The germination ecology of Ambrosia artemisiifolia and A. trifida glyphosate susceptible biotypes sampled in marginal areas, was compared with that of the same species but different biotypes suspected of glyphosate resistance, common and giant ragweed, respectively. The suspected resistant biotypes were sampled in Roundup Ready® soybean fields. Within each weed species, the seeds of the biotype sampled in marginal area were significantly bigger and heavier than those of the biotype sampled in the soybean fields. A. artemisiifolia biotypes exhibited a similar dormancy and germination, while differences between A. trifida biotypes were observed. A. artemisiifolia biotypes showed similar threshold temperature for germination, whereas, the threshold temperature of the susceptible A. trifida biotype was half as compared to that of the resistant A. trifida biotype. No significant differences in emergence as a function of sowing depth were observed between susceptible A. artemisiifolia and suspected resistant A. trifida biotype, while at a six-cm seedling depth the emergence of the A. artemisiifolia susceptible biotype was 2.5 times higher than that of the A. trifida suspected resistant biotype. This study identified important differences in seed germination between herbicide resistant and susceptible biotypes and relates this information to the ecology of species adapted to Roundup Ready® fields. Information obtained in this study supports sustainable management strategies, with continued use of glyphosate as a possibility.

Velvetleaf (Abutilon theophrasti Medik.) is an invasive alien species in many countries and one of the major weeds in summer row crops worldwide. Weed-management techniques that reduce weed production need to be investigated to provide new approaches. The first step in this process is the determination of weed productivity in different competitive conditions. Field experiments were conducted in 2006 and 2008 in an experimental field in Padinska Skela to quantify growth and seed production of velvetleaf in maize, as well as in a velvetleaf monoculture. A density of velvetleaf ranging from 1 to 8 plants m-1 was artificially created. In a mixture with maize, velvetleaf was sown in crop rows. The growth of velvetleaf was estimated based on plant height, fresh aboveground biomass and leaf area index (LAI). Velvetleaf fecundity was determined as seed mass plant-1 and seed mass m-2. Differences between years in plant production were very prominent. In general, velvetleaf productivity in maize depended on its density. Intraspecific competition had a major influence on growth and seed production when velvetleaf density was from 4 to 8 plants m-1 in maize rows. This information indicates that environmental conditions and weed density can promote/reduce inter- and intraspecific competition and help in the construction of population dynamics models to predict population density, seed bank and competitiveness of weeds and reduce inputs for weed management.

In this study, we report genetic characterization of Orobanche cumana, the causal agent of sunflower wilting in Serbia. The genetic diversity of this parasitic plant in Serbia was not studied before. Random amplified polymorphic DNA (RAPD) markers and partial rbcL gene sequences analysis were used to characterize the O. cumana populations at the molecular level. While phylogenetic analyses of RAPD-PCR amplicons were performed using unweighted pair-group Method analyses, rbcL gene sequences were analyzed using neigbor joining method and minimum spanning tree. Molecular analyses of RAPD-PCR analysis revealed high genetic diversity of O. cumana populations which indicated high adaptive potential of this parasitic weed in Serbia. Further analyses of rbcL gene using minimum spanning tree revealed clear differences among diverse sections of Orobanche genus. Although this molecular marker lacked the resolution to display intrapopulation diversity it could be a useful tool for understanding the evolution of this parasitic plant. Our results suggested that O. cumana has great genetic potential which can lead to differentiation of more virulent races which is important for determining crop breeding strategies for their control.

Transportation corridors such as waterways and road networks serve as an entranceway for invasive and economically important weed species. The unstable environment of riparian areas and nutrient enrichment of road verges promotes the establishment and spread of these species, which may have a negative effect on nearby arable land, leading to severe yield reductions. We aimed to register the presence and frequency of five selected weed species (Chenopodium album, Cirsium arvense, Convolvulus arvensis, Cynodon dactylon, and Lactuca serriola) within these linear corridors. Sites along waterways were visited during 2013-2016, and road networks during 2018-2019. At each site, studied weed species were registered along 100 m transects, resulting in 250 localities along waterways and 180 near road networks. The most frequent species is C. arvensis, followed by L. serriola and C. album, while less prevalent species are C. arvense and C. dactylon. The main characteristic of studied species is their preference for roadside habitats, except for Chenopodium album, which is more common in riparian areas.