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  • Author or Editor: L. Rallo x
  • Journal of the American Society for Horticultural Science x
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Experiments with olive (Olea europaea L.) shoot explants were carried out to determine the influence of winter chilling on the release of axillary buds from dormancy. This investigation was designed to explore an alternative explanation for the confusing concept surrounding the role of chilling in olive floral induction. Leafy explants collected from 10 Nov. to 6 Mar. were grown in a greenhouse under mist at 13/24C (night/day) and in a growth chamber at 10/21C (night/day) to determine the end of dormancy. Growth of floral buds from leafy explants was first recorded from 5 Jan. samples. After that date the percentage of developing floral buds and rate of their development increased. Floral bud abscission, increase in bud fresh weight, and simultaneous decrease of relative bud dry weight were associated with growth initiation of floral buds. Manual defoliation of adult trees during the period of shoot explant collection indicated that leaves play a critical role in development once the floral buds had completed dormancy. Supplementary chilling of isolated shoots collected 20 Jan. demonstrated that 7.2C was sufficient to complete chilling requirements, while 12.5C allowed both the completion of chilling requirements and the proper temperature for subsequent floral bud growth. Winter chilling is required to release previously initiated floral buds from dormancy, and we question the previous concept that the role of chilling is to induce olive floral initiation.

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Authors: and

The dramatic postanthesis flower and fruit abscission in olive was found to consist of two distinct but overlapping phases for ovaries following the abscission of imperfect flowers. Imperfect flower abscission peaked 8 days after full bloom (FB), while perfect flower and fruit abscission was greatest between 13 to 15 days after FB. Ovary abscission, expressed as percent ovaries abscising per day (relative abscission rate), peaked 15 and 21 days after FB. The first ovary abscission phase includes fertilized and unfertilized ovaries. The second phase occurs once early fruit growth is in progress, suggesting a possible role for substrate competition.

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Abstract

Experiments with heavily-flowering olive trees showed only one period of abscission of flowers and fruit in the 5-6 weeks following full bloom. This abscission of flowers and fruit is responsible for the small percentage of fruit retained to maturity. Most of the fruit drop was concomitant with initial fruit growth for all cultivars. There were no differences in the number of fruit per inflorescence among cultivars, but the percentage of inflorescences with fruit at harvest was related negatively to final fruit size for each cultivar. Thinning of perfect flowers within the inflorescence did not affect fruit set at the inflorescence level; thus, the inflorescence behaved as a unit of fruitfulness. Competition among fruits played a significant role in fruit set. Initial setting induced by pollination and fertilization is counteracted early by fruit abscission originated by competition among fruit. In light of this early abscission, the use of fruit set to indicate response to pollination in previous experiments is questioned.

Open Access

The aim of this work was to study in depth the resolving power of RAPD markers for rapid and reliable identification of olive cultivars in germplasm collections. The D parameter (the probability that two randomly chosen cultivars have different banding patterns), used for that purpose, showed high values for most of the 21 primers tested and its values ranged from 0.6114 (OPI-13) to 0.9762 (OPK-16) with a mean value of 0.8566. This parameter was used to select the five most discriminating primers: OPK-16, OPA-19, OPX-09, OPF-06 and OPZ-11. The joint confusion probability and the statistical number of indistinguishable pairs of cultivars were estimated for these primers (under independence hypothesis). The combination of three primers (OPK-16, OPA-19 and OPX-09) was found optimal for rapid discrimination of 103 cultivars with a very low value of cumulative confusion probability (1.72 × 10-5), leaving 0.09 pairs of cultivars indistinguishable. This fact, together with the efficiency of the most discriminating primers combination on an increasing number of cultivars, evidenced the utility of RAPD markers for discrimination of olive cultivars in collections and in nurseries.

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Authors: , , and

Abstract

Differences in pistil abortion did not account for variation in fruiting among ‘Manzanillo’ (biennal bearing), ‘Rubra’ (regular cropping), and ‘Swan Hill’ (strong blooming but unfruitful) olives (Olea europaea L.). Competition among normal fruits in an inflorescence seems to be a main factor in regulating final crops. Parthenocarpic fruit of ’Manzanillo’ and ‘Swan Hill’ did not exhibit fruit competition. A high percentage of ovules in ‘Swan Hill’ contained poorly developed embryo sacs at anthesis and were not fertilized. Most of the few parthenocarpic fruit formed eventually shriveled and abscised.

Open Access

Random amplified polymorphic DNA (RAPD) analysis was performed on the main Mediterranean cultivars of olive (Olea europaea L.) from the Germplasm Bank of the Centro de Investigación y Formación Agraria “Alameda del Obispo” in Cordoba, Spain. One hundred and ninety reproducible amplification fragments were identified using 46 random primers followed by agarose gel electrophoresis. Some 63.2% of the amplification products were polymorphic, with an average of 2.6 RAPD markers obtained for each primer. The combination of polymorphic markers resulted in 244 banding patterns. The high degree of polymorphism detected made identification of all the cultivars (51) possible by combining the RAPD banding patterns of just only four primers: OPA-01, OPK-08, OPX-01, and OPX-03. Cultivar-specific RAPD markers and banding patterns were also found. A dendrogram based on unweighted pair-group method cluster analysis was constructed using a similarity matrix derived from the RAPD amplification products generated by the 46 primers. Three major groups of cultivars could be distinguished by RAPD analysis: 1) cultivars from east and northeast Spain, 2) Turkish, Syrian, and Tunisian cultivars, and 3) the majority of common olive cultivars in Spain. The dendrogram thus showed a good correlation between the banding patterns of olive cultivars and their geographic origin. A higher level of polymorphism was observed when polyacrylamide gel electrophoresis was used to separate the amplification products. Thus, adequate use of RAPD technology offers a valuable tool to distinguish between olive cultivars.

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