Young Beom Yun

Differences in Rice Quality and Physiochemical Component between Protox Inhibitor-Herbicide Resistant Transgenic Rice and Its Non-transgenic Counterpart

Characteristics related to grain quality and physiochemical components such as mineral, total amino acid, free amino acid, and free sugar composition were investigated in Protox inhibitor resistanttransgenic rice (MX, PX, and AP37) and its nontransgenic counterpart (WT). Head rice, palatability, protein, and whiteness (except for MX and AP37) of milled transgenic rice were high or similar to those of the non-transgenic counterpart. Immature rice, unfilled grain, and cracked kernels (PX and AP37) of milled transgenic rice were lower than those of its non-transgenic counterpart. However, there were no significant differences in damaged grain between the transgenic rice lines and its counterpart. Potassium content in PX and copper contents in PX and AP37 were only low compared with their non-transgenic counterparts, but other mineral contents in transgenic rice lines were high or showed no significant differences compared with non-transgenic counterparts. Contents of most total amino acid composition in transgenic rice lines were high or similar to those in non-transgenic counterparts, but the content of isoleucine in AP37 was only low compared with its non-transgenic counterpart. On the other hand, free amino acid, leucine and tyrosine in PX and AP37, and total free amino acid in PX were low compared with their non-transgenic counterparts. However, the content of free amino acid in other kinds in transgenic rice lines were similar to those in their non-transgenic counterparts. Contents of sucrose in MX and PX were low compared with non-transgenic counterpars, but contents of fructose, glucose, and maltose in transgenic rice lines were high or similar compared with their non-transgenic counterparts. This results indicated that Protox genes had no negative affect on the nutritional composition of rice.

Mechanism of Growth Inhibition in Herbicide-Resistant Transgenic Rice Overexpressing Protoporphyrinogen Oxidase (Protox) Gene

We investigated the levels of resistance and accumulation of terapyrroles, reactive oxygen species, lipid peroxidation, and antioxidative enzymes for reasons of growth reduction in herbicide-transgenic rice overexpressing Myxococcus xanthus, Arabidopsis thaliana, and human protoporphyrinogen oxidase (Protox) genes. The transgenic rice overexpressing M. xanthus (MX, MX1, PX), A. thaliana (AP31, AP36, AP37), and human (H45, H48, H49) Protox genes showed 43~65, 41~72 and 17~70-fold more resistance to oxyfluorfen, respectively, than the wild type. Among transgenic rice lines overexpressing Protox genes, several lines showed normal growth compared with the wild type, but several lines showed in reduction of plant height and shoot fresh weight under different light conditions. However, reduction of plant height of AP37 was much higher than other lines for the experimental period. On the other hand, the reduction of plant height and shoot fresh weight in the transgenic rice was higher in high light condition than in low light condition. Enhanced levels of Proto IX were observed in transgenic lines AP31, AP37, and H48 at 7 days after seeding (DAS) and transgenic lines PX, AP37, and H48 at 14 DAS relative to wild type. There were no differences in Mg-Proto IX of transgenic lines except for H41 and H48 and Mg-Proto IX monomethyl ester of transgenic lines except for MX, MX1, and PX. Although accumulation of tetrapyrrole intermediates was observed in transgenic lines, their tetrapyrrole accumulation levels were not enough to inhibit growth of transgenic rice. There were no differences in reactive oxygen species, MDA, ALA synthesizing capacity, and chlorophyll between transgenic lines and wild type indicating that accumulated tetrapyrrole intermediate were apparently not high enough to inhibit growth of transgenic rice. Therefore, the growth reduction in certain transgenic lines may not be caused by a single factor such as Proto IX, but by interaction of many other factors.

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.

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.

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.

Difference in Physiological Responses to Environmental Stress in Protox Inhibitor Herbicide-Resistant Transgenic Rice and Non-transgenic Rice

The objective of this research was to confirm the difference in physiological responses to environmental stresses such as chilling, high temperature, NaCl, and chemical stress (paraquat) in Protox inhibitor resistant-transgenic rice (MX, PX, and AP37) and its non-transgenic counterpart (WT). Transgenic and non-transgenic rice plants were exposed to a chilling temperature of for 1 day or a high temperature of for 4 days and allowed to recover at for 6 days after the chilling treatment or 8 days after the high temperature treatment. Leaf injury, shoot fresh weight, porphyrin biosynthesis substances, and chlorophyll content were investigated in transgenic and non-transgenic rice at 6 days after 0.5% and 1% NaCl treatments or at 5 days after 0~300 paraquat treatments. No significant difference in leaf injury and shoot fresh weight were observed between transgenic and non-transgenic rice during chilling and recovery. Plant height and shoot fresh weight were also similar between transgenic and non-transgenic rice during the high temperature and recovery period (0~5 days). However, plant height and shoot fresh weight in transgenic rice line MX and PX were lower than in non-transgenic rice at 6 days for recovery. Leaf injury, chlorophyll, and Mg-Proto IX ME contents had no significant difference between transgenic rice and non-transgenic rice after NaCl treatment, but Proto IX content for AP37 and shoot fresh weight for PX and AP37 in 0.5% NaCl treatment were significantly reduced compared with non-transgenic rice. There was no difference in leaf injury and shoot fresh weight when comparing transgenic rice and non-transgenic rice after paraquat treatment. Although transgenic rice and non-transgenic rice showed a little difference at a particular measurement period in certain environmental stresses, there was generally no difference in physiological responses between transgenic rice and non-transgenic rice.

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.