Molecular characterization of the Fusarium graminearum species complex in Japan

Members of the Fusarium graminearum species complex are important cereal pathogens worldwide and belong to one of at least nine phylogenetically distinct species. We examined 298 strains of the F. graminearum species complex collected from wheat or barley in Japan to determine the species and trichothecene chemotype. Phylogenetic analyses and species-diagnostic polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLPs) revealed the presence and differential distribution of F. graminearum sensu stricto (s. str.) and F. asiaticum in Japan. F. graminearum s. str. is predominant in the north, especially in the Hokkaido area, while F. asiaticum is predominant in southern regions. In the Tohoku area, these species co-occurred. Trichothecene chemotyping of all strains by multiplex PCR revealed significantly different chemotype compositions of these species. All 50 strains of F. graminearum s. str. were of a 15- or 3-acetyl deoxynivalenol type, while 173 (70%) out of 246 strains of F. asiaticum were of a nivalenol type. The possibility of gene flow between the two species was investigated by use of 15 PCR-RFLP markers developed in this study. However, no obvious hybrids were detected from 98 strains examined, including strains collected from regions where both species co-occur.     

Effect of long-term fertilization on 15N uptake and retention in soil

We did a pot experiment with three different fertilized soils (no fertilizer (No-F), inorganic fertilizer nitrogen, phosphorus and potassium (NPK), manure plus inorganic fertilizer (MNPK)) from a 19-year fertilizer trial. Three N treatments, (1) no N, (2) 100 mg/kg urea-¹⁵N (N), (3) 50 mg/kg urea-¹⁵N + 50 mg/kg corn straw-N (1/2N + 1/2S), were applied to each soil. The residual soil from the same treatments was used to grow second wheat crop. The MNPK soil had significantly higher nitrogen use efficiency (NUE) in the first growing season, and lower N loss than the NPK, and No-F soils. The 1/2N + 1/2S treatment decreased NUE on each soil, even though the MNPK soil still had highest NUE and lowest N loss. The residual ¹⁵N use efficiency (RNUE) in 1/2N + 1/2S treatment of MNPK soil was higher than NPK and No-F soils. We concluded that long-term application of manure plus inorganic fertilizer increased NUE and decreased N loss.     

Educational preparedness of veterinarians for foreign animal diseases

Veterinary medical education in FADs has been and will continue to be critically important if veterinarians are expected to fulfill the profession's primary obligations to society--those of protecting our animals' health, conserving our animal resources, and promoting public health. It is imperative that curricula and instruction in veterinary schools and colleges provide the depth and breadth of knowledge and understanding necessary to prepare all veterinarians, including those in private practice, for their key role in defending against FADs. Development and implementation of governmental and military programs to diagnose, prevent, control, and eradicate FADs will require a dedicated cadre of public sector veterinarians who have a solid educational foundation in FADs and understand the contemporary issues and global challenges we face. Animal-related industries, associations, and organizations will increasingly rely on well-educated veterinarians to help guide them in ways that will protect animals, clientele, consumers, and trading partners from effects of FADs. Agencies and organizations concerned with conservation of animal resources will require veterinary expertise necessary to prevent FADs in a multitude of animal species, including marine animals, wildlife, endangered species, zoologic specimens, and important genetic lines as well as our domestic companion and livestock species. Species affected by FADs also include human beings for those disease agents with zoonotic potential; thus, veterinary education also plays a key role in public health.     

Population Analysis of Fusarium graminearum from Wheat Fields in Eastern China

ABSTRACT Wheat heads showing symptoms of Fusarium head blight were collected from four commercial fields in Zhejiang Province, China, an area where epidemics occur regularly. A total of 225 isolates were subjected to population-level analyses using restriction fragment length polymorphism (RFLP) as markers. Diagnostic RFLP markers established that all isolates belonged to Fusarium graminearum lineage 6. Nine polymorphic probes were hybridized to all isolates, resulting in 65 multilocus RFLP haplotypes (MRH). Probing with the telomeric clone pNla17, which reveals differences among isolates in the hypervariable subtelomeric region, differentiated the 65 MRH further into 144 clones. Mean gene diversity for the four field populations was similar, ranging from H = 0.306 - 0.364 over the nine RFLP loci for clone-corrected data. High levels of gene flow were inferred from a low level of population subdivision among all field populations, indicating that they were part of the same population. Pairwise linkage disequilibrium measures did not unequivocally support a random mating population, because one-third of locus pairs were significantly different from the null hypothesis of no-association between alleles. We speculate therefore that sexual recombination may not be frequent and that high levels of genotypic diversity may be maintained by relatively low selection pressure acting on a highly diverse population.     

Neural crest cells contribute to normal aorticopulmonary septation

By analyzing the hearts of quail-chick chimeras, it was found that neural crest cells at the level of occipital somites 1 to 3 migrate to the region of the aorticopulmonary septum. Bilateral removal of this neural crest population prior to migration causes malformation of the aorticopulmonary septum resulting in common arterial outflow channels or transposition of the great vessels.     

Population structure of <Emphasis Type="Italic">Fusarium asiaticum</Emphasis> from two Japanese regions and eastern China

Genetic subdivision of Fusarium asiaticum was investigated using a collection of 478 isolates originating from the Kyushu area and Aichi Prefecture, Japan and Zhejiang Province in China. Trichothecene-type determination by a multiplex PCR-test indicated that all isolates were either of a nivalenol (NIV) or a 3-acetyl deoxynivalenol (3ADON) type. The 15-acetyl deoxynivalenol (15ADON) type was not detected in this collection. Based on a Bayesian model-based clustering method using allele data obtained with 11 variable number of tandem repeats (VNTR) markers, we detected three genetic clusters. The majority of isolates in the clusters were NIV isolates from both Japan and China, Japanese 3ADON and Chinese 3ADON isolates, respectively. High levels of fixation indices and low levels of effective number of migrants were observed between the genetic clusters. Data was re-analyzed by classifying the isolates into six groups according to trichothecene type and geographic location. Population analyses of these re-classified groups indicated that the genetic subdivisions of F. asiaticum were correlated with both trichothecene type and geographic differences. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Multiplex-PCR typing of high molecular weight glutenin alleles in wheat

In Australian commercial cultivars, each high molecular weight glutenin (Glu-1) homoeologous locus consists of one of two predominant alleles: Glu-A1a (subunit Ax1) or Glu-A1b (subunit Ax2*) at the GluA1 locus, Glu-B1b (Bx7 and By8 subunits) or Glu-B1i (Bx17 and By18 subunits) at the Glu-B1 locus, and Glu-D1d (Dx5 and Dy10 subunits) or Glu-D1a (Dx2 and Dy12 subunits) at the Glu-D1 locus. PCR-based assays have been developed in this study to discriminate between these common alleles at each locus. Primers specific for the Glu-A1 Ax2* gene give a single fragment of 1319 bp only in the presence of this gene. Primers targeting the Glu-B1 locus resulted in a co-dominant marker for which the Bx7 genotype produced two fragments (630 bp and 766 bp) and the Bx17 genotype a single fragment (669 bp). The third pair of primers was specific for the Dx5 gene and resulted in a single band of 478 bp. A multiplexed PCR assay was established which permitted the discrimination of the major HMW glutenins in a single PCR reaction and agarose gel assay. As the HMW glutenin composition of a wheat line is extremely important in determining the functional properties of wheat gluten, these markers are useful for the purposes of marker-assisted breeding. These markers may also be useful for the purpose of DNA-based identification of wheat varieties. This revised version was published online in July 2006 with corrections to the Cover Date.     

EFFECT OF EXTERNAL NITRATE CONCENTRATIONS ON NITRATE EFFLUX FROM ROOTS AND ACCUMULATION IN TWO BRASSICA NAPUS L. CULTIVARS

The nutrient solution was replaced on day 72 after sowing, and then the relationship between nitrate (NO₃)-nitrogen(N) concentration in plants and nitrate efflux from roots of two oilseed rape cultivars (Brassica napus L. cv. ‘Zhongyou 821’ (‘ZY821’) and “D89”) was compared on days 73, 74, and 75, respectively. Nitrate-N concentration in petioles of “ZY821” was significantly greater than in “D89”. Nitrate-N concentrations in the nutrient solution and petioles were high on day 73 and nitrate efflux from roots of “D89” was greater than from “ZY821”. On day 75, as nitrate-N concentrations in the nutrient solution declined, both the maximum cumulative efflux and efflux rate of “ZY821” was higher than “D89.” We hypothesized that “ZY821” could remobilize more nitrate-N from the petioles to meet its N needs. This would result in a decline in translocation of nitrate from roots to shoots and an increase in root cytoplasm nitrate concentrations and root efflux.     

Population Subdivision of Fusarium graminearum Sensu Stricto in the Upper Midwestern United States

ABSTRACT A collection of 712 Fusarium graminearum sensu stricto (s.s.) strains, predominantly gathered between 1999 and 2000 from nine states within the United States, was examined for population structure and polymerase chain reaction-based trichothecene type. Most strains belonged to a cohesive genetic population characterized by a 15-acetyldeoxynivalenol (15ADON) trichothecene type. However, using a Bayesian model-based clustering method, we also identified genetically divergent groups of strains in some sampled locations of Minnesota and North Dakota. Strains of the major group of divergent populations were of a 3ADON trichothecene type and formed a distinct cluster with a collection of previously gathered strains from Italy, which displayed all three trichothecene types (15ADON, 3ADON, and nivalenol). The co-existence of genetically divergent populations of F. graminearum s.s. in the Upper Midwest allows for the rejection of the hypothesis that F. graminearum s.s. in the United States consists of a single population. These results also suggest that recombination has been insufficiently frequent in this homothallic (selfing) fungal species to homogenize the divergent populations observed in the Upper Midwest.