Sava Vrbnicanin

Effect of plant growth promoting rhizobacteria on Ambrosia rtemisiifolia L. seed germination

SUMMARY Soil bacteria are able either to stimulate or inhibit seed germination. If seed germination is stimulated, the seedlings of weed species emerge more uniformly, so that they could be killed in the next step of weed control. This investigation focused on testing the germination of Ambrosia artemisiifolia L. on several media: Pseudomonas fluorescens (B1), Azotobacter chroococcum (B2), Bacillus licheniformis (B3), B. pumilus (B4), B. amyloliquefaciens (B5). In control, seeds germinated in water. Seed germination varied depending on bacterial media. Germination was inhibited by bacterial treatments B1 and B3, treatments B2 and B4 stimulated germination, while germination in treatment B5 was similar to control.

Delay in the critical time for weed removal in imidazolinone-resistant sunflower (Helianthus annuus) caused by application of pre-emergence herbicide

The critical time for weed removal (CTWR) is a period in the crop growth cycle when weed control must be initiated to prevent yield losses. Knowing the CTWR is useful for making decisions about the timing of weed control and in achieving efficient herbicide use from both biological and economic perspectives. Field studies were conducted in 2008 and 2009 at three locations in Serbia and one location in the USA to determine the CTWR in imidazolinone (IMI)-resistant sunflower grown with and without application of pre-emergence (PRE) herbicide. A four-parameter log-logistic model was fitted to data relating relative crop yield to increasing duration of weed presence. The CTWR without PRE herbicide treatment ranged from 14 to 26 d after emergence (DAE) corresponding to the V3 (three leaves) to V4 stages compared to 25 to 37 DAE, which corresponded to the V6 to V8 stages with PRE herbicide. The CTWR in IMI-resistant sunflower grown with PRE herbicide can be delayed by an additional 6 to 12 d compared to the crop grown without PRE herbicide under the present experimental conditions. The practical implication of this study is that the use of PRE herbicide could extend post-herbicide treatments by another 6 to 12 d with respect to the critical time required for weed removal without PRE herbicide in IMI-resistant sunflower.

Alien plant species and factors of invasiveness of anthropogenic vegetation in the Northwestern Balkans — a phytosociological approach

We studied the anthropogenic vegetation of the Northwest Balkans in order to determine its susceptibility to invasion by alien plant species. We compiled a dataset of 3089 vegetation plots sampled between 1939 and 2009, recording a set of variables for each sample plot in order to determine which factors have the most effect on a habitat’s vulnerability to invaders. We calculated the proportion of native species, archaeophytes and neophytes for each plot. We used regression tree models to determine the site conditions of the most invaded anthropogenic habitats. The sample plots contained an average of 12.7% alien plant species, with a low proportion of archaeophytes (4.3%) and 8.4% neophytes. Local habitat conditions proved to have the largest effect, rather than climatic variables or propagule pressure. The proportion of archaeophytes follows a different pattern than that seen in central and northern Europe, indicating that macroecological factors are more important. Neophytes show a similar distribution to other European locations.

The Effect of Field Dodder (Cuscuta campestris Yunck.) on Morphological and Fluorescence Parameters of Giant Ragweed (Ambrosia trifida L.)

SUMMARY The effect of the parasitic flowering plant known as field dodder (Cuscuta campestris Yunck.) on morphological and fluorescence parameters of infested giant ragweed (Ambrosia trifida L.) plants was examined under controlled conditions. The parameters of chlorophyll fluorescence (Fo, Fv/Fm, ΦPSII, Fv, Fm, ETR and IF) were measured on infested (I) and non-infested (N) A. trifida plants over a period of seven days, beginning with the day of infestation. Morphological parameters (plant height, dry and fresh weight) were measured on the last day of fluorescence measurements. C. campestris was found to affect the height, fresh and dry weight of the infested A. trifida plants, causing significant reduction in plant height and dry weight. Field dodder also affected several parameters of chlorophyll fluorescence (Fo, Fv/Fm, ΦPSII and Fv) in infested A. trifida plants.

Effect of nicosulfuron on plant traits of Xanthium strumarium

Field experiments were conducted in 2008 and 2009 at the Experimental Field Institute Padinska Skela PKB Agroe-konomik, near Belgrade, to quantify effects of nicosulfuron on plant traits (vegetative production and fecundity) of Xanthium strumarium. Plants of X. strumarium were grown in monoculture on plots of 5 × 4.2 m. Inter-row spacing was 24 cm and the distance between the rows was 70 cm. Plants were treated with nicosulfuron when they developed two pairs of leaves. The applied rates of nicosulfuron were 20, 40 and 80 g a.i. ha−1 and one control treatment (without herbicide application) was included. Vegetative parameters (height, fresh weight, leaf area and leaf area index (LAI)) were recorded just before herbicide application and four times after the herbicide treatment. Measurements were made at intervals of about two weeks. At maturity, fecundity of weeds (bur weight plant−1 and bur number plant−1) was measured. In both years, the application of nicosulfuron caused less growth (height, fresh weight and LAI) of X. stru-marium in comparison with the control. All rates of nicosul-furon reduced vegetative parameters, which decreased as rates of nicosulfuron increased. On the other hand, effects of nicosulfuron on bur production were not equivalent to its effects on vegetative parameters. Only the highest rate of nicosulfuron reduced bur production significantly.

Identification of Glyphosate Resistance in Lolium rigidum Gaudin

Glyphosate resistance was found in Lolium rigidum Gaudin (Rigid ryegrass, LOLRI) in South Africa. Suspected glyphosate-resistant L. rigidum populations were collected and grown under greenhouse conditions. The plants were sprayed with a range of doses of glyphosate 35 days after planting and shoot dry biomass was determined 17 days after herbicide treatment. Based on the dose-response experiment conducted in the greenhouse, one population of L. rigidum suspected to be resistant to glyphosate was approximately 5.3 fold more resistant than susceptible population. The other population was 2.8 fold more resistant than susceptible population. Difference between the two suspected resistant populations was 1.9 fold. All plants were treated with glyphosate (1000 g a.i. ha-1) and shikimic acid was extracted 2, 4 and 6 days after treatment. The plants of susceptible populations accumulated more shikimic acid than other two populations.

Temperature effects on Cuscuta campestris Yunk. seed germination.

Studies of biological characteristics of seeds and conditions for their germination have a major importance for planning and executing rational measures of weed control. The aim of this study was to investigate the effect of different temperatures on germination of C. campestris seeds. Three treatments (T1- storage at room temperature; T2 - exposure to 4°C for 30 days; T3 - scarification by concentrated sulphuric acid) differing in manipulation with seeds before germination were tested at different temperatures (5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C). Germinated seeds were counted daily for ten days and the length of seedlings was measured on the last day. The results showed that differences in germination of C. campestris seeds were very prominent between temperatures, as well as between treatments T1, T2 and T3. Seeds failed to germinate at 5°C and 45°C in all treatments (T1, T2, T3). Germination ranged from 6.25 at 10°C to 96.88%, the highest percentage, achieved at 30°C. [Projekat Ministarstva nauke Republike Srbije, br.III 46008 i br. TR 31043]

Effect of Cuscuta campestris parasitism on the physiological and anatomical changes in untreated and herbicide-treated sugar beet

ABSTRACT The effects of field dodder on physiological and anatomical processes in untreated sugar beet plants and the effects of propyzamide on field dodder were examined under controlled conditions. The experiment included the following variants: N—noninfested sugar beet plants (control); I - infested sugar beet plants (untreated), and infested plants treated with propyzamide (1500 g a.i. ha−1 (T1) and 2000 g a.i. ha−1(T2)). The following parameters were checked: physiological—pigment contents (chlorophyll a, chlorophyll b, total carotenoids); anatomical -leaf parameters: thickness of epidermis, parenchyma and spongy tissue, mesophyll and underside leaf epidermis, and diameter of bundle sheath cells; petiole parameters: diameter of tracheid, petiole hydraulic conductance, xylem surface, phloem cell diameter and phloem area in sugar beet plants. A conventional paraffin wax method was used to prepare the samples for microscopy. Pigment contents were measured spectrophotometrically after methanol extraction. All parameters were measured: prior to herbicide application (0 assessment), then 7, 14, 21, 28 and 35 days after application (DAA). Field dodder was found to affect the pigment contents in untreated sugar beet plants, causing significant reductions. Conversely, reduction in the treated plants decreased 27% to 4% for chlorophyll a, from 21% to 5% for chlorophyll b, and from 28% to 5% for carotenoids (T1). Also, in treatment T2, reduction decreased in infested and treated plants from 19% to 2% for chlorophyll a, from 21% to 2% for chlorophyll b, from 23% to 3% for carotenoids and stimulation of 1% and 2% was observed 28 and 35 DAA, respectively. Plants infested (untreated) by field dodder had lower values of most anatomical parameters, compared to noninfested plants. The measured anatomical parameters of sugar beet leaves and petiole had significantly higher values in noninfested plants and plants treated with propyzamide than in untreated plants. Also, the results showed that propyzamide is an adequate herbicide for control of field dodder at the stage of early infestation.

Gene Flow from Herbicide-Resistant Sunflower Hybrids to Weedy Sunflower

Weedy forms of cultivated sunflower (Helianthus annuus) are invasive species widely distributed in several regions of the world and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides, such as imidazolinones (IMIs) or sulfonylurea (SUs). The widespread adoption of herbicide-resistant crops has exposed the weedy population to the high risk of crop-to-weedy gene flow. The aim of this study was to check and quantify the gene flow from IMI- and SU-resistant sunflower hybrids to weedy sunflower populations. Field experiments were conducted in 2008 at two sites in Serbia to evaluate the relationship of distance between the crop and the weedy sunflower and its impact on the percentage of gene flow. The weedy sunflower progenies were evaluated through herbicide resistance and SSR marker study. Hybridization with IMI-resistant hybrids was not confirmed. Conversly, SU-resistance trials and SSR marker studies partially confirmed the transfer of resistance within the weedy population.

Phytochemical, Free Radical Scavenging and Antifungal Profile of Cuscuta campestris Yunck. Seeds

This work was conceptualized with the goal to investigate the phytochemical, free radical scavenging and antifungal profile of Cuscuta campestrisYunck. seeds. Total phenolics, amino acid and carbohydrate contents were evaluated in ethanolic, acetone and chloroform extract. Effective antioxidant activity was evaluated throughout seven antioxidant methods. The antifungal activity was assessed against eight fungal strains and Candida albicans. The results showed total phenol, flavonoid, flavonols and phenolic acids contents in amount of 1.51 – 6.35 mg GAE/mL, 78 – 425 μg RU/mL, 1.04 – 2.98 mg QU/g and 12.01 – 30.58 μg CAE/mL, respectively. The total amino acids and carbohydrates content ranged from 8.29 to 185.45 μg Gly/mL and from 0.05 to 0.12 μg Glu/mL. The ethanolic extract showed the best antioxidant activity in phosphomolybdenum, DPPH free radical scavenging, ferric reducing power and lipid peroxidation assays. The best activity in ferrous ion chelating and H2O2 assays had the acetone extract, whereas the best hydroxyl radical scavenging activity was observed with the chloroform extract. The ethanolic extract at a concentration of 6 mg/mL proved to be the most effective antimycotic, since it inhibited the growth of all tested fungi except Penicillium verrucosum. The obtained results indicate that C. campestris seeds could be attributed to a potential source of natural antioxidants in food and pharmaceutical products.