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  • Author or Editor: Szilvia Kovács x
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Climate changes in Europe, which is characterized by the decrease of rainy days and the higher average temperature at summer, significantly increase the spreading of Aspergillus species and aflatoxin B1 contamination of the staple food and feed materials. The aim of our study was to estimate the possibility of the aflatoxin production of the Aspergilli on crops. From the isolates that were gained from crop samples, higher than 40% of the Aspergillus isolates contained norA, aflR and omtA genes from the aflatoxin genes cluster. Most of these isolates (63%) showed high homology with A. flavus, while three isolates showed high homology to A. tritici/A. candidus, one to A. cristatus/A. amstelodami and one strain showed the highest homology to A. tritici. Six from the A. flavus isolates (85.7%) with norA, aflR and omtA genes could produce aflatoxin B1 on malate extract agar medium. Parallel PCR and toxin measurements are recommended to evaluate the potentiality of aflatoxin production.

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Cornmeal agar (CMA) is a good to model natural conditions (low C and N, high antioxidants, crude fat) for phytopathogenic fungi. Different CMA media was prepared to model the maize kernel as growth environment for Aspergillus flavus, where stress resistance and aflatoxin B1 (AFB1) production were tested. The CMA medium with high polyphenol and low fatty acid content did not support the mycelial growth and high AFB1 production but the sclerotia development of the cultures. High fatty acid content in the CMA exceeded the inhibitory effect of antioxidant polyphenols of corn and low concentration of AFB1 was detected. Glucose supplement of CMA induced AFB1 production proving the need for free carbon source for the secondary metabolite pathway. The tolerance of the fungus against salt and cell membrane stress was lowered on CMA. At higher fatty acid concentration, the aflatoxin B1 production cannot be hindered by the natural antioxidants and that is important in selection of resistant corn hybrids.

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Authors: Farzaneh Garousi, Béla Kovács and Szilvia Veres

Selenium (Se) is an essential element for animals and humans, but not plants. However, the capacity of some plants to accumulate and transform Se into bioactive compounds has important implications for human nutrition and health. In this study, sunflower (Helianthus annuus) and maize (Zea mays) seedlings were cultivated in soil to investigate the effect of different rates of sodium selenite (1–90 mg kg–1 soil) and sodium selenate (1–30 mg kg–1 soil) on absorption and translocation of Se and sulphur (S). Sodium selenate decreased growth of sunflower roots at all applied rates and of maize roots at the highest rate applied. In contrast, sodium selenite up to 30 mg kg–1 for sunflower and 3 mg kg–1 for maize resulted in increased shoot and root growth. An increase in Se concentration in soil resulted in an increase in Se and a decrease in S accumulation in roots and shoots of both maize and sunflower. Selenium translocation from roots to shoot was higher in sunflower than maize. Root-to-shoot translocation of Se was 5 to 30 times greater in sunflower and 0.4 to 3 times greater in maize in the sodium selenate than sodium selenite treatments. Sunflower, as a Se-hyperaccumulator with up to 1.8 g kg–1 in shoots (with no significant decrease in shoot biomass) can be a valuable plant in biofortification to improve animal/human nutrition, as well as in phytoremediation of contaminated sites to restore ecosystem services.

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Biofertilizers are used to improve soil fertility and plant production in sustainable agriculture. However, their applicability depends on several environmental parameters. The aim of our study was to evaluate the effect of free-living bacteria containing fertilizer on the growth of cucumber (Cucumis sativus L. cvs. Delicates) under aluminium (Al) stress. Different responses to Al stress of cucumber growth parameters were examined in terms of root elongation and physiological traits, such as Spad index (relative chlorophyll value), biomass accumulation of root and shoot, Al uptake and selected element contents (Fe, Mn, Zn, Mg) of leaves and root. The applied bacteria containing biofertilizer contains Azotobacter chroococcum and Bacillus megaterium. The dry weights of cucumber shoots and roots decreased in line with the increasing Al concentration. Due to different Al treatments (10−3 M, 10−4 M) higher Al concentration was observed in the leaves, while the amounts of other elements (Fe, Mn, Zn, Mg) decreased. This high Al content of the leaves decreased below the control value when biofertilizer was applied. In the case of the roots the additional biofertilizer treatments compensated the effect of Al. The relative chlorophyll content was reduced during Al-stress in older plants and the biofertilizer moderated this effect. The root/shoot ratio was decreased in all the Al-treatments in comparison to the control. The living bacteria containing fertilizer also had a modifying effect. The root/shoot ratio increased at the 10−4 M Al2(SO4)2 + biofertilizer and 10−4 M Al(NO3)3 + biofertilizer treatments compared to the control and Al-treatments. According to our results the biofertilizer is an alternative nutrient supply for replacing chemical fertilizers because it enhances dry matter production. Biofertilizer usage is also offered under Al polluted environmental conditions. Although, the nutrient solution is a clean system where we can examine the main processes without other effects of natural soils. The soil can modify the results, e.g. the soil-born microorganisms affect nutrient availability, and also can modify the harmful effects of different heavy metals. The understanding of basic processes will help us to know more about the soil behaviour.

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Authors: Nóra Bákonyi, Éva Gajdos, Brigitta Tóth, Marianna Marozsán, Szilvia Kovács, Szilvia Veres and László Lévai

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A növények tápanyagfelvétele a termés mennyiségét és a minőségét meghatározó egyik fő fiziológiai folyamat. A kedvezőtlen környezeti feltételek csökkentik a tápanyagfelvételt, a növény szervesanyag-felhalmozását, ezzel az elérhető termés mennyiséget is. A növénytermesztés eredményességét meghatározó, egyik legfontosabb abiotikus tényező a talaj pH-ja. Bár a talaj pH-jának hatása sokrétű, mégis az egyik leginkább kutatott terület a pH és a talajok felvehető tápanyagtartalmának összefüggése. Kísérleteinkben a tápoldat és az apoplazmatikus bikarbonát, valamint egy biotrágya (Phylazonit MC®) hatását vizsgáltuk laboratóriumi körülmények között, tápoldaton nevelt fiatal kukorica és uborka csíranövényekre. Meghatároztuk a növények relatív klorofill tartalmát, a hajtás és gyökér növekedését, szárazanyag-felhalmozását, elemtartalmát, különösen az egyik legfontosabb terméslimitáló elem, a vas felvételében. Megállapítottuk, hogy a környezet magas bikarbonát koncentrációja stresszként hat, a tápközeg pH-jának módosításán keresztül jelentősen befolyásolja a vizsgált folyamatokat. Megfigyelésünk alapján arra a következtetésre jutottunk, hogy a gyökér és a mezofillum sejtek tápanyagfelvétele azonos mechanizmus szerint történik. Ezen megfigyelésünk alátámasztja Marschner és Römheld (1994) eredményeit. A tápoldatba és az apoplazmába juttatott bikarbonát hatása hasonló, ami mögött a tápanyagfelvétel hasonló membránfolyamatait valószínűsítjük. A pH mellett a mezofillum sejtközötti járatainak bikarbonát koncentrációja is okozhat tápanyag hiányt (látens tápanyaghiány) megfelelő tápanyagellátás esetén is. Eredményeink szerint a bikarbonát okozta stresszhatás mérsékelhető volt egy baktérium tartalmú biotrágya (Phylazonit MC®) kiegészítő használatával. Feltételezzük, hogy a kedvező hatás mögött a baktériumok és a magasabb rendű növények tápanyag-felvételi hasonlóságai vannak.

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Authors: Farzaneh Garousi, Béla Kovács, Éva Domokos-Szabolcsy and Szilvia Veres

Supplement of common fertilizers with selenium (Se) for crop production will be an effective way to produce selenium-rich food and feed. The value of green pea seeds and forages as alternative protein source can be improved by using agronomic biofortification. Therefore, biological changes of green pea (Pisum sativum L.) and influences of inorganic forms of Se (sodium selenite and sodium selenate) at different concentrations on the accumulation of magnesium (Mg) and phosphorus (P) were investigated in greenhouse experiment. 3 mg kg−1 of selenite had positive effects to enhance photosynthetic attributes and decrease lipid peroxidation significantly. At the same time, Se accumulation increased in all parts of plant by increasing Se supply. Moreover, Mg and P accumulations were significantly increased at 3 mg kg−1 selenite and 1 mg kg−1 selenate treatments, respectively. By contrast higher selenite concentrations (≥30 mg kg−1) exerted toxic effects on plants. Relative chlorophyll content, actual photochemical efficiency of PSII (ФPSII) and Mg accumulation showed significant decrease while membrane lipid peroxidation increased. Thus, the present findings prove Se biofortification has positive effects on biological traits of green pea to provide it as a proper functional product.

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Authors: Tünde Pusztahelyi, L. Radócz, Cs. Gellért, Szilvia Kovács, Zsuzsanna Szabó, I. Pócsi and A. Vad

There are extensive data on effects of antifungal agents on the plant pathogens, especially on Fusariums spp. species. However, investigations on the interaction of chemicals and the treated cultivars are rare. The aim of the study was to test two types of fungicide mixtures, azoxystrobin-propiconazole, and prothioconazole-tebuconazole, which are applied in wheat cultivars intensively, on six fodder maize hybrids that were infected with Fusarium proliferatum in the R1 growth stage in a field trial. The effect of the fungicide treatment was tested on the starch content and antifungal, antioxidant polyphenols of the kernels in the R3–R4 and R6 stage of the cultivars. The level of the fungal presence and the fumonisin concentration of the kernels were increased significantly under the artificial infection. The fumonisin concentration was variable at the R6 stage of the hybrid maize kernels. The treatment with prothioconazole and tebuconazole was found to be suitable when it was done before flowering, while the azoxystrobin-propiconazole treatments were equally successful before and after maize flowering considering the decreasing fumonisin concentration of the kernels. Both fungicide mixtures, when they were applied after maize flowering, affected the starch biosynthesis to the R3–R4 stage significantly. Meanwhile, azoxystrobin-propiconazole also significantly affected the antioxidant flavone/flavanol contents from the R3–R4 stage to the R6 stage.

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