Effect of Frankia inoculation on the growth of Alnus sieboldiana on unsterilized soil

The effect of inoculation with Frankia, a N-fixing actinomycete, on the growth of Alnus sieboldiana seedlings was studied on unsterilized soil from a nursery and an alder stand (forest of Alnus firma). The seedlings of A. sieboldiana were inoculated with Frankia before or after a 2-month culture on sterilized vermiculite, during which they nodulated, and transplanted to unsterilized soil from the nursery and the alder stand. The control seedlings were also cultured on sterilized vermiculite for about 2 months and transplanted to unsterilized soil without Frankia inoculation. The seedling growth, nodulation and N-fixing activity were measured 3, 10 and 16 weeks after the transplantation. Growth and nodule biomass of the seedlings inoculated with Frankia and those grown on the alder soil were better than those without inoculation with Frankia and grown on the nursery soil, respectively. The seedlings inoculated before spontaneous nodulation grew better than those inoculated at the transplantation. Nitrogen-fixing activity measured by acetylene reduction assay at 16 weeks after the transplantation was higher in the seedlings grown on the soil from the nursery than on the soil from the alder stand.     

Fine Mapping of HWC2, a Complementary Hybrid Weakness Gene, and Haplotype Analysis Around the Locus in Rice

Hybrid weakness is a reproductive barrier. In rice, the hybrid weakness caused by two complementary genes––HWC1 and HWC2––has been surveyed extensively. However, their gene products and the molecular mechanism that causes hybrid weakness have remained unknown. We first performed fine mapping of HWC2, narrowing down the area of interest to 19 kb. We thereby identified five candidate genes. Second, we performed haplotype analysis around the HWC2 locus of 33 cultivars. With 15 DNA markers examined, all the 13 Hwc2-1 carriers share the same haplotype for consecutive 14 DNA markers. As for hwc2-2 carriers, five out of 20 have the haplotypes relatively similar to those of Hwc2-1 carriers. However, the other haplotypes differ remarkably from them. These results are useful to identify the HWC2 gene and to study rice varietal differentiation.     

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.     

Vortex flow produced by schooling behavior of arabesque greenling <Emphasis Type="Italic">Pleurogrammus azonus</Emphasis>

Arabesque greenling Pleurogrammus azonus form schools of 30,000–60,000 individuals to feed on mesozooplankton near the sea surface. The fish need to be close to the surface where mesozooplankton production occurs, but the food is not sufficiently dense there for the fish to grow optimally while avoiding predation by sea birds. Arabesque greenling use a unique method to optimize their feeding conditions while avoiding staying on the sea surface. When the school swims upward, water is pushed downward. Upward swimming of a school of 30,000 individuals generates a downward stream of about 0.8–1.1 m/s, resulting in a convergent flow near the surface. This convergence concentrates the mesozooplankton on the sea surface and transports them into deeper layers with a strong vortex about 3.0 m in diameter and 10–20 m long. Thus, schooling of this fish induces vortex flows that provide a rich feeding environment.     

Fisheries management using a pooling fishery system with a competitive sharing rule as a remedy for the “tragedy of the commons”

We propose the concept of a pooling fishery system with a competitive sharing rule as a remedy for the tragedy of the commons without the need to consider the free-riding problem or dissatisfaction of more skillful or eager members. Each fisherman receives his share of pooled income according to his level of achievement, relative to those of other members, of pre-agreed common objectives such as the conservation of depleted stocks. After analyzing the system using the game theoretic approach, we examine its performance as a fisheries management system using a computer simulation. In our example, this system was proven to suppress increases in fishing effort by game theoretic interactions among fishermen, to maintain the stock size at a high level, and to increase the average fishing income. Although there is still much scope for improving this system for practical use, the concept of this system has the potential to contribute to the attainment of sustainable fisheries management.     

Phylogeography of the Japanese eight-barbel loach <Emphasis Type="Italic">Lefua echigonia</Emphasis> from the Yamagata area of the Tohoku district,Japan

The Japanese eight-barbel loach Lefua echigonia, which is a freshwater fish native to Japan, is distributed from the Tohoku to Kinki districts and is divided into six regional populations according to mtDNA analysis. In this study, we investigated L. echigonia collected from several locations in Yamagata Prefecture and neighboring prefectures using mtDNA control region sequences and confirmed the spatial distribution pattern among the new regional population (Yamagata population). The new population was limited to the Mogami river system in the inland area of Yamagata Prefecture and is distinguished from other regional populations by high sequence divergences.     

Utilization of genetically modified soybean meal in Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> diets

The utilization of genetically modified soybean meal (GM SBM) was compared with that of non-GM SBM in Nile tilapia. Four experimental diets were formulated to include either non-GM or GM SBM at 34 or 48%, respectively. These diets were fed to juvenile Nile tilapia (49.5 g average weight) for 12 weeks. The uptake of the cauliflower mosaic virus 35S promoter fragment of the GM SBM in fish muscle was examined at 8th and 12th week. After 12th week, fish were fed the non-GM SBM diets to determine the residual span of the incorporated promoter fragment. There was no significant difference in specific growth rate or feed efficiency between GM and non-GM groups at the same inclusion level. A small number of muscles from fish receiving both levels of GM SBM diet were positive for the promoter fragment. Additionally, the promoter fragment was not detected by the second day after changing to the non-GM SBM diets. These results indicate that the utilization of GM SBM was similar to that of non-GM SBM and the promoter fragment was rarely found in fish muscles, suggesting that suitability and safety of GM SBM in Nile tilapia diet were similar to those of non-GM SBM.     

Distribution of the FoToml gene encoding tomatinase in formae speciales of Fusarium oxysporum and identification of a novel tomatinase from F. oxysporum f. sp. radicis-lycopersici, the causal agent of Fusarium crown and root rot of tomato

The antifungal glycoalkaloid -tomatine accumulates in tomato plants and may protect plants from fungal infection. Fusarium oxysporum f. sp. lycopersici, the causal agent of vascular wilt of tomato, produces a tomatinase (FoToml) that degrades -tomatine to the nontoxic compounds tetrasaccharide lycotetraose and tomatidine. Induction of tomatinases and the distribution of FoToml homologs were examined among 30 strains belonging to 16 formae speciales of F. oxysporum. Tomatinase activity was found in 27 strains belonging to 15 formae speciales, but FoToml homologs (>98% sequence identity) were detected in only six strains belonging to four formae speciales. To identify tomatinases other than FoToml, -tomatine-inducible proteins of another tomato pathogen F. oxysporum f. sp. radicis-lycopersici were analyzed by two-dimensional gel electrophoresis. A protein with a molecular mass of 64kDa accumulated in the -tomatine-induced culture filtrates, and the protein had tomatinase activity, degrading -tomatine to lycotetraose and tomatidine.