterified xanthophylls were detected only in `Arbequina' fruit. The behavior of the Chlase and Lox activities in both cultivars was different. Chlase activity in olives from `Farga' was detected only at the end of the pit hardening period, but in the case of `Arbequina' the presence of dephytilated chlorophyllic derivatives is directly related to a higher Chlase enzymatic activity than that of `Farga' fruit. Although the level of these enzymatic activities decreased when ripening advanced in both cultivars, in `Arbequina' both enzymes showed a slight increase of activity at the latest stages of ripening.

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Marianna Hagidimitriou, Andreas Katsiotis, George Menexes, Constantinos Pontikis and Michael Loukas

The aim of the present study was to develop a reliable reference database to discriminate between the major Greek olive (Olea europaea L.) cultivars and reveal their genetic relationships, since Greece is considered a secondary center of diversity. In order to establish genetic relationships among the 26 Greek and eight international cultivars, four amplified fragment length polymorphism (AFLP) primer pairs, 12 randomly amplified polymorphic DNA (RAPD) primers, along with measurements from 10 morphological traits, were used. A total of 576 AFLP and 113 RAPD markers were produced. Genetic similarities, estimated using the Jaccard algorithim, ranged from 0.45 to 0.83 for the AFLP data and 0.27 to 0.87 for the RAPD data. The cophenetic correlation coefficients between the genetic similarities and the unweighted pair group method of arithmetic averages (UPGMA) phenograms were 0.77 for the AFLPs, 0.81 for the RAPDs, and 0.69 for the morphological traits. However, limited clustering similarities among the phenograms derived from the three methods were observed. This was also reflected by the low correlation between the three genetic similarity matrices produced (AFLP and RAPD, r = 0.39; AFLP and morphological traits, r = 0.11; RAPD and morphological traits, r = 0.02). According to the molecular results, olive cultivars are clustered according to fruit size but not according to geographical origin. Three of the cultivars tested, `Vasilicada,' `Throumbolia', and `Lianolia Kerkiras', were found to branch distantly to the others, according to the AFLP results, and can be considered as ancient Greek cultivars.

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R. Fernández-Escobar, G. Beltrán, M.A. Sánchez-Zamora, J. García-Novelo, M.P. Aguilera and M. Uceda

Mature `Picual' olive (Olea europaea L.) trees growing in two different localities of Córdoba and Jaén provinces, southern Spain, were subjected to annual applications of 0, 0.12, 0.25, 0.50, or 1.0 kg N/tree in the Cordoba's experiment, and to 0 or 1.5 kg N/tree in the Jaén's experiment. Nitrogen was applied 50% to the soil and 50% through foliar application in Córdoba, and 100% to the soil in Jaén. Three years after the initiation of treatments, when the trees showed differences among them in nitrogen content, fruit were sampled at maturity from each experimental tree during six consecutive seasons to determine the effect of nitrogen fertilization on olive oil quality. Tree nitrogen status was always above the threshold limit for deficiency even in control trees, indicating that most treatments caused nitrogen over fertilization. Nitrogen in excess was accumulated in fruit and, consequently, polyphenol content, the main natural antioxidants, significantly decreased in olive oil as nitrogen increased in fruit. The decrease in polyphenols induced a significant decrease in the oxidative stability of the oil and its bitterness. Tocopherol content, on the contrary, increased with nitrogen application, mainly by an increase in α-tocopherol, the main component in the olive oil. No effect was found on pigment content, particularly carotenoid and chlorophyllic pigments, neither on fatty acid composition.