Fruit set is inversely related to flower and fruit weight in olive (Olea europaea L.)

Fruit weight is strongly correlated to ovary weight in olive as big-fruited cultivars have larger ovaries and flowers at bloom. We tested the hypothesis that larger ovaries imply stronger sinks and therefore reduce fruit set, expressed as number of fruits. Flower/fruit load per centimeter of shoot was assessed every month from flowering to harvest, on sample shoots of many different olive cultivars differing in fruit size. Data were taken for two years: 2007 and 2008. Additionally, in 2008, a fruit thinning experiment was carried out by leaving a single fruit per shoot, to assess the maximum potential fruit weight achievable by each cultivar. Results indicated that fruit size was mostly genetically determined as thinned fruits of small-fruited cultivars, although bigger than control fruits, never got as big as fruits from large-fruited cultivars, confirming that large ovaries are a prerequisite for large fruits. Among all cultivars, the number of flowers per inflorescence, the number of inflorescences, and the number of flowers per centimeter of shoot were not correlated to average flower weight while total flower mass per centimeter of shoot was positively correlated to average flower weight (i.e. large flowered/fruited cultivars had greater total flower mass). However, one month after bloom and thereafter, all parameters were negatively and exponentially correlated with fruit average weight across cultivars, except fruit mass per centimeter of shoot which was generally not correlated to fruit average weight, except in one year, at harvest, when fruit mass per centimeter of shoot was positively correlated to fruit average weight. These results suggest that fruit set is a consequence of, and inversely proportional to flower/fruit size in olive.     

Microsatellite markers based assessment of genetic diversity in Iranian olive (Olea europaea L.) collections

To study the genetic variation in Iranian olive collections and some foreign olive cultivars, 47 accessions of 18 local cultivars from 6 olive collections of Iran (Roudbar, Zanjan, Ahvaz, Dezful, Kazeroon and Shiraz), were analyzed along with 30 imported cultivars using 16 microsatellite primer pairs. All the used microsatellite loci revealed polymorphism in the studied genotypes, except GAPU14 and GAPU113 markers. Fourteen microsatellite primers amplified 126 polymorphic alleles in the 87 selected olive accessions. The average number of alleles per locus was 9, ranging from 3 to 14. Polymorphic information content (PIC) was 0.85. The genetic similarity based on Jaccard coefficient ranged from 0.15 to 1. The genetic relationships among accessions were investigated using cluster analysis and principal component analysis (PCA). Most of the accessions with the same name were grouped together; some exceptions were also observed. As expected, close relationship was observed among accessions within same cultivar. Most of the Iranian olive accessions were clustered to a main distinct group. Two-dimensional scatter plot of principal component analysis revealed a clear separation of most of the Iranian olives from Syrian and other introduced cultivars. These suggest that Iranian cultivars have different origin related to West Mediterranean basin cultivars and have evolved independently from the others. Between and within Iranian and foreign cultivars (cultivars including three or more accessions) genetic diversity was analyzed using analysis of molecular variance (AMOVA). AMOVA revealed higher within cultivar genetic variation (62.76%) as compare to that between cultivar variations (37.24%). The intra- and inter-cultivar variance tested by permutation test showed significant genetic variation at both levels. The high level within cultivar genetic variance could be due to mislabeling and presence of homonyms in cultivars produced by vegetative propagation from original plants.     

Pistil abortion is related to ovary mass in olive (Olea europaea L.)

Pistil abortion is considered to be an evolutionary adaptation to save resources in andromonoecious species, balancing the number of pistils with the resources available. It follows that large-fruited species/cultivars should have greater levels of pistil abortion. Working in olive, we found that pistil abortion, expressed as percentage of staminate flowers, was positively correlated to the average ovary mass at bloom, across cultivars with different ovary/fruit mass. Since ovary mass correlated with fruit mass, pistil abortion also correlated with fruit mass. The absolute number of perfect flowers per inflorescence was negatively correlated with both ovary mass and pistil abortion, while the number of staminate flowers per inflorescence increased with both parameters. The total number of flowers (i.e. staminate + perfect) was not correlated to ovary mass or pistil abortion, suggesting that male function was not affected. The results support the hypothesis that pistil abortion is related to competition for resources among ovaries, and suggest that genetic differences in pistil abortion among olive cultivars may be explained by their different pistil mass and sink strength.     

Encapsulation of in vitro-derived explants of olive (Olea europaea L. cv. Moraiolo): II. Effects of storage on capsule and derived shoots performance

The experiments described in this paper were designed to examine the effect of storage at different temperatures for various periods on regrowth and proliferation ability of encapsulated olive microcuttings (capsules). The proliferation and rooting ability of the shoots derived from the capsules were compared with those maintained in normal proliferation by 45 days period of subculturing. A simple method of encapsulated microcuttings storage in plastic cuvettes was used. Interesting feature was the ability of the capsules to retain their viability and regrowth after storage at room temperature as well as at 4 °C for 15 and 30 days and both axillary buds on the nodes of almost all capsules sprouted successfully. Improvement in proliferation and rooting abilities were found in subsequent culturing of the shoots developed from the capsules. The study indicates bright prospects of commercial application of alginate nutrient capsule technology in various situations like supply of certified plant material from both official or private organizations to the plant nurseries and/or exchange of germplasm at international level without refrigerated containers just in plastic cuvettes.     

Effect of water deficit and rewatering on leaf gas exchange and transpiration decline of excised leaves of four grapevine (Vitis vinifera L.) cultivars

Grapevine cultivars are known to differ in their drought adaptation mechanisms, but there is little knowledge on how they behave when recovering after a drought event. The effects of increasing water deficit and recovery after rewatering were evaluated on four widely grown red grapevine cultivars native from different climates (Cabernet Sauvignon, Cs; Garnacha, syn. Grenache, Ga; Merlot, Me; and Tempranillo, Te) through the study of gas exchange (GE) measurements and transpiration decline curves (TDC). As a whole, Ga has proved to be the cultivar best adapted to water deficit, since it showed the highest water use efficiency (WUE) and the greatest water saving ability after leaf excision. Te, on the contrary showed the lowest values for those parameters under increasing stress, although when rewatered showed greater acclimation ability than Cs and Me, remarkably improving its behaviour. The two methodological approaches (GE and TDC) used at different water deficit levels and after rewatering, have complemented each other, allowing a better cultivar characterization than each method would had allowed itself.     

Response of four olive (Olea europaea L.) cultivars to six B concentrations: Growth performance,nutrient status and gas exchange parameters

A greenhouse experiment was conducted to study the effects of boron (B) on growth, nutrient status, B distribution and gas exchange parameters of olive plants (Olea europaea L.). One-year-old own-rooted olive plants of the Greek cultivars Megaritiki, Chondrolia Chalkidikis, Amfissis and Kalamon were grown in a sand–perlite medium and irrigated with nutrient solutions containing: 0.27, 0.5, 1, 2.5, 5 and 10 mg L⁻¹ B (0.27 and 10 mg L⁻¹ were considered as control and excess B treatment, respectively). After culturing for 185 days, leaves and stems (from basal and apical part of the shoots) and roots were separately sampled. Our results showed that the final number of leaves per plant was negatively correlated with B concentration in the nutrient solution. Furthermore, in B10.0 treatment, ‘Megaritiki’ had decreased length and number of lateral stems, ‘Chondrolia Chalkidikis’ and ‘Amfissis’ showed decreased length of lateral stems and ‘Kalamon’ decreased length of lateral stems and plant height. In general, dry weight of stems and leaves was not significantly correlated with B concentration in the nutrient solution. B concentration in leaves and stems was linearly correlated with B supply. A linear correlation existed between B concentration of the nutrient solution and that of leaves and stems. At the end of the experiment, B levels in the leaves and stems of B0.27 and B0.5 treatments did not differ significantly. In general, the increase of B concentration in the nutrient solution, negatively affected the nitrogen (N) concentration of leaves and stems while phosphorus (P) and iron (Fe) concentrations were not affected. Furthermore, potassium (K) and calcium (Ca) concentration in stems of plants supplied with 10 mg L⁻¹ B was decreased. In addition, high B supply resulted in increased magnesium (Mg) and manganese (Mn) concentrations in ‘Chondrolia Chalkidikis’ and ‘Amfissis’ and in the decrease of zinc (Zn) concentrations, in all plants. A significant decline in photosynthetic rate at the end of the experiment was observed in the B5.0 treatment regardless of cultivar.     

Growth,biomass allocation and leaf ion concentration of seven olive (Olea europaea L.) cultivars under increased salinity

Olive (Olea europaea L.) is the major fruit tree in the Mediterranean region, often grown in locations where plants are exposed to increased salinity. To determine the effect of NaCl on shoot and root growth, dry matter allocation, leaf Na⁺ and K⁺ concentration, electrolyte (EL) and K⁺ leakage (KL), seven olive cultivars of different origins were grown in nutrient solution containing 0, 33, 66, 100 or 166 mM NaCl for three months. The general effect of salinity was linear and quadratic decrease of observed plant growth parameters. Different responses of tested cultivars to applied levels of salinity were found for stem dry weight, shoot length and number of leaves. As salinity increased, growth of ‘Manzanillo’ declined sharply, whereas ‘Frantoio’ was the most tolerant to growth reduction in most of the observed growth parameters. Allometric analysis showed that biomass allocation under salinity stress was similar in all cultivars, but the slope between shoot weight and total plant weight decreased as salinity increased. Since the higher allocation in roots was not found, it seems that salinity only slowed the above ground plant canopy growth. Sodium concentration in leaves of all cultivars increased as salinity increased with the highest increment reached when the salinity of nutrient solution was raised from 100 to 166 mM NaCl. Significant differences among genotypes were found in leaf Na⁺ and K⁺ concentration and K⁺:Na⁺ ratio, but they were not related to the growth rate. Generally, ‘Frantoio’ and ‘Oblica’ accumulated less Na⁺ and were able to maintain higher K⁺:Na⁺ ratios as compared to other genotypes. Electrolyte leakage and KL linearly increased with increasing salinity and the magnitude of the response depended upon the olive cultivar.     

Effect of alleviating products with different mode of action on physiology and yield of olive under drought

Two years old self-rooted Koroneiki olive trees (Olea europaea L.) were subjected to two irrigation regimes, i.e. the fully irrigated and the severely water stressed trees, while they were treated with three alleviating products of different mode of action. The products used were the osmolyte glycine betaine, the antioxidant Ambiol and the heat and irradiance reflecting kaolin clay particles. The effects of product application and water regime on leaf characteristics, shoot and root growth, photosynthesis, leaf compatible solids (carbohydrates) concentration and yield were evaluated. All products applied, exhibited significant alleviating action, based on the relative alleviation index. Irrigated trees exhibited greater growth than drought stressed ones, while the ameliorating products maintained the water content of the leaves under drought conditions and resulted in lower leaf tissue density. On the other hand carbon assimilation rate, stomatal conductance and intrinsic water use efficiency were significantly reduced under drought stress, while the opposite stood for intercellular CO₂. Drought stress resulted in elevated sucrose leaf concentration, while the application of Ambiol increased stachyose concentration and that of glycine betaine did the same with the mannitol concentration. Among the alleviating products tested in this experiment Ambiol and glycine betaine had a significant positive effect on leaf water content, photosynthesis and yield under both drought and well irrigated conditions.     

The effect of waste water irrigation on the extra virgin olive oil quality from the Tunisian cultivar Chemlali

The availability of fresh water is very scarce in the Middle East and North Africa. Yet consequently, brackish water or recycled wastewater can be used for irrigation, minimising the exploitation of natural water resources. The aim of this work was to study how irrigation with treated wastewater (TWW) over 4 years affects some parameters of “Chemlali” olive oil quality. Two treatments were considered: trees irrigated with treated wastewater and others cultivated in rain-fed conditions. Results showed that irrigation with TWW over 4 years did not affect free acidity, and specific ultraviolet absorbance at K₂₃₂ and K₂₇₀. For both the crop seasons the mean values of these parameters were lower than the upper limits established for “extra virgin” olive oil. However, irrigation with TWW cumulatively increased palmitic, palmitoleic, linoleic and linolenic acid contents and decreased oleic acid rates. A significant decrease of total phenol contents was also observed at the end of experimental period.     

Coconut water and BAP successfully replaced zeatin in olive (Olea europaea L.) micropropagation

The data presented report on trials conducted during 24 months using the Portuguese olive cultivar ‘Galega vulgar’. The effectiveness of coconut water, BAP, or kinetin, as possible zeatin substitutes in olive micropropagation protocols, was investigated. In all stages of the micropropagation process, the mineral and vitamin formulation of olive medium (OM) was used. Regarding culture establishment the best results were achieved when 50 ml l⁻¹ coconut water and 2.22 μM BAP were used as medium supplements. For the in vitro multiplication stage, the highest proliferation rates with an average of 3.4 new explants on each 30 days were achieved maintaining the coconut water concentration at 50 ml l⁻¹ and increasing BAP up to 8.87 μM. The effects of IBA and activated charcoal on the in vitro root induction were also studied. Rooting rates of over 85% were obtained by basal immersion of the explants in IBA solution at 3 g l⁻¹ for 10 s, followed by inoculation in the OM culture medium, added with 2 g l⁻¹ of activated charcoal and without growth regulators. All in vitro rooted plants were transferred into Jiffy-Pots filled with vermiculite–perlite 3:1 (v/v) substrate. Those were subsequently wetted with the OM mineral solution, placed into polystyrene plates each one with 100 Jiffy-Pots capacity, which were transferred to traditional rooting mist benches, on a water-cooling equipped greenhouse. Such a simple acclimatization procedure allowed for 95% of plants survival.     

Characterization of Tunisian pomegranate (Punica granatum L.) cultivars using amplified fragment length polymorphism analysis

The amplified fragment length polymorphism (AFLP) analysis of DNA was used to characterize 34 pomegranate cultivars. By using a combination of six primers, a total of 327 markers were scored with a mean of 57.5. The high percentage of polymorphic bands (ppb) of 94.7 and the resolving power (R_p) collective rate value of 129.14 were scored. Data proved that the tested primers were informative to discriminate among cultivars and to survey the genetic diversity in this fruit crop. It has been assumed that the local pomegranate germplasm is characterized by a typically continuous genetic diversity. The derived dendrogram proved that cultivars are clustered independently from their geographical origin and their denomination. In addition, AFLP permitted the generation of a nearly unlimited number of molecular markers that are reliable in differentiating the cultivars and/or the polyclonal varieties.     

Effects of water deficit on the vegetative response,yield and oil quality of olive trees (Olea europaea L., cv Coratina) grown under intensive cultivation

An experiment was carried out in a young high-density olive grove (556 plants ha⁻¹—Olea europaea L., cv Coratina) located in Southern Italy to evaluate the effect of different soil water availability on the vegetative and productive performances of olive trees also looking into the quality of the resulting oils. Trials were carried out over a 3-year period on trees subjected to irrigation and grown under rainfed conditions. Vegetative tree response, as shoot elongation and trunk diameter, was evaluated. Yield per plant, fruit characteristics, oil quality indices (free fatty acid content, peroxide value, UV adsorption at 232 and 270 nm, total phenols, α-tocopherol content) were determined for both irrigated and non-irrigated treatments in the ‘on’ years 1997 and 1999 (6th and 8th year after planting, respectively).     

Regeneration and characterization of plants derived from leaf in vitro culture of two sweet orange (Citrus sinensis (L.) Osbeck) cultivars

In the current work attempts were made to investigate culture of leaf explants derived from in vitro seedlings of two sweet orange (Citrus sinensis (L.) Osbeck) cultivars, Bingtangcheng and Valencia. Effects of several factors, including culture medium, lighting condition, explant age and genotype on regeneration response were examined based on three parameters, percentage of explants producing shoots, mean number of shoots per explant and shoot forming capacity. Culture of the explants on shoot-inducing media (SIM) composed of MT salts supplemented with different growth regulators gave rise to disparate shoot regeneration, in which SIM₁ (MT + 0.5 mg L⁻¹ BA + 0.5 mg L⁻¹ Kinetin + 0.1 mg L⁻¹ NAA + 3% sucrose + 0.8% agar, pH 5.8) was shown to be the most effective medium for direct induction of shoots from leaf explants. Highly significant difference in the response of shoot bud regeneration was noted between the two cultivars, with Bingtangcheng being more responsive than Valencia. Culture of explants from fully developed leaves led to better shoot regeneration capacity in comparison to undeveloped ones. However, the two lighting conditions used herein did not cause significant difference in shoot regeneration. Phenotypic observation and randomly amplified polymorphic DNA (RAPD) analysis confirmed that all the regenerated plants from both genotypes were genetically identical to their donor plants, suggesting absence of detectable genetic variation in the regenerated plants. The data presented here demonstrated that direct initiation of plants from leaf explants has been successfully accomplished. To our knowledge, this is the first report on direct regeneration of shoots from leaf explants in Citrus, which will provide an alternative source for citrus genetic manipulation in the future.     

Rootstock influences the response of pistachio (Pistacia vera L. cv. Kerman) to water stress and rehydration

Pistachio cultivation requires the use of rootstock because grafting is the only form of vegetative propagation. The main commercial rootstocks are Pistacia integerrima L., Pistacia atlantica Desf., Pistacia terebinthus L. and Pistacia vera L. Pistachio is considered to be a drought and saline-resistant crop; however, there is little information describing varietal responses of rootstocks to water stress. Some studies have suggested that P. terebinthus L. is the most drought and cold resistant rootstock. The effect of the rootstock on the water relations of the grafted plant is crucial for improving crop performance under water stress conditions and for developing the best irrigation strategy. This work studied the physiological response to water stress of pistachio plants (P. vera L. cv. Kerman) grafted onto three different rootstocks P. terebinthus L., P. atlantica Desf. and a hybrid from crossbreeding P. atlantica Desf. × P. vera L. Plant physiological responses were evaluated during a cycle of drought and subsequent recovery in potted plants. Parameters measured were soil moisture, trunk diameter, leaf area, leaf number, leaf and stem dry weight, stem water potential, leaf stomatal conductance. The results showed different responses of cv. Kerman depending on the rootstock onto which it had been grafted. The hybrid rootstock was associated with a higher degree of stomatal control and reduced leaf senescence compared to P. atlantica and P. terebinthus, despite being associated with the most vigorous shoot growth. P. terebinthus enabled very effective stomatal control but was also associated with the most rapid leaf senescence. P. atlantica was associated with less vigorous shoot growth and similar levels of water stress as occurred with the others rootstocks under conditions of high evaporative demand, which was associated with lower stomatal control. The selection of the most effective rootstock choice for different environmental conditions is discussed.     

Non-destructive leaf area estimation model for faba bean (Vicia faba L.)

In this study, a leaf area estimation model was developed for faba bean (Vicia faba L.) using the linear measurements such as lamina length (L) and width (W) by stepwise regression analysis. Leaflets from fourteen faba bean genotypes, including three cultivars (Eresen-87, Filiz-99 and Lara), two lines (FLIP85-172FB and FLIP86-116FB) and nine local genotypes, were used to develop the model in 2003-2004. The proposed leaf area (LA) estimation model is LA = 0.919 + 0.682LW, R² = 0.977. In 2004–2005 growing season, this model was validated by measuring new leaf samples from the different level of the plant canopy (lower, middle and upper) of faba bean cvs. Eresen-87 and Filiz-99 sown in both autumn and late winter. Produced model in this study can be reliably used for estimating area of leaf samples from the different level of the plant canopy of faba bean cvs. Eresen-87 and Filiz-99 sown in both autumn and late winter.     

Calibration and validation of regression model for non-destructive leaf area estimation of saffron (Crocus sativus L.)

Leaf area measurements are required in several agronomical and physiological studies. Usually, there is an interest for measurement methods that are simple, quick and that will not destroy the leaf. The objectives of this study were to establish equations to estimate leaf area (LA) by using length (L), width (W) and dry weight (DW) of saffron leaves. Leaves of different sizes were collected from the experimental area at different time intervals. Leaf area was measured with an automatic measuring device and leaf dimensions were determined with a ruler. An equation for estimating the leaf area from L and W was developed and validated with the area of leaves collected during different periods. Regression analyses of LA versus L, W, LW and DW led several models that could be used for estimating the area of individual saffron leaves. A exponential model having L as the independent variables [LA = 191.33e^(L)0.0037] provided the most accurate estimate (R² = 0.9373, RMSE = 27.68) of saffron leaf area. Validation of the regression model showed that the correlation between measured and simulated values by the use of this equation was very high.     

Phenotypic variability and genetic structure in plum (Prunus domestica L.), cherry plum (P. cerasifera Ehrh.) and sloe (P. spinosa L.)

In the present study, phenotypic variability of 80 plum (Prunus domestica L.) varieties maintained in the French National Plum Collection was evaluated with 19 quantitative traits. In addition, genetic diversity and genetic structure was studied in three plum species (P. domestica L., Prunus cerasifera Ehrh. and Prunus spinosa L.) using chloroplast DNA (cpDNA) markers and five single sequence repeat (SSR) loci. Based on phenotypic traits, some varieties, such as mirabelle plums, grouped together. Bayesian structure analysis was used to identify different genetic groups, whereby damson plums were clearly distinguished from greengage plums. When examining the three species together, a higher level of cpDNA allelic richness was found in P. cerasifera and in P. spinosa than in P. domestica where only five cpDNA haplotypes were detected in the national plum collection, with one main haplotype that accounted for 80% of the varieties studied. P. domestica cpDNA haplotypes tended to group together with P. cerasifera haplotypes whereas most of P. spinosa haplotypes formed a separate cluster. SSR markers were somewhat able to distinguish the three species. These results provide some clues as to the origin of plum and the various plum varieties. Our results also provide useful information for the management of plum genetic resources.     

Effects of irrigation with treated wastewater on olive tree growth,yield and leaf mineral elements at short term

In arid regions, such as Tunisia, the reuse of treated wastewater (TWW) in agriculture can be a sustainable solution for water scarcity. A two-year field experiment was conducted in order to investigate the short-term effects of TWW on olive growth, yield and concentration of total nitrogen (N_t), potassium (K), phosphorous (P), and heavy metals (i.e. Zn, Mn, Pb and Cd) in olive leaves. Olive trees were subjected to the following irrigation treatments: (i) trees irrigated with well water (WW) and (ii) trees irrigated with treated wastewater (TWW). For both treatments, the TWW and WW were applied at a rate of 4.5 m³ day⁻¹ tree⁻¹ (5000 m³ ha⁻¹ year⁻¹). After two years, non-significant injuries caused by salts and/or heavy metals were observed on shoot growth of trees irrigated with TWW. The application of TWW significantly increased concentration of N_t, P and K in the leaves, whereas heavy metals (Zn and Mn) showed a significant increase only after the second year of irrigation.     

Daily and seasonal variation of water relationship in sugar apple (Annona squamosa L.) under different irrigation regimes at semi-arid Brazil

In the northeast of Brazil the drought period determines the yield period of the sugar apple (Annona squamosa L.). As a result, the use of irrigation is essential to stagger production over the course of the year. The results shown here represent an analysis of water status levels in sugar apples in daylight and seasonal periods in semi-arid regions. Two plant groups were studied: one without irrigation and the other with irrigation during drought months. This study showed that younger leaves displayed greater stomatal conductance and transpiration. In drought months, even in irrigated plants, the high air moisture deficit had a strong influence on the stomatal closure, which did not translate into a reduction in transpiration. Over the same period, the leaf water potential was −1.8 and −2.9 MPa at mid-day in irrigated and non-irrigated plants, respectively, and only the irrigated plants could recover their leaf hydration level at night. With a water deficit, plants showed greater control of transpiration through stomatal closure, with a linear relationship between stomatal conductance and transpiration.