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The activity of Rhizobium japonicum against the soilborne pathogens Fusarium solani and Macrophomina phaseolina as causative agents of soybean root rot disease in both culture medium and soil was evaluated. Rhizobial culture filtrate caused an inhibition of the radial growth of Fusarium solani and Macrophomina phaseolina on potato dextrose agar medium amended with the filtrate compared with control. The addition of rhizobial culture suspension to the soil contaminated by the two pathogens, Fusarium solani and Macrophomina phaseolina and their interaction, in pots improved seed germination percentages and reduced the root rot disease index significantly. The sowing of rhizobial coated seeds in soil contaminated by Fusarium solani and Macrophomina phaseolina (separately and in combination) in the field increased seed germination significantly and induced a high reduction in disease severity. These results indicate that rhizobia could be an important element in root rot disease management.

The nematicidal activity of four molecular weights (2.27 x 10**5, 3.60 x 10**5, 5.97 x 10**5, and 9.47 x 10**5 g/mol) of a biopolymer chitosan was assayed against the root-knot nematode, Meloidogyne incognita, in vitro and in pot experiments. In laboratory assays, the nematode mortality was significantly influenced by exposure times and chitosan molecular weight. Low molecular weight chitosan (2.27 x 10**5 g/mol) was the most effective in killing the nematode with EC50 of 283.47 and 124.90 mg/L after 24 and 48 h of treatment, respectively. In a greenhouse bioassay, all the compounds mixed in soil at one- and five-fold concentrations of the LC50 value significantly reduced population, egg mass, and root galling of tomato seedlings compared with the untreated control. In general, the nematicidal activity of these compounds was increased dramatically with a decrease in the molecular weight. The results suggest that the chitosan at low molecular weight may serve as a natural nematicide.

The influences of arbuscular mycorrhizal (AM) fungi (Glomus intraradices (G) and Acaulospora laevis (A)) with Trichoderma viride (T) and Pseudomonas fluorescens (P) alone and in combinations on growth, mycorrhization, chlorophyll content, nutrient uptakes, and yield of broccoli plants were studied in pot culture under glasshouse conditions. The obtained results demonstrated that the single inoculation of broccoli plants with T significantly increased the above-ground fresh weight, root length, chlorophyll b, head diameter, root phosphorus, and shoot nitrogen in comparison to uninoculated control plants. On the other hand, consortium of G+A+T+P significantly increased plant height, above-ground dry weight, root fresh weight, chlorophyll a, head fresh weight, and root nitrogen content. Similarly, G+T showed maximum leaf area and P alone showed maximum uptake of shoot phosphorus. When P was supplied along with T, early flowering was recorded. AM fungal colonisation was negligible and only root tips were found infected in G or A treated plants which confirms low dependency of broccoli on AM fungi.

Deficit irrigation scheduling is used to increase the efficiency with which water is used in many crops including tomato, however a water deficit is predicted to favour phloem feeding insects. We tested if and how different cultivars of tomato grown under water deficit conditions affect the population growth of the aphid Macrosiphum euphorbiae. Three tomato cultivars (Scintilla, Beefmaster and Rio Grande) were used in the experiments. The results for three watering regimes were compared with those of a control, which was well watered every three days: stressed plants received one third of the water supplied to the control over each three-day interval (experiment 1); stressed plants received a gradually decreasing amount of water (100% at the first watering and then 80%, 60%, 50%, 40% and 20%) every three days (experiment 2); stressed plants received the same amount of water as the control but at longer intervals, that is when evident signs of wilting appeared (experiment 3). The results showed that water stress either enhanced, had an adverse effect or had no effect on aphid population growth, depending on the cultivar and watering regime. No difference was recorded in the population dynamics of M. euphorbiae feeding on Beefmaster tomato plants subjected to different levels of water stress. In the case of the cultivar Scintilla, live aphids were less abundant on stressed plants than on well watered ones in experiment 1 and 3 but not in experiment 2. The highest variability in aphid population dynamics on the plants grown under the different water stress protocols was recorded on the cultivar Rio Grande. In experiment 1, the initial peak in aphid numbers was higher on the water stressed plants than on the control and then decreased to lower numbers than on the control. In experiment 2, there were no differences in the numbers of aphids infesting stressed and control plants. In experiment 3, there were fewer aphids on stressed than on control plants after six days, as in experiment 1, but there was no initial peak in aphid numbers.

The effect of municipal wastewater irrigation on the yield and quality of vegetables and crops was studied by means of pot and lysimetric experiments. The pots were seeded with lettuce salad, radishes, and carrots in all experimental years; the lysimeters were planted with early potatoes in 2005 and 2007, and with sugar beet in 2006. Secondary-treated wastewater (in 2005) or only primary-treated wastewater (in 2006 and 2007) were used in the experiments. The control treatment involved the irrigation with water from a local well (in 2005) or public water supply (in 2006 and 2007). Contrarily to the secondary-treated wastewater, the primary-treated wastewater increased the yield of all vegetables and crops, the increase having been statistically significant in most cases. The irrigation with secondary-treated wastewater increased only the sodium content in radishes and carrots. However, the irrigation with primary-treated wastewater led to a statistically significant increase in the sodium content in the consumable parts of all vegetables, sugar beet bulbs, and potato tubers in both years, and in 2007, in the nitrate contents in lettuce salad and radishes as well. A high bacterial contamination of vegetables and crops irrigated with this wastewater was found out, but there was no evidence for the contamination with pathogens. Also, no risk was shown of contamination of the crops with intestinal nematodes.

We established a greenhouse experiment based on replicated mini-ecosystems to evaluate the effects of defoliation intensity on soil food-web properties in grasslands. Plant communities, composed of white clover (Trifolium repens), perennial ryegrass (Lolium perenne) and plantain (Plantago lanceolata) with well-established root and shoot systems, were subjected to five defoliation intensity treatments: no trimming (defoliation intensity 0, or DI 0), and trimming of all plant material to 35 cm (DI 1), 25 cm (DI 2), 15 cm (DI 3) and 10 cm (DI 4) above soil surface every second week for 14 weeks. Intensification of defoliation reduced shoot production and standing shoot and root mass of plant communities but increased their root to shoot ratio. Soil microbial activity and biomass decreased with intensification of defoliation. Concentrations of NO3- N in soil steadily increased with intensifying defoliation, whereas NH4- N concentrations did not vary between treatments. Numbers of microbi-detritivorous enchytraeids, bacterial-feeding rotifers and bacterial-feeding nematodes steadily increased with intensifying defoliation, while the abundance of fungal-feeding nematodes was significantly enhanced only in DI 3 and DI 4 relative to DI 0. The abundance of herbivorous nematodes per unit soil mass was lower in DI 3 and DI 4 than in DI 0, DI 1 and DI 2, but when calculated per unit root mass, their abundance tended to increase with defoliation intensity. The abundance of omnivorous and predatory nematodes appeared to be highest in the most intensely defoliated systems. The ratio of abundance of fungal-feeding nematodes to that of bacterial-feeding nematodes was not significantly affected by defoliation intensity. The results infer that defoliation intensity may significantly alter the structure of soil food webs in grasslands, and that defoliation per se is able to induce patterns observed in grazing studies in the field. The results did not support hypotheses that defoliation per se would cause a shift between the bacterial-based and fungal-based energy channels in the decomposer food web, or that herbivore and detritivore densities in soil would be highest under intermediate defoliation. Furthermore, our data for microbes and microbial feeders implies that the effects of defoliation intensity on soil food-web structure may depend on the duration of defoliation and are therefore likely to be dynamic rather than constant in nature.

A pot experiment was conducted to study interactive effects of arbuscular mycorrhizae (AMs) and maize (Zea mays L.) straws on wheat (Triticum aestivum L.) growth and organic carbon (C) storage in a sterilized sandy loam soil. The experiment included four treatments: control, inoculation with AM fungus Glomus caledonium (M), amendment with maize straw (S), and amendment with maize straw plus inoculation with G. caledonium (S + M). The inoculation of G. caledonium significantly (P < 0.05) increased wheat root biomass and root-to-straw ratio, but had no significant effects on shoot biomass, grain yield, and soil parameters. The amendment of maize straw significantly (P < 0.05) decreased soil pH, wheat root biomass, and root-to-straw ratio, and significantly (P < 0.05) increased soil invertase and alkaline phosphatase activities, but had no significant effects on shoot biomass, grain yield, soil organic C content, and urease activity. The combined application of G. caledonium and maize straw had no significant effects on root mycorrhizal colonization rate compared to the M treatment, while significantly (P < 0.05) increased wheat root biomass and significantly (P < 0.05) decreased soil pH compared to the S treatment, and also significantly (P < 0.05) increased grain yield, soil organic C content, and urease activity compared to the control. The Two-Way ANOVA also showed interactive effects of G. caledonium and maize straw on soil pH (P < 0.05) and wheat grain yield (P < 0.01), and the redundancy analysis result indicated the potential application of AM fungi in straw-returned fields.

The genus Hypericum L. (St. John's-wort, Hypericaceae) has received scientific interest in recent years, because it is a source of a variety of bioactive compounds including the phenolics. We determine whether the typical phenolic constituents of Hypericum plants, namely chlorogenic acid, rutin, hyperoside, isoquercetine, quercitrine, and quercetine, may be implicated as part of an inducible plant defence response in two St. John's-wort species, Hypericum perforatum L. and Hypericum triquetrifolium Turra. To achieve this objective, greenhouse-grown plantlets were inoculated with the fungal pathogen Diploceras hypericinum and the plant growth promoting bacterium Pseudonomas putida. Phenolic compounds levels of the Hypericum plantlets increased significantly in response to inoculation with both organisms. So far, little effort has been dedicated to investigate whether phenolic compounds are inducible by pathogen/herbivore attack or if they could play a role in plant defence. Results from the study indicate that the phenolic compounds investigated could be involved in the plant defence system and implicated as part of an inducible plant defence response in both St. John's Wort species.

The aim of this paper was to investigate the occurrence of AMF associated with plants colonizing sandy soils of the Bledowska Desert. A total of 134 mixtures of soils and roots were sampled during the study in 1995-97. The mixtures represented 26 plant species in 14 families and one unrecognized plant. Spores of AMF were found in 188 soil-root mixtures. The AMF spore populations comprised 20 described species of the genera Acaulospora, Gigaspora, Glomus and Scutellospora, as well as two underscribed morpho-species of the Glomus. The overall spore in 100 g dry soil. The highest abundance of spores occurred among roots of the families Cupressaceae, followed by the Rosaceae, Asteraceae and Poaceae

We test the hypothesis that the expansive horizontal clonal growth of Carex arenaria may provide a method of escape from soil-borne pathogens (fungi and nematodes) by growing away from the site of infection. Plants were grown in non-sterilized or sterilized dune sand, i.e., with or without soil-borne pathogens. The effects of soil-borne pathogens were studied on the whole genet, on the mother alone, and on the first primary rhizome. Genets with the mother plant infected produced less total biomass and had less biomass allocated to roots than genets with uninfected mothers. Infected genets had fewer primary rhizomes and lower total rhizome length, but rhizome specific weight or the distance between shoots did not decrease in infected plants. In C. arenaria, uninfected mothers with an infected first primary rhizome produced shorter and fewer rhizomes than uninfected genets. The infected first rhizome continued to grow at the same speed as uninfected rhizomes, probably by support from the uninfected mother plant. However, secondary rhizome branching was affected only by direct exposure to soil pathogens and not by the status of the mother plant. The results provide evidence that clonal growth may facilitate escape from soil-borne pathogens. The rhizome explores a patchy environment by supporting the growth of young tillers when passing pathogenic patches.