Dejan Prvulović

Changes in antioxidant systems in soybean as affected by Sclerotinia sclerotiorum (Lib.) de Bary

Changes in antioxidant systems in soybean [Glycine max (L.) Merr., Fabaceae] genotypes infected with Sclerotinia sclerotiorum were studied 12, 24, 48 and 72h after inoculation. Generation of superoxide and hydroxyl radicals was evaluated together with the production of malonyldialdehyde, main end product of lipid peroxidation. Several enzymatic and non-enzymatic parameters were monitored as well, such as the activity of antioxidant enzymes superoxide dismutase and pyrogallol and guaiacol peroxidases, reduced glutathione, soluble proteins and total carotenoids content. Results showed that genotypes expressed oxidative burst as well as different antioxidant systems in response to biotic stress caused by pathogen invasion. It has been confirmed that, although hypersensitive cell death is efficient against biotrophic pathogens, it does not protect soybean plants against infection by the necrotrophic pathogen such as S. sclerotiorum. Still, some genotypes showed distinctive and combined activity of several biochemical parameters which may point to further directions in exploring host-pathogen relations and lead to selection and production of new genotypes with higher levels of tolerance.

Effects of nitrogen fertilization on the biochemical and physiological parameters in leaves and root of sugar beet associated with Azotobacter chroococcum.

A field experiment was conducted to investigate the effect of nitrogen (N) application on the growth and metabolism of sugar beet (Beta vulgaris L.). Changes in nitrate, ammonium, soluble protein and pigment levels, nitrogen metabolism enzyme activity, biomass of leaves and beet, and sucrose and α-amino-N were studied in relation to five different NPK application rates (0, 50, 100, 150, and 200 kg N ha−1) and association with Azotobacter chrooccocum. The availability of nitrate and ammonium ions in the leaves proved to be influenced by the different nitrogen treatments. The most important enzymatic activities within nitrogen metabolism were affected negatively by the highest NPK rate. With increasing nitrogen supply, the concentration of α-amino-N increased considerably and that of sucrose decreased. Application of NPK had a significant positive effect on the growth and biomass production. The measured parameters of plants associated with A. chrooccocum were of similar magnitude comparing to the controls.

Antioxidant Activity and Phenolic Content of Soybean Seeds Extracts

Plants are a good source of natural antioxidants and could provide protection against harmful free radicals. Phenolic compounds were found to be an important part of human diet and are considered as active principles in many medicinal and agricultural plants. Detailed information about health-promoting components of different soybean cultivars could lead to a better understanding and an increased consumption of this crop, including its use in functional foods. The objective of this study was to determine total phenolics, total tannins, total flavonoids and antioxidant capacity with different assays of five Serbian soybean cultivars (Merkur, Sava, Valjevka, Venera and Victoria) extracted with three different solvents (70% acetone, 70% ethanol and 70% methanol). Total phenolics varied among cultivars and among applied solvents. Antioxidant properties highly depended on a solvent used for extraction. Such results highlight an existing variability in soybean seeds and emphasise the need to evaluate diversity and to support conventional breeding programs to improve soybean nutritional value.

Screening for Polyphenol Compounds and Antioxidant Capacity of Sweet Cherry Fruits Infected with Monilinia Laxa

Summary Monilinia laxa Aderh. and Ruhl. is the predominant causal agent of brown rot disease of stone fruit orchards, especially sweet cherries. The objective of this study was to identify reaction in response of nine genotypes cherry, with different pomological properties, against brown rot. These genotypes were harvested at commercial maturity from orchard in the Fruit Research Institute in Rimski Šančevi. The studied genotypes showed significant differences in terms of the occurrence of disease on fruits, both under artificial inoculation and infection in the field. Given the fact that sweet cherry fruits are prone to infection by a number of pathogens in the field, biochemical parameters were analysed on artificially inoculated fruits. Biochemical analysis of fruits determined significant differences in contents of total phenols, flavonoids and anthocyanins, as well as in antioxidant activity. It was genotype specificities and intensity of infection, as well as the interaction of the two that induced differences in the secondary biomolecules content and antioxidant activity. The majority of the genotypes examined showed high polyphenolics content, while under the infection, the content was significantly lower. Based on the results obtained, the secondary metabolites content can be used as one of the parameters for evaluating the resistance of sweet cherry genotypes to brown rot.