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1.
The sensitivity of 22 major crops, pastures and weeds from the north-east grain region of Australia to atrazine and chlorsulfuron residues was determined in a glasshouse using a soil-free bioassay system. A logistic equation was fitted to the seedling fresh weights as a function of the logarithm of herbicide concentration by non-linear regression and used to calculate the doses for 10%, 30% and 50% inhibition of seedling growth (ID10, ID30 and ID50). The ID50 for atrazine ranged from 0.03 to 0.04 mg a.i. L–1 for Salvia reflexa Hornem. and barley to 1.47 mg a.i. L–1 for sorghum. The ID50 for chlorsulfuron ranged from 0.19 to 0.21 μg a.i. L–1 for lucerne and snail medic to 102 μg a.i. L–1 for wheat. Based on ID50 values measured, the predicted responses of each species to a range of concentrations of atrazine and chlorsulfuron were classified into four categories ranging from no damage to severe damage. These sensitivity data will assist in planning cropping sequences in soils previously treated with atrazine or chlorsulfuron.  相似文献   

2.
A total of 651 isolates of cucumber corynespora leaf spot fungus ( Corynespora cassiicola ) collected from cucumber in Japan, either with (438 isolates) or without (213 isolates) a prior history of boscalid use, were tested for their sensitivity to boscalid by using a mycelial growth inhibition method on YBA agar medium. Additionally, seven isolates of C. cassiicola obtained from tomato, soybean, eggplant (aubergine) and cowpea in different locations in Japan were tested before boscalid registration. Minimum inhibitory concentration (MIC) and 50% effective concentration (EC50) values for 220 isolates from crops without a prior history of boscalid use ranged from 0·5 to 7·5 μg mL−1 and from 0·04 to 0·59 μg mL−1, respectively. Two hundred and fourteen out of 438 isolates collected from ten cucumber greenhouses in Ibaraki Prefecture, Japan, which received boscalid spray applications showed boscalid resistance, with MIC values higher than 30 μg mL−1. Moreover, resistant isolates were divided into two groups: a moderately resistant (MR) group consisting of 189 isolates with EC50 values ranging from 1·1 to 6·3 μg mL−1, and a very highly resistant (VHR) group consisting of 25 isolates with EC50 values higher than 24·8 μg mL−1. MR isolates were detected from all ten greenhouses, but VHR isolates were detected from only three. As a result of fungus inoculation tests which used potted cucumber plants, control failures of boscalid were observed against resistant isolates. Efficacy of boscalid was remarkably low against VHR isolates in particular. This is the first known report on boscalid resistance in Japan.  相似文献   

3.
The dissipation behaviour of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, triasulfuron and amidosulfuron were studied in soil following post-emergence spring applications to cereal crops. Incorporation or removal of straw and different fertilizer applications had no influence on the disappearance time (DT50) of the herbicides. However, in laboratory trials dissipation of metsulfuron-methyl, triasulfuron and amidosulfuron at higher application rates was accelerated after incorporation of straw into the soil. The addition of straw decreases soil pH thereby causing faster hydrolysis of the compounds. Addition of nitrogen fertilizer increased the half-lives (t1/2) of the herbicides. Combination of both straw and N fertilizer, however, had no effect. Neither straw nor N influenced the degradation of tribenuron-methyl and thifensulfuron-methyl.
The DT50 of all herbicides investigated varied from 6 to 17 days in the field trials. Except for amidosulfuron, herbicides could not be detected 38–68 days after application. In the laboratory, t1/2 values were higher than those in the field at 75 days (amidosulfuron), 63 days (metsulfuron-methyl), 35 days (triasulfuron) and 13 days (tribenuron-methyl). Only the t1/2 of thifensulfuron-methyl was at 29 h faster under laboratory conditions. T1/2 values of all herbicides were influenced by their initial concentration. The t1/2 values of amidosulfuron and tribenuron-methyl at 1 mg a.i. kg−1 soil were 2–2.5 times higher than at the recommended field application rate of 42 μg a.i. kg−1 soil.  相似文献   

4.
A HUSSNER 《Weed Research》2009,49(5):506-515
Crassula helmsii , Hydrocotyle ranunculoides , Ludwigia grandiflora and Myriophyllum aquaticum are four well known invasive aquatic plants in European waters. In this study, plant growth at different nutrient availabilities, regeneration capacity and photosynthesis were investigated. Results show high relative growth rates (RGR) of the species of up to 0.132 ± 0.008 g g−1 dry weight (dw) day−1 ( H. ranunculoides ) and a significant increase in RGR with increasing nutrient availability. All species show a high regeneration capacity and the ability to form new shoots from single nodes, even though it differs between the species. Ludwigia grandiflora and M. aquaticum also show regeneration from single leaves. Species differed in maximal amounts, and in temperature and light optima of net assimilation rates: H. ranunculoides leaves reach maximum photosynthetic rates of up to 3500 μmol CO2 × h−1 g−1 dw, L. grandiflora (leaves) up to 2200 μmol CO2 × h−1 g−1 dw, M. aquaticum (shoots) 400   μmol CO2 × h−1 g−1 dw and C. helmsii (shoots) up to 200 μmol CO2 × h−1 g−1 dw. Hydrocotyle ranunculoides , L. grandiflora and M. aquaticum preferred high light intensity and high temperatures, whilst C. helmsii was negatively affected by intense sunlight. Summarising, it can be assumed that at least H. ranunculoides , L. grandiflora and M. aquaticum can grow well under current and likely future central European climate conditions.  相似文献   

5.
Paddy herbicides have the potential to cause adverse effects on non-target plants. Susceptibilities of some aquatic ferns ( Azolla japonica Franch. et Savat., Isoetes japonica A. Braun, Marsilea quadrifolia L. and Salvinia natans All.) and duckweeds ( Lemna minor L. and Spirodela polyrhiza Schleid.) to paddy herbicide bensulfuron methyl (BSM) were evaluated with a 20 day exposure experiment using 200 cm2 pots. The BSM concentrations in the surface water of monitoring pots with no plants dissipated exponentially with half lives of 3.5 and 3.9 days at application rates of 15 and 150 g ha−1, respectively. The BSM concentrations in the surface water 1 day after application in the culture pots were comparable among plant species, and were lower than those in the monitoring pots. Bensulfuron methyl reduced the plant growth in all species. I . japonica showed the lowest intrinsic relative growth rate (RGR) and the lowest susceptibility with an effective dose resulting in 50% growth inhibition (ED50) of 21 g ha−1. Except for I . japonica , the RGR of the duckweeds was similar to the ferns, and ED50 for the duckweeds was higher than the ferns. ED50 for Sa . natans , A . japonica and M . quadrifolia were 1.1, 1.8 and 1.2 g ha−1, respectively, which were smaller than 1/20 of the recommended field dose (51–75 g ha−1) and ranged from 1/2 to 1/6 of ED50 for L . minor and Sp . polyrhiza (6.5 and 3.2 g ha−1, respectively). These results suggest that BSM application in paddy fields and its runoff in some localities is expected to have adverse effects on the growth of Sa . natans , A . japonica and M . quadrifolia .  相似文献   

6.
RASHID  O'DONOVAN  KHAN  BLACKSHAW  HARKER  & PHARIS 《Weed Research》1998,38(6):461-466
Avena fatua L. populations from numerous fields in Alberta have simultaneously developed resistance to recommended rates of two dissimilar herbicides, triallate and difenzoquat. We used exogenous applications of gibberellic acid (GA3) to investigate the possibility that endogenous gibberellins were involved in the A. fatua 's resistance mechanism. For control plants, without applied GA3, shoots of the most resistant (R) populations emerged more rapidly and elongated faster than shoots of the susceptible (S) populations. Increases in shoot elongation in response to exogenous GA3 were significantly lower in R populations compared with S populations. This suggests that R populations may have elevated endogenous gibberellin levels, relative to S populations. Additionally, inhibition of S population shoot elongation and shoot anatomical abnormalities caused by relatively low concentrations of triallate and difenzoquat could be prevented by exogenous application of GA3. These results suggest that there may be a phytohormonal involvement in the mechanism of triallate/difenzoquat resistance in A. fatua . That is, higher endogenous gibberellin levels in R populations may result in meristematic growth that is rapid enough to preclude phytotoxic levels of these herbicides from reaching the shoot meristem, which is the likely site of action.  相似文献   

7.
Single and combined effects of smoke pollution and the root-knot nematode, Meloidogyne incognita race 1, were studied on eggplant in 1988 and 1989 at two sites (K1 and K2) 1 and 2 km respectively away from a coal-fired thermal power plant, and a control site at the Department of Botany, Aligarh Muslim University (AMU). Mean concentrations of SO2, NO2 and suspended particulate matter (SPM) were respectively 172, 95 and 626 μg/m3 in 1988 and 144, 97 and 556 μg/m3 in 1989 at K1; and 258, 150 and 344 μg/m3 in 1988 and 226, 113 and 293 μg/m3 in 1989 at K2. Peak levels of the gases and SPM were recorded in the early (12.00–15.00) and late (15.00–18.00) afternoon respectively. Concentrations of the pollutants at a control site were very low. Marginal browning appeared on the leaves of eggplants grown at site K2 whether or not they were infected by the nematodes. The galling caused by nematodes was severe at both polluted sites but egg mass production was inhibited at K2. Egg laying was significantly reduced at both polluted sites. M. incognita significantly reduced plant growth, yield and leaf pigment production of eggplant at the control and polluted sites. Most non-infected plants also showed significant reductions in these plant varieties i.e. from the effects of pollution at K2. Foliar concentrations of sulphur were significantly increased at both polluted sites, being greater in infected plants. The interaction of smoke pollution and M. incognita infection led to greater suppressions at the polluted sites, which were mostly significant at K1. At the polluted sites, leaves had more and longer trichomes; also the number and size of stomata were decreased but their openings were wider especially in infected plants at the two polluted sites.  相似文献   

8.
Hollaway  Kookana  McQuinn  Moerkerk  Noy  & Smal 《Weed Research》1999,39(5):383-397
The ability of bioassay, enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (hplc) methods to detect sulfonylurea herbicides in soil was evaluated as part of a project studying the leaching and persistence of these herbicides in the alkaline soils of south-eastern Australia. Soil samples with known concentrations between 0.1 and 10 μg a.i. kg−1 chlorsulfuron, metsulfuron-methyl or triasulfuron were prepared by an independent laboratory and supplied in coded bags to separate laboratories for testing. The accuracy of the results was analysed, and the merits of each method are discussed. Bioassay was suitable for measuring biologically active residues from 0.1 to 1.0 μg a.i. kg−1. ELISA accurately measured residues in the range of 0.1–10 μg a.i. kg−1, making it the most widely adaptable assay tested. It will be useful for measuring residues in sodic subsoils where bioassay plants grow poorly. There was good reproducibility between the bioassay and ELISA. The hplc technique used in this study was not as accurate as bioassay or ELISA at quantifying residues of 3.0–10 μg a.i. kg−1 and could not detect residues at or below 1.0 μg a.i. kg−1.  相似文献   

9.
Cultivars of soyabean [ Glycine max (L.) Merr.] resistant to the herbicide imazethapyr were identified by suspending the roots of 5-day-old seedlings in nutrient culture containing 2.5 mg a.i. L–1 imazethapyr and then comparing the inhibitory effect on root length and shoot dry weight. The four most resistant cultivars were subsequently screened as regenerating tissue cultures in a medium containing 2.0 mg a.i. L–l imazethapyr to select somaclonal cells with increased resistance. Surviving portions of cultures were regenerated to give shoots, the plants isolated, allowed to flower and seed. These progeny were then used for further seed multiplication and seedlings from this latter generation were exposed to imazethapyr in vivo and callus and cell suspension cultures derived from these seedlings were exposed to imazethapyr in vitro . A reduction in the inhibitory effect of the imazethapyr was noted in the somaclone seedlings and tissue cultures. However, measurement of acetolactate synthase (ALS) activity showed no differences among the parent cultivars and in the selected somaclones in this trait.  相似文献   

10.
Sunder  Satyavir 《Plant pathology》1998,47(6):767-772
Twenty-eight isolates of Fusarium moniliforme were established from bakanae-infected rice plants of a range of cultivars collected from various localities in Haryana, India. They were characterized by vegetative compatibility, virulence pattern on five paddy cultivars, and biosynthesis of gibberellins and were assigned to 10 vegetative compatibility groups (VCGs). Isolates from different VCGs and also within the same VCG varied considerably in virulence and GA3 production. The 28 isolates were categorized into five gibberellic acid production groups (GPG-I–GPG-V) and five virulence groups (VG-I–VG-V). Vegetative compatibility was independent of pathogenicity and of ability to produce GA3. However, GA3 production was positively correlated ( r  = 0.731) with pathogenic behaviour.  相似文献   

11.
Genetic variation of the barley powdery mildew fungus ( Erysiphe graminis f.sp. hordei ) was estimated in three Danish local populations. Genetic variation was estimated from the variation amongst clones of Egh , and was therefore an estimate of the maximum genetic variation in the local populations. The average gene diversity, Ĥ , was estimated as 0.84. The effective population size was estimated as: log10 ( N^ e ) = 0.64 − log10(μ), or 4.4 × 109, assuming a nucleotide mutation rate ( μ) of 10−9 per base per generation. There was no significant genetic differentiation between locations.  相似文献   

12.
The inheritance of tolerance to the herbicide metribuzin was studied in two durum wheat cultivars, one of which, 'Anton', is resistant and one, 'Nita', susceptible. Parents, F1, F2 and F3 of the crosses 'Anton' × 'Nita' and 'Nita' × 'Anton' were tested for herbicide response. The character evaluated was the increase in weight of plants treated with the herbicide. As there were no significant differences between progenies of reciprocal crosses, cytoplasm was not involved in tolerance. Tolerance was semi-dominant with means values of F1, F2 and F3 progenies in the range of mid-parent. The heritability of this trait estimated by regression of the average of progeny F3 in their parent F2 had a value of 0.23 ± 0.063 and a value of 0.52 ± 0.150 estimated by the relation V G/ V P for full-sib F2 families.  相似文献   

13.
The herbicide mefenacet has recently been developed for pre–emergence control of graminaceous and some dicotyledonous weeds in rice. Whereas mefenacet is known to inhibit root growth, its effect on the components of growth, cell division and cell enlargement, have not been determined. The purpose of this study was to evaluate the influence of mefenacet on growth, cell enlargement and cell division in Chlamydomonas (a green alga) and oats. Cell division in Chlamydomonas was completely inhibited and cell enlargement was inhibited by an average of 18% during the first cell cycle period when cells were treated with 6–7 μM mefenacet. The rate of oat root growth in sand culture between 12 and 24 h after initiation of treatment was reduced 90% at 10 μM mefenacet. Cell enlargement of oat coleoptile sections in culture solution was inhibited 25% at 10 μM. Mefenacet inhibited mitotic entry rather than disrupted the mitotic sequence. Cell division in oat roots was inhibited 54% by 10 μM mefenacet. This shows cell division inhibition occurs in G1, S, or G2 of the cell cycle. The action of mefenacet is most like that of the chloroacetamides among the herbicide classes known to inhibit growth.  相似文献   

14.
Host–parasite relationships in root-knot disease of spinach caused by Meloidogyne incognita race 1 were studied under glasshouse conditions. Nematode-induced mature galls were large and usually contained one or more females and egg masses with eggs. Feeding sites were characterized by the development of giant cells containing granular cytoplasm and many hypertrophied nuclei. The cytoplasm in these giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P i) in a series from 0–128 eggs and second-stage juveniles per cm3 soil and growth of spinach cv. Symphony F1 seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z P–T ] was fitted to fresh top- and total plant-weight data for inoculated and control plants. Tolerance limits ( T ) of spinach cv. Symphony F1 to M. incognita race 1 for fresh top and total plant weights were 0·25 and 0·5 eggs and second-stage juveniles per cm3 soil, respectively. The minimum relative values for fresh top and total plant weights were zero in both cases at P i ≥ 32 eggs and second-stage juveniles per cm3 soil. Root galling was least at low initial population densities and greatest at 16 eggs and second-stage juveniles per cm3 soil. Maximum nematode reproduction rate was 33·1-fold at the lowest P i.  相似文献   

15.
Conditioned seeds of Striga asiatica (L.) Kuntze release ethylene, which elicits germination. We investigated the activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and respiration during conditioning. Seeds incubated in vivo with ACC, the substrate for ACC oxidase, produced negligible ethylene at the beginning of conditioning or if they were dormant (i.e. would not germinate after conditioning and treatment with stimulant). Non-dormant seeds produced 3000 ηL of ethylene/600 seeds/24 h after 12 days of conditioning. In vitro ACC oxidase activity at day 0 of conditioning produced 500 ηL of ethylene/μg protein/h and 8000 ηL of ethylene/μg protein/h after 12 days of conditioning. Incubation of seeds in strigol before protein extraction did not enhance enzyme activity. Seeds released 4000 μL/L CO2 in the first 24 h of conditioning, with the rate increasing to 15 000 μL/L/24 h on day 4 and then remaining roughly unchanged. Maximum in vitro activity of ACC oxidase required ACC, catalase, O2, Fe2+, ascorbate and CO2. In vivo activity of ACC oxidase required ACC and/or germination stimulant(s), suggesting that stimulants may be involved in providing substrates for the ACC oxidase. No difference was observed in the separation of extracted proteins, which suggests that ACC oxidase is activated during conditioning, perhaps as a result of changes in co-factor concentration. Application of these findings to Striga control is discussed.  相似文献   

16.
Triadimenol residues in sandy and clay soils, following applications of up to 1 g/m2 in previous seasons to tobacco seedlings 2 days before they were transplanted, had little effect on seedling emergence and growth. Residues were beneficial to transplants; they improved growth and controlled stem and root infection caused by Rhizoctonia solani and Fusarium solani. During the first 4 weeks after transplanting, stem infection was negatively correlated with loge of the pre-sowing rate of triadimenol and with loge of the soil concentration in seedbeds at pulling. Plant growth increased linearly according to the equation l/Y=a+b/(x-c), where Y = plant dry mass (g/plant), .x = triadimenol pre-sowing (mg/m2) and c= - 1 1, determined iteratively, r2 = 0-94; P < 0.001. Triadimenol applications to bare soil increased the soil concentration by 1 μ/g per 50 mg/m2 applied.  相似文献   

17.
The in vitro response of five different Sorghum halepense biotypes against the non-selective, broad-spectrum herbicide glyphosate was assessed. Seeds from donor plants (collected in various sites all over Greece) were aseptically germinated on a hormone-free liquid Murashige and Skoog (MS) medium and emerging plantlets were inoculated on a solid MS medium supplemented with 13.6 μM 2.4-dichlorophenoxyacetic acid and 4.6 μM kinetin for callus induction. Exponentially growing calli were initially subcultured twice on induction medium and then transferred to a selection medium containing 10−3 M or 10−4 M (a.i.) glyphosate. The fresh weight of the cultured calli and the callus viability (expressed as callus dehydrogenase activity) were reduced as glyphosate concentration increased. Significant differences were observed among different biotypes. Regenerated plantlets were submitted to a conventional evaluation for glyphosate tolerance. The observed in vitro response of S. halepense to glyphosate was directly related to the in vivo herbicide tolerance observed both on donor and on regenerant plants.  相似文献   

18.
Antifungal activity of bergenin, a constituent of Flueggea microcarpa   总被引：1，自引：0，他引：1  
The antifungal activity of bergenin against some plant pathogenic fungi, namely, Alternaria alternata , A. brassicae , A. carthami , Fusarium udum , F. oxysporum f.sp. ciceri , Curvularia lunata and Erysiphe pisi , was studied. Bergenin as its monosodium salt was effective against all the fungi and the effective dose for complete inhibition of spore germination varied from 15 μg mL−1 for F. udum to 125 μg mL−1 for E. pisi . Experiments on the effect of bergenin on powdery mildew development under glasshouse conditions revealed that it can control powdery mildew of pea at 2000 μg mL−1 by postinoculation treatment, the results being comparable with those of carbendazim (1000 μg mL−1) and wettable sulfur (2000 μg mL−1). It affected hyphal elongation and the number of primary and secondary branches.  相似文献   

19.
A wettable powder (WP) formulation providing 5–25 μg mL−1 of 2,6-dichloroisonicotinic acid (INA) and 15–75 μg mL−1 of WP applied to cotton cotyledons significantly increased the resistance of the next two leaves to challenge inoculation by Alternaria macrospora . The wettable powder alone at 15–75 μg mL−1 had a lesser effect. A wettable granule (WG) formulation supplying 35 μg mL−1 of benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) and 35 μg mL−1 of WG, applied as a cotyledonary treatment, significantly reduced the formation of lesions on the subsequent two leaves when challenged with A. macrospora . The WG control had no effect. Each treatment except for the WG control also raised the activities of β-1,3-glucanase in unchallenged leaf and stem tissue. Each of the components of the wettable powder without INA applied to cotyledons raised enzyme activities in the next leaves. Individual components, as suspensions of silicic acid and kaolin and solutions of the detergent Attisol II, the wetting agent Ultravon W300 and pure INA, applied to cotyledons increased the resistance of the next leaves to A. macrospora . The responsiveness of cotton to BTH and to each of the components of formulated INA is discussed in relation to knowledge of the effects of BTH and INA on other plants and to possible ways in which the other components of the wettable powder may affect the process of signalling for systemic resistance to disease.  相似文献   

20.
Extract of soil under colonies of Hypnum plumaeforme inhibited the growth of roots and shoots of cress, lettuce, lucerne, ryegrass, timothy, Digitaria sanguinalis and Echinochloa crus-galli . Increasing the extract concentration increased the inhibition, which suggest that the soil may contain growth inhibitory substances and possess allelopathic potential. The extract of the soil under H. plumaeforme was purified and two main inhibitory substances were isolated and determined by MS and 1H- and 13C-NMR spectral data as momilactone A and B. Momilactone A and B inhibited hypocotyls and roots of cress seedlings at concentrations >10 and 1 μ m respectively. The endogenous concentration of momilactone A and B in H. plumaeforme was 58.7 and 23.4 μg g−1 dry weight respectively and the concentration of momilactone A and B in MS growth medium of H. plumaeforme was 4.3 and 6.4 μg g−1 dry weight of H. plumaeforme , respectively. These results suggest that momilactone A and B were probably secreted into the medium during the incubation and momilactone A and B found in the soil under H. plumaeforme may have been released by the moss. Therefore, growth inhibitory activity of the soil under H. plumaeforme may be caused by momilactone A and B, which may act as allelopathic agents of H. plumaeforme .  相似文献   

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