• Weed & Turfgrass Science
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• v.2 no.1
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• pp.38-46
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• 2013

With increasing environmental issues from synthetic chemical herbicides, microbe-originated herbicides could be a fascinating alternative in current agriculture. We isolated Streptomyces strains that produced herbicidal active metabolite(s) against a grass weed Digitaria sanguinalis. According to the result from 16S rDNA sequence comparison with the close strains, the best isolate (Code name MS-80673) was identified as Streptomyces scopuliridis KR-001. The closest type strain was Streptomyces scopuliridis RB72 which was previously reported as a bacteriocin producer. The optimal culture condition of S. scopuliridis KR-001 was $28^{\circ}C$, pH 7.0 and culture period 4 to7 days. Both of soil and foliar application of the crude culture broth concentrate was effective on several troublesome or noxious weed species such as a Sciyos angulatus in a greenhouse and field condition. Phytotoxic symptoms of the culture broth concentrate of S. scopuliridis KR-001 by foliar application were wilting and burndown of leaves, and stems followed by discoloration and finally plant death. In crops such as rice, wheat, barley, hot pepper and tomato, growth inhibition was observed. These results suggest that the new S. scopuliridis KR-001 strain producing herbicidal metabolites may be a new bio-herbicide candidate and/or may provide a new lead molecule for a more efficient herbicide.

• Weed & Turfgrass Science
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• v.3 no.3
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• pp.196-205
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• 2014

In this study, to obtain basic data for searching potential resources as new natural fibers, we investigated morphological and classificatory characteristics of 21 weed seed fibers. According to classification keys in this study, the collected weed seed fibers could be classified into total 13 types, showing their diversity. Seven species among them belonged to BOT3 type. Two species belonged to B2N0 and DOS3 type, respectively. Many of weed seed fibers had not branched. However, three species had various branched fibers at one main fibers on the seed. Three species had various branched fibers at several main fibers on the seed. Eight species had a smooth fiber surface but 13 species had a weakly or significantly developed-corniculum on the fiber surface. In the fiber cell shape, fiber cells of eight weed species were composed of one long cell without septum. But others had a fiber cell shape composed of a bunch of several long cells. Based on the easiness of harvesting, productivity of fibers, and morphological characteristics of seed fiber, it seemed that five seed fibers (TYPLA, METJA, HEMLY, IMPCK, and EREHI) should be additionally investigated if they are practically applicable as renewable resources for new natural fibers.

• Korean Journal of Weed Science
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• v.17 no.1
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• pp.52-58
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• 1997

Rice (Oryza sativa L.) contains water-soluble substances that inhibit the germination of Echinochloa crus-galli. This study investigated the allelopathic potential of rice in which rice had been grown with E. crus-galli in the field. Extracts of forty-seven rice varieties were screened for allelopathic potential in the laboratory. Double distilled water was used as a control. Based on the germination percentage, the varieties may be classified in the following order of decreasing inhibition : Namweon(36%) and Gyehwa(38%) hulls extracts and Sambaeg(43%) and Seoan(46%) leaves extracts. In the comparison of allelopathic activity test between leaves and hulls extracts, hulls extracts contain more allelopathic toxic substances. In the effect of concentration treatment on the six levels of extract solutions(3, 6, 12, 25, 50, 100%, v/v) germination percentage was significantly inhibited as the extract concentration increased. The highest concentration(100%) caused the greatest reduction in E. crus-galli. Allelopathic potential effects were significantly different among the various varieties and between '94 and '95 year extracts. The results indicate that there are genetic differences among varieties for allelopathic potentiality on E. crus-galli. Allelopathic potential in the ecological aspects can be decided through variety selection.

• Korean Journal of Weed Science
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• v.7 no.1
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• pp.84-89
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• 1987

This study was conducted to determine the combining effects of a synthetic brassinolide such as homobrassinolide (HBR) with auxin types on the curvature of radish petiole. HBR has no direct effect on the petiole curvature of radish, regardless of concentrations used. Among the natural known plant growth regulators, NAA at 100ppm showed the highest ourvature at 12 hours after treatment. The synthetic auxins such as 2,4-D and MCP resulted in about three times greater effect on curvature than the untreated control, and their effects lasted till 36 horns after treatment, showing much better effect on curvature than that of the natural auxin types of plant growth regulators. The mixture of MCP at 3 ppm with HBR at 100ppm increased petiole curvature of radish seedlings as much as three times greater than that of a single application of HBR. However, the mixture of HBR at 100 ppm plus 2, 4-D at 100ppm increased the petiole curvature of radish seedlings about eight times greater than that of the HBR single application, showing existance of strong synergistic reaction and the most effective combination, and suggesting possibility of a prectical implementation in agriculture.

• Weed & Turfgrass Science
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• v.4 no.2
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• pp.118-123
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• 2015

Metagenomics is a powerful tool to isolate novel biocatalyst and biomolecules directly from the environmental DNA libraries. Since the metagenomics approach bypasses cultivation of microorganisms, un-cultured microorganisms that are majority of exists can be the richest reservoir for natural products discovery. To discover novel herbicidal substances from soil metagenome, we established three easy, simple and effective high throughput screening methods such as cucumber cotyledon leaf disc assay, microalgae assay and seed germination assay. Employing the methods, we isolated two active single clones (9-G1 and 9-G12) expressing herbicidal activity which whitened leaf discs, inhibited growth of microalgae and inhibited root growth of germinated Arabidopsis seeds. Spraying butanol fraction of the isolated active clones' culture broth led to growth retardation or desiccation of Digitalia sanguinalis (L) Scop. in vivo. These results represent that the screening methods established in this study are useful to screen herbicidal substances from metagenome libraries. Further identifying molecular structure of the herbicidal active substances and analyzing gene clusters encoding synthesis systems for the active substances are in progress.

• Weed & Turfgrass Science
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• v.5 no.3
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• pp.136-143
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• 2016

This study was conducted to investigate the algicidal characteristics of cashew nut oil (CNO) and to develop CNO mixtures with other compounds having synergistic effects on the growth inhibition against a blue-green alga, Microcystis aeruginosa. Among tested CNOs, CNO with higher anacardic acid contents (Ana-A) exhibited the best algicidal activity against M. aeruginosa. Ana-A showed broad algicidal spectrum with particular greater activity against blue-green algae than green algae. Ana-A showed the greatest activity against to Oscillatoria tenuis ($IC_{50}=0.19{\mu}g\;mL^{-1}$) among the tested blue-green algae and to Chlorella vulgaris ($IC_{50}=4.54{\mu}g\;mL^{-1}$) among the tested green algae, respectively. In a mixture experiment to evaluate a chemical interaction in M. aeruginosa control, Ana-A showed a strong synergistic effect with MSB and menadione, mild synergistic effect with citric acid, and additive effect with chryspophanol, copper sulfate and quinoclamine. Taken together, our results suggest that CNO containing higher anacardic acid can be used as an eco-friendly natural algicide for selective control of blue-green algae such as M. aeruginosa and O. tenuis through an optimization of application rate and in combination with synergists such as MSB and menadione.

• Korean Journal of Weed Science
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• v.31 no.1
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• pp.112-117
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• 2011

A series of experiments was conducted to investigate the herbicidal activity of natural compound chrysophanic acid under the greenhouse condition in 16 weed species. Chrysophanic acid showed non-selective herbicidal activity. While chrysophanic acid exhibited severe injury by foliar treatment, little or no injury was found by the soil treatment. Among the tested weeds, the most effective activity was found in grass and broad leaf weeds, a lower significant difference in herbicidal activity was found in sedge. At early post-emergence, weeds appeared to be very susceptible to chrysophanic acid with $2,000{\mu}g\;mL^{-1}$. The higher the natural compound concentrations, the lower weed growth. At middle post-emergence, weeds appeared to be very effective to chrysophanic acid with $30,000{\mu}g\;mL^{-1}$.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.253-261
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• 2014

In this study, we investigated several chemical and physical characteristics of 4 weed seed fibers; Hemistepta lyrata (HEMLY), Imperata cylindrica var. koenigii (IMPCK), Metaplexis japonica (METJA) and Typha latifolia (TYPLA). In chemical composition, there were 74 (TYPLA)-88.5% (METJA) of holocellulose, 17 (IMPCK)-24% (METJA) of lignin, 0.22 (METJA)-4.2% (IMPCK) of ash, 2.2 (HEMLY)-7.8% (IMPCK) of hot water extractives and 0.4 (IMPCK)-6.3% (TYPLA) of solvent extractives. Alpha-cellulose proportion to holocellulose was similar among weed seed fibers as 45-48%. The crystallinity index (CI) of raw seed fibers was 53.2 (TYPLA)-65.9% (HEMLY). However, CI of the chemical treated fibers (EDA fibers) was a little increased and showed 61.1 (IMPCK)-71.8% (METJA). The maximum thermal decomposition temperature (MTDT) of the raw seed fibers were 312, 321.8, 331.5 and $341.6^{\circ}C$ in METJA, TYPLA, HEMLY and IMPCK, respectively. But the MTDT of the EDA fibers were 327, 327, 341.7 and $360.0^{\circ}C$ in HEMLY, TYPLA, METJA and IMPCK, respectively. Taken together, they showed a similar or better characteristics compared to the reported or commercial natural fiber resourses. Accordingly, they seem to be practically applicable as renewable resources for a new natural fibers.

• Korean Journal of Weed Science
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• v.4 no.1
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• pp.39-51
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• 1984

Effects of major phenolic acids identified from barley residues (straw, root) on the germination of rice and 3 paddy weeds such as Echinochloa crusgalli, Cyperus serotinus, and Potamogeton distintus were evaluated to obtain the basic informations on the development of naturally occurring herbicides. The predominant phenolic compounds extracted from barley residues in both straw and root were identified as p-coumaric, p-hydroxybenzoic, ferulic, vanillic, and salicylic acids by means of paper chromatography. Total phenol content of barley straw and root at the harvesting stage was 0.169% and 0.127% per dry weight, respectively. During the decomposing process, total phenol content slightly increased and then decreased. The germination of test plants was inhibited by treatments of 4 major authentic phenolic acids identified, most significantly on rice, and less on E. crusgalli, and C. serotinus. P. distintus, however, was markedly stimulated by them as the concentration increased, and then sprouted buds of pondweeds were changed to dark brownish color, resulting in the death as the treatment prolonged. The greater inhibitory effect appeared on shoot growth rather than germination. The aqueous extracts of barley residues showed the similar inhibitory effect on the germination and shoot growth of rice and three paddy weeds as the treatments of 4 authentic phenolic acids.

• Korean Journal of Weed Science
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• v.30 no.3
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• pp.191-198
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• 2010

The objective of this study was to find herbicidal compounds from seven different plant essential oils such as amyris (Amyris balsamifera), cajuput (Melaleuca cajeputi), geranium (Pelargonium graveolens), lavender (Lavendula spp.), mandarin (Citrus reticulata), pine (Pinus spp.) and rosemary (Rosmarius officinale), and determine their herbicidal activities. The in vitro herbicidal activity of cajuput essential oil was the highest among six essential oils ($GR_{50}$ value, $425{\mu}g\;g^{-1}$) and major chemical components in cajuput essential oil were eucalyptol (37.2%), ${\alpha}$-terpineol (11.6%), benzaldehyde (5.2%), linalool (4.1%), ${\alpha}$-pinene (2.5%) and ${\beta}$-pinene (2.4%), and their $GR_{50}$ values were 2,731, 500, 50, 372, 4,363, and $4,671{\mu}g\;g^{-1}$, respectively. Soil application of cajuput essential oil and benzaldehyde did not show any herbicidal activity at 80 kg $ha^{-1}$. When cajuput essential oil was applied to foliar at 80 kg $ha^{-1}$, narrow-leaved plants such as sorghum (Sorghum bicolar), barnyardgrass (Echinochloa crus-galli), and southern crabgrass (Digitaria ciliaris) were killed 100%, however, broad-leaved plants indian jointvetch (Aeschynomeme indica), velvet leaf (Abutilon theophrasti), cocklebur (Xanthium strumarium), Japanese morningglory (Calystegia japonica) were not killed, indicating the cajuput essential oil was effective to control narrow-leaved plants. Herbicidal activities of benzaldehyde at 80 kg $ha^{-1}$, to those plants were 20, 60 and 95%, respectively. Overall data showed that the herbicidal activity of cajuput essential oil was in part due to benzaldehyde.