Archives - Allelopathy Journal

We examined the allelopathic effects of persimmon rhizosphere soil and leaf extracts on seed germination, initial development of cabbage seedlings and their effects on the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), content of malondialdehyde (MDA), and antimicrobial activity. Both extracts at higher concentrations (15% and 30%) inhibited the germination, root number and root length. The extracts also had variable inhibitory effects on the test fungi and bacteria.

We evaluated 12-synthetic allelochemicals (linalool, terpinolene,menthone, citral, trans-2-hexen-1-al,  geranyl  acetate,  acetophenone,  benzaldehyde,  cis-jasmone,  hexanal, β-caryophyllene and p-cymene) for their fumigant toxicity against adults of Pulse beetles, Callosobruchus maculatus and C. chinensis. The bioassay was done in airtight flat bottom flask and applied7-doses of test allelochemicals viz., 0.2, 0.6, 1.0, 1.4, 1.8, 2.5 and 3.5 µl/250 ml air with exposure time of 24 h. The results showed that most of these volatile compounds have significant fumigant toxicity against tested insects. Among these acetophenone was most promising as fumigant (LC50 0.23 µl/250 ml air against C. maculatus and 0.27 µl/250 ml air against C. chinensis) followed by cis-jasmone (LC50 0.33 µl/250 ml air against C. maculatus and 0.28 µl/250 ml air against C. chinensis). Hexanal and β-caryophyllene were found least effective with 0 % and 3.33% adult mortality, respectively, at the highest dose against both species.Cis-jasmone was found best oviposition inhibiting volatile among all tested chemicals.

A new method was developed to quantify the phenolic acids in soil. It is based on alkali
NaOH ethylacetate extraction (LLE) followed by gas chromatography tandem mass
spectrometry (GC MS/MS). The Na 2 SO 4 was used to improve the silanization (pre column
derivatization, to reduce the boiling point and improved m olecular stability of phenolic
compounds) effect and to improve the signal to noise ratio. Eleven phenolic acids were analyzed
in peanut ( Arachis h ypog a ea L.) cultured rhizosphere soil. The highest extraction recovery rates
of the phenolic acids were achieved, when the alkaline soil extract was made acidic to pH of 2.5.
Signal to noise ratio was improved (Higher the signal to noise ratio (SNR), the better detection
effect) by 12.33 times. The matrix matched standard was used to avoid the soil matrix effects
and the coefficient R 2 was > 0.99 for each phenolic acid. The sensitivity, accuracy and precision
of analysis method were evaluated by limit of detection (LOD < 2.97 ng/g), standard recovery
rate (90 105%) and relative standard deviation (RSD < 5.94%), respectively. The method was
ap plied to soil samples and accurate contents of phenolic acids extracted form soil were
calculated by the matrix matched calibrations and extraction recovery rates.

The Brazilian pepper plant (Schinus terebinthifolius Raddi) is an invasive species that displays multiple characteristics that allow habitat invasion, including allelopathy. This review analyzes the existing literature that characterizes the Brazilian pepper’s essential oil from multiple geographic regions globally. This review reveals that the terpenoid constituents of the essential oil varies based on region, season and plant part. Laboratory bioassays and greenhouse studies demonstrating the allelopathic effects of its oils on several plant species are discussed. We suggest that future bioassays or pot cultures investigating allelopathy of Brazilian pepper should include the geographic location, plant part used (leaves vs. fruit), season harvested, phenological phase of plant and the terpenoids characterization. We also suggest field studies to investigate the persistence of Brazilian pepper’s allelopathic chemicals in their surrounding environment.

We investigated the qualitative and quantitative composition of phenolic compounds in tomato (Lycopersicon esculentum Mill L.) leaves with and without infestation of tomato borer (Tuta absoluta Meyrick). Infested and healthy leaves of tomato were extracted with aqueous methanol, which was partitioned with ethyl acetate and n-butanol. Infested leaves contained higher levels of total phenolics, flavonoids, flavonols and tannins. The HPLC analysis of the n-butanol fraction indicated that the leaves contained the catechin and two unknown compounds, which are likely to be phytoalexins. The protective role of these molecules need to be investigated, to incorporate this finding in the tomato breeding programmes against the tomato borer.

As a traditional Chinese medicinal plant, Coptis chinensis Franch contains more than 30 alkaloids which are toxic to other plants and microorganisms. This review covers mainly the habitat, morphology, toxicity research on the main chemical berberine. Besides, it also provides the possibility for its application in management of microorganisms and weeds

Barnyard grass (Echinochloa crus-galli L.) was used as test target plant in both Sandwich and Relay seeding methods. The allelopathic effects of rice accessions were observed on seed germination, mean germination time, shoot length, root length and dry matter production of test plants. Average percent inhibition (API) due to allelopathic effects in the growth of barnyard grass was also determined. Both bioassays revealed that the selected rice accessions adversely affected the quantitative traits of barnyard grass seedlings. Rice accession MR73, caused > 40% API in the growth of barnyard grass. Some traditional and modern rice accessions also showed > 30% API. Reductions in traits like shoot length, root length and dry weight were positively and significantly correlated with API. Finally, rice accession MR 73 was selected for further improvement. It is expected that this accession would contribute not only in biological weed control but also reduce the use of synthetic herbicides and problems associated with the chemical weed control

This study was done to evaluate the phytotoxic potential of weed Urtica dioica L. (common nettle) on germination and early seedling growth of cereals (wheat, barley and oat) and vegetables (lettuce, spinach and radish). The seeds of test plants were grown in U. dioica leaf leachate-amended soil, the leachates influenced the germination and seedlings growth of all tested plants. The U. dioica leachate were rich in total phenolic and flavonoids as well as had significant antioxidant activity. Based on vigour index, vegetables were very sensitive to U. dioica leachate, while cereals were tolerant (except barley). Thus U. dioica negatively affects the germination and growth and may cause problems in cultivation of these plants, hence, the U. dioica should be removed from the crop fields to avoid its harmful effects on crops and vegetables

Bt (Bacillus thuringiensis) corn is the most commercialized anti-insect transgenic crops. We examined the effects of jasmonic acid (JA) on the changes in contents of defence chemicals and expression of defence-related genes in the treated part (first leaf) and non-treated part (second leaf and root) of Bt corn varieties 5422Bt1 and 5422CBCL and their conventional corn 5422 (non-Bt corn). The JA exposure did not affect the Bt protein content of two Bt corns. Among the three corn varieties JA-induced effects in the first leaf did not differ. However systemically induced effects in the second leaf and root in Bt corns were significant than in non-Bt corn. It can be concluded that Bt gene introduction and endogenous chemical defence responses of corns act synergistically during the JA systemically induced defence processes

Potato onion (Allium cepa L. var. agrogatum Don.) when intercropped with tomato (Solanum lycopersicum L.) reduces the verticillum wilt of tomato significantly. Hence the root exudates from Potato onion was used to examine its effect on the growth and enzyme activities of V. dahliae, a soil-borne pathogen of tomato. Results showed that the root exudate inhibited the growth of V. dahliae and also inhibited its amylase, pectinase and cellulase activities.

The allelopathic effects and potent allelochemicals of the invasive weed Tridax procumbens L. were examined in this study. Methanol extract from whole plant of T. procumbens was fractionated and assayed on germination and growth of radish (Raphanus sativus). The F1, fraction separated from the ethyl acetate extract was most inhibitory (IC50 = 0.22 mg/mL). This fraction induced physiological changes in radish seedlings, by reducing amounts of chlorophylls (41.06%) and carotenoids (35.44%), but increased activity of malondialdehyde (MDA) (21.28%), a cell-membrane responding mechanism against oxidative stresses. Twenty-six compounds were identified from the F1 fraction by gas chromatographymass spectrophotometry (GC-MS), to reveal the presence of 9-principal constituents [guaiacol, benzeneacetic acid, phenol, benzeneacetic acid methyl ester, methyl salicylate, vanillic acid, syringol, vanillic acid methyl ester and benzoic acid]. Phenolics accounted for major quantity (41.15%), followed by fatty acids and their derivatives. We found that T. procumbens had strong allelopathic activity, possess potent plant growth inhibitors, which might play role in the invasiveness of T. procumbens. This plant may be a promising source for weed control in agricultur

Bt (Bacillus thuringiensis) corn is one of the most rapidly commercialized anti-insect transgenic crops around the world. In the present study, we tested the Bt protein content, defense chemicals contents and defense enzymes activities in both leaves and roots of Bt corn varieties 5422Bt1 and 5422CBCL, as well as their conventional corn 5422 seedlings with two fully expanded leaves, which had been treated with 1.0 µM jasmonic acid (JA) to the belowground part for 24 h. The result showed that JA treatment to the belowground part could significantly increase the peroxidase activity in the roots of conventional corn 5422, the polyphenol oxidase and peroxidase activities in the roots of Bt corn 5422Bt1 and the Bt protein content and peroxidase activity in the roots of Bt corn 5422CBCL. Meanwhile, the DIMBOA content, polyphenol oxidase, peroxidase and catalase activities in the leaves of conventional corn 5422, the Bt protein content, polyphenol oxidase, peroxidase and catalase activities in the leaves of Bt corn 5422Bt1 and the polyphenol oxidase and peroxidase activities in the leaves of Bt corn 5422CBCL were systematically increased after JA was applied to the belowground part. These findings suggest that Bt gene introduction affects the induced defense effects of JA treatment to the belowground part of corn, leading to a stronger defense response in the root of Bt corns than the conventional corn. Systematic defense response is weak in the leaf of Bt corn 5422CBCL as compared to the conventional corn, while the systematic defense response in the leaf of Bt corn 5422Bt1 is similar to conventional corn 5422

Cucumber seedlings grown in soil were treated with different concentrations of vanillin (0.02-0.2 µmol/g dry soil). The rhizosphere Pseudomonas and Bacillus community structures and their abundances were determined by PCR-denaturing gradient gel electrophoresis and quantitative PCR analyses targeting the 16S rRNA genes, respectively. Vanillin at 0.02 µmol/g dry soil significantly increased the abundance of Pseudomonas community. At 0.1 and 0.2 µmol/g dry soil, it significantly increased the abundance of Bacillus community, but inhibited that of Pseudomonas spp. community. At 0.2 µmol/g dry soil, it changed the community structure of Pseudomonas and increased the Shannon-Wiener and evenness indices of Pseudomonas spp. community.

The effect of asymmetric warming on allelopathic control of the toxic Microcystis aeruginosa, was examined using four temperatures and two coumarin concentrations. In the exponential growth phase, the coumarin was slightly inhibitory and the microalga exhibited maximum resistance to the allelochemical. Compared with day/night temperatures of 25?C/20?C, the algal inhibition was significantly weakened by increasing the temperature by 2?C. The inhibition ratio was decreased by 63.27% with increasing the temperature by 2?C in the day, by 38.78% with increasing it by 1?C in both the day and night and by 12.24%, with increasing it by 2?C only in the night. Coumarin suppressed the M. aeruginosa by decreasing the algal cell diameter, cell division, light conversion efficiency (Fv/Fm) and maximum electron transfer ratio (ETRmax). Asymmetric warming weakens the negative effect. Our results imply that increases in temperature can significantly improve the photosynthesis in M. aeruginosa and enhance its resistance to allelopathic chemicals.

We separated and purified the plant growth-promoting bioactive compounds from the fermentation filtrate of Stremptomyces sampsonii KJ40 to investigate its effects on the growth of maize. Column chromatography and high performance preparative chromatography (HPPC) were used to obtain the monomer compound 16-M4. Its structure was identified using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). In greenhouse experiments, the effects of different concentrations of bioactive compounds was determined on seed germination, biomass, photosynthesis characteristics and the identification of lipid peroxidation and related resistant enzymes activities (malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) of maize seedling. The results showed that the monomer compound 16-M4 was identified as cyclo- (Val-Pro). Inoculation of maize seeds with cyclo- (Val-Pro) (150 µg L-¹), significantly increased the germination index and vigour of maize seed and root length by 76.03%, 73.64%, and 54.52%, respectively. Besides, the photosynthesis, chlorophyll (Chl) content and net photosynthetic rates were increased by 27.97% and 103.81% than control. Results of this study suggested that the cyclo- (Val-Pro) had positive effects on seed germination and seedling growth of maize