Institute of Olive Tree

Irákleion, Greece

Institute of Olive Tree

Irákleion, Greece
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Markakis E.A.,Institute of Olive Tree | Koubouris G.C.,Institute of Olive Tree | Sergentani C.K.,Institute of Olive Tree | Ligoxigakis E.K.,Laboratory of Plant Pathology
European Journal of Plant Pathology | Year: 2017

In the present study, four Greek (Agiorgitiko, Asyrtiko, Roditis and Xinomavro) and one international (Soultanina) grapevine cultivars (Vitis vinifera L.) were screened for their resistance to Phaeomoniella chlamydospora. Artificial inoculation was carried out by drilling a hole into the trunk and injecting a concentrated conidial suspension into the vessels. Disease reactions were evaluated in an 87-day assessment period, on the basis of external symptoms (disease incidence, disease severity and mortality) and by calculating the relative areas under disease progress curves (relative AUDPC). The extension of vascular browning as well as the isolation ratio along the inoculated vine trunks were also taken into account as additional parameters for evaluating resistance. The results indicated that the resistance of grapevine cultivars to P. chlamydospora varied significantly. ‘Agiorgitiko’ and ‘Soultanina’ were susceptible, whereas ‘Asyrtiko’ and ‘Xinomavro’ were resistant; ‘Roditis’ showed an intermediate level of resistance. Cultivars’ resistance was mostly distinguished in terms of the extension of vascular browning and pathogen isolation ratio. On the contrary, the disease incidence, final disease severity, mortality and relative AUDPC provided less distinctive efficiency in resistance evaluation. The robust methodology presented here could be useful in rapid evaluation experiments for future screening programs to search and recognize natural resistant sources within grapevine genotypes against P. chlamydospora. © 2017 Koninklijke Nederlandse Planteziektenkundige Vereniging

Vakalounakis D.J.,Institute of Olive Tree | Kavroulakis N.,Institute of Olive Tree | Lamprou K.,Institute of Olive Tree
Plant Disease | Year: 2016

In January 2015, a severe foliar disease of Barbados aloe (Aloe barbadensis Miller) was observed at an incidence of approximately 80% in two commercial fields of 0.4 ha each in the Tympaki area of Crete, Greece, after heavy hail. Symptoms were observed on lower and middle leaves of both surfaces as small, circular, brown to black, sunken necrotic spots with an average diameter of 1.0 cm. A dark, olivaceous to black fungus with profuse, golden brown, branched, septate hyphae was isolated consistently on potato dextrose agar (PDA) from infected tissue of 15 leaf samples. Young cultures of two representative single-spore isolates (X1, G1) of the fungus on potato carrot agar (PCA) produced moderately long to long chains of 12 to 20 conidia on short conidiophores; branching of chains was minor or lacking. Conidia were olive brown, obpyriform, with a body length of 21.6 ± 5.60 (9.5 to 36.9) μm, a body width of 11.3 ± 2.17 (7.1 to 19.0) μm, and a beak length of 4.5 ± 1.36 (2.4 to 7.1) μm. The percentage of spores with beaks was 43.8%. Based on these morphological characteristics, the fungus was identified as Alternaria tenuissima (Nees & T. Nees: Fr.) Wiltshire (Simmons 1992, Simmons and Roberts 1993). The internal transcribed spacer (ITS) region of ribosomal DNA, Alternaria major allergen (Alt a 1), glyceraldehyde-3-posphate dehydrogenase (gapdh), elongation factor 1-alpha (tef1), endopolygalacturonase (endoPG), and RNA polymerase second largest subunit (rpb2) gene regions of the X1 isolate were amplified and sequenced with primers ITS1-ITS4, Altfor-Altrev, gpd1-gpd2, EF1-728F-EF1-986R, PG2b-PG3ab, and fRPB2-RPB2, respectively (Woudenberg et al. 2013). A BLASTn search showed that ITS, Alt a 1, tef1, and endoPG gene regions could not distinguish between A. tenuissima and A. alternata, while those with gapdh and rpb2 showed a higher identity of our isolate with the reference strain (CBS 918.96) of A. tenuissima (gapdh, 100%; rpb2, 99% with difference in one nucleotide located in position 156) than the ex-type strain (CBS 916.96) of A. alternata (gapdh, 99%; rpb2, 99% with differences in three nucleotides located in positions 32, 156, and 248), further supporting identification as A. tenuissima. Sequences of the studied DNA regions were deposited to GenBank as Accession Nos. KU162948 (ITS), KU162953(Alt a 1), KU162951 (gapdh), KU162949 (tef1), KU162952 (endoPG), and KU162950 (rpb2). Pathogenicity tests were carried out by inoculating four 90-day-old aloe plants (three leaves per plant). Inoculum consisted of 5-mm mycelial discs as well as of 15-μl droplets of a spore suspension (106 conidia/ml) taken from 5-day-old cultures of the X1 isolate. Four discs and four droplets were applied on different sites of both upper and lower leaf surfaces. Inoculation sites consisted of both wounded and unwounded 20-mm2 areas. Healthy plants treated similarly with sterile water served as controls. Plants were enclosed in polyethylene bags for the first 3 days and incubated at 15 to 20°C with a 10/14-h light/dark photoperiod. After 5 days, leaf spots similar to those observed on the original plants appeared on all inoculated wounded areas and A. tenuissima was reisolated consistently. Control plants as well as unwounded inoculated areas remained symptomless and A. tenuissima was not reisolated, indicating that the fungus is a weak pathogen. Several outbreaks of leaf spots caused by A. alternata have been reported on Barbados aloe in Korea, India, Pakistan, Iran, and the United States, and by A. brassicae in India (Farr and Rossman 2015). However, to our knowledge, this is the first record of A. tenuissima on commercially grown A. barbadensis in Greece and worldwide. The distribution of this disease in Crete is confined at present to these fields, but an outbreak during winter could represent a serious issue for aloe gel production and ornamental commerce in Greece. © 2016, American Phytopathological Society. All rights reserved.

Vakalounakis D.J.,Institute of Olive Tree
Plant Disease | Year: 2016

Onion (Allium cepa L., Liliaceae) is an important commercial crop in Greece, used as a vegetable and condiment and cultivated under open field conditions on approximately 8,000 ha. In June 2015, a severe outbreak of powdery mildew on the local cultivar ‘Kassanou’ (red bulb) of onion in the late vegetative growth stage occurred in an isolated field of 0.1 ha in the Heraklio area, Crete, Greece, at an incidence of approximately 95%. Disease symptoms included circular to oblong (0.5 to 2.0 cm diameter), white to grayish-white patches of fungal growth with irregular margins. Leaf tissue beneath the fungal growth was chlorotic and later necrotic. Lesions often coalesced and covered large areas on the leaf surface. On the basis of microscopic examination, the whitish powdery colonies consisted of conidiophores and conidia. Conidiophores emerged singly or branched in groups of 2 to 4 from stomata, were multiseptate, and bore dimorphic conidia. Conidia were either lanceolate with a narrowed apex and 58.2 ± 4.84 (50.0 to 69.0) × 16.1 ± 2.85 (11.90 to 21.4) µm, or cylindrical to ellipsoid and 51.7 ± 5.87 (40.5 to 61.9) × 15.3 ± 3.08 (11.9 to 21.4) µm. Vegetative hyphae grew superficially on the epidermal surface or intercellularly among mesophyll cells. The fungal teleomorph was not observed. The above structures are typical of the anamorph Oidiopsis sicula Scalia or the illegitimate synonym O. taurica E.S. Salmon of Leveillula taurica (Lév.) G. Arnaud (teleomorpoh) (Palti 1988). To confirm pathogenicity, conidia from diseased onion leaves were brushed onto leaves of each of three 35-to 40-day-old onion potted plants of the local cultivar “Kassanou” (red bulb) in mid-July 2015. Inoculated plants were covered with polyethylene bags and kept in a plastic house at 20 to 30°C. After three days, polyethylene bags were removed. Three healthy plants treated similarly with aka talcum (hydrated magnesium silicate) served as a control treatment. Twelve days after inoculation, symptoms that had developed on the inoculated plants were similar to those observed in the field. No symptoms developed on the control plants. Powdery mildew, caused by L. taurica, on onion was first described in Israel in 1958 (Palti 1959) and later reported from additional countries in Asia (India, Iran, Pakistan, Saudi Arabia, and Turkey), Africa (Ethiopia), Europe (Italy), and America (Argentina, Brazil, and the USA) (Reis et al. 2004, Farr and Rossman 2015.) Although a powdery mildew caused by Oidiopsis spp. has previously been recorded on leek (Allium porrum L.) in Greece (Demetriades et al. 1979), to our knowledge, this is the first record of powdery mildew of onion from Greece, and the distribution of this disease is confined at present to the field in Crete where it was observed. However, powdery mildew should be monitored to be sure it does not become a significant economic disease. © 2016, American Phytopathological Society. All rights reserved.

Vakalounakis D.J.,Institute of Olive Tree | Kavroulakis N.,Institute of Olive Tree
Crop Protection | Year: 2017

Chard [Beta vulgaris L. subsp. cicla (L.) Koch] is a tall leafy green vegetable with a thick, crunchy stalk, which is one of the most popular vegetables in the Mediterranean region. In late September 2016, a severe outbreak of powdery mildew on the chard cultivar Verde a Costa’ Argentata 2 occurred in an isolated 0.1 ha field in the Heraklio area, Crete, Greece, at an incidence of approximately 90%. Initial disease symptoms included small, scattered, circular, white, dust-like colonies of powdery mildew mainly on adaxial surfaces of older leaves. As the disease progressed, white mycelia covered the whole of the foliar parts, and the plant took on a dusty white appearance. No chasmothecia were found on collected samples. Based on morphological characteristics of the imperfect stage, pathogenicity and internal transcribed spacer (ITS) analysis, the pathogen was identified as Erysiphe betae (Vaňha) Weltzien. To our knowledge, this is the first report of E. betae infections on chard in Greece. © 2017 Elsevier Ltd

PubMed | Martin Luther University of Halle Wittenberg, Bayer AG, Technical University of Cartagena, Institute of Olive Tree and 5 more.
Type: | Journal: Insect biochemistry and molecular biology | Year: 2016

Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were recently described in some European populations of T.absoluta, however, the mechanisms of resistance remained unknown. In this study the molecular basis of diamide resistance was investigated in a diamide resistant strain from Italy (IT-GELA-SD4), and additional resistant field populations collected in Greece, Spain and Brazil. The genetics of resistance was investigated by reciprocally crossing strain IT-GELA-SD4 with a susceptible strain and revealed an autosomal incompletely recessive mode of inheritance. To investigate the possible role of target-site mutations as known from diamondback moth (Plutella xylostella), we sequenced respective domains of the RyR gene of T.absoluta. Genotyping of individuals of IT-GELA-SD4 and field-collected strains showing different levels of diamide resistance revealed the presence of G4903E and I4746M RyR target-site mutations. These amino acid substitutions correspond to those recently described for diamide resistant diamondback moth, i.e. G4946E and I4790M. We also detected two novel mutations, G4903V and I4746T, in some of the resistant T.absoluta strains. Radioligand binding studies with thoracic membrane preparations of the IT-GELA-SD4 strain provided functional evidence that these mutations alter the affinity of the RyR to diamides. In combination with previous work on P.xylostella our study highlights the importance of position G4903 (G4946 in P.xylostella) of the insect RyR in defining sensitivity to diamides. The discovery of diamide resistance mutations in T.absoluta populations of diverse geographic origin has serious implications for the efficacy of diamides under applied conditions. The implementation of appropriate resistance management strategies is strongly advised to delay the further spread of resistance.

PubMed | Benaki Phytopathological Institute, Institute of Olive Tree and University of Thessaly
Type: | Journal: FEMS microbiology ecology | Year: 2016

Synthetic carbamates constitute a significant pesticide group with oxamyl being a leading compound in the nematicides market. Oxamyl degradation in soil is mainly microbially mediated. However the distribution and function of carbamate hydrolase genes (cehA, mcd, cahA) associated with the soil biodegradation of carbamates is not yet clear. We studied oxamyl degradation in 16 soils from a potato monoculture area in Greece, where oxamyl is regularly used. Oxamyl showed low persistence (DT

Garantonakis N.,Institute of Olive tree | Varikou K.,Institute of Olive tree | Birouraki A.,Institute of Olive tree
Biocontrol Science and Technology | Year: 2016

A series of bioassays were conducted under laboratory conditions to determine the relative toxicities of various pesticides (acetamiprid, cypermethrin, chlorantraniliprole and emamectin benzoate, Bacillus thuringiensis var. kurstaki and Helicoverpa armigera nucleopolyhedrovirus, copper oxychloride, iprodione, mandipropamid, a mixture of propamocarb + fluopicolide and mixture of fludioxonil + cyprodinil) on Aphidius colemani adults and mummies, as well as sublethal effects on female fecundity. Cypermethrin was highly toxic to pupa of A. colemani within host mummies. Acetamiprid, cypermethrin, emamectin benzoate, a mixture of propamocarb + fluopicolide and mixture of fludioxonil + cyprodinil were also highly toxic to A. colemani adults (92–100% mortality at 48 h post treatment). Mandipropamid, iprodione and copper oxycloride treatments significantly reduced fecundity of the female parasitoids. In contrast B. thuringiensis var. kurstaki, H. armigera nucleopolyhedrovirus and chlorantraniliprole were harmless (<30% mortality) to the parasitoid species tested according to International Organisation for Biological Control toxicity classification and are likely to be compatible with integrated pest management programmes. © 2016 Taylor & Francis.

Kourgialas N.N.,Technical University of Crete | Kourgialas N.N.,Institute of Olive Tree | Karatzas G.P.,Technical University of Crete
Environmental Monitoring and Assessment | Year: 2015

The water flow and the mass transport of agrochemicals in the unsaturated and saturated zone were simulated in the extended alluvial basin of Keritis river in Crete, Greece (a predominantly flat and most productive citrus growing area) using the hydrological model MIKE SHE. This model was set up based on information on land use, geology, soil structure, meteorological data, as well as groundwater level data from pumping wells. Additionally, field measurements of the soil moisture at six different locations from three soil depths (0.1, 0.2, and 0.3 m) were used as targets to calibrate and validate the unsaturated flow model while for saturated condition, groundwater level data from three well locations were used. Following the modeling approach, the agrochemical mass transport simulation was performed as well, based on different application doses. After the successful calibration processes, the obtained 1D modeling results of soil moisture-pressure related to soil depth at different locations were used to design a proper and cost-effective irrigation programme (irrigation timing, frequency, application rates, etc.) for citrus orchards. The results of the present simulation showed a very good correlation with the field measurements. Based on these results, a proper irrigation plan can be designed at every site of the model domain reducing the water consumption up to 38 % with respect to the common irrigation practices and ensuring the citrus water productivity. In addition, the effect of the proposed irrigation scheduling on citrus yield was investigated. Regarding the agrochemical concentration in the groundwater for all dose cases was below the maximum permissible limit. The only exception was for the highest dose in areas where the water table is high. Thus, this modeling approach could be used as a tool for appropriate water management in an agricultural area estimating at each time and location the availability of soil water, contributing to a cost-effective irrigation plan. © 2015, Springer International Publishing Switzerland.

Tzortzakakis E.A.,Institute of Olive Tree | Dos Santos M.-C.V.,University of Coimbra | Conceicao I.,University of Coimbra
Hellenic Plant Protection Journal | Year: 2016

The available published information on the occurrence of resistance-breaking populations of root-knot nematodes (Meloidogyne spp.) on resistant tomato in Greece is updated. Within the period 1994-2013, 13 populations (11 M. javanica and 2 M. incognita) able to reproduce on resistant tomato had been recorded in the regions of Crete, Epirus, Thrace, Peloponissos and Macedonia. In the present study six more resistance-breaking populations, four M. javanica and two M. incognita, were detected in the period 2013-2014, all originating from greenhouse vegetables in Crete. Four of these populations, two M. javanica and two M. incognita, originated from the region of Ierapetra. This is the first time that such populations are found in this major area of greenhouse vegetable production of Crete. © 2016 E.A. Tzortzakakis et al., published by De Gruyter Open 2016.

PubMed | Institute of Olive Tree and Technological Educational Institute of Crete
Type: | Journal: The Science of the total environment | Year: 2017

Recent findings show that halophytes have the ability to accumulate salts in their tissues, making them a very interesting group of plants for domestic wastewater treatment in constructed wetlands (CWs). In that case, it might be possible to reduce the salinity of the final effluent, which is a crucial parameter for wastewater reuse in agriculture. During this study three halophytes, Atriplex halimus, Juncus acutus and Sarcocornia perennis, were tested for phyto-desalination of domestic wastewater in a vertical flow constructed wetland (VFCW) and compared with common reeds (Phragmites australis). In addition, the effect of this alternative vegetation on the overall performance of the system regarding organic matter, nutrients, boron and pathogen removal was monitored. The organic loading rate (OLR) was about 21gCOD/m

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