Global ecological niche conservatism and evolution in Olea species

Background and AimsClimate is an important parameter in delimiting coarse-grained aspects of fundamental ecological niches of species; evolution of these niches has been considered a key component in biological diversification. We assessed phylogenetic niche conservatism and evolution in 24 species of the family Oleaceae in relation to temperature and precipitation variables. We studied niches of 17 Olea species and 7 species from other genera of Oleaceae globally.MethodsWe used nuclear ribosomal and plastid DNA to reconstruct an evolutionary tree for the family. We used an approach designed specifically to incorporate uncertainty and incomplete knowledge of species’ ecological niche limits. We performed parsimony- and likelihood-based reconstructions of ancestral states on two independent phylogenetic hypotheses for the family. After detailed analysis, species’ niches were classified into warm and cold niches, wet and dry niches, and broad and narrow niches.Key ResultsGiven that full estimates of fundamental niches are difficult, we explore the alternative approach of explicit incorporation of knowledge of gaps in the information available, which allows avoidance of overestimation of amounts of evolutionary change. The result is a first synthetic view of evolutionary dynamics of ecological niches and distributional potential in a widespread plant family. Temperate regions of the Earth were occupied only by lineages that could derive with cold and dry niches; Southeast Asia held species with warm and wet niches; and parts of Africa held only species with dry niches.ConclusionsHigh temperature in Lutetian (Oligocene) and low temperature in Rupelian (Eocene) with major desertification events play important role for niche retraction and expansion in the history for Oleaceae clades. Associations between environmental niche characteristics and phylogeny reconstruction play an important role in understanding ecological niche conservatism, the overall picture was relatively slow or conservative niche evolution in this group.     

Centennial olive trees as a reservoir of genetic diversity

Background and Aims

Genetic characterization and phylogenetic analysis of the oldest trees could be a powerful tool both for germplasm collection and for understanding the earliest origins of clonally propagated fruit crops. The olive tree (Olea europaea L.) is a suitable model to study the origin of cultivars due to its long lifespan, resulting in the existence of both centennial and millennial trees across the Mediterranean Basin.

Methods

The genetic identity and diversity as well as the phylogenetic relationships among the oldest wild and cultivated olives of southern Spain were evaluated by analysing simple sequence repeat markers. Samples from both the canopy and the roots of each tree were analysed to distinguish which trees were self-rooted and which were grafted. The ancient olives were also put into chronological order to infer the antiquity of traditional olive cultivars.

Key Results

Only 9·6 % out of 104 a priori cultivated ancient genotypes matched current olive cultivars. The percentage of unidentified genotypes was higher among the oldest olives, which could be because they belong to ancient unknown cultivars or because of possible intra-cultivar variability. Comparing the observed patterns of genetic variation made it possible to distinguish which trees were grafted onto putative wild olives.

Conclusions

This study of ancient olives has been fruitful both for germplasm collection and for enlarging our knowledge about olive domestication. The findings suggest that grafting pre-existing wild olives with olive cultivars was linked to the beginnings of olive growing. Additionally, the low number of genotypes identified in current cultivars points out that the ancient olives from southern Spain constitute a priceless reservoir of genetic diversity.     

Phenolics and antimicrobial activity of traditional stoned table olives 'alcaparra'

In the present work, we report the determination of phenolic compounds in ‘alcaparra’ table olives by reversed-phase HPLC/DAD, and the evaluation of their extract in vitro activity against several microorganisms that may be causal agents of human intestinal and respiratory tract infections, namely Gram positive (Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus), Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae) and fungi (Candida albicans and Cryptococcus neoformans). Three flavonoidic compounds were identified and quantified: luteolin 7-O-glucoside, apigenin 7-O-glucoside, and luteolin. At low concentrations (0.05 mg/mL) ‘alcaparra’ extract revealed significant inhibition of both Gram positive and Gram negative bacteria growth, with exception of P. aeruginosa. Nevertheless, no antifungal activity was observed at the tested concentrations.     

Modelling the combined effect of temperature,pH and aw on the growth rate of Monascus ruber,a heat-resistant fungus isolated from green table olives

AIMS: Growth modes predicting the effect of pH (3.5-5.0), NaCl (2-10%), i.e. aw (0.937-0.970) and temperature (20-40 degrees C) on the colony growth rate of Monascus ruber, a fungus isolated from thermally-processed olives of the Conservolea variety, were developed on a solid culture medium. METHODS AND RESULTS: Fungal growth was measured as colony diameter on a daily basis. The primary predictive model of Baranyi was used to fit the growth data and estimate the maximum specific growth rates. Combined secondary predictive models were developed and comparatively evaluated based on polynomial, Davey, gamma concept and Rosso equations. The data-set was fitted successfully in all models. However, models with biological interpretable parameters (gamma concept and Rosso equation) were highly rated compared with the polynomial equation and Davey model and gave realistic cardinal pHs, temperatures and aw. CONCLUSIONS: The combined effect of temperature, pH and aw on growth responses of M. ruber could be satisfactorily predicted under the current experimental conditions, and the models examined could serve as tools for this purpose. SIGNIFICANCE AND IMPACT OF THE STUDY: The results can be successfully employed by the industry to predict the extent of fungal growth on table olives.     

A kaolin‐based particle film for suppression of the olive fruit fly Bactrocera oleae Gmelin (Dip., Tephritidae) in olive groves

The efficacy of a kaolin‐based particle film formulation M‐99‐099 to control olive fruit fly, Bactrocera oleae Gmelin, field infestations was investigated in north‐western Syria. The results showed that fruit infestation levels were significantly reduced on kaolin‐treated trees compared with untreated trees. Kaolin particle film successfully suppressed B. oleae populations and provided season‐long insect control (>14 weeks) whereas the insecticide dimethoate failed to protect olives for as long a period after the last spray. Consistent with previous findings, the M‐99‐099 kaolin particle film proved to be a promising alternative method to synthetic insecticides and could be used to control B. oleae in olive groves.     

Bioavailability of the phenolic compounds of the fruits (drupes) of Olea europaea (olives): Impact on plasma antioxidant status in humans

To examine the bioavailability of olive polyphenols and to correlate it with their antioxidant efficacy, plasma and urine from healthy volunteers who had consumed 20 olives were subjected to (a) GC-MS analysis for individual phenolics, (b) estimation of plasma total polyphenol content and (c) estimation of plasma total antioxidant potential. Olive polyphenols were absorbed and metabolized within the body, occurring in plasma mainly in the conjugated form with glucuronic acid and reaching C(max) in 1-2h. Excretion rates were maximum at 0-4h. Tyrosol and hydroxytyrosol increased in plasma after intervention. Total antioxidant potential increased (p<0.05). The results indicate that olive polyphenols possess good bioavailability, which is in accordance with their antioxidant efficacy.     

Micropropagation of olive (<Emphasis Type="Italic">Olea europaea</Emphasis> L.) and application of mycorrhiza to improve plantlet establishment

Micropropagation methods were developed for the three French varieties of olive (Olea europaea L.), Aglandau and Tanche, that have the Appelation d’Origine Contrôlée (AOC) status and one ecotype (05300, Laragne, France). Explants consisting of partially lignified nodal segments were collected from rejuvenated glasshouse-grown plant material. Nodal explants with axillary buds were cultured on different media. For AOC varieties, olive medium modified (OM mod) to contain half the concentration of macroelements was the most efficient in inducing bud break and growth when supplemented with 30 g l^?1sucrose and 4 mg l^?1 zeatin. The resulting shoot buds were further multiplied and maintained on OM mod medium. Rooting was best achieved on OM supplemented with 4 mg l^?1 indole-3-butyric acid (IBA). For the Laragne ecotype, maximal shoot proliferation occurred when explants were cultured on woody plant medium supplemented with 15 g l^?1 sucrose and 0.1 mg l^?1 zeatin. Efficient rooting was achieved with 1 mg l^?1 IBA combined with 0.75 mg l^?1 naphthaleneacetic acid. After acclimatization in the glasshouse, survival rates ranged from 57 to 92%, depending on the genotype. Inoculation of Laragne ecotype microplantlets with the arbuscular mycorrhizal fungus Glomus mosseae significantly improved plant survival and subsequent plant development and growth.     

Yeast heterogeneity during spontaneous fermentation of black Conservolea olives in different brine solutions

Aims: To assess the yeast community structure and dynamics during Greek‐style processing of natural black Conservolea olives in different brine solutions. Methods and Results: Black olives were subjected to spontaneous fermentation in 6% (w/v) NaCl brine solution or brine supplemented with (i) 0·5% (w/v) glucose, (ii) 0·2% (v/v) lactic acid and (iii) both glucose and lactic acid. Yeast species diversity was evaluated at the early (2 days), middle (17 days) and final (35 days) stages of fermentation by restriction fragment length polymorphism and sequence analyses of the 5·8S internal transcribed spacer and the D1/D2 ribosomal DNA (rDNA) regions of isolates. Analysis revealed a relatively broad range of biodiversity composed of 10 genera and 17 species. In all treatments, yeasts were the main micro‐organisms involved in fermentation together with lactic acid bacteria that coexisted throughout the processes. Metschnikowia pulcherrima was the dominant yeast species at the onset of fermentation, followed by Debaryomyces hansenii and Aureobasidium pullulans. Species heterogeneity changed as fermentations proceeded and Pichia membranifaciens along with Pichia anomala evolved as the main yeasts of olive elaboration, prevailing at 17 and 35 days of the process. Molecular techniques allowed for the identification of five yeast species, namely A. pullulans, Candida sp., Candida silvae, Cystofilobasidium capitatum and M. pulcherrima, which have not been reported previously in black olive fermentation. Conclusions: By using molecular techniques, a rich yeast community was identified from Conservolea black olive fermentations. Metschnikowia pulcherrima was reported for the first time to dominate in different brines at the onset of fermentation, whereas Pichia anomala and P. membranifaciens evolved during the course. The addition of glucose and/or lactic acid perturbed yeast succession and dominance during fermentation. Significance and Impact of the Study: Yeasts have an important role in black olive fermentation and contribute to the development of the organoleptic characteristics of the final product. At the same time, certain species can cause significant spoilage. The present study adds to a better knowledge of yeast communities residing in olive fermentations towards a well‐controlled process with minimization of product’s losses.     

The combined effects of black oxidising table olive process and ripening on the cell wall polysaccharides of olive pulp

Olive fruits harvested at cherry and black stages of ripening were processed according the table olive black oxidising processing and sampled after the three main steps: storage in brine, lye treatment and thermal treatment (final product). The results show that the storage in brine contributed positively to the stabilisation of cell wall polysaccharides of olive pulp as the amounts of main polysaccharides practically were maintained in both stages of ripening. The lye treatment introduced degradation of cell walls due to the generalised loss of pectic and hemicellulosic polysaccharides and cellulose, caused by the breakage of ester and hydrogen bonds. On the other hand, the lye treatment introduced shifts in the solubilisation of polysaccharides rendering them more difficult to extract by alkali solutions and enabling their retention in the cellulosic residue, which should contribute positively to cell wall firmness. The thermal treatment introduced degradation of cellulose and increased the solubilisation of polysaccharides with a higher extent in the black olives. This work showed that the differences on the cell wall polysaccharides between stages of ripening are magnified after processing and allowed to conclude that the stage of ripening of olive fruits is determinant for obtaining a final product with adequate texture properties for table olive consumption.