Kil-Ung Kim’s research while affiliated with Kyungpook National University and other places

This study was conducted to study the seasonal changes of dry matter productivity and photosynthesis ability of Gerbera hybrida cv. Cosmo in greenhouse cultivation. For growth analysis, dry weight and leaf area were measured every month during growing period (Apr. 2006~Mar. 2007). Photosynthesis rates in accordance with light intensity, CO and leaf characteristics were measured by LI-6400 and seasonal changes were also checked. The maximum RGR (relative growth rate) and NAR (net assimilation rate) were observed at early growth stage. Among the growth analysis characters, NAR of individual plant and LAI (leaf area index) of canopy were the main factors in plant productivity and it could be assumed that CGR (crop growth rate) was the maximum at 3.42 g.m.day when LAI was 2.09. Light saturation and compensation points were 804 and 32 mol.m.s, respectively. Intercellular CO concentration and photosynthesis were positively correlated and regressed as binomial. Maximum photosynthesis rate would be achieved at 784 mol.mol of intercellular CO concentration. Photosynthesis rates were increased until 4 months after transplanting and then decreased during winter season. Leaf area/leaf dry weight ratio and vapor pressure deficit in leaf were positively correlated with photosynthesis.

Experiments were conducted for four consecutive years (2004~2007) in the greenhouse of Experiment and Practice Station. Kyungpook National University to determine genetic characteristics of the hybrids in the succeeding generations. F₁ hybrid were obtained by crossing weed rice with the glufosinate-ammonium resistant lines harboring ABC-promoter and ubiquitin promoter transgenic lines. respectively. F₁ hybrid obtained from crossing between weed rice and ABC-promoter transgenic rice found to have greater chances of genetic integration because of its higher rate of spikelet fertility. The response to the recommended dose of glufosinate-ammonium at 30 DAS (days after seeding) in F₂ followed Mendelian pattern of segregation. This indicated that the herbicide-resistant trait acquired from transgenic lines introgressed in the progeny generations. The days to heading and maurity in F₁ was delayed by as much as 30 days than the both parents. However, heading/flowering of F₂ was found highly variable, with approximately one fourth of the tillers maturing earlier like that of weedy rice parent. In this study, segregation to glufosinate response, heading dates and shattering of seeds in F₁, F₂, and F₃ were acquired from weedy parent.

This experiment was conducted to evaluate pollen viability of Nakdongbyeo, transgenic rice lines, an F1 hybrid from a cross between Milyang weedy rice and ABC-promoter transgenic rice line containing basta-resistant (bar) gene and subsequent selfed progenies, F₂ and F₃. The reaction of pollen with 3-{4,5 dimethylthiazolyl-2}-2,5-diphenyl monotetrazolium bromide (MTT) as a staining chemical immediately after pollen shedding showed maximum pollen viability of 86% in Nakdongbeyo, 75% in ABC-promoter transgenic rice line, 62% in ubiquitin-promoter transgenic line, 68% in F1, 79% in F₂ and 78% in F₃. Viability gradually declined during subsequent observations at 20-minute intervals. However, there was a drastic decline in pollen viability after 40 minutes of pollen shedding. The mean difference of pollen viability among rice lines and time was highly significant, indicating significantly different pollen viabilities at different time intervals. Maximum viability of 36.2% was observed in F₃ and minimum viability of 3.5% was found in F₂ at 90 min after pollen shedding. Results of this experiment on pollen viability and longevity elucidate potential risks of pollen-mediated flow of herbicide-resistant gene from transgenic rice lines and possible integration of it into the weedy rice population.

Allelopathy has the potential to reduce the herbicide use as a component of integrated weed management technology. To develop a new bioassay method, we studied the effects of extracts from 3 rice cultivars (Kouketsumochi, Dongjinbyeo and K21) on the haustorium induction rate, phytotoxicity and ROS (reactive oxygen species) activity of parasitic plant Triphysaria versicolor as the target plant. The three cultivars influenced the different rates of haustorium induction. Kouketsumochi caused the highest haustorium induction rate followed by K21 and Dongjinbyeo (lowest response at varying concentrations of rice tissue extracts). Application of UV irradiation to the rice cultivars increased the phytotoxic effects on root growth of T. versicolor. Activity of reactive oxygen species (ROS) was assayed by staining root tip of parasitic plant with probe CM-H2DCFDA [5-(and 6)-chloromethyl-2', 7'-dichlorodihydro-fluorescein diacetate, acetyl ester] and monitoring the change of fluorrescence. The fluorescence increased when the dye was oxidized by ROS. Fluorescence appeared in the shortest time in Kouketsumochi (allelopathic cultivar), followed by K21 and Dongjinbyeo (non-allelopathic cultivar). Results indicated that different haustorium rates of rice cultivars were related to different ROS activity. Thus T. versicolor can be used as a new target plant to evaluate the allelopathic potential of plant species.

Three rice (Oryza sativa L.) cultivars (cv. Daesanbyeo, cv. Dongjinbyeo, cv. Junambyeo) were analyzed for endogenous gibberellin (GA) and jasmonic acid (JA) contents and their changes in response to elevated nitrogen (N) levels. The N fertilizer was applied in the form of urea [(NH 2) 2 CO] at three rates (0, 36.8, 73.6 kg N ha ±1). Plant growth (height and dry weight) was enhanced by the first N rate but not further enhanced by the highest rate. The endogenous GA contents were analyzed through high-performance liquid chromatography (HPLC) and gas chro-matography±mass spectrometry±selected ion monitoring (GC-MS-SIM) while that of JA with GC-MS-SIM. They were analyzed one week after N application and were significantly increased with elevated N levels in all rice cultivars. The bioactive GA 1 markedly increased, but its concentration differed in different rice cultivars. Similar fluctuations were observed for endogenous GA 8 , GA 12 , GA 19 , GA 20 , and GA 53 in response to elevated N levels, showing that the rates of bio-synthesis of GAs were differently affected by elevated N levels within different rice cultivars. The level of GA 20 , a precursor of GA 1 biosynthesis, was not significantly increased, though GA 19 , a precursor of GA 20 , was found to be the most abundant GA type in all rice cultivars. Jasmonic acid content in the plants increased with the basic urea application (36.8 kg N ha ±1), but significantly decreased with the double urea level (73.6 kg N ha ±1). The results demonstrate that GA and JA are differentially affected in response to elevated N application in rice.

An improvement in allelopathic potential in rice will have a great impact on both low-input and high-input management systems. Alleopathy alone is not likely to replace other weed control practices, but it surely functions as a component of integrated weed management technology. Marginally reduced use of herbicide over time will provide significant economical benefits to farmers and will also reduce adverse effects on the environment. There is a great possibility of breeding new allelopathic rice by regulating their capacity to produce allelopathic substances. Allelopathic potential in rice was greatly improved by the classical breeding method of crossing between a non-allelopathic commercial cultivar and an allelopathic cultivar. The first priority research areas are identification of allelochemicals and genes responsible for allelopathic effects and these traits can be easily incorporated into improved cultivars by either classical breeding or biotechnology. Allelopathic activities of rice seem to be derived from the joint action of momilactones with phenolic compounds. Phenolics, however, are unlikely to be the primary allelochemicals since they never reach a phytotoxic level in soil. However, it is believed that phenolics like other multiple compounds present at concentrations below the activity threshold could have pronounced allelopathic effects through their joint action. Momilactone B seems to be the responsible allelochemical because its activities were 30-fold to 300-fold greater than phenolic acids. Insertion of two specific genes such as CA4H for p-coumaric acid and OsDTS2 for momilactone into one commercial rice cultivar by biotechnology will lead to the development of allelopathic rice cultivar. Further studies on genetic control of rice allelopathy, the complete array of the responsible chemicals in rice root exudates and their mode of action will shed more light on developing an allelopathic rice crop.

Diurnal changes in levels of endogenous gibberellins (GAs) were investigated in three rice cultivars i.e. Sangjubyeo, Shingeumobyeo (photo-neutral) and Chucheongbyeo (photosensitive). The rice cultivars were grown under a 12-hr photoperiod and endogenous GA levels were assayed by gas chromatography-mass spectrometry (GC-MS-SIM) every 3 h for 24 h. The endogenous bioactive GA1 and its immediate precursor GA20 contents were significantly different in both photosensitive and photo-neutral rice cultivars, though less pronounced differences were observed for endogenous GA12, GA53, GA19, and GA8 levels with in the three rice cultivars. The levels of bioactive GA1 and its immediate precursor GA20 were significantly higher in Chucheongbyeo than in the other two cultivars. In Chucheongbyeo, the GA1 contents increased significantly from 11.00 to 17.00 o'clock, thus indicating a corre- lation with light. In Shingeumobyeo, GA1 contents slightly increased during morning hours, while a similar hike in GA1 contents was observed for Sangjubyeo during evening hours. GA19 was found to be the most abundant GA form in the three rice cultivars. Our results suggested that GA production in rice depends upon the response potential of rice cultivars and that light positively correlated to GA production in photosensitive rice cultivar.

This study was conducted to identify physiologically active substances from leaves and stems of peony plant. MeOH extracts and column chromatography were employed to isolate active compounds and chemical structure were identified by IR, UV, Mass and NMR. The results obtained can be summerized as followings : Chemical structure of compound 1 was identified as oleanolic acid (white color form) of triterpenoid group, which is firstly identified from the above part of peony. Compound 2 was identified as kaempferol (yellow needle form) of flavonoid group, which was firstly identified from the root, leaf and stem of peony. Compound 3 was identified as methyl gallate (white power form) of phenol group, which was firstly identified from the above part of peony. Compound 4 was identified as astragalin (bright yellow needle form) of flavonoid group, that was firstly identified from the leaf and stem of peony. Compound 5 was identified as paeoniflorin (white color form) of monoterpene group, that was firstly identified from the above part of peony.