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Chlorine dioxide (ClO2) has been widely used as an effective disinfectant to control fungal contamination during postharvest crop storage. In this study, Fusarium oxysporum f. sp. batatas SP-f6 from the black rot symptom of sweetpotato was isolated and identified using phylogenetic analysis of elongation factor 1-α gene; we further examined the in vitro and in vivo inhibitory activities of ClO2 gas against the fungus. In the in vitro medium tests, fungal population was significantly inhibited upon increasing the concentration and exposure time. In in vivo tests, spore suspensions were drop-inoculated onto sweetpotato slices, followed by treatment using various ClO2 concentrations and treatment times to assess fungus-induced disease development in the slices. Lesion diameters decreased at the tested ClO2 concentrations over time. When sweetpotato roots were dip-inoculated in spore suspensions prior to treatment with 20 and 40 ppm of ClO2 for 0–60 min, fungal populations significantly decreased at the tested concentrations for 30–60 min. Taken together, these results showed that ClO2 gas can effectively inhibit fungal growth and disease development caused by F. oxysporum f. sp. batatas on sweetpotato. Therefore, ClO2 gas may be used as a sanitizer to control this fungus during postharvest storage of sweetpotato.

Chlorine dioxide (ClO2) can be used as an alternative disinfectant for controlling fungal contamination during postharvest storage. In this study, we tested the in vitro and in vivo inhibitory effects of gaseous ClO2 against Diaporthe batatas SP-d1, the causal agent of sweetpotato dry rot. In in vitro tests, spore suspensions of SP-d1 spread on acidified potato dextrose agar were treated with various ClO2 concentrations (1-20 ppm) for 0-60 min. Fungal growth was significantly inhibited at 1 ppm of ClO2 treatment for 30 min, and completely inhibited at 20 ppm. In in vivo tests, spore suspensions were drop-inoculated onto sweetpotato slices, followed by ClO2 treatment with different concentrations and durations. Lesion diameters were not significantly different between the tested ClO2 concentrations; however, lesion diameters significantly decreased upon increasing the exposure time. Similarly, fungal populations decreased at the tested ClO2 concentrations over time. However, the sliced tissue itself hardened after 60-min ClO2 treatments, especially at 20 ppm of ClO2. When sweetpotato roots were dip-inoculated in spore suspensions for 10 min prior to treatment with 20 and 40 ppm of ClO2 for 0-60 min, fungal populations decreased with increasing ClO2 concentrations. Taken together, these results showed that gaseous ClO2 could significantly inhibit D. batatas growth and dry rot development in sweetpotato. Overall, gaseous ClO2 could be used to control this fungal disease during the postharvest storage of sweetpotato.

M. × giganteus, a hybrid of tetraploid M. sacchariflorus and diploid M. sinensis, is a good bioenergy crop because of its high biomass yield and non-invasiveness in non-native countries. However, this species has a single cultivar that was derived from the same clone, and would, therefore, have higher susceptibility to biotic and abiotic stress. To breed M. × giganteus cultivars, we developed an interspecific crossing method and assessed the breeding efficiency of this method. From the hybrid seeds of 14 crossing combinations, we obtained 323 young plants, of which 290 plants became necrotized during the seedling stage. Of the surviving 33 plants, 12 were assumed to be triploid based on their stomatal length, relative fluorescence intensity values, rhizome elongation, and growth habit, which were similar to those of ‘legacy M. × giganteus’ but were different from M. sacchariflorus and M. sinensis. In the first planting year, four plants headed during the first 10 days of October. Pollen grain size in some hybrid plants was not different from that in the fertile, diploid M. sinensis. The percentage of abnormal pollen and the coefficient of variation of pollen size in all hybrid plants and legacy M. × giganteus were different from those in tetraploid M. sacchariflorus and diploid M. sinensis. At 10 days after flowering, ovules were viable in diploid M. sinensis and tetraploid M. sacchariflorus but aborted in the interspecific hybrid and legacy M. × giganteus. Owing to its sterility, the newly bred Miscanthus interspecific hybrid has low invasion potential, posing minimal threat to the native flora, and is, therefore, suitable for cultivation in non-native countries. These results can be applied to future Miscanthus breeding programs designed to secure the genetic diversity of M. × giganteus and to develop a range of Miscanthus cultivars that can produce high biomass yield under diverse biotic and/or abiotic conditions.

In this study, we aimed to characterize fungal samples from necrotic lesions on collar regions observed in different sweetpotato growing regions during 2015 and 2016 in Korea. Sclerotia appeared on...

Miscanthus are perennial rhizomatous grasses and considered as an ideal cellulosic bioenergy crop. Recently, it was reported that Miscanthus was damaged by the larvae of rice stem borer, Chilo suppressalis Walker, one of the most destructive pests of rice in Korea since the 1960s. This study was thus conducted to evaluate the insecticidal effects against rice stem borer in the Miscanthus cultivation fields for two years. The experiment consisted of four chemical agent plots, one environment-friendly agent plot, and untreated plot. Untreated plot showed significantly high damage of 50%, while Buprofezin·Tebufenozide and Carbosulfan·Methoxyfenozide treatment plots showed low damage rate of 2% with low larvae density of 1 and 2.3 larvae m−2, respectively. Damage rates of Tebufenozide, ChlorantraniliproleIndoxacarb, and environment-friendly agent(MatrineWood vinegar solution) were 15, 26, and 18%, respectively, which were lower than that of untreated plot but higher than those of Buprofezin·Tebufenozide and Carbosulfan·Methoxyfenozide. In conclusion, rice insecticides were effective against rice stem borer in Miscanthus field. In particular, the treatments with Buprofezin·Tebufenozide and Carbosulfan·Methoxyfenozide showed excellent control effects with control value of 93.3 and 95.2. However, further studies with different types of insecticides should be carried out for the selection of insecticides with more effective control of rice stem borer.

본 연구는 국내에 자생하는 억새 유전자원의 생육특성을 구명하기 위하여 국내외로부터 1,200 여점의 유전자원을 수집하였으며, 그 중에서 재배연수가 3년 이상인 유전자원 960여점을 대상으로 2013년과 2014년 억새의 주요 생육기간 동안인 맹아일로부터 지엽전개일 및 출수일까지의 생육특성을 분석하였다. 그 결과를 요약하면 다음과 같다. 1. 억새의 맹아가 진행되는 4월초부터 생육말기인 11월까지의 2013년도 평균기온은 $19.1^{\circ}C$ 이었고, 2014년의 평균 기온은 $13.9^{\circ}C$ 로 관측되었다. 평균 강수량 및 누적 강수량은 2013년에 3.8 mm와 921.0 mm 이었으며, 2014년에는 4.5 mm와 1092.5 mm 이었다. 2. 2013년 및 2014년 3월초부터 11월말까지의 지표로부터 10 cm 이내의 평균 토양수분 조사결과, 2013년에는 24.9%이었으며 2014년에는 32.2%로 나타났다. 하지만 2013년에는 3월초부터 8월 20일까지 20.7%의 평균 토양수분을 나타낸 반면, 2014년 동일시기의 평균 토양수분은 31.7%로 나타났다. 3. 수집지역별 억새 유전자원의 맹아일로부터 지엽전개일까지 평균 생육일수를 분석한 결과, 경기지역에서 수집한 억새 유전자원의 평균 생육일수가 가장 짧았으나 남부지역으로 내려갈수록 평균 생육일수가 긴 것을 알 수 있었다. 이러한 경향은 2014년도에서도 동일하게 확인되었으며, 지역별로 유의적인 차이를 보였다. 4. 2년간의 조사결과, 전남지역에서 수집한 물억새 중에서 거대 1호(Miscanthus sacchariflorus cv. Geodae 1) 및 우람억새(M. sacchariflorus cv. Uram)는 지엽전개가 가장 늦은 것으로 조사되었으며 맹아일로부터 소요되는 생육일수가 가장 긴 것으로 나타나, 타 억새종에 비하여 영양생장기간이 긴 것으로 판단된다. 5. 2013년도 맹아일로부터 출수일까지의 생육일수와 2014년도 생육일수와의 상관관계 분석결과, 물억새 유전자원의 경우 상관계수(r)가 0.70으로 나타났으며, 참억새 유전자원은 0.89로 나타나 2년간의 생육일수 사이에 높은 상관관계가 있음을 확인하였다. 6. 2014년에 비하여 2013년도 출수가 지연된 요인으로는 높은 기온, 낮은 강수량 및 토양수분의 영향인 것으로 추측할 수 있으며, 3년 이상 동일조건에서 재배한 억새 유전자원의 생육일수는 수집지역간의 유의적인 차이가 있었으며, 억새 유전자원의 출수특성은 현재 재배지역의 환경적 요인보다 자생지에서 다년간 적응되며 나타난 고유한 유전자형의 영향을 받는다는 것을 추측할 수 있다. 【Miscanthus has been considered as the most promising bioenergy crop for lignocellulosic biomass production. In Korea, M. sacchariflorus and M. sinensis can be found easily in all regions. It is a great advantage to utilize as important species with respect to genetic and cross-breeding programs materials for creation of novel hybrids. For successful breeding programs, it is important to precisely understand the variability of flowering traits among Miscanthus species as breeding parents materials. In this study, flowering traits were observed daily in 960 germplasms of two Miscanthus species (M. sacchariflorus and M. sinensis) for growing seasons over 2 years. The flowering process was divided into three stages. ST (sprouting time) was recorded when first leaf of the plant emerged on soil. FS1 (flowering stage 1) and FS2 (flowering stage 2) were recorded when flag leaf was firstly observed, and 1 cm of panicle was showing on at least one stem, respectively. For 2013 and 2014, the latest germplasms exerted flag leaf, i.e. September 30 (DOY of FS1 164.1) and September 4 (DOY of FS1 141.0) occurred M. sacchariflorus cv. Geodae 1 and M. sacchariflorus cv. Uram collected from Southern Korea (Jeollanam-do), while Miscanthus germplasms collected from northern Korea (Gyeonggi-do) which emerged the earliest flag leaf in July and August, significantly decreased DOY. For DOY from ST to FS2, M. sacchriflorus germplasms ranged from 140 to 190 days, and 110 to 170 days for 2013 and 2014. The highest frequency showed to 160 days for 2013, and 150 days for 2014. In M. sinensis germplasms, the highest frequency showed to 180 days for 2013, and 170 days for 2014. In the results of correlation between the day of years from ST to FS2 for 2013 and 2014, M. sacchriflorus and M. sinensis showed high coefficient of correlation (0.70 and 0.89). It can be supposed that flowering characteristics of Miscanthus are largely affected by the unique phenotypic characteristic of native habitat than environmental factors of the current planted site. This study for flowering traits of Miscanthus may provides an important information in order to expedite the introduction as breeding materials for creation of new hybrid.】

This study firstly provides basic data for selection of cultivatable bioenergy grass in barren reclaimed lands applied with solidified sewage sludge. The experimental plots consisted of a plot containing reclaimed land mixed with solidified sewage sludge (MSS 50), a plot covered by solidified sewage sludge (CSS 100), and an original reclaimed soil plot (ORS). The growth, biomass production of bioenergy grasses and soil chemical properties were investigated in each experimental plot for 5 years. The organic matter (OM) and total nitrogen (T-N) content in both MSS 50 and CSS 100 were considerably higher than those in ORS. In bioenergy grasses, M. sacchariflorus cv. Geodae 1 showed an excellent growth and adaptability on reclaimed land applied with solidified sewage sludge. The application of solidified sewage sludge may provided soil nutrition in the reclaimed land due to the fact that bioenergy crops grew better in soils applied with solidified sewage sludge than in untreated soils, and treated soils had higher OM and T-N content than untreated soils. This study suggests that M. sacchariflorus cv. Geodae 1 is the most suitable biomass feedstock crop for biomass production and that solidified sewage sludge may be used as a soil material for cultivation of bioenergy grass on reclaimed lands.

This study was firstly conducted to investigate changes of vegetation and soil characteristics in reclaimed land applied with solidified sewage sludge for the cultivation of bioenergy crops. Each vegetation survey site was approximately on the inside of each experimental plot that consisted of 50% (A-1), 30% (A-2), 15% (A-3), and 5% (A-4) mixture of solidified sewage sludge, and original reclaimed soil (ORS). After the application of solidified sewage sludge, we monitored the changes of vegetation and soil properties for three years. In first year, soil pH, electrical conductivity (EC) and exchangeable content was 9.4~10.8, , and , respectively, while three years later, it decreased to 8.1~8.4, , and , respectively. These results indicated that several of soil chemical elements which have nagative impacts on the plant growth in the plots of mixtures of solidified sewage sludge, steadily declined as the years go by. The vegetations in each survey site were recorded as 6 families and 12 species in 2014, while the vegetations were not occurred at all survey sites in 2012, and only halophytes as Phragmites australis and Suaeda asparagoides were observed in 2013. Diversity of vegetation, which was calculated by shannon index (H'), increased as the season progressed at each experimental plot applied with solidified sewage sludge. In original reclaimed soil, however, there was showed the high community similarity of vegetation due to the fact that P. australis and S. asparagoides were only occurred for survey periods.

One major obstacle of simultaneous saccharification and fermentation (SSF) is that enzymatic hydrolysis in SSF is conducted at non-optimal temperature. To break through this bottleneck, thermotolerant Saccharomyces cerevisiae strains mbc 1-4 were screened by spot-assay from respiration-deficient mutants induced by ethidium bromide. When four strains placed in liquid medium, the strains exhibited significant increased growth and fermentability at 42 °C in comparison to the host. Consequently, S. cerevisiae mbc 2 was selected to be the most suitable for bioethanol production at 42 °C. Miscanthus was pretreated with 1.5 M NaOH at 150 °C for 30 min in 1 L-vessel. As a result, 42.6% of solids containing 77.9% cellulose were recovered. Next, SSF was conducted with pretreated Miscanthus containing 3% glucan to estimate the fermentability of S. cerevisiae mbc 2 at 42 °C. In results, Ethanol concentration and theoretical ethanol yield by S. cerevisiae mbc 2 in 48 h were 15.3 g/L and 90.1%, respectively, whereas those by the control were 8.3 g/L and 49.3%, respectively. In addition, SSF with increased substrate concentration upto 9% glucan resulted in 86.3% and 82.2% of theoretical ethanol yield, respectively. Thus, our approach for SSF with high solid loading using thermotolerant S. cerevisiae mbc 2 contributes to process and microbial strain development for bioethanol production.

Miscanthus sacchariflorus 'Goedae-Uksae 1' (GU) was developed as an energy crop of high productivity in Korea. For the practical use of GU for bioethanol production, a bench-scale continuous pretreatment system was developed. The reactor performed screw extrusion, soaking and thermochemical pretreatment at the following operating conditions: 3 mm particle size, 22% moisture content, 140 °C reaction temperature, 8 min residence time, 15 g/min biomass feeding and 120 mL/min NaOH input. As a result of minimizing NaOH concentration and enzyme dosage, 90.8±0.49% glucose yield was obtained from 0.5 M NaOH-pretreated GU containing 3% glucan with 10 FPU cellulase/g cellulose at 50 °C for 72 h. The separate hydrolysis and fermentation of 0.5 M NaOH-pretreated GU containing 10% glucan with 10-30 FPU for 102 h produced 43.0-49.6 g/L bioethanol (theoretical yield, 75.8-87.6%). Thus, this study demonstrated that continuous pretreatment using a single screw reactor is effective for bioethanol production from Miscanthus biomass.

In this study, we aimed to characterize fungal samples from necrotic lesions on collar regions observed in different sweetpotato growing regions during 2015 and 2016 in Korea. Sclerotia appeared on the root zone soil surface, and white dense mycelia were observed. At the later stages of infection, mother roots quickly rotted, and large areas of the plants were destroyed. The disease occurrence was monitored at 45 and 84 farms, and 11.8% and 6.8% of the land areas were found to be infected in 2015 and 2016, respectively. Fungi were isolated from disease samples, and 36 strains were preserved. Based on the cultural and morphological characteristics of colonies, the isolates resembled the reference strain of Sclerotium rolfsii. Representative strains were identified as S. rolfsii (teleomorph: Athelia rolfsii) based on phylogenetic analysis of the internal transcribed spacer and large subunit genes along with morphological observations. To test the pathogenicity, sweetpotato storage roots were inoculated with different S. rolfsii strains. ‘Yulmi’ variety displayed the highest disease incidence, whereas ‘Pungwonmi’ resulted in the least. These findings suggested that morphological characteristics and molecular phylogenetic analysis were useful for identification of S. rolfsii.

The rice stem borer (Chilo suppressalis Walker) was one of the most destructive pest of rice for the 1960s and 1970s in Korea. Recently, it is newly recognized as a potential risk factor to the biomass yield of bioenergy crops. The current research was firstly conducted to investigate overwintering larvae population density and pattern of rice stem borer attacking Miscanthus sacchariflorus cv. Geodae 1 which is referred to as an ideal lignocellulosic bioenergy crop in Korea. Population density of larvae per 1 m 2 in stems and rhizomes at the Miscanthus experimental plots and rates of damage (wormhole, abscission) of M. sacchariflorus cv. Goedae 1 were investigated from October 2012 to March 2013. The population of larvae per 1 m 2 in stems of Miscanthus were 23, 4, 1, and 1 in October, November, December 2012, and January 2013, respectively. Over the same period, the population of larvae in basal stem rots and rhizomes were increased, whereas decreased in stems. Interestingly, the positions of larvae for overwintering in Miscanthus were confirmed to 5~10 cm below the soil surface such as basal stem rot and rhizome, whereas the most common overwintering position known in rice is a part of stem on the ground such as rice straw and rice stubble. It would suggest that the larvae gradually moved to bottom of stems and rhizomes in soil in line with decline in temperature. Moreover, the damage rates of stems per 1 m 2 were up to more than 50% in some places. In conclusion, this might be the first report that rice stem borer could affect the productivity of biomass of Miscanthus in case of mass cultivation. Moreover, it should be necessary to make a decision in insect control management for this bioenergy feedstock and other related crops.

In this study, alkaline pretreatment at a bench scale (15-L capacity) was performed to obtain a higher solid residue for the SSF (simultaneous saccharification and fermentation) of Miscanthus sacchariflorus “Goedae-Uksae 1” (GU) under the following conditions: 1 M NaOH concentration, 150 °C, and 60 min residence time. Compositional analysis and scanning electron microscope analysis revealed the pretreatment to be highly effective for achieving delignification and morphological changes. Spiral impellers were used for the rapid liquefaction of pretreated GU into slurry, and no additional nutrients were added to the fermentation mixture to reduce overall process costs. The SSF was subsequently conducted in a laboratory-scale fermenter (5-L capacity) for 108 to 120 h with 12% and 16% glucan containing pretreated GU. Consequently, 62.8 g/L and 81.1 g/L of ethanol were obtained. Based on these data, the theoretical ethanol yields from 1 kg of GU (dry weight base) were estimated at 164.6 to 171.1 g/L.

A CO2-added ammonia explosion pretreatment was performed for bioethanol production from rice straw. The pretreatment conditions, such as ammonia concentration, CO2 loading level, residence time, and temperature were optimized using response surface methodology. The response for optimization was defined as the glucose conversion rate. The optimized pretreatment conditions resulting in maximal glucose yield (93.6 %) were determined as 14.3 % of ammonia concentration, 2.2 MPa of CO2 loading level, 165.1 °C of temperature, and 69.8 min of residence time. Scanning electron microscopy analysis showed that pretreatment of rice straw strongly increased the surface area and pore size, thus increasing enzymatic accessibility for enzymatic saccharification. Finally, an ethanol yield of 97 % was achieved via simultaneous saccharification and fermentation. Thus, the present study suggests that CO2-added ammonia pretreatment is an appropriate process for bioethanol production from rice straw. Electronic supplementary material The online version of this article (doi:10.1007/s00449-014-1165-x) contains supplementary material, which is available to authorized users.