Simonida Đurić

Microbiological Activity in the Soil of Various Agricultural Crops in Organic Production

Summary The purpose of this study is to investigate the microbial activity and the number of different groups of microorganisms in the soil under organic agricultural systems. A range of analyses was conducted on soil samples taken from calcareous chernozem soils managed under organic (7 sites) and conventional agricultural systems (1 site). Laboratory measurements were performed in the Laboratory of Microbiology, Faculty of Agriculture, Novi Sad. The total number of bacteria, actinomycetes, fungi, aminoheterotrophs and azotobacters was determined using the dilution method. Soil dehydrogenase activity was measured spectrophotometrically. The greatest number of the Azotobacter sp. bacteria was recorded in the soil devoted to pumpkins (132.61 × 102) and in the soil devoted to apples (126.39 × 102). The greatest number of aminoheterotrophs (1786.05 × 106) and the total number of bacteria (1370.82 × 106) and actinomycetes (235.45 × 104) were determined in the soil devoted to carrots. Fungi were more abounded in the soil devoted to chard (36.82 × 104) than in the soil devoted to other plants. The research results show that the soil devoted to wheat in organic production indicated a greater number of aminoheterotrophs, total bacteria, actinomycetes and fungi, whereas only the number of Azotobacter sp. was greater in the soil devoted to wheat in the conventional agricultural system. The highest dehydrogenase activity level was determined in the soil devoted to radishes, whereas the lowest dehydrogenase activity level was determined in the soil devoted to apples.

Microbial Activity in Forest Soil Under Beech, Spruce, Douglas Fir and Fir

Summary The aim of this research was to investigate the microbial activity in forest soil from different sites under deciduous and coniferous trees in Serbia. One site on Stara planina was under beech trees (Fagus sp.) while another under mixture of spruce (Picea sp.) and Douglas fir (Pseudotsuga sp.). The site on Kopaonik was under mixture of beech (Fagus sp.) and spruce (Picea sp.) trees. The site on Tara was dominantly under fir (Abies sp.), beech (Fagus sp.) and spruce (Picea sp.). The total number of bacteria, the number of actinobacteria, fungi and microorganisms involved in N and C cycles were determined using standard method of agar plates. The activities of dehydrogenase and ß-glucosidase enzymes were measured by spectrophotometric methods. The microbial activity was affected by tree species and sampling time. The highest dehydrogenase activity, total number of bacteria, number of actinobacteria, aminoheterotrophs, amylolytic and cellulolytic microorganisms were determined in soil under beech trees. The highest total number of fungi and number of pectinolytic microorganisms were determined in soil under spruce and Douglas fir trees. The correlation analyses proved the existence of statistically significant interdependency among investigated parameters.

Nematophagous Activity of Duddingtonia Flagrans MUCL 9827 Against Sheep Gastrointestinal Nematodes

Summary Gastro-intestinal nematodes (GIN) of sheep are one of major constraints in grazing production systems worldwide. Control is commonly achieved using anthelmintics, but global occurrence of anthelmintic resistance to different drugs and the emergence of multi-resistant GIN species seriously limit the efficiency of their use. Therefore, integrated parasite management is widely recommended, with nematophagous fungi as one of control tools. Duddingtonia flagrans is one of the most used species, with various effect of different isolates. In previously performed coproculture assay, we showed low efficacy of D. flagrans MUCL 9827 against infective larvae (L3) of sheep GIN. The aim of current experiment was to reevaluate its nematophagous potential, using the medium where direct interaction between the fungus and L3 could be observed. Nematophagous activity was tested on 2% water agar with addition of chloramphenicol on three series of plates seeded with 500 and 1000 chlamidospores and agar blocks with 7 days old mycelium. At Days 0 and 5, 500 L3 of sheep GIN were added to test the trapping activity. The cultures, including control plates with only L3, were incubated at 25°C for 10 days, followed by evaluation of their number and reduction percentage. Nematophagous activity of D. flagrans MUCL 9827 against L3 was clearly demonstrated. However, the overall efficacy was poor since trapping was observed only in one out of nine plates containing fungal material. Potential reasons for such poor performance of the isolate of fungal species, otherwise known as successful in trapping animal parasitic nematodes, are discussed.