Bidens Subalternans Research Articles

A Revision of Bidens (Asteraceae: Coreopsideae) from Bolivia

The genus Bidens L. is the largest genus of the Coreopsideae that comprises about 280 species with a global distribution in tropical and temperate climates. An account of the 12 species and three varieties of Bidens occurring in Bolivia is provided, i.e., B. andicola Kunth var. andicola, B. andicola var. heterophylla Kuntze, B. aurea (Aiton) Sherff, B. cynapiifolia Kunth, B. exigua Sherff, B. gardneri Baker, B. herzogii (Sherff) D. J. N. Hind, B. mandonii (Sherff) Cabrera, B. pilosa L., B. pseudocosmos Sherff, B. squarrosa Kunth, B. subalternans DC. var. subalternans, B. subalternans var. simulans Sherff, B. tenera O. E. Schulz, and B. triplinervia Kunth var. macrantha (Wedd.) Sherff. The following three taxa are placed in synonymy: B. buchtienii Sherff is synonymized under B. andicola var. heterophylla; and B. andicola var. tarijensis Sherff and B. andicola f. dissecta Sherff under B. triplinervia var. macrantha. Diodonta coronata (L.) Nutt. is selected as the generitype of Diodonta Nutt. (= Bidens), and 23 lectotypes are designated: one for B. andicola, one for B. andicola var. heterophylla, one for B. gardneri, nine for names applicable to B. pilosa, one for B. pseudocosmos, five for names applicable to B. squarrosa, one for a name applicable to B. tenera, five for names applicable to B. triplinervia var. macrantha; and an epitype is proposed for the name B. odorata Cav. Four taxa are excluded from Bolivia, i.e., B. bipinnata L., B. reptans (L.) G. Don, B. rubifolia Kunth, and B. grandiflora Balb. var. longiloba Kuntze for which specimens have not been traced that confirmed their occurrence in Bolivia. Bidens subalternans var. simulans and B. aurea are reported for the first time from Bolivia. Descriptions, distribution maps, identification key, illustrations, and local vernacular names of all taxa are provided.

THE ALLELOPATHIC EFFECT OF SORGHUM AND ITS LINKS TO THE EXTRACT COMPOSITION AND THE SORGOLEONE

The use of sorghum on the no-tillage system has contributed to weed control but has generated problems infuture soybean development. The objective of this work was to extract and quantify sorghum root exudate ofthree genotypes to determine the sorgoleone content, the chromatographic profile, and the relative toxicity of the root extracts through the evaluation of germination parameters in soybean (Glycine max), brachiaria grass (Brachiaria decumbens) and beggarticks (Bidens subalternans) seeds under laboratory conditions.Considering the average root density, BRS 716 presented 50% more numbers of hairs per mm² than the othertwo sorghum genotypes. Sorgoleone was found predominantly in the three evaluated sorghum extracts, andthe chromatographic profile detected five other compounds for the BR 007, CMSXS 206 B, and 6 BRS 716compounds. There was a difference between the dry mass of roots, dry mass of extract, and sorgoleone content among the three genotypes, with BRS 716 having the highest ratio of sorgoleone per dry mass of roots, followed by BR 007 B, and CMSXS 206 B. The BR 007 B extract was the one that reduced germination and the germination speed index (GSI) of soybean and hairy beggarticks, followed by BRS 716 and CMSXS 206B. The results showed that sorgoleone is a potent inhibitor of plant germination, but the allelopathic actionmay be linked to the composition of each extract and not specifically to the sorgoleone.

Terbuthylazine herbicide: an alternative to atrazine for weed control in glyphosate-tolerant maize

It is proposed that the herbicide terbuthylazine is more effective than atrazine in controlling weeds in maize. This study aimed to evaluate the efficacy of terbuthylazine and atrazine in a mixture with glyphosate in glyphosate-tolerant maize for post-emergence application. The experiment was conducted over three trials using randomized blocks with 4 repetitions and 10 treatments, composed by terbuthylazine rates + glyphosate, atrazine rates + glyphosate, [atrazine + mesotrione] + glyphosate, atrazine + tembotrione, isolated glyphosate, and nontreated control. Trial 1 were infested with Bidens subalternans DC. and Commelina benghalensis L; trial 2 with Urochloa plantaginea (Link) R. D. Webster, Ipomoea spp., volunteer soybean, B. subalternans, and grasses; and trial 3 infestation with C. benghalensis, U. plantaginea, Ipomoea spp., volunteer soybean, B. subalternans, Amaranthus hybridus L., and grasses. Weed control, crop injury, and yield were evaluated. Terbuthylazine + glyphosate showed an efficacy equivalent to that of atrazine or [atrazine + mesotrione] + glyphosate in the control of broadleaves and C. benghalensis. In contrast, the efficacy of terbuthylazine was similar or greater than that observed for atrazine in controlling grasses, depending on the location. Terbuthylazine is an important partner of glyphosate in controlling weeds in maize and is an alternative to atrazine.

WATER DEFICIT ON GROWTH AND PHYSIOLOGICAL INDICATORS OF Bidens pilosa L. AND Bidens subalternans DC.

ABSTRACT Stress caused by soil water deficit has been one of the main factors that inhibit plant growth. The knowledge of the factors related to the behavior of weed species under water stress conditions can contribute to the elaboration of effective control strategies. Two experiments were carried out to evaluate the effects of the degree and duration of water deficit on physiological and growth indicators of two weed species (Bidens pilosa L. and Bidens subalternans DC.). The stress degree was simulated by four soil moisture: 100, 75, 50, 25% of total soil capacity. The water deficit duration was evaluated by five intervals of water supply: 0, 1, 2, 3, 4, 5, and 6 days. The experiments were carried out in a randomized complete block design with six replicates. The evaluated variables were: the photosynthetic rate (A; μmol CO2 m-2), stomatal conductance (gs; μmol H2O m-2 s-1), transpiration (E; mmol H2O m-2 s-1), number of leaves per plant, and dry matter of the roots, stems, leaves, and total. The results showed that the species of B. pilosa and B. subalternans tolerate low water availability conditions. Low stomatal opening and loss of leaves are mechanisms that ensure the survival of Bidens plants to the water deficit. However, water stress close to 25% of field capacity caused the death of species. The B. subalternans had higher sensitivity to the water deficit, showing a lower dry matter of leaf, stem, and root than B. pilosa.

Seed germination of Bidens subalternansDC. exposed to different environmental factors.

Bidens subalternans DC. is a weed found in several tropical countries such as Brazil. Large number of produced seeds and easy dispersion favor the colonization of agricultural fields by this species. To know the factors that affect the germination of B. subalternans can help to understand its ecology, permitting to develop control strategies. Laboratory experiments were carried out to evaluate how the temperature, photoperiod, burial depth, water deficit, and salt stress affect the seed germination of B. subalternans. The means of the treatments of each experiment were shown in scatter plots with the bars indicating the least significant difference (LSD, p≤0.05). The results showed a germination percentage above 77% for a wide alternating temperature (15/20 C to 30/35 C night/day). The highest germination and uniformity occurred at 25/30°C night/day. Only 11% of the seeds germinated at a temperature of 35/40°C night/day. The deeper burial of seeds reduced their germination. Only 17% of the seeds germinated in darkness conditions. However, in constant light and 12 hours of light/dark conditions the germination percentage was over 96%, confirming the light dependence of the B. subalternans during germination. In constant light and 12 hours of light/dark, the germination was over 96%. B. subalternans seeds showed sensitivity to water and salt stress, and their germination was inhibited under a water potential of -0.4 MPa and 100.09 mM, respectively. The sensitivity of B. subalternans seeds to high temperatures, water stress, and salt stress explains the high frequency of this weed in south-central Brazil. The light and sowing depth showed that burial of seeds by mechanical control is a strategy to reduce the high infestation of B. subalternans.

Chemical composition and phytotoxic activity of Lippia origanoides essential oil on weeds

Studies in the area of allelopathy in agriculture have increased due to search on alternative methods of weed control compared to conventional herbicides. Thus, the objective of this work was to evaluate the chemical composition and phytotoxicity of the Lippia origanoides essential oil on weeds of the species Bidens subalternans, Euphorbia heterophylla and Macroptilium lathyroides. The essential oil was extracted from the leaves of L. origanoides by means of hydrodistillation and diluted in the concentrations of 0.01 to 1%. The chemistry composition was determined by a gas chromatograph coupled with a mass spectrometry. Phytotoxic activity was evaluated in pre and post-emergence by tests of germination, seedling growth, chlorophyll content and cellular respiration. The results demonstrated an essential oil rich in monoterpenes, mainly oxygenated, with camphor as the major compound. In general, both germination and seedling development were entirely inhibited by essential oil, decreasing with increasing concentrations. The concentrations 0.5 and 1.0% totally inhibited the germination of B. subalternans, but did not affect the germination of M. lathyroides. The essential oil sprayed on the weed leaves had no effect on chlorophyll content but was able to induce visible injuries such as necrosis and chlorosis. Only the cellular respiration of E. heterophylla was affected by the essential oil. All the phytotoxic effects observed are due to the high content of monoterpenes in the essential oil, mainly the oxygenates, and also the concentration used. Therefore, the L. origanoides essential oil have bioherbicidal potential for the tested species.

Phytoplasmas diversity and identification of new aster yellows subgroup (16SrI) associated with weed species in Argentina.

Symptoms of phytoplasma infection were observed in different weed species, Bidens subalternans, Conyza bonariensis, Heterosperma ovatifolium and Conium maculatum, collected from diverse geographical regions in Argentina. To confirm the association of phytoplasma infection with symptomatic plants, PCR, RFLP and phylogenetic analyses based on 16S rRNA-encoding sequences were performed. In this work, we report the presence of phytoplasmas from group 16SrVII (subgroup 16VII-B) infecting C. bonariensis and B. subalternans and from group 16SrIII (subgroup 16SrIII-X) B. subalternans, H. ovatifolium, and C. maculatum. Phytoplasmas from the aster yellows group were detected infecting C. bonariensis and B. subalternans. Analysis of 16S rRNA-encoding genes revealed the presence of two distinct operons, rrnB (16SrI-B) and newly described rrnA, which is different from the reference RFLP patterns of all previously established 16SrI-subgroups. A single rp operon sequence analysis reveals the presence of simple infection and confirms a description of a novel subgroup. On the basis of these results we propose a designation of new subgroup 16SrI-(B/AJ) AJ (rp-AJ). To our knowledge, this is the first report of phytoplasmas infecting Bidens subalternans¸ Heterosperma ovatifolium and Conium maculatum.

A novel TIPT double mutation in EPSPS conferring glyphosate resistance in tetraploid Bidens subalternans.

Bidens subalternans (greater beggarticks) is a tetraploid and troublesome weed infesting annual crops in most tropical regions of the world. A glyphosate-resistant (GR) B. subalternans biotype was detected in a soybean field from Paraguay. A series of physiological and molecular analyses were conducted to elucidate its resistance mechanisms. The GR biotype had a high level of resistance (> 15-fold LD50 ), relative to a glyphosate-susceptible (GS) biotype. Shikimate accumulation was up to ten-fold greater for GS compared with GR. We found no differences in sensitivity when plants were treated and kept under lower (10/4 °C) or higher temperatures (25/20 °C). GS and GR had the same relative EPSPS gene copy number, and similar glyphosate absorption and translocation rates. Neither biotype metabolized glyphosate. A double amino acid substitution (TIPT - Thr102Ile and Pro106Thr) was found in only one EPSPS allele from one of the two EPSPS homoeologs present in tetraploid GR B. subalternans. This is the first report of a TIPT double mutation conferring high levels of glyphosate resistance in a weed species. The presence of both wild-type and TIPT mutant EPSPS on the polyploid genome of GR B. subalternans may offset a potential fitness cost, requiring additional research to confirm the absence of deleterious effects. © 2019 Society of Chemical Industry.

Multiple resistance to glyphosate and imazethapyr in Bidens subalternans

ABSTRACT Glyphosate has been widely used to control greater beggarticks populations that are resistant to acetolactate synthase (ALS) inhibitors in South America. However, herbicide control failures has been observed over the last three growing seasons in grain production areas of Paraguay. In this research, we report the first case of multiple resistance to glyphosate (EPSPs) and imazethapyr (ALS) in greater beggarticks (Bidens subalternans) population from Paraguay. This conclusion was supported by dose-response experiments conducted in two consecutive years (2018 and 2019) with a putative resistant (R) and a susceptible (S) population. Alternative herbicides were also tested for post-emergence control of R population. For glyphosate, the resistant factor (RF) values were 8.8- (2018) and 15.7-fold (2019). For imazethapyr, the RF values were 59- and 58-fold, in 2018 and 2019, respectively. Treatments with 2,4-D, dicamba, 2,4-D + glyphosate, dicamba + glyphosate, lactofen, fomesafen, ammonium-glufosinate, atrazine, and bentazon provided more than 80% control of the R population. This is the first case of multiple resistance to glyphosate and imazethapyr in greater beggarticks (Bidens subalternans) in the world. The mechanisms underlying resistance in this biotype should be evaluated in future research.

Identification and Mapping of Cross-Resistance Patterns to ALS-Inhibitors in Greater Beggarticks (Bidens spp.)

ABSTRACT: Greater beggarticks (Bidens pilosa and Bidens subalternans) biotypes have been under selection pressure of ALS-inhibitors since early 90’s in Brazil. The objectives of this work were to investigate whether there are different cross-resistance patterns among ALS-inhibitors herbicides in Bidens spp. biotypes; to understand the geographic distribution of resistance patterns in grains producing regions in Brazil; and evaluate the possibility of multiple resistance to ALS-inhibitors, EPSPs inhibitor and photosystem II inhibitors. Dose-response experiments were carried out with imazethapyr, chlorimuron and diclosulam in three populations. Sensibility to others 34 populations both from Paraná State (PR) and from others Brazilian regions were also evaluated. The dose-response assay revealed cross-resistance with different patterns. One population was resistant to all three herbicides, the second population was tolerant to both imazethapyr and chlorimuron, but not to diclosulam, while a third population was resistant merely to imazethapyr. The results exhibited different cross-resistance patterns, since they can be found in other Bidens spp. populations. However, no relationship was observed between geographic areas where samples were collected and resistance patterns. Conclusively, the most frequent resistance pattern was R2 (resistance to imazethapyr, chlorimuron and diclosulam).

Water Stress Affect Germination, Seed Vigor and Seedlings Growth of Bidens subalternans

The beggartick (Bidens subalternans L.) is one of the main weeds present in agricultural crops, capable of adapting to different environmental conditions. The water stress caused by water deficiency can affect the germination of weed seeds and, consequently, their capacity to colonize the agroecosystem. Knowledge of germination under water stress can be important to obtain an adequate management of the species in the agricultural systems. The objective of this study was to determine the effects of water stress on the germination process and vigor of two batches of Bidens subalternans seeds under different osmotic agents. It was completely randomized experimental design was used, with four replicates of 25 seeds. The treatments were arranged in factorial 6 × 2, with the first factor corresponding six levels of osmotic potentials (0.0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa) and the second the batches (Pernambuco and Ceará). For the simulation of the water stress, the test of germination was installed in substrate paper blotting, moistened with solutions of polyethylene glycol (PEG 6000) and mannitol. The analyzed variables were germination, germination speed index, length and seedling dry mass. Water stress reduced germination, seed vigor and growth of seedlings in all batches of B. subalternans. Seeds of B. subalternans presented greater tolerance to stress induced by mannitol than to PEG-6000 in terms of germination and germination speed index. Regardless of the osmotic agent used for stress induction, B. subalternans seeds did not tolerate water stress higher than -0.4 MPa.

Liquid fermentation of Colletotrichum truncatum UFU 280, a potential mycoherbicide for beggartick

One isolate of Colletotrichum truncatum was found recently causing severe anthracnose symptoms and leading to the death of beggartick (Bidens pilosa L. and Bidens subalternans DC.), one of the major weeds of Brazilian agriculture. This isolate, namely UFU 280, was selected for development of a mycoherbicide against this weed. Associated of beggartick, one of the, Here, results of a preliminary attempt to develop a protocol for mass production of inoculum (conidia) and fungal biomass of C. truncatum was performed aimed at paving the way for greenhouse and field evaluations of this biocontrol candidate. Isolates of Colletotrichum spp. have been successfully produced in the past to serve as the active ingredients of mycoherbicides. The method of choice has been the production of propagules through liquid fermentation. We assessed the effect of several options of liquid media recipes, type of seeding of medium, pH levels, incubation lengths, incubation temperatures and agitation speeds on the shaking speed on the concentration of conidia obtained per volume of medium. Additionally, a possible effect of the kind of medium utilized over the virulence of the inoculum was also evaluated through an inoculation study. We found that an adequate amount of conidia of C. truncatum (isolate - UFU 280) can be obtained in ME liquid culture medium, adjusted to a pH of 9.0, seeded with a conidial suspension and incubated for 6 days, under a regime of orbital shaking of 150 rpm, at temperatures ranging from 20 to 25 °C. Mortality of beggartick plants using conidia produced in different liquid culture media was of 100%.

<b>Phytosociology of weed in the southwestern Goiás region

Roundup Ready® technology adoption and the cultivation of a second crop have changed chemical control methods and weed management in the southwest region of Goiás State, Brazil. Considering these changes, this study aimed to perform a phytosociological survey in areas with glyphosate resistant soybeans and conventional soybeans as the main harvest and sorghum, maize, millet or fallow in succession as the second harvest. A multivariate matrix of the floristic composition was constructed, and the indicator values of the individual number and dry biomass of species were measured. Based on the number of individuals, the species Chamaesyce hirta, Bidens subalternans, and Cissampelos ovolifolia were typical of areas cultivated with glyphosate-resistant soybean, while Euphorbia heterophyla presented indicator values of areas with conventional soybean cultivation. During the second harvest period, significant indicator values were observed for Crotalaria spectabilis in maize areas, Cenchrus echinatus in sorghum, and Commelina benghalensis, Sida glaziovii, Ipomoea grandifolia, Sida rhombifolia, and Ipomoea cordifolia in areas with millet. The species Conyza bonariensis was typical in the period before the herbicide application at post-emergence in harvest. Volunteer soybean presented as typical for the period before the herbicide application at post-emergence in the second harvest. Weeds that were difficult to control or were tolerant and resistant to the herbicide applications were recorded in the areas studied.

English

The objective of this work was to evaluate the interference resulting from the use of different phytomass quantities of Uroclhoa brizantha cv. Marandu and the management of straw to control beggar-ticks (Bidens subalternans). The experiment was performed under greenhouse from May to August, 2014, using a randomized block experimental design with four replicates, in a factorial scheme (3 × 4) + 1, with Factor A constituted by three management methods (incorporated, incorporated+surface and surface), and Factor B constituted by five straw levels (3; 6; 9 and 12 t ha-1), plus one treatment without the usage of any cover plant (control treatment). The variables evaluated were the total number of plants emerged, the index of emergence velocity, dry phytomass of the aerial plant portion, leaf area, dry phytomass of roots and the volume of roots. Different management methods at different straw levels were efficient, with an emphasis to the surface management in the suppression of beggar-ticks (B. subalternans).          Key words: Allelopathy, beggar-tick, Brachiaria brizantha, weed

Optimal weed population control using nonlinear programming

A dynamic optimization model for weed infestation control using selective herbicide application in a corn crop system is presented. The seed bank density of the weed population and frequency of dominant or recessive alleles are taken as state variables of the growing cycle. The control variable is taken as the dose–response function. The goal is to reduce herbicide usage, maximize profit in a pre-determined period of time and minimize the environmental impacts caused by excessive use of herbicides. The dynamic optimization model takes into account the decreased herbicide efficacy over time due to weed resistance evolution caused by selective pressure. The dynamic optimization problem involves discrete variables modeled as a nonlinear programming (NLP) problem which was solved by an active set algorithm (ASA) for box-constrained optimization. Numerical simulations for a case study illustrate the management of the Bidens subalternans in a corn crop by selecting a sequence of only one type of herbicide. The results on optimal control discussed here will give support to make decision on the herbicide usage in regions where weed resistance was reported by field observations.

THE URBAN FLORA OF PODGORICA (MONTENEGRO, SE EUROPE): ANNOTATED CHECKLIST, DISTRIBUTION ATLAS, HABITATS AND LIFE-FORMS, TAXONOMIC, PHYTOGEOGRAPHICAL AND ECOLOGICAL ANALYSIS

The paper presents a taxonomic, ecological and phytogeographical study of the native and alien flora of the urban area of Podgorica (Capital of Montenegro, SE Europe). The surveyed terrain extends over 86 km2, and apart from the urban it also entails the peri-urban zone. The checklist of vascular plants of the urban area includes1222 species and subspecies from 561 genera and 121 families which represents a little over a third of the total flora of Montenegro. The richness and diversity of the city’s flora are caused by the local geomorphology and climatic conditions of the area, the high diversity of habitats with different anthropogenic impact and the increased immigration of plants from the surrounding ecosystems. Concerning the distribution of the species number by quadrant in the city area of Podgorica ther is no gradient between growing number of species and distance from the urban core. However, if the distribution of the number of taxa per habitat is taken into consideration, it is clear that the homogeneity of habitats and the increase in the urbanisation leads to decline of the number of wild growing taxa. The families represented by the highest number of taxa are Poaceae (11.5%), Asteraceae (11.2%) and Fabaceae (9.2%). while the genera represented most are Trifolium (2.1%), Euphorbia (1.4%), Carex, Ranunculus and Bromus (1.3 each%), Veronica (1.2%), Allium (1.1%), Vicia and Lathyrus (1% each). Apart from the expected high presence of synanthropic, ruderal and ruderal-segetal taxa, the flora of Podgorica is characterised by a significant number of typical urbanophobes. Comparing to the flora of selected European cities (Zurich, Vienna, Rome, Patras and Thessaloniki), Podgorica showed the biggest similarity with Rome (Sørensen’s quotient of similarity (Q/S)= 69.4). The general life form spectrum has therophytic-hemicryptophytic character, which, on one hand, reflects the climatic conditions and on the other the intensive urbanisation of the surveyed area. Like in the spectrum of other Mediterranean cities, the participation of the geophytes is relatively high (11.7%). Conserning phenology, Podgorica is a city in which no interruption of vegetation growth and something is always in flower. The majority of plants flower in May, the smallest number flowers in December. Regarding the ecological temperature index, dominating in the city area are thermophilic plants (T7 and T8), an indication of the Mediterranean character of the city area. Prevalent in terms of the light index are heliophyllic plants (L7 and L8), conditioned by exposure of the terrain to sunlight, as well as by the degradation of the primary forest cover and the domination of open and sunny habitats. Dominant in terms of soil reaction are neutrophilic and neutro-basophilic species (R5 and R7), and in terms of nutrients oligotrophic plants (N2 and N3). Dominating in terms of the humidity index are H3 and H4 plants, as expected considering the climatic conditions and hydrography of the area. The phytogeographic spectrum of Podgorica fits into the general spectrum of South European cities and is characterised by the prevailing presence of Mediterranean species s.l. (39.7%). The participation of aliens is relatively small (14.1%), probably due to the short history of the settlement and the poorly developed transportation and trading networks. Dominant among aliens are taxa of Asteraceae (15.7%) and plants of Asian (43%) and North American origin (23.2%). The most aggressive aliens in the city area are Ailanthus altissima, Artemisia annua, A. verlotiorum, Bidens subalternans, Broussonetia papyrifera, taxa of the genus Erigeron, Symphyotrichum squamatum and Xanthium orientale subsp. italicum.The comparative analysis of selected habitat types in the area of Podgorica showed that two habitat types are distinguished by prominent floristic richness: meadows (46.1%) and dikes along railroad tracks (32.1%). Due to constant degradation and loss of habitat in the strict urban zone of Podgorica which on one hand causes the loss of native flora, and on the other facilitates the expansion of the alien flora, we expect the effect of the biotic homogenisation to be noticeable in the area of Podgorica.The allergenic flora of Podgorica includes 253 taxa of wild vascular plants whose pollen has been grouped into three categories: woody plants pollen (32 taxa), weed pollen (76 taxa) and grass pollen (145). Tree pollen is present from February to April, while weed and grass pollen from April to October.

In vitro antiviral activity of plant extracts from Asteraceae medicinal plants

BackgroundDue to the high prevalence of viral infections having no specific treatment and the constant appearance of resistant viral strains, the development of novel antiviral agents is essential. The aim of this study was to evaluate the antiviral activity against bovine viral diarrhea virus, herpes simplex virus type 1 (HSV-1), poliovirus type 2 (PV-2) and vesicular stomatitis virus of organic (OE) and aqueous extracts (AE) from: Baccharis gaudichaudiana, B. spicata, Bidens subalternans, Pluchea sagittalis, Tagetes minuta and Tessaria absinthioides. A characterization of the antiviral activity of B. gaudichaudiana OE and AE and the bioassay-guided fractionation of the former and isolation of one active compound is also reported.MethodsThe antiviral activity of the OE and AE of the selected plants was evaluated by reduction of the viral cytopathic effect. Active extracts were then assessed by plaque reduction assays. The antiviral activity of the most active extracts was characterized by evaluating their effect on the pretreatment, the virucidal activity and the effect on the adsorption or post-adsorption period of the viral cycle. The bioassay-guided fractionation of B. gaudichaudiana OE was carried out by column chromatography followed by semipreparative high performance liquid chromatography fractionation of the most active fraction and isolation of an active compound. The antiviral activity of this compound was also evaluated by plaque assay.ResultsB. gaudichaudiana and B. spicata OE were active against PV-2 and VSV. T. absinthioides OE was only active against PV-2. The corresponding three AE were active against HSV-1. B. gaudichaudiana extracts (OE and AE) were the most selective ones with selectivity index (SI) values of 10.9 (PV-2) and >117 (HSV-1). For this reason, both extracts of B. gaudichaudiana were selected to characterize their antiviral effects. Further bioassay-guided fractionation of B. gaudichaudiana OE led to an active fraction, FC (EC50=3.1 μg/ml; SI= 37.9), which showed antiviral activity during the first 4 h of the viral replication cycle of PV-2 and from which the flavonoid apigenin (EC50 = 12.2 ± 3.3 μM) was isolated as a major compound.ConclusionsThe results showed that, among the species studied, B. gaudichaudiana seemed to be the most promising species as a source of antiviral agents.

한국산 가막사리속(국화과)의 미기록 귀화식물: 왕도깨비바늘

We report a newly naturalized species of the genus Bidens L. (Asteraceae) in Korea, specifically Bidens subalternans DC. var. subalternans. This naturalized plant was discovered Geumjung-gu in Busan; Gyeongsan-si, Jillyang-eup in Gyeongbuk-do; and in Buk-gu in Daegu. Bidens subalternans var. subalternans is distinguishable from other Bidens in Korea by the following combination of characteristics: an odd-pinnate leaf, deeply lobed, narrow lanceolate, four lobes in the corolla, an oblong achene shape. This taxon is termed `Wang-do-kka-bi-ba-neul` as a common Korean name based on its large size (in particular, the size of leaf). The key for all taxa of the genus Bidens in Korea is also provided here.

Evaluation of Vineyard Weeds as Potential Hosts of Black-Foot and Petri Disease Pathogens

Weeds were sampled in grapevine rootstock mother fields, open-root field nurseries, and commercial vineyards of Albacete, Alicante, Castellón, Murcia, and Valencia provinces in Spain between June 2009 and June 2010 and evaluated as potential hosts of black-foot and Petri disease pathogens. Isolations were conducted in the root system and internal xylem tissues for black-foot and Petri disease pathogens, respectively. Cylindrocarpon macrodidymum was successfully isolated from the roots of 15 of 19 weed families evaluated and 26 of 52 weed species. Regarding Petri disease pathogens, one isolate of Phaeomoniella chlamydospora was obtained from Convolvulus arvensis, and three isolates of Cadophora luteo-olivacea were obtained from Bidens subalternans, Plantago coronopus, and Sonchus oleraceus. Pathogenicity tests showed that Cylindrocarpon macrodidymum isolates obtained from weeds were able to induce typical black-foot disease symptoms. When inoculated in grapevines, isolates of Cadophora luteo-olivacea and Phaeomoniella chlamydospora were also shown to be pathogenic on grapevine cuttings. Our ability to recover grapevine pathogens from vineyard weeds and to demonstrate pathogenicity of recovered strains on grape suggests that these weeds may serve as a source of inoculum for infection of grapevine.

Competitiveness of ALS inhibitors resistant and susceptible biotypes of Greater Beggarticks (Bidens subalternans)

The continuous use of ALS-inhibiting herbicides has led to the evolution of herbicide-resistant weeds worldwide. Greater beggarticks is one of the most troublesome weeds found in the soybean production system in Brazil. Recently, a greater beggarticks biotype that is resistant (R) to ALS inhibitors due to Trp574Leu mutation in the ALS gene was identified. Also, the adaptive traits between susceptible (S) and R to ALS inhibitors biotypes of greater beggarticks were compared. Specifically, we aimed to: (1) evaluate and compare the relative growth rates (RGR) between the biotypes; (2) analyze the seed germination characteristics of R and S biotypes under different temperature conditions; and (3) evaluate their competitive ability in a replacement series study. The experiments were conducted at the University of Arkansas, USA, in 2007 and at Universidade Federal do Rio Grande do Sul (Federal University of Rio Grande do Sul), Brazil, in 2008. Plant proportions for replacement series studies were respectively 100:0, 75:25, 50:50, 25:75 and 0:100, with a total population of 150 plants m-2. There was no difference in RGR between R and S biotypes. The R-biotype germination rate was lower than that of the S biotype. However, at low temperature conditions (15 ºC), the reverse was observed. In general, there is no difference in the competitive ability between R and S greater beggarticks biotypes.