Se Ji Jang

Effect of Yacon (Smallanthus sonchifolius H. Robinson) Extracts on Herbicidal, Fungicidal, and Insecticidal Activities

*ABSTRACT This research has been carried out to find out the highest effect on insecticidal, fungicidal and herbicidal activities in leaves, stem and tuber extracts of yacon (Smallanthus sonchifolius) and extraction methods such as water, boiling water and methanol. Characteristics of potential herbicidal components among extraction methods were investigated by solvent fractions such as hexane, chloroform, ethyl acetate, butanol, and water. Generally, methanol extract was the best on inhibition of germination rate, plant height, and root length in cucumber and barley. On the other hand, the inhibition effect on growth in cucumber and barley was the best in tuber among plant parts of yacon. Inhibition of germination rate, plant height, and root length in cucumber and barley in s olvent fractions was the best in water fraction, but there were no differences in other fractions. Digitaria sanguinalis L. and Solanum nigrum L. by 5 and 10% extractions of yacon tuber were controlled by more than 70～80% and 95～100%, respectively. However, there was no inhibition effect on foliar treatment in cucumber and barley as affected by 5 and 10% extractions of yacon tuber. Mortality of green peach aphid (Myzus persicae Sulzer) was 50% at 3 days after treatment of 5% extracts of yacon leaves. Mortality of brown plant hopper (Nilaparvata lugens Stal) was only 24% in 5% extracts of stems and leaves with midr ib, but was 57% in 5% extracts of leaves without midrib. There was no fungicidal effect on anthracnose (Colletotrichum truncatum), wilt disease (Fusarium oxysporum), verticillium wilt (Verticillium dahliae), bacterial blight (Xanthomonus oryzae) in 5% extracts of yacon leaves.Key words: fungicidal activity; herbicidal activity; insecticidal activity; plant extract; yacon.

Effect of plant extracts and emulsifiers on control of anthracnose (Colletotrichum coccodes) in persimmon trees

ABSTRACT This study was conducted to determine suppression of the anthracnose fungus (Colletotrichum coccodes), causing disease in persimmon trees (Diospyros kaki Thunb), by (1) extracts from various parts of 45 plant species from 27 families obtained using different extraction methods, and (2) selected plant extracts and emulsifiers. Fermentation extracts of Torilis japonica roots and Portulaca oleracea, all above ground parts, as well as ethanol extracts of Rheum palmatum roots and Cinnamomum cassia barks were found to effectively suppress anthracnose, leading to 83%, or more, suppression by 10% plant extracts in laboratory tests. Additionally, anthracnose was suppressed by 100% by 3% brown rice vinegar, 3% powder soap, 5% loess sulphur, and by 5% natural emulsifier-B in a laboratory test. In the field trial with organically grown persimmon trees, treatments with plant extracts used on their own, resulted a reduction of anthracnose by 63% and 51% by 5% fermentation extract of T. japonica and 5% ethanol extract of R. palmatum, respectively, compared with a control. However, in treatments with combinations of plant extracts and emulsifiers, anthracnose was reduced by 79%, 67%, 63% and 56% when treated with 5% fermentation extract of T. japonica + natural emulsifier-B (1%), 5% fermentation extract of T. japonica + loess sulphur (1%), 5% ethanol extract of R. palmatum + natural emulsifier-B (1%), and 5% ethanol extract of R. palmatum + loess sulphur (1%), respectively, compared with the control. Thus, mixtures of plant extracts and emulsifiers may be used to control anthracnose in organic production systems.

Differences in suppression rates of crop pathogens and antioxidant activity at different harvesting times of Taraxacum mongolicum

This study was conducted to determine the suppression rates of extracts of the aerial parts of T. mongolicum collected at different harvesting times and prepared using different extract methods (water, boiled water and ethanol) on Pyricularia oryzae, Rhizoctonia solani Kuhn and Colletotrichum coccodes. Additionally, the aerial parts of plants collected at different harvesting times were analyzed for phenol and flavonoid contents, DPPH scavenging activities and growth differences. Although the suppression rates of P. oryzae, Phytophthora capsici and Colletotrichum acutatum increased with increasing concentrations of water or boiled water extracts of T. mongolicum, the levels of suppression were low. In addition, the levels of suppression of the above three pathogens differed with harvesting time. P. oryzae, C. acutatum and P. capsici were 20–65, 10–60 and 5–95% suppressed by 5% ethanol extracts of T. mongolicum collected at different harvesting times, respectively. Generally, the order of suppression rates against the above three pathogens by T. mongolicum extract was July > June > May > April. Total phenol and flavonoid contents and DPPH radical scavenging activities of T. mongolicum extracts did not differ significantly among harvesting times. However, plant height and shoot dry weight of T. mongolicum sampled in July were much higher than those of plants collected in April, May and June. Thus, growth of T. mongolicum harvested at different times may be related to the higher suppression rates of ethanol extracts of T. mongolicum harvested in July.

Controlling levels and tolerance mechanisms of red rice accessions to protox inhibitor herbicide, oxyfluorfen

Red rice (Oryza sativa L.) is one of the most troublesome weeds in most rice growing regions of the world. Thus, this study was conducted to determine the tolerance levels of various red rice accessions to the protox inhibitor, oxyfluorfen and also examined tolerance mechanisms in selected red rice accessions. Tolerance levels obtained from seed bioassay were lower than those obtained from whole-plant bioassay. Twenty-one of 38 red rice accessions in seed bioassay and 37 of 38 accessions in whole-plant bioassay were tolerant to oxyfluorfen. The most tolerant accession, R 2, was >20 times more tolerant in wholeplant bioassay and 13 times more tolerant in seed bioassay than the susceptible accession, R 116. This was supported by the results of experiments on levels of superoxide, H2O2 and MDA productions. In addition, the accumulations of proto IX in R 116 were more increased than in R 2 after oxyfluorfen treatment. The tolerance mechanism in R 2 was not related to higher antioxidant enzyme activities. However, higher ascorbate contents may contribute to greater tolerance of R 2 to oxyfluorfen.

Differences in growth characteristics and tricin contents of Alopecurus aequalis Sobol. at different harvesting times

Alopecurus aequalis Sobol. has long been known as an effective treatment for systemic edema, chicken pox, abdominal pain and diarrhea. However, studies of functional materials using A.aequalis have been very limited. Thus, this study was conducted to determine the growth characteristics and tricin content of A.aequalis at different harvesting times. Growth characteristics, yield and tricin content of A.aequalis were measured at 30, 45, 60, 75 and 90 days after seeding (DAS). Plant height, root length, leaf number, shoot fresh weight and shoot dry weight were significantly increased with increasing seeding stand period until 75 DAS, but decreased after 90 DAS. Yield of A.aequalis was also increased until 75 DAS, after which (90 DAS) it decreased. The highest yield was 9, 300 kg/ha at 75 DAS. In addition, tricin content increased significantly until 75 DAS (0.231 mg/g), then decreased at 90 DAS. These findings suggest that proper harvesting time for A.aequalis was at 75 DAS because both yield and tricin contents were high at this time.

Physiological responses of resistant and susceptible rice cultivars to HPPD-inhibiting herbicides

The objectives of this research were to quantify resistance levels in different rice biotypes to HPPD-inhibiting herbicides, benzobicyclon, mestrione, and tefuryltrione and determine mechanisms of resistance of benzobicyclon in different rice biotypes. In terms of shoot fresh weight, japonica-type, Ilmibyeo and Baekokchal were 17-and 53-73-fold more resistant to benzobicyclon and mestrione, respectively, than indica x japonica-type, Hyangmibyeo-1 and Dasanbyeo. However, responses of shoot fresh weight in rice cultivars of japonica-type to tefuryltrion were similar to those of indica x japonica-type. Carotenoids and chlorophylls contents of the japonica-type, Iilmibyeo and Baekokchal were also less affected by the benzobicyclon, than the indica x japonica-type, Hyangmibyeo-1 and Dasanbyeo. The levels of MDA and H2O2 in rice cultivars of indica x japonica-type after benzobicyclone treatment were much higher than those of rice cultivars of japonica-type. Thus, the resistance in rice cultivars of japonica-type may be caused by the result of less lipid peroxidation, less H2O2, higher carotenoid and chlorophyll contents when exposed to HPPD-inhibitibg herbicide, benzobicyclon.

Isolation, Identification and Characterization of Paraquat Activity-Inhibiting Substances in Squash (Cucurbita moschata Duchesne ex Poiret) Leaves

The fourth leaves (younger leaves) amongst extended 4-upper leaves in 18 squash cultivar were the highest tolerance to the paraquat application, followed by third, the second, and the first leaves (older leaves). The forth leaves in Joongangaehobak showed more than three times higher tolerance to the paraquat application than did the first leaves. When the combining of water extract from the fourth leaves with paraquat were applied to the leaves and stems of maize, the paraquat phytotoxicity in maize was reduced compared to the paraquat application alone. Therefore, this study continued to investigate if the phytotoxicity inhibitor exist in the fourth leaves. The water extract in the fourth leaves were isolated by silica gel column chromatography, Sephadex LH-20 column chromatography, TLC, and HPLC, and the substance in the extract was speculated as a malic acid by identifying through NMR. The mixture malic acid and paraquat were applied to the maize to verify the application effect of malic acid on paraquat toxicity. The 100 µM of paraquat application alone showed 62% of paraquat toxicity to the corn leaves, while the combined application of 100 µM paraquat with malic acid at 0.1, 0.3, 0.5, and 1.0% did not show the symptom.