Suzbijanje korova u organskoj poljoprivredi

Organic agriculture as a production system based on ecological production, soil biological activity, biodiversity conservation and use of natural substances and processes is the only certified food production in Serbia. This system provides users of organic products with a guarantee that the end product is the result of consistent farming practices. Since 2010, three laws and a number of regulations underlying the development of this food production system have been adopted. The global organic market has seen a continuous rise in demand for organic products, whereas a relatively slight increase in their supply from organic crop growing areas of Serbia has been recorded. Reasons for the insufficient farmers' interest in organic agriculture include lack of information, lack of intermediate goods, fear of change and, very often, underestimation by conventional producers and professional agrarian circles. An important part of the mosaic-like fear of organic farming among producers is lack of knowledge regarding weed control methods in this production concept. As with other elements of organic farming practices, the basis for weed control rests on preventive action, as well as on direct methods of eliminating undesirable plants from agricultural biotopes.Organska poljoprivreda kao proizvodni sistem baziran ne ekološkoj proizvodnji, biološkoj aktivnosti zemljišta, očuvanju biodiverziteta, uz primenu prirodnih suspstanci i postupaka, jedina je sertifikovana proizvodnja hrane u Srbiji. Korisnicima organskih proizvoda se garantuje da je finalni proizvod rezultat dosledno sprovedene tehnologije gajenja. Od 2010 godine, usvojena su tri zakona i niz pravilnika, koji su osnov za razvoj ovog sistema proizvodnje hrane. Na svetskom tržištu organskih proizvoda, kontinuirano raste potražnja, dok je povećanje ponude ovih proizvoda iz agrosinuzija Srbije, u relativno blagom porastu. Razlozi nedovoljnog interesovanja proizvođača za bavljenje organskom poljoprivredom su neobaveštenost, nedostatak repro materijala, strah od promena i veoma često omalovažavanje od strane konvencionalnih proizvođača i stručne agrarne javnosti. Jedan od važnih elemenata u mozaiku kreiranja straha od organske poljoprivrede među proizvođačima je i nepoznavanje načina suzbijanja korova u ovom proizvodnom konceptu. Kao i u drugim elementima tehnologije gajenja, osnova suzbijanja korova jesu preventivne mere, ali postoje i direktni načini eliminisanja nepoželjnih biljaka iz agrobiotopa

Nutrients and soil structure influence furovirus infection of wheat

Soil-borne wheat mosaic virus (SBWMV) and Soil-borne cereal mosaic virus (SBCMV), genus Furovirus, family Virgaviridae, cause significant crop losses in cereals. The viruses are transmitted by the soil-borne plasmodiophorid Polymyxa graminis. Inside P. graminis resting spores, the viruses persist in the soil for long time, which makes the disease difficult to combat. To open up novel possibilities for virus control, we explored the influence of physical and chemical soil properties on infection of wheat with SBWMV and SBCMV. Moreover, we investigated, whether infection rates are influenced by the nutritional state of the plants. Infection rates of susceptible wheat lines were correlated to soil structure parameters and nutrient contents in soil and plants. Our results show that SBWMV and SBCMV infection rates decrease the more water-impermeable the soil is and that virus transmission depends on pH. Moreover, we found that contents of several nutrients in the soil (e.g. phosphorous, magnesium, zinc) and in planta (e.g. nitrogen, carbon, boron, sulfur, calcium) affect SBWMV and SBCMV infection rates. The knowledge generated may help paving the way towards development of a microenvironment-adapted agriculture

Degradation of linuron in soil by two fungi

Two fungal strains were applied to soil polluted with herbicide in order to determine their degradation potential. Three experimental setups were used. In the first setup, the soil in pots was contaminated by linuron in final concentration of 1 ppm. Suspensions of Phanerocheate chrysosporium and Trichoderma asperellum were applied sepa­rately or in combination. Tomato plantlets were transplanted and chlorophyll content in their leaves was determined at two time points during plant growth. In the second setup in pots, the final concentration of linuron was lower, 0.45 ppm. In the third setup 0.1 ppm of linuron was applied in the field plot. Plantlets of lettuce were transplanted and chlorophyll content was measured as indicator of plant stress. The content of linuron in soil was determined by HPLC. The applied fungal strains significantly reduced toxic effect of 0.45 ppm linuron on plants, which was not the case for 1 ppm linuron. Both fungi, applied separately or in combination, were effective in decreasing the linuron content in the soil. However, in field conditions the combination of both fungi was the most effective. [Projekat Ministarstva nauke Republike Srbije, br. III43010

Application of molecular markers in sunflower breeding

The results of the application of molecular markers in sunflower breeding obtained in the Institute of Field and Vegetable Crops in the last decade are reviewed. Our results on genetic distance (GD=7-75%) between sunflower inbred lines obtained with RAPD and SSR markers, indicate large variability and provide important information for the selection of parental lines for future crosses. Interspecific hybridization is often used in sunflower breeding. As only some populations of H. giganteus and H. maximiliani are resistant to sunflower diseases, the investigation of genetic variability in/between two species is of interest. The results obtained with SSR markers are presented. The successful hybridization between H. rigidus and H. annuus was confirmed with RAPD markers, and the variability between F1 and BC1F1 plants is discussed. Desirable alleles and haplotypes can be detected with molecular markers both in early phases of plant development and in early phases of the production of improved lines, which reduces or completely eliminates the large number of testing cycles for desirable phenotypes. CAPS markers for resistance to downy mildew, that can be used in marker assisted selection are presented.

Effect of the edaphic factors and metal content in soil on the diversity of Trichoderma spp.

Influence of edaphic factors and metal content on diversity of Trichoderma species at 14 different soil sampling locations, on two depths, was examined. Forty-one Trichoderma isolates from 14 sampling sites were determined as nine species based on their internal transcribed spacer (ITS) sequences. Our results indicate that weakly alkaline soils are rich sources of Trichoderma strains. Also, higher contents of available K and P are connected with higher Trichoderma diversity. Increased metal content in soil was not inhibiting factor for Trichoderma species occurrence. Relationship between these factors was confirmed by locally weighted sequential smoothing (LOESS) nonparametric smoothing analysis. Trichoderma strain (Szeged Microbiology Collection (SZMC) 22669) from soil with concentrations of Cr and Ni above remediation values should be tested for its potential for bioremediation of these metals in polluted soils

Screening of Trichoderma strains isolated from rhizosphere samples for laccase production

In this study we screened formerly isolated Trichoderma strains for laccase production on solid media supplemented with two different substrates, ABTS [2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate)] or guaiacol. We detected outstandingly strong colour changes in the case of three Trichoderma strains in this experiment. The strains were identified based on internal transcribed spacer (ITS) sequence analysis as T. asperellum (SZMC 20786 and SZMC 20866) and T. atroviride (SZMC 20780). We also investigated the production of laccase enzymes in the case of these Trichoderma strains in two types of liquid media. The pH dependence of the secreted laccases was determined in cell free ferment broths at pH 3.5, 4, 5, 5.5, 6 and 6.5 adjusted with 25 mM succinate buffer. Laccase activities from liquid cultures were measured with ABTS as substrate. The results showed that the best laccase producer among the investigated Trichoderma strains was T. atroviride SZMC 20780 under these conditions. This strain shows the highest laccase enzyme activity on the second day of incubation in a rotary shaker at 25 °C