Germination Inhibitory Effect Research Articles

Research to Fungicide Sensitivity of Colletotrichum spp. Isolated from Apple Fruits in Cheongsong, Korea

Apple grower in the Cheongsong region, Korea has reported the increased loss of apple yield due to severe bitter rot incidence. We noticed that this indience is because the <i>Colletotrichum</i> population has developed resistance to commonly used fungicides. We isolated 39 <i>Colletotrichum</i> isolates from 13 orchards in Cheongsong, and all the isolated <i>Colletotrichum</i> species were identified as <i>C. siamense</i> or <i>C. fructicola</i>. These 39 strains were tested for mycelial growth and conidial germination against 12 fungicides. trifloxystrobin (30–55% in recommended concentrations) was shown lower inhibitory effect on mycelial growth. However, the inhibition of conidial germination was shown higher than mycelial growth (62–100%). Kresoxim-methyl was shown lower inhibitory effect on mycelial growth (29–55%). conidial germination inhibitory effect was shown 51% to 96%. dithianon was shown diversity response to inhibition of mycelial growth (43–100%). tebuconazole was shown high inhibitory effect on mycelial growth (84–100%) and conidial germination inhibitory effect was shown to be 64 to 100%. metconazole has been found to display with high inhibitory effect on mycelial growth (79–100%) and conidial germination (70–80%). fluazinam was shown to possess high inhibitory effect on mycelial growth (87–100%) and conidial germination (94–100%). This study provides basic information for the effective management of apple bitter rot.

Selective Phytotoxic Effects of Sesquiterpenoids from Sonchus arvensis as a Preliminary Approach for the Biocontrol of Two Problematic Weeds of Wheat.

The objective of this study is to find new selective allelochemicals for managing two problematic weeds redroot pigweed (Amaranthus retroflexus) and common lambsquarters (Chenopodium album) with minimal negative effects on wheat, thereby facilitating the development of eco-friendly botanical herbicide. Three new sesquiterpenoids, sonarvenolide A-C (1-3), and nine known sesquiterpenoids (4-12) were isolated from Sonchus arvensis. Compound 1 was a rare peroxide-substituted eudesmane-type sesquiterpenoid, and compound 3 was a rare iphionane-type sesquiterpenoid. Notably, compounds 1, 3, 4, 6-8, and 11 showed selectivity phytotoxic activity. In particular, compounds 1, 3, and 4 exhibited excellent germination inhibitory effect on A. retroflexus (IC50 = 32.0-129.0 μM), higher than that of the positive control triasulfuron (IC50 = 141.7 μM), and compound 4 showed excellent inhibition on C. album (IC50 = 82.0 μM), higher than that of triasulfuron (IC50 = 100.9 μM). In addition, compounds 1, 3, and 4 showed allelopathy to the growth of two weeds, which were more potent than or close to that of triasulfuron. Furthermore, these compounds were not toxic to wheat even at a high concentration (1000 μM). Structure-activity relationships (SARs) revealed that the presence of peroxides or the absence of hydroxyl at C-5 in the eudesmane-type sesquiterpenoids could strengthen the inhibitory activities. The discovery of selective allelochemicals provides not only a new choice to control two problematic weeds of wheat but also new natural lead compounds for herbicides.

Alleviation of the Germination Inhibitory Effect of Salt Stress in Pepper (Capsicum annuum L.) Seeds by Serotonin

Salinity stress is one of the important factors affecting all growth processes, from seed germination to seedling development, plant growth, yield and quality. In this study, the effects of serotonin treatments on the germination of pepper seeds (Capsicum annum L.) under salt stress were investigated. Different doses of salt (0, 75 and 150 mM NaCl) and serotonin (S0:0 µM, S1:5 µM, S2:10 µM, S3:15 µM, S4: 20 µM) were used. The applied seeds were placed between the papers in petri dishes, watered with the prepared salt solutions and left to germinate at 25 °C. In the study, parameters related to germination percentage, germination speed, mean germination time, daily mean germination time, peak value and germination value were investigated. As a result of the research, it was determined that the germination of pepper seeds decreased in parallel with increasing salt concentrations, and this negative effect of salt stress decreased with serotonin applications. Although it changes depending on the serotonin doses, it has been observed that significant effects occur on the measured germination parameters, and the best germination was observed at S1 and S2 doses. It is thought that the application of serotonin will have positive effects on the germination of pepper seeds under salt stress, and these effects may also occur during the plant growth period.

Chemical components and insecticidal effects of essential oils from three lavender cultivars against adult Sitophilus granarius (L., 1758) (Coleoptera: Curculionidae)

The study was conducted to determine the insecticidal and behavioral effect of essential oils (EOs) extracted from three lavender cultivars, Hemus, Raya and Yubileina, against adult stage of Sitophilus granarius (L., 1758) (Coleoptera: Curculionidae) under laboratory conditions. The contact, fumigant and repellent effects of plant EOs were investigated and possible germination inhibitory effects of the EOs on wheat germination were evaluated. EOs were extracted from the plant samples using a Neo-Clevenger type apparatus where the plant material is subjected to hydro distillation. The chemical constituents of EOs were detected by gas chromatography-mass spectrometry. The experiments were conducted under laboratory conditions in 2019 and 2020. As a result of the study, it was determined that the fumigant activity changed according to the cultivars. While the LC90 value in the fumigant activity of the EOs of the Hemus was determined as 0.157 µl/ml air, this value was recorded as 0.139 µl/ml air and 0.118 µl/ml air in Raya and Yubileina, respectively. Six h after treatment, the highest repellent activity was 86% at 0.05 µl/cm2 with Yubileina. Main EOs components of each cultivar were: Yubileina, linalool (36.0%), linalyl acetate (24.2%) and lavandulyl acetate (5.86%); Hemus, linalool (28.5%), linalyl acetate (23.1%) and lavandulyl acetate (6.59%); and Raya, linalool (42.5%), linalyl acetate (30.0%) and ɑ-terpineol (5.45%). There was no negative effect on the germination of wheat with any of essential oils. These results show that lavender EOs could be useful for the control of S. granarius .

Role of Tartaric Acid in the Ecology of a Zoochoric Fruit Species, Tamarindus indica. L

ABSTRACT Zoochoric plants usually produce fruits with a mechanical barrier in the exocarp, or chemical inhibitors in the fruit pulp (mesocarp) or seed coat (endocarp) to achieve required dormancy. Tamarindus indica L. is one such zoochoric tree species, but the role of possible bioactive chemicals in the ecology of its fruit and seed dispersal has not been explored before. We investigated the germination inhibitory effects of T. indica fruit pulp by comparing germination of intact T. indica fruits with depulped T. indica seeds. This experiment revealed that attached pulp (including exocarp) delayed or decreased germination via an unverified mechanism. We then analyzed the pulp (including exocarp) to find out if there was a dominant bioactive chemical, by creating extracts using both alcohol and aqueous fractionation, and then analyzed them using GLC-MS analysis. We discovered that tartaric acid was the main bioactive chemical present in the methanol fraction (but not aqueous), so decided to test its effect on T. indica seed germination. We exposed viable depulped T. indica seeds to varying concentrations of pure tartaric acid in distilled water and found germination inhibition was observed at a concentration of 0.4 mg/ml. Therefore, since tartaric acid is the major chemical component in T. indica fruit pulp, it is possible that it could play a crucial role in the zoochoric dispersal of seeds by inhibiting germination while they are still attached to the tree or have just fallen close to the parent tree so that they have an opportunity to reach distant sites favorable for germination.

Chemical composition analysis of Eucalyptus essential oil and allelopathic effects of α-terpineol

We extracted Eucalyptus essential oil by steam distillation and analyzed its chemical components by GC-MS. The inhibitory effects of α-terpineol, a component in Eucalyptus essential oil, were tested in Petri dishes on the germination and growth of Amaranthus retroflexus. The allelopathic effects of α-terpineol on A. retroflexus were examined with a pot experiment by measuring germination rate and biomass. The yield of essential oil was 0.04%. Ninety-two chemical components were detected from the essential oil. In Petri dish experiment, the germination inhibitory effect under 5 μL and 7.5 μL of α-terpineol per dish reached 100%. In pot experiment, germination, aboveground fresh and dry weights of A. retroflexus were significantly affected by α-terpineol. At the concentration of 1.6 μL·cm-3, the inhibition effect was strongest, with the allelopathic response index being -0.51 for germination, -0.62 for aboveground fresh weight, and -0.44 for aboveground dry weight, and the inhibition ratio being 51%, 62% and 44%, respectively.

Characteristics and Function of the Chitin Binding Protein from Xenorhabdus nematophila.

Genome sequence analysis (GenBank access No.: FN667742.1) shows that Xenorhabdus nematophila ATCC19061 contains one gene (Xn-cbp) encoding chitin binding protein (Xn-CBP). The present work aims to clarify the characteristics and function of Xn-CBP from X. nematophila HB310. In this study, the Xn-cbp gene was cloned and expressed in Escherichia coli BL21 (DE3). Substrate binding assays were performed to explain the ability of Xn-CBP combined with the polysaccharide. The insecticidal toxicity of Xn-CBP against the second-instar larvae of Helicoverpa armigera was determined by feeding method. Besides, the antifungal activity of Xn-CBP against Coniothyrium diplodiella, Verticillium dahlia, and Fusarium oxysporum was tested by spore germination assay and hyphal extension assay. Xn-CBP encoded 199 amino acids with a calculated mass of 28 kDa, which contained a signal peptide and a chitin binding domain. The Bmax and Kd values of Xn-CBP to colloidal chitin were 2.46 and 4.08, respectively. Xn-CBP had insecticidal activity against the H. armigera with a growth inhibition rate of 84.08%. Xn-CBP had the highest spore germination inhibitory effect on C. diplodiella with the inhibition rate of 83.11%. The hyphal growth inhibition rate of Xn-CBP to F. oxysporum, 41.52%, was higher than the other two fungi. The Xn-CBP had the highest binding ability to colloidal chitin and it showed insecticidal activity and antifungal activity. The present study laid a foundation for further exploitation and utilization of X. nematophila.

Seed germination inhibitory effect of Caryota urens L. seed pericarp on rice and associated weeds

Seed germination inhibitory effect of Caryota urens L. seed pericarp on rice and associated weeds

Assessment of the allelopathic potential of 17 Iranian barley cultivars in different development stages and their variations over 60 years of selection

Laboratory experiments were conducted to determine the allelopathic potential of 17 Iranian barley cultivars in four development stages and their variations over the last 60 years of collection. Imbibed seeds and water leachates that were extracted from the barley plants at the seedling, tillering, stem elongation, and heading stages were used for the bioassays, including filter paper, neighboring barley seeds in soil, and soil mixed with dried barley residues. The experiments were conducted with the use of wild mustard (Sinapis arvensis) as the test plant. The Germination Rate Index (GRI) and emergence of S. arvensis were inhibited on both the filter paper and soil. The highest inhibitory effect was seen with the tillering stage's water leachate on filter paper. The GRI decreased in response to the increased density of barley imbibed seeds. The germination was less affected by the presence of barley seeds from the soil than those from the filter paper. The GRI of S. arvensis seeds was lower in the older than in the recently developed cultivars. Although there were some fluctuations in the GRI value with time, the germination inhibitory effect has decreased as new, higher‐yielding cultivars have been released.

Laboratory study on the bioremediation of petrochemical sludge-contaminated soil

This study evaluated by biological and chemical analyses the effectiveness of bioremediation of sludge from the petrochemical industry in systems containing artificially contaminated soil. The sludge–soil systems were prepared with three different initial concentrations of sludge, and during bioremediation 86–95% of the hydrocarbons was eliminated. Simultaneously, soil bacterial populations and inhibition of seed germination by aqueous extracts increased in all sludge–soil systems during the first 180 days of treatment. After 1 year of bioremediation, a loss in the catabolic capacity of the Gram-negative bacterial population was observed, but was not dependent on the initial sludge concentration. Furthermore, residual levels of hydrocarbons and seed germination inhibitory effect decreased sharply, but some level of toxicity remained in the systems containing the highest initial sludge concentration. Independent of the initial sludge concentration, the contaminated soils did not re-establish their original features even when residual hydrocarbon concentrations suggested the end of the process.

A microtiter fluorometric assay to detect the germination of Bacillus anthracis spores and the germination inhibitory effects of antibodies

Bacillus anthracis spore germination is usually detected in vitro by alterations in spore refractility, heat resistance, and stainability. We developed a more quantitative, sensitive, and semi-automated procedure for detecting germination by using a microtiter kinetic reader for fluorescence spectrophotometry. The procedure was based on the increase in fluorescence of spores with time during their incubation in germination medium containing a fluorescent nucleic acid-binding dye which stained germinated B. anthracis but not ungerminated (UG) spores. Spore germination in the presence of several germinants was characterized. Although l-alanine and inosine alone stimulated rapid germination in this assay, a medium containing optimal concentrations of l-alanine, adenosine, and casamino acids gave low background fluorescence, stimulated germination completely, and at a reasonable rate. Suspensions of heat-activated, UG spores of B. anthracis strain Ames were preincubated with antibodies (Abs) against whole spores to assess their effect on germination. Analyses of the germination data obtained revealed significant differences between spores pretreated with these Abs and those treated with non-immune sera or IgG. Germination inhibitory activity (GIA) was detected for several polyclonal rabbit anti-spore Ab preparations. These included anti-Ames strain spore antisera, IgG purified from the latter, and spore affinity-purified Abs from antisera elicited against four strains of B. anthracis. Abs elicited against UG as well as completely germinated Ames spores inhibited germination. Abs were ranked according to their GIA, and those specific for UG spores usually exhibited greater GIA. Direct binding to spores of these Abs was detected by an ELISA with whole un-germinated Ames spores. Although specific binding to spores by the anti-spore Abs was shown, their titers did not correlate with their GIA levels. Current efforts are focused on identifying the spore antigens recognized by the anti-spore Abs, characterizing the role of these targeted antigens in disease pathogenesis, and evaluating the ability of specific anti-spore Abs to protect against infection with B. anthracis.

Effects of Various Synthetic Sucrose Esters on Weed Seed Germination and Crop Growth: Structure−Activity and Dose−Response Relationships

Twelve synthetic sucrose ester (SE) products with C7−C10 chain lengths and various degrees of esterification (DE) were tested for their influence on seed germination of prosomillet and velvetleaf and on growth of broccoli and bell pepper plants. At 100 ppm most SE caused virtually total inhibition of germination; at lower concentrations dose−response and structure−activity relationships were apparent. Sucrose esters with seven and eight carbon acyl groups were most effective, and activities decreased for nonanoyl and decanoyl esters, respectively. With respect to DE, products high in di-, tri-, and tetraacyl esters were most active. Increased DE caused decreasing activities; however, the lowest DE (higher in monoacyl esters) was also less active. The biologically most active SE product was characterized by mass spectrometric techniques. The product consisted of 7.5% monoheptanoyl and 20.7% di-, 33.5% tri-, 23.6% tetra-, 7.7% penta-, and 1.3% hexaheptanoyl esters. Structure−activity relationships with respect to published insecticidal activities paralleled their germination inhibitory effects. Growth of young broccoli and bell pepper plants, the leaves of which were treated with the 12 SE samples, was not affected by concentrations far above those used for effective insecticidal action. Since the SE products are nontoxic to humans and higher animals, fully biodegradable, and not harmful to the crops tested, they appear to be good candidate insecticides. Potentials for suppression of weed seed germination need field evaluation. Keywords: Sucrose esters; dose−response; structure−activity; seed germination; crop growth; broccoli; bell pepper; Panicum milliaceum; Abutilon theophrasti

Identification and Biological Activity of Germination-Inhibiting Long-Chain Fatty Acids in Animal-Waste Composts

Long-chain fatty acids in germination-inhibiting animal-waste composts were identified by gas chromatography-mass spectrometry as myristic, palmitic, stearic, oleic, linoleic, and linolenic acids. These acids were found at concentrations greater than 0.25 mg (g dry compost)-1. The identified acids, together with lauric acid, and five kinds of short- and medium-chain fatty acid, were tested for their effects on the germination process of sorghum seeds. The authentic long-chain fatty acids, which were dissolved in a 1:9 (v/v) mixture of methanol and distilled water at 40 mg liter-1, significantly reduced the alpha-amylase activity, physiological water uptake, and ATP content of the germinating seeds during the first 24 h of inhibition, as well as the rate of germination of seeds. Among the tested fatty acids, myristic and palmitic acids were the most potent inhibitors of germination. The inhibitory effects of long-chain fatty acids were stronger than those of the phenolic acids. The short- and medium-chain fatty acids did not have any significant germination-inhibitory effects at 40 mg liter-1. The results indicate that the long-chain fatty acids are the dominant inhibitors of germination in animal-waste composts, and that the inhibition of the alpha-amylase activity in germinating sorghum seeds is one aspect of the mode of action of these long-chain fatty acids.

Inhibition of Germination by Growth Retardants AMO-1618 and Ancymidol, and its Reversal by Gibberellin A3 in Amaranthus caudatus L. Seeds

AMO-1618 and ancymidol, inhibitors of gibberellin biosynthesis, retarded germination of Amaranthus caudatus L. seeds, ancymidol being more active than AMO-1618. Transfer of seeds to ancymidol after imbibition in water for 12 h caused inhibition of germination. Longer imbibition in water led to reduced sensitivity of seeds to subsequently applied ancymidol. The germinating capacity of seeds preincubated in ancymidol for 3–17 h was restored markedly following transfer to water. Gibberellic acid (GA 3 ) greatly reduced or reversed the germination inhibitory effect of either AMO-1618 or ancymidol. It is suggested that endogenous GAs are required for induction and/or stimulation of early growth of the radicle.

Effect of straw extract on water absorption and germination of wheat (Triticum aestivum L. variety RR-21) seeds

Freshly prepared straw extract inhibited wheat seed germination by about 18 per cent but did not affect water absorption by germinating wheat seeds. The maximum germination inhibition (47 per cent) was noticed with extract of straw rotted for 15 days. The germination inhibitory effect of rotting straw was over at 31 days of straw rotting.