Olive Twigs Research Articles

Nanopore-Sequencing Metabarcoding for Identification of Phytopathogenic and Endophytic Fungi in Olive (Olea europaea) Twigs.

Metabarcoding approaches for the identification of plant disease pathogens and characterization of plant microbial populations constitute a rapidly evolving research field. Fungal plant diseases are of major phytopathological concern; thus, the development of metabarcoding approaches for the detection of phytopathogenic fungi is becoming increasingly imperative in the context of plant disease prognosis. We developed a multiplex metabarcoding method for the identification of fungal phytopathogens and endophytes in olive young shoots, using the MinION sequencing platform (Oxford Nanopore Technologies). Selected fungal-specific primers were used to amplify three different genomic DNA loci (ITS, beta-tubulin, and 28S LSU) originating from olive twigs. A multiplex metabarcoding approach was initially evaluated using healthy olive twigs, and further assessed with naturally infected olive twig samples. Bioinformatic analysis of basecalled reads was carried out using MinKNOW, BLAST+ and R programming, and results were also evaluated using the BugSeq cloud platform. Data analysis highlighted the approaches based on ITS and their combination with beta-tubulin as the most informative ones according to diversity estimations. Subsequent implementation of the method on symptomatic samples identified major olive pathogens and endophytes including genera such as Cladosporium, Didymosphaeria, Paraconiothyrium, Penicillium, Phoma, Verticillium, and others.

Land use change rather than surrounding vegetation affects fungal endophyte assemblages in the African wild olive

ContextLand use change can significantly affect plant-fungal interactions.ObjectivesWe assessed how fungal endophytes within African wild olive (Olea europaea subsp. cuspidata) twigs are influenced by different levels of land use change and differences in surrounding vegetation types.MethodsTwigs were sampled in the Western Cape Province (South Africa) and their fungal endophyte assemblages were characterised using culture-independent DNA metabarcoding. We assessed the effects of land use change (natural, semi-natural and planted (completely transformed)) and differences in surrounding vegetation types (grasses/low-growing plants versus shrubs/trees versus other olives) using fungal endophyte alpha and beta diversity measures. Co-occurrence networks were constructed to assess assemblage connectivity under different scenarios and to identify OTUs of potential ecological significance.ResultsOTU richness, but not abundance, was significantly influenced by both land use change and differences in the surrounding vegetation types. Planted African olives and those surrounded by heterospecific trees harboured the highest OTU richness. Only levels of land use change significantly influenced fungal endophyte assemblage composition. Specifically, fungal assemblages from natural habitats were distinct from those in planted and semi-natural habitats, which were similar to each other. Co-occurrence network analyses revealed that cohesive and species rich networks could only be maintained within the natural habitats.ConclusionThese findings suggest that although the African olive is widespread, the identity and composition of their associated fungal assemblages are particularly sensitive to land use change. This study highlights the importance of conserving natural habitats, not just for the plants, but also for the maintenance of their associated fungal endophytes.

A Colorimetric LAMP Detection of Xylella fastidiosa in Crude Alkaline Sap of Olive Trees in Apulia as a Field-Based Tool for Disease Containment

Xylella fastidiosa subsp. pauca (Xfp) infects olive trees and other hosts in Southern Apulia (Italy), devastating agriculture and landscape. A containment strategy of the disease requires quick and sensitive detection tools. Therefore, a colorimetric LAMP protocol was developed using as a template a crude alkaline sap obtained from incubation of 50–60 mg of thin slices of olive twigs in a NaOH-containing buffer. This rapid molecular assay can be performed directly in the field, as it needs only a portable isothermal block. Tissues of the same olive trees analysed by this technique were also compared to qPCR (using purified total plant DNA as template) as well as digital droplet PCR (on the same crude alkaline extracts used in cLAMP). A titration of the cLAMP reaction with healthy olive sap, spiked with dilutions of in vitro cultivated Xfp cells and plasmid DNA containing the target sequence, gave positive detection results as low as 102 CFU/mL and up to 169.2 target copies/µL, equivalent to about 0.9 pg of the genomic DNA. A portable, sensitive and target-specific Xfp field test was developed, which has a 40 min sample-to-answer time and does not require any DNA isolation procedure or laboratory equipment. The application of this detection assay could help the monitoring and containment of the disease spread.

First Report of Phaeoacremonium iranianum Causing Olive Twig and Branch Dieback.

In an olive orchard on the western part of Istria, Croatia, twig and branch dieback was observed on several olive trees. In total, seven samples from symptomatic trees were collected. Samples were analyzed, and four fungal isolates showed morphological similarities to the species Phaeoacremonium. One isolate, chosen as a representative, was taken for molecular identification and pathogenicity tests. Based on the DNA sequence data of the ITS, TUB, and EF1α gene regions, the isolate was identified as P. iranianum. Pathogenicity tests were conducted on detached olive branches and olive trees in the greenhouse. To the best of our knowledge, this is the first report of twig and branch dieback on olive caused by Phaeoacremonium iranianum.

Field and Laboratory Efficacy of Low-Impact Commercial Products in Preventing Olive Fruit Fly, Bactrocera oleae, Infestation.

Simple SummaryThe adoption of sustainable methods for herbivore pest control has become mandatory in Europe, with the EU directive 128/09. Since then, stringent evaluation protocols have been applied to insecticides and several molecules (that are suspected to be unsafe for the environment or human health) have been banned. Hence, the evaluation of sustainable methods, e.g., preventive tools based on the manipulation of pest behaviour, must be considered. Using field and laboratory assays, we tested the efficacy of different products in preventing infestation of a key pest of olive orchards, the olive fruit fly Bactrocera oleae. Our findings may be useful for the development of control strategies in integrated pest management (IPM) and organic agriculture.The olive fruit fly, Bactrocera oleae, is the key pest of olive trees in several areas of the world. Given the need for the development of sustainable control methods, preventive tools, based on the manipulation of pest behaviour, must be considered. Here, under field and laboratory conditions, we tested the efficacy of different products in preventing B. oleae infestation. A field trial was conducted, from July to November 2020, in an olive orchard located in Central Italy. A table olive variety was selected and sprayed with rock powder, propolis, the mixture of both, copper oxychloride, or water (control). All treatments, except propolis, caused a reduction of B. oleae oviposition in olives, compared to the control. The mixture allowed the strongest reduction of fly infestation throughout the season, suggesting a synergistic effect. Behavioural no-choice assays were conducted to better understand the effects of treatments on B. oleae females. Compared to the control, females showed a lower preference for the central area of an arena containing an olive twig bearing two olive fruits, fully developed, but still green, treated with rock powder, plus propolis mixture. For all treatments, B. oleae showed lower oviposition events, suggesting deterrence to oviposition. Our results indicate that the tested products may have value against B. oleae, within integrated pest management (IPM) and organic agriculture.

Effect of olive tree leaves and twigs on intake, digestibility, growth performance and blood variables of Shami goats.

The effect of replacing wheat straw and a portion of commercial concentrate with olive twigs and leaves treated with urea and molasses on nutrient digestibility, growth performance and blood variables was determined. Forty‐two Shami goat kids (20 ± 2.47 kg live weight and 133 ± 5.44 days of age) were randomly allotted to three dietary treatment groups, control (75% commercial concentrate and 25% wheat straw), OTU (62.3% commercial concentrate + 37.7% olive twigs and leaves treated with 4% urea for 14 days), OTUM (51.5% concentrate mixture + 48.5% olive twigs and leaves treated with 4% urea for 14 days then sprayed by 10% molasses). Cost (SYP/t) of control, OUT and OTUM was 12,600, 10,066 and 10,106 respectively. The study consisted of a growth trial of 100 days and a digestibility trial of 12 days (7 days of adaptation and 5 days of urine and faeces collection). Serum urea, total protein, albumin, alanine aminotransferase activity, aspartate aminotransferase activity, glucose, cholesterol, creatinine, haemoglobin and packed cell volume were determined. Daily dry matter intake, digestibility of crude protein, ether extract and nutrient detergent fibre did not significantly differ among the dietary treatments (p > .05). Nitrogen intake, nitrogen excretion in urine and faeces and nitrogen balance was not significantly affected (p > .05) by the dietary treatment. The dietary treatment did not have any significant effect on average daily gain, feed conversion ratio or blood variables (p > .05). Olive twigs treated with 4% urea and OTUM replaced 37.7% and 48.5% of conventional diets of growing Shami goat kids without negative effects on growth performance nor health and potentially reduced fattening costs for farmers in olive‐livestock mixed systems by 19.8 and 20%, respectively. OUT is technically simpler than OTUM, thus, it could replace the conventional fattening ration of Shami male goat.

Filamentous fungi isolated from Tunisian olive mill wastes: use of solid-state fermentation for enzyme production

Olive mill wastewaters and olive cake are effluents generated during olive oil production process. They represent a major disposal and potentially severe pollution problem for the industry, also promising source of substances of high value. The aim of this study is the valorization of olive mill wastes (OMWW, olive cake, olive twigs and leaves) to produce enzymes with high industrial and biotechnological potential, by the solid-state fermentation technique (SSF), from isolated fungi present in olive mill wastewater and olive cake. A total of 47 strains were isolated and purified from these two residues. The metabolic potential of isolated strains was study by testing the hydrolytic enzymes activities of lipase, protease, amylase, cellulase, invertase, phytase and tannase on agar plate media containing different substrate. The monitoring of SSF has shown that the metabolic activity of these strains is extremely rapid using this technique. Our fungi collection contains a diversity of strains capable to producing a variety of enzymes of biotechnological interest.

Olive Twig and Branch Dieback in California Caused by Cytospora oleicola and the Newly Described Species Cytospora olivarum sp. nov.

Field surveys conducted throughout California olive-growing regions in 2008 and 2009 resulted in a collection of 101 Cytospora-like isolates from olive twig and branch dieback symptoms. Cytospora isolates were isolated from multiple cvs. in different olive orchards in Fresno, Madera, Merced, Napa, Riverside, Santa Barbara, Sonoma, Tulare, and Ventura counties. Taxonomic studies of macro- and microscopic structures along with multigene phylogenetic analyses of the internal transcribed spacer region, including the 5.8S rDNA (ITS1-5.8S-ITS2), and fragments of the translation elongation factor 1-α, beta-tubulin, and actin genes identified two species, Cytospora oleicola and C. olivarum sp. nov. Pathogenicity studies conducted in mature olive trees cvs. Manzanillo and Sevillano showed both species to be pathogenic and able to cause vascular necrosis and cankers in olive branches. This study adds to the current knowledge on the etiology of olive twig and branch dieback and provides new important information for the development of effective control strategies against canker diseases affecting olive in California.

Anatomical pathogenesis and histological interaction between Pseudomonas savastanoi pv. savastanoi strain KT11 and Pseudomonas fluorescens strain PICF4 in olive knots

The development of the olive knot disease, caused by Pseudomonas savastanoi pv. savastanoi was studied taking into consideration the anatomical changes at the inoculation sites. The genesis of knots was investigated in the absence and presence of Pseudomonas fluorescens bv. PICF4, a natural colonizer of olive roots and an effective biocontrol agent (BCA) of verticillium wilt of olive. This bacterium was investigated for its potential as a BCA against olive knot disease. Bioassays using 5-month-old olive plants (cv. Arbequina) were performed to assess the interaction between olive plant stems, Pseudomonas savastanoi KT11, isolated from active knots of naturally infected olive twigs, and PICF4. Thus, we studied whether strain PICF4 controlled knot development and anatomy compared with those observed in the absence of PICF4, and the population size of both bacteria when co-inoculated together in stems or separately injected at different intervals after inoculation. Results revealed that PICF4 was able to settle, colonize and persist in stem tissues upon artificial inoculation. While PICF4 was unable to suppress disease development, its presence affected the pathogen population size (reduction of ≈ 25% at 54 days post inoculation) and produced smaller knots. Histological sections (± 40 μm thicknesses) cut with a vibrotome and observed under a light microscope showed less tissue alterations and less cavities inside the knots, compared with those produced when the pathogen was inoculated without PICF4.

Isolation of an antiviral compound from Tunisian olive twig cultivars

(1) Many studies demonstrated that olive oil and the leaves have several biological activities, but the works on olive twigs remain very limited. In this report, we investigated for anti-coxsackievirus B-3 (CVB-3) and anti-herpes virus type 2 (HSV-2) activities of olive twigs from two Tunisian varieties: Chemlali (CM) and Chétoui (CT). Extraction from the olive twigs was carried out using successively hexane, dichloromethane, ethyl acetate and methanol. The obtained extracts were evaluated for their anti-CVB-3 and anti-HSV-2 activities by MTT and plaque reduction assays, respectively. Only hexane extracts exhibited significant activity with a selectivity index of 6.32±0.67 and 5.24±0.82 for CM and CT, respectively. The active compound was isolated through bio-guided assays using Thin Layer Chromatography (TLC) and identified as 2,4-di-tert-butylphenol (2,4-DTBP) by gas chromatography coupled with mass spectrometry (GC-MS). This work is the first study that demonstrated an antiviral activity of both olive twigs and DTBP.

First Report of Pleurostomophora richardsiae Causing Branch Dieback and Collar Rot of Olive in Istria, Croatia

During 2016 and 2017, a survey for olive (Olea europaea L.) diseases was carried out in Istria, Croatia. Samples were collected from trees showing wilt, decline, and branch dieback and were analyzed in the laboratory for the presence of potential pathogens. The fungus Pleurostomophora richardsiae (Nannf.) L. Mostert, W. Gams and Crous was found in four out of 23 orchards inspected. It was isolated from six trees in two orchards, from cankers and purple-brown streaking on olive twigs and branches after placing fragments of diseased tissue onto carrot piece agar. The same fungus was also isolated in two orchards from four declining trees showing necrotic areas beneath the bark of root collars and lower part of the trunk. P. richardsiae was identified by morphology of pure cultures, conidiophores, phialides, and two types of conidia (Schol-Schwarz 1970 ; Vijaykrishna et al. 2004) after transferring colonies on potato dextrose agar (PDA) and incubation for 25 days in darkness. Colonies on PDA were cottony, brown with whitish edge, gray-brown in reverse, abundantly producing two types of conidia on phialides: spherical brown conidia (2.1-μm diameter) and hyaline allantoid to reniform conidia (5.4 to 6 × 2 μm). Two isolates (PI 2-17 and ZT 1/17) were selected to confirm species identification by amplification and sequencing of the internal transcribed spacer (ITS) region using ITS1/ITS4 primer pair (White et al. 1990). Sequences showed 99% identity with P. richardsiae strain CBS406.93 (GenBank accession no. AB364703) and were deposited in GenBank (MH014999 and MH015000). Both Croatian isolates were selected to assess their pathogenicity to olive plants. Pathogenicity tests were performed on 2-year-old potted plants of local olive cultivar Buza maintained in a growth chamber set on 18/22°C and 12-h dark/12-h light regime. Five microliters of conidial suspensions (106 conidia/ml) of selected isolates was injected in 2-mm wounds made in basal, middle, and upper part of the trunk of each plant. Another set of plants was inoculated by placing mycelial plugs (5-mm diameter) from 10-day-old colonies on PDA into circular wounds made on the same positions described above. Twelve plants in total were inoculated: three with conidial suspension and three with mycelial plugs for each fungal isolate. Twelve control plants were inoculated with sterile water and noncolonized PDA plugs. Four months after inoculation, four out of 12 P. richardsiae-inoculated seedlings wilted above the inoculation point. Two plants wilted completely, and two plants wilted from the middle inoculation points. Necrosis under the bark developed in 25 out of 36 P. richardsiae-inoculation points (69%). Necrosis developed on all 18 points inoculated with mycelial plugs and on seven out of 18 points inoculated with conidial suspensions. Necrotic area length beneath the bark ranged from 17 to 44 mm. The fungus was reisolated from necrotic areas in 24 out of 25 attempted reisolations (96%). Wilting or necrosis was not recorded on control plants, and the pathogen was not reisolated. This is the first report of P. richardsiae associated with dieback and collar rot of olive in Croatia, although P. richardsiae was previously reported as a pathogen of olive in southern Italy (Carlucci et al. 2013). Presence of P. richardsiae in Croatia indicates that this olive pathogen might be more broadly distributed in European olive-growing regions than previously reported.

Sites and Time of Oviposition of Euphyllura phillyreae Foerster on Olive Trees and οon Phillyrea latifolia

The distribution of eggs of Euphyllura phillyreae Foerster (Homoptera: Aphalaridae) was recorded on twigs of olive trees and of Phillyrea latifolia L. in various locations of the Thessaloniki and Halkidiki prefectures of coastal northern Greece. On olive, the first eggs were observed in the last ten days of March and oviposition was intensified and became abundant only when the apical bud and the axillary leaf and flower buds started to swell. Eggs were laid mostly on swollen buds and on developing inflorescences. Oviposition preference was related to the stage of development of a bud and not to its location on the olive twig. On swollen leaf buds, most eggs were laid on the inner (upper) surface of the middle (second) pair of developing leaves, and fewer on the inner surface of the outer (first) pair and on the innermost (third) pair of leaves. On Phillyrea, eggs were deposited much earlier than on olive, on developing inflorescences. In choice and no-choice laboratory experiments, more eggs were laid on olive twigs bearing developing inflorescences, fewer eggs on twigs bearing only swollen terminal or axillary buds, and no eggs at all on twigs with only fully developed leaves of the previous year.

Development and reproduction of Lobesia botrana on vine and olive inflorescences

Grape vine (Vilis vinifera F.) inflorescences were caged in a bag of organdy in the field, and artificially infested with 15 neonate larvae of Lohesia botrana (Denis and Schiffermueller) (Lepidoptera: Tortricidae). Olive twigs, each bearing 5 pairs of inflorescences were caged likewise. In laboratory experiments 15 neonate larvae were placed in each Petri dish containing one vine inflorescence or an olive twig bearing two pairs of inflorescences. Three stages of inflorescence development were used, an early, an intermediate and a late one. Larvae, pupae and adults were maintained at L:D 16:8 and 24″:22°C. In the field, when comparing inflorescences of the earliest developmental stage, the rate of larval development was significantly faster on olive than on vine inflorescences. In the laboratory, when comparing inflorescences of similar developmental stages, the rate of larval development on olive inflorescences was significantly faster than that on vine inflorescences. Pupae of both sexes were significantly heavier on olive inflorescences in all the cases in the laboratory, but in only some cases in the field. In the field the number of eggs per female and the coefficient of multiplication of the insect’s population from generation to generation were greater on olive (102.6 and 3.8 respectively) than on vine inflorescences (81.7 and 2.9). In the laboratory, the respective values were 118.5 and 12.3 on olive, and 90.2 and 4.9 on vine inflorescences. In two-choice tests in the laboratory, vine inflorescences were preferred for oviposition to olive inflorescences and to vine or olive leaves. In no-choice tests, vine leaves, vine inflorescences, olive leaves and olive inflorescences in the least advanced stage, were all equally accepted for oviposition.

Olive Twig and Branch Dieback: Etiology, Incidence, and Distribution in California.

Eighteen different fungal species were isolated from symptomatic wood of olive trees (Olea europaea) affected by twig and branch dieback in California and identified by means of morphological characters and multigene sequence analyses of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), a partial sequence of the β-tubulin gene, and part of the translation elongation factor 1-α gene (EF1-α). These species included Diaporthe viticola, Diatrype oregonensis, Diatrype stigma, Diplodia mutila, Dothiorella iberica, Lasiodiplodia theobromae, Phaeomoniella chlamydospora, Phomopsis sp. group 1, Phomopsis sp. group 2, and Schizophyllum commune, which are for the first time reported to occur in olive trees; Eutypa lata, Neofusicoccum luteum, Neofusicoccum vitifusiforme, and Phaeoacremonium aleophilum, which are for the first time reported to occur in olive trees in the United States; and Botryosphaeria dothidea, Diplodia seriata, Neofusicoccum mediterraneum, and Trametes versicolor, which have been previously reported in olive trees in California. Pathogenicity studies conducted in olive cultivars Manzanillo and Sevillano showed N. mediterraneum and Diplodia mutila to be the most virulent species and Diatrype stigma and D. oregonensis the least virulent when inoculated in olive branches. Intermediate virulence was shown for the rest of the taxa. This study demystifies the cause of olive twig and branch dieback and elucidates most of the fungal pathogens responsible for this disease in California.

Stem and whole-plant hydraulics in olive (Olea europaea) and kiwifruit (Actinidia deliciosa)

A field study and an experiment under controlled conditions using pressure-flux relationships were conducted to compare the stem and whole-plant conductance in olive (Olea europaea) and kiwifruit (Actinidia deliciosa) species. Anatomical observations were also made on one-year-old stem to determine the conductive area of vessels (A ves) and the total xylem area (A xyl). Results show that A ves of kiwifruit twigs was ~2.5-fold of that in olive twigs, and the hydraulically weighted mean diameter was up to threefold that of the olive ones. One-year-old olive twigs had lower hydraulic conductivity (k) than the kiwifruit, while values of leaf-specific conductivity (i.e. k normalised per unit leaf area) were higher than the kiwifruit (i.e. ~49 and 29 × 10−6 kg m−1 s−1 MPa−1, respectively). In the field experiment, the flux of sap (heat balance method) and differences in water potential through the soil–plant system (ΔP) were used for both species to calculate the whole-plant conductance that was normalised per unit leaf area (leaf-specific whole-plant conductance, K plant,LA). Values of K plant,LA are attributable to the combined effect of the ΔP and anatomical features of conduits. Olive species showed a larger ΔP (2.4 MPa at midday) than the kiwifruit (0.5 MPa) which contributed to lower K plant,LA in Olea than the Actinidia plants. This information, combined with vessel density data, contributes to explain differences amidst olive and kiwifruit species, in terms of susceptibility to some drought-related hydraulic impairments induced by the Mediterranean environment.

Heat shock response in olive (Olea europaea L.) twigs: Identification and analysis of a cDNA coding a class I small heat shock protein

The objective of this study was to investigate at the molecular level the heat shock response in olive by identifying sequences coding for heat shock proteins (HSPs). Young twigs of Olea europaea trees (cv Cellina di Nardò) were subjected to different temperature treatments in order to induce the expression of heat shock genes. In order to identify genes induced by heat treatment, we used a PCR-based approach to amplify specific HS cDNAs. Search for low molecular weight HSP sequences was performed in public domain databases in order to design specific primers based upon multisequence alignments. By this approach, we isolated the first full length cDNA encoding a low-molecular weight HSP from O. europaea. This is a class I low molecular weight HSP of 18.3 kDa, which is highly expressed in young twigs subjected to heat stress.

Accumulation of xylem transported protein at pit membranes and associated reductions in hydraulic conductance

Proteins and traces of polysaccharide are the only polymeric colloids consistently transported in the xylem sap of plants. The hypothesis that such proteins could have physical inhibitory effects on xylem water transport was investigated. Ovalbumin, with a molecular weight of 45 kDa and a molecular diameter of 5.4 nm, is an inert, water-soluble protein that is midway along the size range of endogenous xylem sap proteins. Solutions of ovalbumin conjugated to a fluorescent marker and supplied to transpiring shoot explants of tobacco (Nicotiana tabacum L.) and olive (Olea europaea L.) were shown by confocal laser scanning microscopy to accumulate specifically at wall-based pit membranes that connect neighbouring xylem conduits. In addition, pressure-induced perfusion of micro-filtered ovalbumin solutions, at concentrations similar to those of endogenous xylem sap proteins, through the xylem of tobacco stem or olive twig segments resulted in the retention of c. 40% of the ovalbumin and reductions in the axial hydraulic conductance of the xylem. Smaller molecules such as Texas Red 3000 (MW 3 kDa) and Alexafluor 488–cadaverin conjugates (MW 0.64 kDa) did not show similar characteristics. The partial reduction in xylem hydraulic conductance appeared to be related to the accumulation of ovalbumin at xylem pit membranes and the consequent fouling of trans-membrane water-conducting pores with smaller diameters than those of the ovalbumin molecules. Potential implications of these novel findings for whole-plant water relations are considered.

THE EFFECTS OF THE DIFFERENT DOSES OF IBA (INDOL BUTRIC ACID) ON THE ROOTING PERFORMANCES IN THE REPRODUCTION OF “GEMLIK” AND “DOMAT” OLIVE TREES BY USING THE GREEN TWIG PROCEDURE IN THE ECOLOGY OF ÇUKUROVA REGION

The effects of the different doses (0, 2000, 4000 and 6000 ppm) of IBA (Indol Butric Acid) on the rooting performances in the reproduction of “Gemlik” and “Domat” olive trees by using the green twig procedure in the ecology of Cukurova region were investigated. The research was conducted in the research area of the Agricultural Faculty at Cukurova University. According to the obtained results, while rooting was not observed in “Domat” olive twigs, “Gemlik” olive twigs yielded better results in the 4000 and 6000 ppm of IBA procedures than those in the control group. Moreover, the conditions of the species of the olive trees, the application period and the dose of the hormone used, the time the twigs were collected, and the condition of the misting unit were also found to be effective in the rooting of the olive twigs.

Vegetative Compatibility and Pathogenicity of Verticillium dahliae Kleb. Isolates from Olive in Israel

AbstractFifty‐two isolates of Verticillium dahliae from olive trees grown at different locations in Israel were assigned to vegetative compatibility groups (VCGs), using nitrate non‐utilizing (Nit) mutants. A higher frequency of nit1/nit3 mutants (95%) was obtained compared with NitM (5%), with 81% of the isolates being assigned to VCG4B and 19% to VCG2A. The pathogenicity of 14 randomly selected isolates (seven of each VCG) was tested on olive twigs (cv. Picual) and tomato. VCG4B and VCG2A isolates were similarly aggressive on olive. However, VCG2A isolates were more aggressive on tomato (line 139) than the VCG4B isolates as indicated by a higher colonization index.

Egg Distribution Patterns of Olive Psyllid Euphyllura phillyreae (Homoptera: Aphalaridae) on Phillyrea latifolia and Olea europaea in Northern Greece

Egg distribution patterns of Euphyllura phillyreae Foerster among buds and inflorescences of olives and Phillyrea latifolia L. ( Phillyrea media L.), a perennial, bushy, evergreen plant that blooms from March to May, were quantified in the field and in the laboratory. In the field, the 1st eggs on olive were observed in early April in 1989 and 1990 on developed buds. Eggs became abundant only when the apical bud and the axillary buds started to swell. In May the eggs were observed on inflorescences. Eggs were deposited 8 wk earlier on P. latifolia than on olives, mostly on developing inflorescences. Preference for oviposition at different sites of the developing bud changed over the season on olive. Initially, the outer and the median pair of bud scales were preferred. Later in the season the eggs were uniformly distributed on all 3 pairs of scales of developed (expanding) buds. On inflorescences the petals of closed flowers were the most preferred site, followed by the sepals. On P. latifolia the most preferred site of developing inflorescences was the bracts, followed by the sepals. Young, actively growing tissue, such as developing buds or inflorescences, apparently were the preferred sites for oviposition on both olive and P. latifolia . In choice and no-choice laboratory tests, more eggs were laid on olive twigs bearing developing inflorescences, fewer eggs on twigs bearing only swollen terminal or axillary buds, and few eggs or no eggs at all were laid on the other plant parts.