The cultivar Oblonga may have originated from a volunteer seedling at an orchard near Corning, Calif., about 1940. Its main virtue is its high degree of resistance to Verticillium dahliae. `Frantoio' is the main variety in Italy and has been planted worldwide because of its high content of top-quality oil. In the present study, we show that both cultivars have the same fifteen morphological and eight agronomical traits and both have amplified the same patterns for 22 RAPD primers and five SSRs. This indicates that `Oblonga' and `Frantoio' are probably the same cultivar.
Diego Barranco, Isabel Trujillo and Pilar Rallo
Javier Sanzol, Pilar Rallo and María Herrero
Apples and pears are fruit crops particularly susceptible to cropping irregularities. A strong relationship has been observed between the effective pollination period (EPP) and the general cropping of the orchard. The EPP concept has also been proven to be a useful parameter to establish a relationship between the variation in the reproductive process and cropping behaviors. For apples and pears, a slow pollen tube growth has been shown to be the main limiting factor of the EPP in the traditional cooler temperate cultivation regions. However, while higher temperatures speed up the pollen tube growth, the expansion of these crops into warmer areas often results in failures of fruit set. Thus, with the aim to ascertain the main limiting factor responsible for fruit set failures in Mediterranean conditions we have evaluated the EPP for two consecutive years in `Agua de Aranjuez' pear, the main Spanish cultivar, by studying the stigmatic receptivity, pollen tube kinetics, and ovule development. Complete flower fertility was maintained for just 2 days after anthesis in both years. Pollen tube kinetics and ovule degeneration do not appear to limit flower receptivity. However, the stigmatic receptivity expressed as flowers with at least one receptive stigma, closely matches the duration of the EPP evaluated from fruit set experiments. This was consistent over the 2 years of experiments, in spite of the differences recorded in the EPP, suggesting that stigmatic receptivity is clearly the limiting factor of flower receptivity. This is the first report for stigmatic receptivity limiting the EPP in pears and suggests that stigmatic receptivity could be an important factor limiting pear flower receptivity and hence cropping performance under warmer conditions.
Aurora Díaz, Antonio Martín, Pilar Rallo and Raúl De la Rosa
Previous analyses of olive (Olea europaea L.) crosses have revealed an important degree of pollen contamination. For this reason, the authors tested the paternity of a set of progenies coming from crosses among different cultivars within the olive breeding program of Córdoba, Spain, using four polymorphic microsatellites. They found that the expected pollen sired 141 (83.4%) of the 169 samples analyzed. The contamination rate was either almost total or almost null within each particular cross considered, not being comparable between different crosses. In a second experiment the authors evaluated the influence of several factors on the success of olive crosses, the type of isolation bag, the timing and number of pollinations, and the cross-compatibility of the parents in a multifactorial assay in 2003. They observed no differences in the type of pollination bag used or the number and timing of pollen additions when they analyzed 145 seeds. The main factor affecting the success of the crosses seems to be the intercompatibility among cultivars, because it had a significant influence on the rate of contamination. In the failed crosses, the authors clearly detected the contribution of more than one cultivar to the paternity. The results obtained here indicate that some knowledge of cross-compatibility relationships in olive is required to design crosses in olive breeding programs effectively. To achieve this objective, the progeny parentage analysis could be of great help because of the high level of pollen contamination found among those studied here.
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.
Ana Morales-Sillero, Pilar Rallo, María Rocío Jiménez, Laura Casanova and María Paz Suárez
At a time of increasing demand, the extremely high cost of manual labor required to harvest fruit in table olive groves is limiting the economic survival of the crop in many producing countries. New grove designs and management practices such as superhigh-density (SHD) groves now in use in oil olive production should be explored as an option to facilitate mechanical harvesting in table olives. The feasibility of two table olive cultivars, Manzanilla de Sevilla and Manzanilla Cacereña, to be harvested in a 5-year-old SHD grove (1975 trees/ha) was studied in 2012 when trees of both cultivars formed highly productive continuous hedgerows (≈10,000 and 18,000 kg·ha−1, respectively). The differences between manual and mechanical harvesting using a grape straddle harvester were evaluated taking into consideration harvesting time, efficiency in fruit removal, and fruit quality both before and after processing as Spanish-style green olives. The average harvest time per hectare with a grape straddle harvester was less than 1.7 hours compared with 576 person/hour or more when done manually. Fruit removal efficiency was high in both cases, 98% for mechanical treatment and 100% for hand treatment. Mechanically harvested fruits had a high proportion of bruising damage (greater than 90%) and the severity of the damage was greater in ‘Manzanilla de Sevilla’ than in ‘Manzanilla Cacereña’. After Spanish-style green processing, however, the proportion of bruised fruits was below 3% in each cultivar. The fruit size in both cultivars was suitable for table olive processing and only 7% and 4% of ‘Manzanilla de Sevilla’ and ‘Manzanilla Cacereña’ fruits, respectively, were diverted to oil extraction as a result of insufficient size. Small differences were found between processed ‘Manzanilla Cacereña’ fruits that were manually or mechanically harvested. In contrast, mechanically harvested ‘Manzanilla de Sevilla’ fruits showed a significantly higher proportion of cutting (18%), a type of damage that may take place during harvesting, and lower firmness and texture than those harvested manually.
Ana Morales-Sillero, María Paz Suárez, María Rocío Jiménez, Laura Casanova, José Ordovás and Pilar Rallo
The germination of seeds and the growth of the generated plant are two phases of great importance in an olive breeding program. In this work, three stratification treatments and five cultivars (Hojiblanca, Manzanilla Cacereña, Manzanilla de Sevilla, Toffahi, and Uovo di Piccione) used as female parents in a breeding program for table olive were evaluated along two years to improve germination protocols. The stratification treatments affected seed germination (percent seeds with radicle), radicle length, seedling emergence (percent emerged hypocotyls), and the average time of emergence. The cultivars have shown great variability with respect to the requirements of the seeds and seedling growth performance. None of the treatments with heat application (25 °C) after chill (14 °C) improved the percentage of germinated seeds and seedling emergence in any year compared with the control treatment (30 days at 14 °C). Cultivars such as Manzanilla de Sevilla and Toffahi seem to be a good choice of female progenitors to improve emergence rates and to obtain early vigorous progenies, a character that has been related to a shorter juvenile period of the seedlings. Moreover, in these progenies, a clear lower apical dominance was found from the first stages of seedling growth. The olive fruit and seed traits were also influenced by the female parent. In fact, ‘Hojiblanca’ and ‘Uovo di Piccione’ showed a higher number of empty seed fruits and double seed fruits compared with the other studied cultivars.