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The microbiological spoilage of foods depends on the initial microbiological contamination and some factors which influence the growth of microorganisms. Therefore, reducing the initial cell count is necessary for both extending shelf-life and improving food safety. Physical, chemical and combined treatments serve this purpose. In these experiments, the effect of trisodium phosphate dipping (0-15% solutions) was studied. Chicken wings were used, which after dipping (1 min) in the solution were packed in PE-PA-PE pouches and stored at 4 °C. Aerobic mesophilic (Nutrient Agar, Merck), pseudomonad (Pseudomonas Selective Agar, Oxoid), and Enterobacteriaceae counts (VRBD Agar, Merck) were determined by Spiral Plate Technique at 30 °C incubation temperature. Effect of 3.8, 5.7, 7.6% trisodium phosphate dipping solutions was studied as a function of storage time. Immediately after treatment, total colony count was reduced by maximum 1.5 log cycles. Pseudomonads were the most sensitive. One day after treatment with these low concentration solutions, the colony count was reduced by 2 log cycles. Na3PO4concentration higherthan 7.6% practically did not result in higher effectivity. The growth rate and maximum cell count of surviving fraction were estimated as a function of trisodium phosphate concentration. It can be concluded from fitted survival curves that immediately after treatment the initial viable cell count was reduced and the critical spoilage level (107g-1) has been reached 2-3 days later than in case of the untreated samples, i.e. the shelf-life was extended.

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An efficient regeneration system is described based on the use of several genotypes and combining different cytokinins in the regeneration process. Optimal regeneration efficiency can be obtained if the factors affecting regeneration are examined with special attention to the maintenance of the stock plants, the composition of the medium, and the pre-treatment. The maintenance of stock plants proved to be optimal if the plants were kept on modified LS medium supplemented with 0.125 mg L −1 6-benzylaminopurine (BAP) and 0.01 mg L −1 indole-3-butyric acid (IBA) in large vessels. Pre-treatment was found to increase the regeneration efficiency. Placing the leaves on to medium containing 1.5 mg L −1 BAP-riboside and 0.1 mg L −1 thidiazuron (TDZ) without wounding, and keeping them in the dark for 6 days gave the best results. The highest regeneration rate was observed on medium containing MS salts with B5 vitamins complemented with 20 g L −1 glucose, 3 mg L −1 BAP-riboside, 0.2 mg L −1 TDZ and 0.2 mg L −1 IBA. This system made it possible to achieve regeneration in each of the varieties examined, though to different extents.

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In our present study we aimed to recognize the temporal and spatial patterns of Noctuinae communities (Lep.Noctuidae)of four differently managed apple orchards laying in different localities of Hungary.Data were obtained by light trap collection. The quantitative data resulting from our investigations were analyzed by multivariate methods and were also analyzed by their diversity characteristics.As a result connections were found regarding the diversities of species and individuals,the patterns of occurrence and phenological properties.The studies were based on 8497 individuals of 39 species.

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A recombinant Bacillus subtilis strain containing a plasmid encoding a luxAB fusion, which gave bioluminescence upon addition of an exogenous long-chain aldehyde as substrate for the endogenous luciferase enzyme, was used as test organism. Its populations were treated with 300 MPa for 20 min, or 600 MPa for 20 min at around room temperature, and this treatment is foreseen as a quality-friendly, non-thermal pasteurisation of foods. Besides the estimation of viable cell counts, the extent of pressure-induced germination and post-process development were investigated by phase-contrast microscopy, turbidimetry and luminometry. Increased heat sensitivity of pressurized spore populations was observed both by viable cell counting during a linearly programmed elevation of temperature and a simultaneous differential scanning calorimetry. This was related to pressure-induced germination of spores, although a small fraction remained ungerminated. The luciferase pool built into the spores during their formation seemed to have withstood pressurization. Spore germination was accompanied by the emergence of bioluminescence which also indicated sensitively the characteristic changes of metabolic activity running parallel with the development of untreated cell populations and that of the survivors of the hydrostatic pressure treatments when the cells were incubated in a nutrient broth.

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The effect of high hydrostatic pressure (HHP) and nisin was studied on micro-organisms in minced chicken and beef meat. Pressure in the range of 0-800 MPa and nisin (670 IU g-1) were applied for vacuum packed minced meat. In chicken meat the total viable cell count decreased by 3 log cycles as an effect of HHP at 300 MPa and by 5 log cycles in combination with nisin. The D value is 35-39 MPa for pseudomonads in minced chicken meat. In case of inoculation with L. monocytogenes, the cell count in beef meat was reduced only by pressure higher than 200 MPa (“shoulder”) with a characteristic value of D=37-38 MPa. B. cereus spores, both dormant and heat activated, were very resistant (D=800 MPa) in beef. However, the survival of pressurised spores after chilled storage (for two weeks at 4 °C) was smaller for non-heat activated spores than for heat activated spores. Efficiency of HHP combined with nisin needs further research work.

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Studying fungal diversity in various environmental samples provides us with valuable knowledge about the occurrence of fungi of medical and ecological importance. Moreover, fungal composition may also characterise well the botanical and geographical source of food products, such as the origin of the spore enriched honeydew honeys. Thereby, we identified a wide spectrum of fungi found in 100 of honey samples from various geographical sources – most of them were from Italy, Greece and Hungary. Our honeydew honeys had a higher mean of the number of spore types found in them than floral honeys had. Statistically significant differences in diversity were found regarding the botanical source (p = 1.29 × 10–9) and the climatic classification (p = 2.28 × 10–2) according to Kruskal– Wallis rank sum tests. Most frequently encountered genera included ubiquitous saprotrophic species (Alternaria, Cladosporium, Epicoccum nigrum, Stemphylium), both in floral and honeydew honeys. On the other hand, certain sooty moulds like Aureobasidium pullulans, Tripospermum and Capnobotrys were rather present in different types of honeydew honeys. Metschnikowia reukaufii, the nectar inhabiting yeast reached considerably high quantities in floral honey samples. Present findings encourage further studies on quantifying the occurrence and the indicator value of specific fungal elements in honey, concerning its origin.

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To check the importance of Cd-induced iron deficiency in Cd stress, symptoms of Cd stress were compared with those of iron deficiency or the combination of these two stresses. Poplar plants grown in hydroponics with Fe-EDTA (e) or Fe-citrate (c) up to four-leaf stage were treated for two weeks either by the withdrawal of iron (Fedef), or supplying 10 μM Cd(NO3)2 in the presence (Cad) or absence of an iron source (Fedef + Cad). Cadmium and iron content of leaves developing under the stress was in the order of cCad > eCad > cFedef + Cad and cCad ≈ eFedef ≈ cFedef + Cad < eCad < cFedef, respectively. Growth inhibition was much stronger in Cad than Fedef plants. The inhibitory effects on CO2 fixation, maximal and actual efficiency of PSII, chlorophyll synthesis, as well as the stimulation of the accumulation of violaxanthin cycle components and increase in non-photochemical quenching were the strongest in cFedef+Cad plants, otherwise these parameters changed parallel to the iron deficiency of leaves. Tendency of changes in thylakoid composition were similar under Cad treatments and strong iron deficiency: particularly PSI and LHCII decreased. Therefore, the development of the photosynthetic apparatus under Cd stress was mainly influenced by the Cd-induced strong iron deficiency, while leaf growth was affected primarily by the presence of Cd.

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Facing contrasting light regimes during a vegetation season and depending on canopy position, physiological plasticity of leaves is vital for tree species to sustain the optimal ratio between the benefit of carbon assimilation and the costs of photoprotection in a given leaf. We tested the seasonal adjustment of sun and shade leaf photochemistry of sessile oak (Quercus petraea (Matt.) Liebl.) to changing light environments by parallel investigation of the meteorological conditions, photosynthetic pigment content, PSII quantum efficiency and excitation energy quenching. Sun and shade leaves got adapted to their prevailing light regimes till mid of May. High LMA was a favourable trait in avoiding water loss and decreasing photoinhibition in both flushing and sun leaves, while low LMA optimized the light absorbing leaf surface in the lower canopy layer. Partitioning of excitation energy dissipation pathyways that is PSII photochemistry-Y(II), regulated-Y(NPQ) and non-regulated-Y(NO) quenching changed significantly during leaf ontogeny and with the position of leaves in the canopy. At 800 μmol m−2 s−1Y(II) < Y (NO) < Y (NPQ) was characteristic to early developmental stage of leaves from both canopy layers and to mature shade leaves, and Y(NO) < Y (II) < Y (NPQ) to mature sun leaves but the magnitude of Y(NPQ) and violaxanthin cycle activity differed in different canopy positions.

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In this study sap flow dynamics of mature sessile oak trees (Quercus petraea) in a marginal sessile oakturkey oak forest was investigated in 2009. That year spring was dry without significant rain in April and May and the driest month was August. Due to the extreme weather conditions the volumetric soil water content (SWC) of upper 30 cm was low on experimental days in May (0.13–0.14 cm3 cm−3) but it reached the lowest value in August (0.08 cm3 cm−3). Sap flow was measured in a dominant and a co-dominant tree by heat dissipation method from 26 March till 30 October. In the present paper several three-day long periods of the continuous seasonal recordings were chosen to represent the effects of typical weather conditions and different stages of canopy development on sap flow dynamics. The daily maximum sap flow density values of dominant and co-dominant trees were similar (0.30–0.32 cm3 cm−2 min−1) in moist period (July). Rains and transient increase of SWC after proceeding drought resulted in change of diurnal course of sap flow in experimental days of July. In this period dominant trees also showed considerable sap flow (0.19 cm3 cm−2 min−1) during night hours and short sap flow peaks in early morning (6:00 to 8:00 a.m.) indicating the refilling of desiccated tissues. After the progressive drought in August the daily maximum sap flow density decreased to 0.07 cm3 cm-2 min-1 in dominant tree and to 0.12 cm3 cm−2 min−1 in the co-dominant. Both trees exhibited gradual stomatal closure from morning hours.

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Acta Agronomica Hungarica
Authors:
L. Sági
,
M. Rakszegi
,
T. Spitkó
,
K. Mészáros
,
B. Németh-Kisgyörgy
,
A. Soltész
,
F. Szira
,
H. Ambrus
,
A. Mészáros
,
G. Galiba
,
A. Vágújfalvi
,
B. Barnabás
, and
L. Marton

Research with transgenic plants in the Agricultural Research Institute of the Hungarian Academy of Sciences is primarily related to applications that are essential for the genetic improvement of cereals. The two main directions are connected to wheat and maize breeding and are focused on improving agronomic and nutritional traits. This paper highlights experiments in these areas, which are conducted in national as well as international collaborations. The transparency of this work is ensured by the dissemination of information about approved confined field tests to the public via the internet.

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