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Irákleion, Greece

Markakis E.A.,Institute of Olive Tree | Fountoulakis M.S.,Technological Educational Institute of Crete | Daskalakis G.C.,Technological Educational Institute of Crete | Kokkinis M.,Technological Educational Institute of Crete | Ligoxigakis E.K.,Laboratory of Plant Pathology
Crop Protection

The suppressive effect of six different compost amendments (A, B, C, D, E and Z) against Fusarium oxysporum f.sp. radicis-cucumerinum (Forc) in cucumber and Verticillium dahliae in eggplant was tested. The evaluation of composts in each pathosystem was carried out by recording external symptoms, isolations and plant growth. The concentration of total phenols was determined in the root and stem tissues of eggplant as well as in pure composts and in potting mixtures (soil amended with 20% of compost) at the beginning and the end of eggplant - V. dahliae bioassays. It was shown that composts A, B, C and D were effective against Forc, and composts C, D, E and Z were effective against V. dahliae. The decreased symptom severity and V. dahliae isolation ratio in eggplant was associated with significantly lower accumulation of phenols in stem tissues; whereas the concentration of total phenols in stem tissues of V. dahliae-infested eggplants was significantly higher compared to the non infested. In addition, total phenols content in the pure V. dahliae-suppressive composts was significantly higher than in the non-suppressive ones. Moreover, total phenols content in soil substrate and in potting mixture A decreased, whereas in mixtures B, C, D, E and Z was significantly increased during the time of bioassays process. Interestingly, total phenols content in the V. dahliae-suppressive potting mixtures C, D, E and Z was 3.8-, 3.7-, 3.7- and 4.4-fold higher compared with the non-suppressive control (100% soil), at the end of bioassays process (68 days post inoculation). This is the first insight in the role of phenols in the suppressive effect of composts against soil-borne pathogens, in planta. © 2015 Elsevier Ltd. Source

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

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. Source

Markakis E.A.,Institute of Olive Tree | Tjamos S.E.,Agricultural University of Athens | Antoniou P.P.,Agricultural University of Athens | Paplomatas E.J.,Agricultural University of Athens | Tjamos E.C.,Agricultural University of Athens

In the present study, the efficiency of the biocontrol agent Paenibacillus alvei (strain K165) to suppress Verticillium wilt of olive tree was evaluated in greenhouse and field experiments. In planta bioassays were conducted under greenhouse conditions and revealed that K165 significantly decreased symptoms on the susceptible cultivar ‘Amfissis’ by 44.5 and 51.6 % of the final disease severity index and relative area under disease progress curve (AUDPC), respectively. Thereafter, the suppressive effect of K165 against Verticillium dahliae was studied for two consecutive years (2007 and 2008) in a newly established olive orchard of the susceptible cv Amfissis and the resistant cv Kalamon, naturally infested with V. dahliae. The evaluation of K165 was carried out by recording symptoms, isolations and qPCR quantification of the pathogen in olive tissues. In both years, ‘Amfissis’ trees treated with K165 showed significantly lower final disease severity and relative AUDPC values compared to the non treated controls, whereas, in 2008 decreased symptom severity was associated with significantly lower V. dahliae DNA levels in plant tissues, indicating the suppressive effect of the biocontrol agent. However, no significant suppression was observed in ‘Kalamon’. Pathogen isolations along with qPCR quantification revealed a seasonal fluctuation of V. dahliae biomass in olive tissues with higher amounts occurring in May, and lower amounts in February, August and November. This is the first report of biological control of Verticillium wilt of olive tree under field conditions, associated with reduced pathogen levels inside the xylem tissues. © 2015 International Organization for Biological Control (IOBC) Source

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

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. Source

Dabbou S.,University of Sfax | Brahmi F.,University of Sfax | Taamali A.,Center de Biotechnologie de la Technopole de Borj-Cedria | Issaoui M.,University of Sfax | And 4 more authors.
JAOCS, Journal of the American Oil Chemists' Society

The effects of the contents of lipids, pigments, α-tocopherol and phenols were studied in relation to the antioxidant capacity of five virgin olive oils obtained from five olive cultivars planted in Tunisia (Arbequina, Koroneiki, Leccino, Oueslati and Chemchali). The antioxidant capacities were evaluated by two different radical scavenging activities: radical scavenging activity by the DPPH assay (RSA-DPPH) and total antioxidant status by the ABTS test (TAA-ABTS). The highest contents of antioxidant compounds (75.96, 10.34, 6.32, 15.39 and 241.52 mg kg-1 for oleic acid, O/L ratio, carotenes, chlorophylls and total phenols, respectively) were found for the Koroneiki cultivar except for a-tocopherol and o-diphenols, which had the highest contents (369 and 160.7 mg kg-1, respectively) in the Leccino and Chemchali cultivars (cvs). Furthermore, the highest antioxidant capacity in virgin olive oil was observed in the Koroneiki cultivar (0.24 mmol TE kg-1) followed by the Chemchali and Leccino cvs (0.22 and 0.13 mmol TE kg -1) for the TAA-ABTS test. However, the RSA-DPPH activity was higher for the Chemchali cultivar (19.9%) than for the Koroneiki and Leccino cvs (18.4 and 13.5%, respectively). Correlation between these capacities and the oil composition revealed that they were mainly influenced by the carotene content, followed by chlorophyll and phenolic contents where the ABTS test was more pronounced. Then, the antioxidant capacity of the virgin olive oils was correlated with polar components and the lipid profile which are important for its shelf life. © AOCS 2010. Source

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