The Biochemical Response of Soybean Cultivars Infected by Diaporthe Species Complex.

Oxidative stress in soybean plants infected with Diaporthe isolates was evaluated in order to select (1) the least aggressive inoculation method, (2) to determine the most aggressive Diaporthe isolate, and (3) to determine the most tolerant soybean cultivar to this isolate. Based on the present malondialdehyde (MDA) content, the main end product of the lipid peroxidation process, and the biomarker for oxidative stress, the mycelium contact method was chosen as the least aggressive inoculation method, compared to the toothpick method and plug method. The activity of the antioxidant enzymes (superoxide-dismutase (SOD), catalase (CAT), and peroxidase (PX)), the reduced glutathione (GSH) content, and the level of lipid peroxidation (LP) were measured in soybean cv. Sava infected by five different Diaporthe species (DPM1F-D. aspalathi, DPC/KR19-D. caulivora, DPC004NY15-D. eres, 18-DIA-SOY-14-D. gulyae, and PL157A-D. longicolla). The most pathogenic Diaporthe species to cv. Sava was D. eres. The screening of the antioxidant enzymes activity in the leaves of 12 different soybean cultivars (Altona, Atlas, Capital, Chico, CX134, Favorit, Lakota, McCall, Morsoy, Strain, Rubin, and Victoria) infected with D. eres by the mycelium contact inoculation method showed that Capital, McCall, and Morsoy were the cultivars with the highest tolerance to D. eres, followed by Chico, Favorit, Lakota, and Rubin. The most sensitive cultivars were Atlas, CX134, Victoria, and Strain.

Susceptibility of the Most Popular Soybean Cultivars in South-East Europe to Macrophomina phaseolina (Tassi) Goid.

Oxidative stress in soybean seedlings and the length of the soybean stem lesions infected with the fungus Macrophomina phaseolina (Tassi) Goid were evaluated to determine the most tolerant soybean cultivar to this pathogen. The level of superoxide anion radical (O2•-) production, the activity of the antioxidant enzyme superoxide-dismutase (SOD), and the intensity of lipid peroxidation (LP) were measured in four soybean cultivars: Favorit, Atlas, Victoria, and Rubin. Results showed that O2•- radical production and SOD activity were the most elevated in the cv. Favorit inoculated with M. phaseolina, while the level of lipid peroxidation intensity was the lowest compared to the control. This indicates that the soybean cv. Favorit has managed to prevent infection with M. phaseolina. Furthermore, higher O2•- radical production and lower SOD enzyme activity were measured in cv. Victoria, with enhanced lipid peroxidation. This means that the cv. Victoria was infected with M. phaseolina, and was the most sensitive. None of the tested oxidative stress parameters showed a significant difference in the cvs. Atlas and Rubin compared to the control. Furthermore, the highest lesion length was measured in the cv. Victoria, followed by cv. Favorit, while the lowest lesion length was measured in the cv. Atlas followed by the cv. Rubin; and thus, the cv. Atlas followed by the cv. Rubin, were the most tolerant soybean cultivars to this pathogen.

The Effect of Thymus vulgaris L. Hydrolate Solutions on the Seed Germination, Seedling Length, and Oxidative Stress of Some Cultivated and Weed Species.

The aim of this study was to determine the effect of the hydrolates obtained as the by-products of the Thymus vulgaris essential oil steam distillation process. The bioassays, which were undertaken in order to determine the effect on germination and initial growth of seedlings of some cultivated and weed species, were performed under controlled conditions with different concentrations of the hydrolates. Seeds of Glycine max, Helianthus annuus, Zea mays, Triticum aestivum, Daucus carota subsp. sativus, Allium cepa, Medicago sativa, and Trifolium repens, and six weed species-Amaranthus retroflexus, Chenopodium album, Portulaca oleracea, Echinochloa crus-galli, Sorghum halepense, and Solanum nigrum-were treated with 10, 20, 50, and 100% T. vulgaris hydrolate solution. The obtained results showed that the T. vulgaris hydrolate had the least negative effect on the germination of cultivated species, such as soybean, sunflower and maize, whereas clover and alfalfa were the most sensitive. By comparison, all the tested weed species expressed high susceptibility. It can be concluded that the T. vulgaris hydrolate has an herbicidal effect, in addition to its potential as a biopesticide in terms of integrated weed management.

Chemical Composition of Ambrosia trifida L. and Its Allelopathic Influence on Crops.

Phytotoxic substances released by invasive plants have been reported to have anti-pathogen, anti-herbivore, and allelopathic activity. The aim of this study was to determine the allelopathic influence of the Ambrosia trifida L. on oxidative stress parameters (the lipid peroxidation process; reduced glutathione (GSH) content; and activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (PX)) and phenolic compounds (total phenolic and tannin content) in maize (Zea mays L.), soybean (Glycine max L.), and sunflower (Helianthus annuus L.) crops to explore the effect of released allelochemicals through A. trifida root on crops. An analysis by HPLC confirmed the presence of protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, and syringic acid as major components in the A. trifida. Based on the obtained results for oxidative stress parameters, it can be concluded that the sunflower was the most sensitive species to A. trifida allelochemicals among the tested crops. The other two crops tested showed a different sensitivity to A. trifida. The soybean did not show sensitivity, while the maize showed sensitivity only 10 days after the sowing.