Klara Barić

Bio: Klara Barić is an academic researcher from University of Zagreb. The author has contributed to research in topics: Ambrosia artemisiifolia & Weed. The author has an hindex of 7, co-authored 55 publications receiving 215 citations.

Allelopathic potential of segetal and ruderal invasive alien plants

Abstract: At the global level, the invasion of alien organisms is considered the second largest threat to biodiversity. The assumption is that the high allelopathic potential is one of the features that helps invasive plant species to spread to new areas. In the study was determined allelopathic potential of eight invasive plant species (donor species) and their impact on test-species. Donor species were Abutilon theophrasti Med. - velvetleaf (Malvaceae), Ambrosia artemisiifolia L. - ragweed (Asteraceae), Datura stramonium L. - white jimsonweed (Solanaceae), Xanthium strumarium L. - cocklebur (Asteraceae), Ailanthus altissima (Mill.) Swingle - tree of heaven (Simaroubaceae), Amorpha fruticosa L. - indigo bush (Fabaceae), Reynoutria japonica Houtte. - Japanese knotweed (Polygonaceae), Solidago gigantea Aiton - giant goldenrod (Asteraceae). Three cultivated plant species from three different plant families were used as test-species: Avena sativa L. - oats (Poaceae), Brassica napus L. - oilseed rape (Brassicaceae) and Helianthus annuus L. - sunflower (Asteraceae). Water extracts made of whole plants of donor species were applied to the seeds of the test-species. High allelopathic potential was proven for all species included in experiment. Allelopathic effects were exclusively negative. Impact on the germination for all species is much smaller in relation to the impact on the radicle and shoot length of the test-species. Perennial species had a stronger allelopathic potential than annual species. Tree of heaven is species with the strongest allelopathic potential. Its extracts inhibited germination, radicle and shoot length of oilseed rape 19%, 94.88% and 98.91% respectively. Applying allelopathy in agriculture can reduce the use of synthetic pesticides.

Distribution of invasive weed Ambrosia artemisiifolia L. in Croatia.

Abstract: Summary Ambrosia artemisiifolia L., is an invasive alien plant in Europe that has been the subject of research of many scientifi c disciplines, particularly in last twenty years. In addition to being known as a noxious weed, it came into the public interest as a source of very strong allergenic pollen that causes allergic responses in 10% of the Croatian population, a fi gure similar to that of other European countries. Th e genus Ambrosia consists of about 40 species but in Europe just fi ve of them are present. Th e most widespread is Ambrosia artemisiifolia L. It is present normally in row crops, particularly in sunfl ower (Helianthus annuus L.) fi elds. Furthermore, its presence is noticed along communication lines, in urban, industrial and building areas, and other non-agricultural areas. Distribution monitoring of Ambrosia artemisiifolia L. was conducted during three years, from 2004 to 2006, by recording its presence or absence in settlements of districts in the 21 counties of Croatia. Inland parts of Croatia are highly infested with Ambrosia artemisiifolia L. while in the coastal area it is mainly concentrated on bands along communication lines. In this area we observed individual (solitary) plants. Systematic and well organized monitoring of the Ambrosia artemisiifolia L. spread and distribution in the coastal parts of Croatia would reduce its progression to the more southern parts and the Croatian islands.

Variability in seedling emergence for European and North American populations of Abutilon theophrasti

Abstract: Weeds have to adapt their biological cycles according to the different combinations of environmental and agronomic conditions and large intra-specific variability regarding dormancy and germination has been reported. This variability, controlled by the interaction of genetic diversity and maternal effect, could hinder the adoption of IWM strategies and tools. A collaborative project was conducted to compare emergence dynamics under diverse environmental conditions of 12 European and North American populations of A. theophrasti. Seeds were sown at 6 different experimental sites located in Southern and Eastern Europe and seedling emergence was monitored. AlertInf model was tested to evaluate its ability to predict emergence dynamics of the different populations according to weather data. Large inter-population variability was observed in terms of emergence percentage and dynamic with trends consistent across the different sites and related to different seed dormancy level. Populations from Catalonia, Iowa and Minnesota reached higher emergence percentage with earlier and concentrated emergence flushes probably due to low dormancy level, while populations from Croatia, Serbia and Hungary presented high dormancy level considering their low average emergence percentage. Good predictive accuracy of AlertInf model was obtained at the different sites, confirming the possibility of adopting AlertInf model across a wide range of environmental conditions. Achieving better knowledge on inter-population variability can allow to design specific and efficient control strategies, facilitating the replacement of solely herbicide-based managements with real IWM strategies.

Sulfur-Containing Agrochemicals

Abstract: Modern agricultural chemistry has to support farmers by providing innovative agrochemicals. In this context, the introduction of sulfur atoms into an active ingredient is still an important tool in modulating the properties of new crop-protection compounds. More than 30% of today’s agrochemicals contain at least one sulfur atom, mainly in fungicides, herbicides and insecticides. A number of recently developed sulfur-containing agrochemical candidates represent a novel class of chemical compounds with new modes of action, so we intend to highlight the emerging interest in commercially active sulfur-containing compounds. This chapter gives a comprehensive overview of selected leading sulfur-containing pesticidal chemical families namely: sulfonylureas, sulfonamides, sulfur-containing heterocyclics, thioureas, sulfides, sulfones, sulfoxides and sulfoximines. Also, the most suitable large-scale synthetic methods of the recently launched or provisionally approved sulfur-containing agrochemicals from respective chemical families have been highlighted.

Palladium-Catalyzed Cross-Coupling Reactions: A Powerful Tool for the Synthesis of Agrochemicals.

Abstract: Pd-catalyzed cross-coupling reactions have become essential tools for the construction of carbon-carbon and carbon-heteroatom bonds. Over the last three decades, great efforts have been made with cross-coupling chemistry in the discovery, development, and commercialization of innovative new pharmaceuticals and agrochemicals (mainly herbicides, fungicides, and insecticides). In view of the growing interest in both modern crop protection and cross-coupling chemistry, this review gives a comprehensive overview of the successful applications of various Pd-catalyzed cross-coupling methodologies, which have been implemented as key steps in the synthesis of agrochemicals (on R&D and pilot-plant scales) such as the Heck, Suzuki, Sonogashira, Stille, and Negishi reactions, as well as decarboxylative, carbonylative, α-arylative, and carbon-nitrogen bond bond-forming cross-coupling reactions. Some perspectives and challenges for these catalytic coupling processes in the discovery of agrochemicals are briefly discussed in the final section. The examples chosen demonstrate that cross-coupling chemistry approaches open-up new, low-cost, and more efficient industrial routes to existing agrochemicals, and such methods also have the capability to lead the new generation of pesticides with novel modes of action for sustainable crop protection.

Biological Flora of the British Isles: Ambrosia artemisiifolia.

Abstract: This account presents information on all aspects of the biology of Ambrosia artemisiifolia L. (Common ragweed) that are relevant to understanding its ecology. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, and history, conservation, impacts and management. Ambrosia artemisiifolia is a monoecious, wind-pollinated, annual herb native to North America whose height varies from 10 cm to 2.5 m, according to environmental conditions. It has erect, branched stems and pinnately lobed leaves. Spike-like racemes of male capitula composed of staminate (male) florets terminate the stems, while cyme-like clusters of pistillate (female) florets are arranged in groups in the axils of main and lateral stem leaves. Seeds require prolonged chilling to break dormancy. Following seedling emergence in spring, the rate of vegetative growth depends on temperature, but development occurs over a wide thermal range. In temperate European climates, male and female flowers are produced from summer to early autumn (July to October). Ambrosia artemisiifolia is sensitive to freezing. Late spring frosts kill seedlings and the first autumn frosts terminate the growing season. It has a preference for dry soils of intermediate to rich nutrient level. Ambrosia artemisiifolia was introduced into Europe with seed imports from North America in the 19th century. Since World War II, it has become widespread in temperate regions of Europe and is now abundant in open, disturbed habitats as a ruderal and agricultural weed. Recently, the North American ragweed leaf beetle (Ophraella communa) has been detected in southern Switzerland and northern Italy. This species appears to have the capacity to substantially reduce growth and seed production of A. artemisiifolia. In heavily infested regions of Europe, A. artemisiifolia causes substantial crop-yield losses and its copious, highly allergenic pollen creates considerable public health problems. There is a consensus among models that climate change will allow its northward and uphill spread in Europe.

A process-based approach to predicting the effect of climate change on the distribution of an invasive allergenic plant in Europe

Abstract: Ambrosia artemisiifolia is an invasive weed in Europe with highly allergenic pollen. Populations are currently well established and cause significant health problems in the French Rhone valley, Austria, Hungary and Croatia but transient or casual introduced populations are also found in more Northern and Eastern European countries. A process-based model of weed growth, competition and population dynamics was used to predict the future potential for range expansion of A.artemisiifolia under climate change scenarios. The model predicted a northward shift in the available climatic niche for populations to establish and persist, creating a risk of increased health problems in countries including the UK and Denmark. This was accompanied by an increase in relative pollen production at the northern edge of its range. The southern European limit for A.artemisiifolia was not expected to change; populations continued to be limited by drought stress in Spain and Southern Italy. The process-based approach to modelling the impact of climate change on plant populations has the advantage over correlative species distribution models of being able to capture interactions of climate, land use and plant competition at the local scale. However, for this potential to be fully realised, additional empirical data are required on competitive dynamics of A.artemisiifolia in different crops and ruderal plant communities and its capacity to adapt to local conditions.