Radmila Pivić

Antifungal activities of indigenous plant growth promoting Pseudomonas spp. from alfalfa and clover rhizosphere

To select isolates suitable for use in biological control of pathogenic fungi and as plant growth promoting (PGP) agents, Pseudomonas spp., indigenous to the rhizosphere of wild alfalfa and clover plants growing on the old magmatic hill Vagan (Serbia), were isolated. Isolates were selected on the basis of intrinsic antibiotic resistance (IAR) and PGP traits: phosphate solubilization, production of siderophores, hydrogen cyanide (HCN), acyl homoserine lactones (AHLs), indole acetic acid (IAA) and enzymatic activities. The results of the genotyping by repetitive sequence-based polymerase chain reaction, using ERIC and (GTG)5 primers, and phenotyping by IAR clustered the isolates in five groups, represented by two isolates from alfalfa (Q1 and Q16) and three from white clover (B25, B28 and B29). Isolates Q16 and B25 showed production of HCN, IAA and AHLs. Good phosphate solubilization and production of siderophores were observed on Q1 and Q16. The Q16 isolate exhibited high enzymatic activity. The most promising PGP isolates, Q16 and B25, showed the best antifungal activity against Trichoderma viride, and good antifungal effect against Aspergillus fumigatus and Aspergillus niger, while Penicillium verrucosum was the most resistant fungus. Pseudomonas sp. B25 exhibited higher antifungal potential than Q16. The selected isolates could be further investigated as biological control agents and tested in field conditions to confirm their PGP efficacy.

Cultivated and wild plantain (Plantago major) as a host of Stolbur phytoplasma in Serbia

The wild plantain (Plantago major) is an important medicinal plant. Symptoms suggestive of phytoplasma diseases were observed in infected plantain plants in Serbia. A new disease on P. major has symptoms of reduced leaf size, leaf reddening and crinkling, and occasionally rolling of flowers and early drying up. This disease was found first on the plantain plantation in Pancevo locality, but later has been found in some other localities in Serbia (Kovin, Vrdnik). Restriction fragment length polymorphism (RFLP) analysis of amplification products of 1.2 kb, obtained in nested PCR with R16F2n/R16R2 primer pair after amplification with P1/16S-Sr primers, in 24 from 26 symptomatic plants indicated the presence of phytoplasma from the 16SrXII-A subgroup. Plantain plants collected from all three affected localities in Serbia were determined to be hosts of this phytoplasma. This is the first report of the natural occurrence of Stolbur phytoplasma in cultivated and wild P. major in Serbia.

Typing of Indigenous Campylobacter spp. From Serbia by M-PCR and RAPD

Abstract Campylobacteriosis is an infectious human disease caused by thermophilic Campylobacter species, mainly C. jejuni and C. coli. It is the leading cause of human gastroenteritis today with the number of cases surpassing the number of Salmonella poisoning cases. The epidemiology of the agent is not completely clear, but a number of investigations indicate an important role of broiler meat in human infections. The purpose of this study was to investigate the diversity of Campylobacter jejuni strains present in the Republic of Serbia and to determine a fast and reliable system for the confirmation and typing of the isolated strains. Samples taken at slaughterhouses, broiler farms, as well as two human isolates of Campylobacter species have been investigated. Strain identification was performed by multiplex-PCR. Genotyping was performed by Random Amplified Polymorphic DNA (RAPD) with multiple primers. Using several unusual primers and a newly designed one (DJP17), we report on the RAPD types of indigenous Campylobacter species. RAPD profiles showed different levels of discrimination between the isolates, depending on the primer: SPH1 and AG15 were informative only in part and better results were obtained with AP10, AK16 and DJP17.

Evaluation of Mineral and Bacterial Fertilization Influence on the Number of Microorganisms from the Nitrogen Cycle in Soil under Maize

In 2006, the influence of different rates of applied mineral fertilizers and their combinations with bacterial inoculants [nitrogen (N)–fixing Klebsiella planticola and Enterobacter spp.] on the number of microorganisms from the N cycle in a Cambisol and the yield of maize was evaluated in this study. The results obtained implied that high rates of mineral fertilizers brought about an increase in the number of fungi and a decrease in the number of Azotobacter spp., oligonitrophiles, ammonifiers, and nitrifiers in soil. Combined application of microbial inoculants and low rates of mineral fertilizers resulted in the greatest increase in the number of Azotobacter spp., oligonitrophiles, and ammonifiers in soil. The greatest number of soil nitrifiers, as well as the grain yield of maize studied, were determined in the variants where combinations of the microbial inoculants and low and high rates of mineral fertilizers were applied.

Effect of Indigenous Pseudomonas sp. and Bacillus sp. Strains on Yield and Main Chemical Growth Parameters of Radicchio

Summary Pseudomonas sp. and Bacillus sp. belong to plant growth promoting rhizobacteria which are able to colonize the plants roots and stimulate growth. In this study, the effect of two indigenous plant growth promoting rhizobacterial strains Pseudomonas sp. Q4 and Bacillus sp. Q10 and their mixture (mix Q4+Q10) on content of the main chemical growth parameters (nitrogen, phosphorus, potassium, calcium and magnesium) and the yield of dry biomass of radicchio (Cichorium spp. var. rossa di treviso) aerial parts and root, was investigated. The study was carried out with stagnosol type of soil in pot experiments under semi-controlled conditions in the Institute of Soil Science (Belgrade), in the period from July to October in 2013. Phosphorus was determined by spectrophotometer, potassium - by flame emission photometry and total nitrogen and carbon - using elemental CNS analyzer, while calcium and magnesium were determined by AAS. The data on yield of both aerial parts and root dry biomass of radicchio showed that its treatment with Q4 and Q10 strains, as well as with their mixture, caused noticeably increase in this parameter in relation to the control, whereby the strain Q4 was more effective for aerial parts, while mix Q4+Q10 - for roots. The obtained data on the studied chemical parameters of radicchio root and aerial parts were in total accordance with their yield. Concluding, studied strains have a potential in promoting the biomass yield and main chemical growth parameters of both aerial parts and root of radicchio.

Molecular characterization of Pseudomonas syringae pvs. from different host plants by repetitive sequence-based PCR and multiplex-PCR@@@Įvairių augalų-šeimininkų Pseudomonas syringae pvs. molekulinis apibūdinimas taikant pasikartojančių sekų ir jungtinę PGR

Pseudomonas syringae pvs., isolated from different cultivars of sweet cherry grown in several locations in Serbia, were characterized and compared with strains collected earlier from sour and sweet cherry and oil pumpkin growing in this region, as well as with reference strains P. syringae pv. morsprunorum race 1 CFBP2119, P. s. pv. lachrymans 765R and P. s. pv. syringae H-1. By employing LOPAT and GATTa tests, isolates were identified as P. syringae pv. syringae and P. s. pv. morsprunorum race 1. Simultaneous detection of syringomycin synthesis (syrB) and syringomycin secretion (syrD) genes in multiplex-polymerase chain reaction (m-PCR) was used for P. syringae pv. syringae confirmation. All isolates detected as P. syringae pv. morsprunorum race 1 after biochemical characterization were positive for cfl gene amplification. Using a repetitive sequence-based PCR (rep-PCR) both syringae and morsprunorum race 1 pathovars were clustered separately, with 42% similarity. No significant differences between isolates in each pathovar were noted, although they were collected from different sweet cherry cultivars and varying localities. The most similar to the P. syringae pv. syringae isolates was strain T6 with 19% similarity, followed by strain Tk21 from oil pumpkin – 25%. The isolates of both pathovars were detected on the same location (Selenca, Serbia) and the same cultivar (‘Merchant’), albeit in two different years.

Chemical composition and yield of maize green biomass as affected by bacterial and mineral fertilization

The purpose of the study was to evaluate the influence of an application of different rates of composite mineral fertilizers and their combination with bacterial inoculants (N-fixing Klebsiella planticola and Enterobacter spp.) on chemical composition and yield of the maize green biomass (without spikes) on acid Eutric Cambisol during the two growing seasons: 2006 and 2008. Unfertilized soil was used as a control. The contents of nitrogen, phosphorus, potassium and crude proteins in biomass samples were determined three times during the maize vegetation season, as follows: stage of intensive growth, milk-waxy maturity stage and full maturity stage. Measuring of the green biomass yield was carried out at the end of the vegetation. The results of the study showed that the use of high rates of composite mineral fertilizers and their combination with bacterial inoculants resulted in increased contents of nitrogen, phosphorus, potassium and crude proteins in the maize biomass during the both study years, which was noticeably observed in the stage of intensive growth. The highest increase in the biomass yield was obtained by the same mentioned treatments, although the combination of bacterial inoculants and lower rates of mineral fertilizers resulted in higher yields comparing to the application of lower rates of the pure mineral nutrients. The data suggest that the studied bacterial inoculants can be used in further investigations as the potential agents of new biofertilizers for improved maize production and other agriculture crops in animal nutrition.

The possibilities of intensive field crop production on the pseudogley type of soil using the complex amelioration measures.

In Republic of Serbia the pseudogley type of soil outspreads on approximately 443.000 ha or 4,7 % of the total area. At the area of West and North-West Serbia this type of soil outspreads on approximately 360.000 ha or 20% of the total area. The main characteristics of Pseudogley are unfavorable chemical properties, heavy mechanical composition, compaction and low hydraulic conductivity, which result in an unregulated water-air regime. An ameliorative action that could regulate unfavorable water regime of these soil types is the implementation of the horizontal pipe drainage. On experimental drainage field Varna near Sabac, owned by Institute of Soil Science, on the pseudogley type of soil, it was established an experiment in order to follow the effect of different spaces of the horizontal pipe drainage on increase of the yields of main crops (wheat and maize) in relation to the undrained areas. The processing of data of the realized yields in the period 2004-2009 shows that on the plots on which the pipe drainage was implemented, compared to the undrained areas, the yield of wheat increased 8-60%, while the yield maize increased 6-43%. Regarding the areas at which this type of soil outspreads, by implementation of the complex amelioration measures this potentially productive soil would enable economically profitable agricultural production, especially crops for animal food. This will increase the opportunity for intensifying animal production.