Comparison of Allelopathic Potential of Rice Leaves, St... ^Featured

The use of rice (Oryza sativa L.) allelopathy for weed control is a new technology in agronomy. A laboratory bioassay using water extracts was conducted to determine the allelopathic potential of rice body parts on seed germination and growth of barnyardgrass (Echinochloa crus-galli P. Beauv. var. oryzicola Ohwi) and to determine rapid and simple methods for selecting allelopathic rice varieties using genetic characters and phenotypes. In this study, the highest inhibition rate was for ‘Danganeuibangju’ (76.9%) in straw extracts, ‘Dongobyeo’ (74.1%) in the leaves, and ‘Baek’ (31.7%) in the hull. ‘CUBA 65-v-58’ (38.6%) had the highest inhibition as a whole (average of leaves, straw, and hull), and there was a higher average inhibitory effect for straw extracts (21.6%) than for hulls (8.2%) and leaves (12.4%). With regard to classification by phenotypic and genetic characteristics, these groups showed a higher inhibitory effect in domestic varieties (14.2%), middle-maturing varieties (15.3%) ...

Allelopathic substance in rice root exudates: Rediscove... ^Featured

Much research on rice allelopathy has been directed toward the selection of allelopathic rice strains and the identification of allelochemicals in rice. This paper briefly summarizes recent progress in the rice allelopathy and focuses on rediscovery of momilactone B as an allelochemical. A large number of rice varieties were found to inhibit the growth of several plant species when grown together under field and/or laboratory conditions. These findings suggest that rice probably produces and releases allelochemical(s) into the environment. The putative compound causing the inhibitory effect of rice was recently isolated from rice root exudates, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. In addition, it has been found that momilactone B is released from rice roots into the neighboring environment, and the release level of momilactone B from rice may be sufficient to cause growth inhibition of neighboring plants. These findings suggest that momilactone B ma ...
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Inter- and intra-cultivar variations in the allelopathi... ^Featured

We assessed the inter-cultivar variation in allelopathic potential of buckwheat on growth of lettuce seedlings among 50 cultivars of different agroecotypes . We also analyze intra-varietal variation in the cultivars, "Botansoba" and "Shinano No.1". An aqueous extract offresh leaves was found to be highly phytotoxic; it significantly reduced seedling growth. The degree of inhibition varied among the varieties and also among the agroecotypes. The suppression effectvaried between cultivars as well as among individuals in a cultivar. These results indicate that buckwheat leaf aqueous extract may suppress seeding growth of certain weeds and that these responses could be attributed to an allelopathic effect. In addition, these also suggest the possibility of breeding varieties with high allelopathic activity.

Estimation of allelopathic potential of white mustard, ... ^Featured

The Second European Allelopathy Symposium, "Allelopathy from understanding to application", was held June 3-5, 2004 in Pulawy,Poland. The integral part of the Symposium was a workshop on "Fate and toxicity of allelochemicals (natural plant toxins) in relation to environment and consumer" (FATEALLCHEM) - work programme Quality of Life, contract no. QLK5-CT-2001-01967. The sponsor of the meeting was the Polish Ministry of Science and Information Technology. The guest of the Symposium was Mr. Jo Ottenheim, representative of the European Commission. The 78 scientists from 11 European countries and from Australia, Canada, Mexico, Japan and the USA who attended the meeting discussed the latest achievements and new directions in allelopathy research. In the 8 thematic sessions they have delivered 45 lectures and presented 32 posters. Abstracts have been published in the Proceedings of the Second European Allelopathy Symposium, "Allelopathy from understanding to application" and FATEALLCHEM WORKSHOP "Fate and tox ...
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The Use of Allelopathic Legume Cover and Mulch Species ... ^Featured

Traditional weed control practices in Mexico use legumes as cover crops or manures. Legumes used in these practices play a dual role in agroecosystems by protecting the soil from erosion and by enriching it with organic matter and N through Rhizobium symbiosis. Farmers in the tropical regions of Mexico use Mucuna spp., Canavalia spp. and other legumes to control weeds in their fields. We conducted in vitro bioassays and greenhouse experiments to evaluate the toxic effect of four legumes velvetbean [Mucuna deeringiana (Bort) Merr.], jackbean [Canavalia ensiformis (L.) DC.], jumbiebean [Leucaena leucocephala (Lam.) de Wit], and wild tamarind [Lysiloma latisiliquum (L.) Benth.] on weed growth, and on the survival of insects and nematodes. The aqueous leachates (1%) of the four legumes were tested on three test plants by seed germination and radicle growth bioassays in petri dishes. The aqueous leachates of all four legumes exhibited strong phytotoxic effect on the radicle growth of the test plants. The effec ...
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Allelopathy of Sorghum on Wheat under Several Tillage S... ^Featured

Allelopathy by grain sorghum [Sorghum bicolor (L.) Moench] frequently harms wheat (Triticum aestivum L.) when the crops are grown in rotation. Responses of seven wheat cultivars to different methods of tilling sorghum stover were investigated to determine if the problem might be remedied by genetic resistance or improved management of the stover. Field trials on Kahola silt loam soil (fine-silty, mixed mesic Cumulic Hapludolls) compared effects of fallow, tilled sorghum stover, and no-till sorghum stover during the first season and the same treatments plus no-till millet [Pennisetum glaucum (L.) R. Br.] stover the second season. The seven wheat cultivars were planted after the sorghum and millet were harvested and tilled, and their emergence, stand density, and yield components were measured. Tilled sorghum residue often delayed development of the following wheat crop but did not affect grain yields, probably because allelopathic compounds degraded in the soil. No-till sorghum stover had little effect on ...
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Soil: Environmental Effects on Allelochemical Activity ^Featured

To exert phytotoxic effects on other plant species, chemicals may have to move to the roots of the target plant through the soil. However, during movement, abiotic (physical and chemical) and biotic (microbial) soil barriers can limit the phytotoxicity of chemicals in terms of quality and quantity required to cause injury. Organic matter, reactive mineral surfaces, ion exchange capacity, inorganic ions, and abiotic and biotic factors of soil environment significantly influence allelochemical activity. In this article, the significance of soil in laboratory and field studies on allelochemical interference is discussed.

Relationships between Biomass and Phenolic Production i... ^Featured

The total phenol pool (kg ha-1) of the aerial parts and roots of sorghum (Sorghum bicolor L. cv. CE145-66) crops and their relationships to dry matter and total phenol concentrations (g kg-1) were studied in four different data sets (2 sites x 2 yr for a total of 52 smallholder fields) in Senegal. The total phenol pool size varied from 4 to 156 kg ha-1 in the aerial parts and from 1 to 16 kg ha-1 in the roots. The phenol pool size was closely correlated with the amount of dry matter in both the aerial parts (r = 0.95, P<0.001) and the roots (r = 0.91, P<0.001). In contrast, the phenol concentrations varied less between fields than the dry matter content, and therefore had less impact on the phenol pool size. Using a N nutrition index (NNI) to assess the N nutrition of the sorghum crops, both phenol the pool and concentration were higher when N nutrition was better. Grain yield and the phenol pool of aerial parts were also positively correlated. The data indicate that the environmental factors that promote ...
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Rice—A Step Toward Use of Allelopathy ^Featured

Rice (Oryza sativa L.) allelopathy has been on the research agenda for a decade. Now it is important to step back and look at its progress to enable priority setting for future research. This paper aims to do so primarily using the following five-step protocol for allelopathy research: (i) carrying out laboratory, greenhouse, and field studies to illustrate the effect of released allelochemicals; (ii) isolating, identifying, and characterizing allelochemicals; (iii) establishing a correlation between growth inhibition and allelochemicals; (iv) performing genetic mapping of quantitative trait loci (QTLs) correlated with allelopathy; and (v) breeding for allelopathic cultivars tested for competitive ability in greenhouse and field experiments. Recent research on rice allelopathy has resulted in the following research milestones:There is large variation in allelopathy among rice cultivars.Allelopathy plays a role under field conditions.Allelopathic rice can suppress both mono- and dicot weed species.Progress ...
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Allelopathy Symposium ^Featured

The papers in this special section were presented at a symposium, "Allelopathy in Natural and Managed Ecosystems," of the Second World Congress on Allelopathy, held at Lakehead University, Thunder Bay, Canada, 9–13 Aug. 1999. The symposium aimed to provide a forum to present and discuss the latest results of allelopathy research related to agriculture, forestry, and other forms of vegetation management. A total of 44 oral communications were presented in two sessions; of these, 16 are presented in this issue. In addition to the oral presentations in all of the sessions, 56 posters were presented on different aspects of allelopathy along with a CD-ROM demonstration on the history of allelopathy. Two hundred scientists from 34 countries representing five continents attended the congress. The Second World Congress on Allelopathy was organized under the auspices of the International Allelopathy Society, and Lakehead University provided excellent conference facilities.

Evaluating Maize for Allelochemicals That Affect Europe... ^Featured

European corn borer (ECB), Ostrinia nubilalis (Hübner), larvae develop resistance to management protocols in laboratory and field environments. Laboratory bioassays, tissue elemental analyses, and field resistance evaluations were conducted on ear tissues of maize, Zea mays L., to (i) identify genotypes and tissues which affect ECB development, (ii) isolate tissue extracts detrimentally affecting larvae, (iii) determine if high performance liquid chromatography (HPLC) absorption peaks are associated with biological activity, (iv) determine if ferulic acid and p-coumaric acid affect ECB larvae, and (v) determine if laboratory and field resistance are related. Tissue and genotype did not affect larval survival. Silk tissue from W182E, ‘Apache’, MN 3153, and MN 276 reduced 10-d larval weight, increased time to pupation, reduced pupal weight, and increased time to moth emergence compared with kernel tissue, which did not differ from the cellulose control. Methanol fractions of silks reduced 10-d larval w ...
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Allelopathic Potential of Bermudagrass and Johnsongrass... ^Featured

Field experiments were conducted in northern Greece during the 2002 and 2003 growing seasons to study interference between bermudagrass [Cynodon dactylon (L.) Pers] or johnsongrass [Sorghum halepense (L.) Pers] and cotton (Gossypium hirsutum L.) or corn (Zea mays L.). Moreover, bioassay studies were also conducted to assess allelopathic potential of these two weeds on cotton and corn as well as on barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] and bristly foxtail [Setaria verticillata (L.) P. Beauv.]. The bioassay experiments showed that cotton, barnyardgrass, and bristly foxtail germination, total fresh weight, and root length were inhibited by bermudagrass or johnsongrass extracts more than those of corn. In addition, johnsongrass extracts caused greater germination, fresh weight, and root length inhibition than bermudagrass extracts. In the field, growth and yield of cotton were reduced due to bermudagrass (200 and 400 stems m–2 from planted rhizomes) or johnsongrass (100 and 200 stems m–2 f ...
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Allelopathic Potential of Various Plant Species on Down... ^Featured

Allelopathy, the ability of plants to inhibit germination of other plants, is an untapped resource for weed control in crops that could revolutionize organic crop production. The main objective of the study was to evaluate allelopathic potential of various plant species on downy brome (Bromus tectorum L.), a major pest of wheat (Triticum aestivum L.). To screen for potential allelopathy, plants were grown to flowering stage in a greenhouse, separated into shoots and roots, dried, and ground. Five percent aqueous extracts (w/v) were prepared by extracting 5 g of dried, ground plant samples with 100 mL of deionized water. Downy brome seeds were germinated on extract-amended sand. Extracts from most plant species tested inhibited downy brome and wheat seed germination. Extracts from broadleaf plants were more inhibitory than extracts from cereal plants. In most plant species, shoot extracts were more inhibitory to growth of the root and shoot of downy brome than root extracts. Meadowfoam seed meal (Limnanthe ...
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Allelopathy of rice husks on barnyardgrass ^Featured

Research efforts in seeking allelopathic compounds play an important role in developing natural herbicides. The objective of this research was to investigate the allelopathic effects of rice (Oryza sativa L.) husk extracts and to bioassay allelopathic compounds. The husk extracts of seven rice varieties were used to examine allelopathic effects on the growth of barnyardgrass (Echinochloa crusgalli (L.) Beauv.). After that, allelopathic substances effective on the growth of barnyardgrass were sought using an open chromatography and analyzed using a GC/MS. Husk extract from Ilpum rice (a national variety in South Korea) showed the prominent allelopathic effect on barnyardgrass. The organic compounds analyzed by the GC/MS were found to be 9-octadecenoic acid; 7-octadecenoic acid; 5, 8, 11-heptadecatriynoic acid and androstan-17-one. The minimum inhibition concentration of the isolated allelochemical compounds was 50 ppm. The results suggest that there is a possibility of developing a rice husk oriented natur ...
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Ecological Effects of Allelopathic Plants – a Review ^Featured

This report is based on a literature review on allelopathy from an ecological impact point of view carried out in 1999. The study was initiated because recently published research results have suggested that the allelopathic activity of agricultural crops can be improved by genetic engineering. The report describes allelopathy of selected crops and also summarises available information concerning the genetic studies on allelopathy in these crops. It discusses the ecological effects of allelopathic plants in natural ecosystems and factors of importance for the effects of these plants are pointed out. Finally the report presents suggestions for an ecological risk assessment of crops with an enhanced release of allelochemicals. The report has been thoroughly reviewed and commented by Jan G. Højland from the National Forest and Nature Agency, Gösta Kjellsson, Christian Kjær and Helle Ravn from the National Environmental Research Institute.

Allelopathy - a practical weed management tool? ^Featured

What is allelopathy?The term allelopathy refers to the production, by a plant, of chemicals (allelochemicals) which can influence the growth and development of another plant. Such an effect can be varied and can be negative (e.g. reduced germination) or positive (e.g. increased growth). For weed management we are interested in the inhibition of one plant (the weed or weeds) by another (usually the crop) through the production of allelochemicals. These allelochemicals may be actively produced by a growing plant or arise from the residues after death. The effects of the allelochemicals may be reduced or enhanced by microorganisms.

Allelopathy, a natural strategy for weed control ^Featured

Weed Suppression by Buckwheat ^Featured

Allelopathy - An update ^Featured

The latest previous comprehensive review of allelopathy (Rice, 1974) covered research done primarily prior to 1973. There have been numerous reviews published in recent years on specific phases of allelopathy (see III), but most of them covered research results published primarily through 1972 also. This review has been restricted, therefore, largely to research conducted subsequent to 1972, except for background information and significant papers overlooked in previous reviews. There has been almost an exponential increase in the rate of publication of papers concerned with allelopathy. Research has been particularly active in relation to the roles of allelopathy in agriculture, forestry, phytopathology, patterning of vegetation, algal succession, and old-field succession. Our increasing knowledge of the conditions under which certain crop residues cause allelopathic effects to subsequent crops should enable us soon to guard against such effects. We are on the threshold of breeding crop plants that will ...
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Buckwheat as cover crop succeeds in controlling weeds ^Featured

Buckwheat cover cropping can reduce both the emergence and growth of weeds, thereby presenting an easy and economical alternative to herbicides, according to a new study that analyzed the roles of both nitrogen and fungal pathogens in weed inhibition. Results of the study are published in the latest issue of Weed Science.Growing environmental and health concerns over the use of herbicides have resulted in an increasing demand for alternative weed management strategies, including cover crops. Buckwheat, a short-duration broadleaved annual cover crop, is useful as a summer cover crop because it grows rapidly, establishes canopy faster than most weeds, and hence provides very effective weed suppression during establishment.