Population structure of and mycotoxin production by Fusarium graminearum from maize in South Korea.

Fusarium graminearum (Gibberella zeae) is an important pathogen of wheat, maize, barley, and rice in South Korea, and harvested grain often is contaminated with trichothecenes such as deoxynivalenol and nivalenol. In this study, we examined 568 isolates of F. graminearum collected from maize at eight locations in South Korea. We used amplified fragment length polymorphisms (AFLPs) to identify four lineages (2, 3, 6, and 7); lineage 7 was the most common (75%), followed by lineage 6 (12%), lineage 3 (12%), and lineage 2 (1%). The genetic identity among populations was high (>0.98), and the effective migration rate between locations was higher than that between lineages. Female fertility varied by lineage: all lineage 7 isolates were fertile, while 70%, 26%, and 14% of the isolates in lineages 6, 3, and 2, respectively, were fertile. All lineage 3 and lineage 7 isolates produced deoxynivalenol, whereas most lineage 2 and 6 isolates produced nivalenol. Genotypic diversity in lineage 3 and lineage 6 populations is similar to that found in previously described Korean rice populations, but genotypic diversity in lineage 7 is much lower, even though similar levels of gene flow occur between lineage 7 populations. We conclude that lineage 7 was relatively recently introduced into South Korea, perhaps accompanying imported maize seeds.

Transitional wall pressure fluctuations on axisymmetric bodies.

This paper reports the characteristics of wall pressure fluctuations in the transition region of the flow over axisymmetric bodies. Measurements are conducted in a low noise wind tunnel to obtain the boundary-layer flow field, the local static pressures, and the wall pressure fluctuations using hot wires, micromanometers and flush-mounted microphones. The spatial and the temporal developments of Tollmien-Schlichting (T-S) waves were first observed in the time domain. The wall pressure fluctuations in the transitional boundary-layer flows were of intermittent pulses and intensified as they were convected downstream at typically 63% of the upstream velocity. The Wigner-Ville distributions are then obtained to examine the energy evolution jointly in time and in frequency. The center frequency of the T-S wave is decreased with increases of the boundary-layer thickness and the bandwidth of the energy distribution is broadened as the local Reynolds number is increased. Finally the nondimensional spectra of the transitional wall pressure fluctuations scaled on the outer variables was obtained and it was then found that the characteristic frequency of the T-S wave was related to the outer variables as omegadelta( *)/U(infinity) approximately 0.2. The peak level of the pressure fluctuations during late transition at the characteristic frequency is about 10 dB higher than that of the fully developed flow.

Effect of culture temperature on erythropoietin production and glycosylation in a perfusion culture of recombinant CHO cells.

To investigate the effect of culture temperature on erythropoietin (EPO) production and glycosylation in recombinant Chinese hamster ovary (CHO) cells, we cultivated CHO cells using a perfusion bioreactor. Cells were cultivated at 37 degrees C until viable cell concentration reached 1 x 10(7) cells/mL, and then culture temperature was shifted to 25 degrees C, 28 degrees C, 30 degrees C, 32 degrees C, 37 degrees C (control), respectively. Lowering culture temperature suppressed cell growth but was beneficial to maintain high cell viability for a longer period. In a control culture at 37 degrees C, cell viability gradually decreased and fell below 80% on day 18 while it remained over 90% throughout the culture at low culture temperature. The cumulative EPO production and specific EPO productivity, q(EPO), increased at low culture temperature and were the highest at 32 degrees C and 30 degrees C, respectively. Interestingly, the cumulative EPO production at culture temperature below 32 degrees C was not as high as the cumulative EPO production at 32 degrees C although the q(EPO) at culture temperature below 32 degrees C was comparable or even higher than the q(EPO) at 32 degrees C. This implies that the beneficial effect of lowering culture temperature below 32 degrees C on q(EPO) is outweighed by its detrimental effect on the integral of viable cells. The glycosylation of EPO was evaluated by isoelectric focusing, normal phase HPLC and anion exchange chromatography analyses. The quality of EPO at 32 degrees C in regard to acidic isoforms, antennary structures and sialylated N-linked glycans was comparable to that at 37 degrees C. However, at culture temperatures below 32 degrees C, the proportions of acidic isoforms, tetra-antennary structures and tetra-sialylated N-linked glycans were further reduced, suggesting that lowering culture temperature below 32 degrees C negatively affect the quality of EPO. Thus, taken together, cell culture at 32 degrees C turned out to be the most satisfactory since it showed the highest cumulative EPO production, and moreover, EPO quality at 32 degrees C was not deteriorated as obtained at 37 degrees C.

Paenibacillus elgii sp. nov., with broad antimicrobial activity.

Two novel spore-forming bacteria with broad antimicrobial activity were isolated from roots of Perilla frutescens. The isolates, SD17(T) and SD18, were facultatively anaerobic and showed variable Gram reaction. Growth was observed between 20 and 45 degrees C. DNA G+C content of SD17(T) was 51.7 mol%, and the major fatty acid was anteiso-C(15 : 0) (54.1 %). 16S rRNA gene sequence similarity of SD17(T) ranged from 98.6 to 91.3 % with other Paenibacillus species. The phylogenetic tree showed that isolate SD17(T) formed a significant monophyletic clade with Paenibacillus koreensis KCTC 2393(T) and Paenibacillus ehimensis IFO 15659(T). DNA-DNA relatedness values for strain SD17(T) with Paenibacillus koreensis KCTC 2393(T) and Paenibacillus ehimensis IFO 15659(T) were 17.4 and 19.8 %, respectively. These isolates thus merit species status within Paenibacillus, for which the name Paenibacillus elgii sp. nov. is proposed. The type strain is SD17(T) (=KCTC 10016BP(T)=NBRC 100335(T)).

Synthesis and fungicidal activity of ethaboxam against Oomycetes.

This study describes the chemical synthesis and intrinsic fungicidal activity of ethaboxam [(RS)-N-(alpha-cyano-2-thenyl)-4-ethyl-2-(ethylamino)-1,3-thiazole-5-carboxamide], a new Oomycetes fungicide. In in vitro tests, ethaboxam showed inhibitory activity against isolates of Phytophthora and some Pythium spp, with MIC values ranging from 0.1 to 0.5 mg litre(-1) for nine isolates of Phytophthora infestans (Montagne) de Bary and from 1.0 to 5.0 mg litre(-1) for eight isolates of Phytophthora capsici Leonian. In tests to determine time and concentration for complete inactivation of each pathogen (five isolates of P infestans and five isolates of P capsici), ethaboxam inactivated all isolates of P infestans within 48h at 10 mg litre(-1) and those of P capsici within 96 h at 10 mg litre(-1). Ethaboxam effectively suppressed development of tomato late blight caused by P infestans and pepper Phytophthora blight caused by P capsici in the studies conducted to determine its preventive, curative, persistent and systemic activity. These results show that ethaboxam has desirable fungicidal characteristics as an Oomycetes fungicide.

Double-stranded RNA mycovirus from Fusarium graminearum.

Double-stranded RNA (dsRNA) viruses in some fungi are associated with hypovirulence and have been used or proposed as biological control agents. We isolated 7.5-kb dsRNAs from 13 of 286 field strains of Fusarium graminearum isolated from maize in Korea. One of these strains, DK21, was examined in more detail. This strain had pronounced morphological changes, including reduction in mycelial growth, increased pigmentation, reduced virulence towards wheat, and decreased (60-fold) production of trichothecene mycotoxins. The presence or absence of the 7.5-kb dsRNA was correlated with the changes in pathogenicity and morphology. The dsRNA could be transferred to virus-free strains by hyphal fusion, and the recipient strain acquired the virus-associated phenotype of the donor strain. The dsRNA was transmitted to approximately 50% of the conidia, and only colonies resulting from conidia carrying the mycovirus had the virus-associated phenotype. Partial nucleotide sequences of the purified dsRNA identify an RNA-dependent RNA polymerase sequence and an ATP-dependent helicase that are closely related to those of Cryphonectria hypovirus and Barley yellow mosaic virus. Collectively, these results suggest that this dsRNA isolated from F. graminearum encodes traits for hypovirulence.