Artificial Infection of Rosellinia necatrix with Purified Viral Particles of a Member of the Genus Mycoreovirus Reveals Its Uneven Distribution in Single Colonies

ABSTRACT Rosellinia necatrix mycoreovirus 3 (W370) (RnMYRV-3/W370, described as RnMYRV-3 in this paper), a member of the newly established genus Mycoreovirus within the family Reoviridae, is the hypovirulence factor of the white root rot fungus, Rosellinia necatrix. Two virus-free fungal isolates (W37 and W97) that were somatically incompatible with the virus-harboring field isolate (W370) were transfected with purified RnMYRV-3 particles. Virus infection was confirmed by electrophoresis and northern hybridization of viral double-stranded RNA. RnMYRV-3 was transmissible from transfected strains to their respective, virus-free counterparts via hyphal anastomosis. Virus-transfected strains produced smaller lesions on apple fruits than did their virus-free counterparts. Virus-cured strains were indistinguishable from wild-type strains in culture morphology and displayed approximately the same virulence level on apples. Virus-transfected strains had "mosaic" colony portions consisting of thin, fast-growing and dense, slow-growing mycelia, and grew more slowly as a whole than their virus-free, parental strains. The level of virus accumulation varied among virus-transfected subcultures and within its single colonies. Virus-transfected strains were occasionally cured, as was W370. Such a phenomenon may be ascribed to uneven viral distribution in single colonies and the difficulty in viral transmission to virus-free hyphae.     

Vibriosis of Swimming Crab Portunus trituberculatus in Larviculture

Since 1985, frequent mass mortalities due to a bacterial infection have occurred in zoeal larvae of swimming crab Portunus trituberculatus reared at the Tamano Station of the Japan Sea-Farming Association. A bacterium was predominantly isolated from diseased larvae and was demonstrated by experimental infection to be the causative agent of the disease. Based on morphological, physiological, biochemical, serological and genetic characteristics of the pathogen, it was thought to be a new species and tentatively named Vibrio sp. Zoea. Challenge experiments with the bacterium in several aquatic animals indicate that Vibrio sp. Zoea appears to be a pathogen specific for crustaceans.     

Daily age and food habits of Lateolabrax latus larvae and juveniles occurring in the innermost shallow waters of Uwajima Bay, Japan

ABSTRACT:   Daily age and food habits of Lateolabrax latus larvae and juveniles were investigated at two different habitats in Uwajima Bay, western Shikoku, Japan. In the shallow zone at Miura, which contained eelgrass beds, larvae occurred from January and were collected abundantly in March. The size, age, and hatch-date distributions suggested that late-hatched specimens stay longer than early-hatched specimens at this station. On the contrary, in the intertidal flats of the Kunomura River mouth larvae were rarely collected, but juveniles were collected in relative abundance from April. The distributions in the intertidal flats station suggested that specimens had migrated from another location and then resided in the intertidal flats. Spatial and temporal trophic variations increased remarkably with metamorphosis, and thus, the spatial differences in growth rate were considered in relation to the trophic diversity of prey items. Our results suggest that the nursery environment, nursery utilization pattern, and food habits of early life stages of L. latus show remarkable flexibility. From the similarity of these ecological aspects with L. japonicus , which is a closely related species, we suggest the important role of the interspecific competition to the realized niche difference between Lateolabrax congeners.     

Low-dose recombinant canine interferon-γ for treatment of canine atopic dermatitis: An open randomized comparative trial of two doses

The purpose of this study was to investigate the minimum effective dose of recombinant canine interferon-γ (rCaIFN-γ) for the treatment of dogs with atopic dermatitis (AD). Thirty-four dogs with AD from 17 animal hospitals in Japan were administered half or one-fifth of the approved rCaIFN-γ dose of 10 000 units/kg, three times a week for 4 weeks, followed by once weekly for an additional 4 weeks. Pruritus, excoriation, erythema and alopecia were evaluated and scored by the investigators on weeks 2, 4, 6, 8 and 12. The efficacy rate (number of excellent cases + number of good cases/total number of cases) at week 8 in the 2000 units/kg group was 36.4% for pruritus, 36.4% for excoriation, 45.5% for erythema and 36.4% for alopecia. In contrast, in the 5000 units/kg group, the efficacy rate was 64.3% for pruritus, 57.1% for excoriation, 78.6% for erythema and 78.6% for alopecia. The efficacy rate of the 5000 units/kg group was high for all signs evaluated and comparable to that of the 10 000 units/kg group reported in a previous study. The results of this study showed that 2000 units/kg of rCaIFN-γ is less effective than 5000 units/kg to treat dogs with AD, and the efficacy of the 5000 units/kg dose is comparable to that of 10 000 units/kg at week 8.     

Life-history traits of walleye pollock, Theragra chalcogramma, in the northeastern Japan Sea during early to mid 1990s

I examined the age, growth, maturity, mortality, and body condition of walleye pollock, Theragra chalcogramma, in the northeastern Japan Sea (northern Japan Sea population) and evaluated their resilience to exploitation. Walleye pollock were collected in pre-spawning (October 1991-1995) and post-spawning (April 1990-1996) seasons. Estimated ages ranged from 3 to 18 years for both sexes. A von Bertalanffy growth model showed that females had longer asymptotic fork length (460 mm) than males (425 mm). Fifty percent of females and males were mature at 348 mm (4.6 years) and 322 mm (3.9 years), respectively. The instantaneous natural mortality rate was estimated to be 0.22. These life-history traits in the northern Japan Sea population were compared to those in the Bering Sea, the Gulf of Alaska, and the Japan Pacific populations. As a result, female walleye pollock in this population matured at small body sizes, grew rapidly toward small maximum sizes, and had short reproductive lifespans with low size-specific fecundity and poor body condition. Low prey availability and habitat temperatures are considered as a possible mechanism for the small maximum sizes in this population. The potential rate of population increase of both the northern Japan Sea population and other pollock populations tended to be lower than other exploited populations of non-viviparous marine fishes, suggesting potentially lower resilience to exploitation in this population and walleye pollock populations in general.     

Multiplex PCR for the identification of Agrobacterium biovar 3 strains

A biovar 3-specific primer set Ab3-F3/Ab3-R4 was designed based on the comparison of sequences of the 16S rDNA region of agrobacteria and related rhizobia for rapid identification of Agrobacterium biovar 3 strains. A 570-bp 16S rDNA fragment was amplified from cell lysates of Agrobacterium biovar 3 strains by polymerase chain reaction (PCR) using Ab3-F3/Ab3-R4 primers. Discrimination of Agrobacterium tumefaciens biovar 3 from Agrobacterium radiobacter biovar 3 and of Agrobacterium biovar 3 strains from other Agrobacterium strains was done simultaneously using multiplex PCR with a mixture of two primer sets (Ab3-F3/Ab3-R4 and VCF3/VCR3) previously designed for the virC region of Ti-plasmid and Ri-plasmid.     

Detection of tumorigenic Agrobacterium strains from infected apple saplings by colony PCR with improved PCR primers

With the colony polymerase chain reaction (PCR), the specificity of newly prepared primer sets VCF2/VCR2, VCF3/VCR3, VCF4/VCR4, and VCF5/VCR5 to Ti or Ri plasmids in Agrobacterium strains were compared to that of the conventional set VCF/VCR. At first, control strains, which consisted of a nonpathogenic strain and phytopathogenic strains carrying Ti or Ri plasmid, were used. VCF3/VCR3 and VCF5/VCR5 were highly specific to all the phytopathogenic strains, whereas the others were not. These two primer sets were superior to VCF/VCR in their specificity with colony PCR to tumorigenic Agrobacterium strains isolated from apple saplings.     

Effects of thiophanate-methyl and azoxystrobin on the composition of Cercospora kikuchii populations with thiophanate-methyl-resistant strains

Azoxystrobin was recently registered in Japan for the control of purple seed stain of soybean caused by Cercospora kikuchii, because the pathogen has developed resistance to thiophanate-methyl. To investigate the effects of these fungicides on the frequency of C. kikuchii strains resistant to thiophanate-methyl and on the genotype structure of the population, we sowed purple-stained seeds, approximately 40% of which were infected with resistant strains, as inocula with asymptomatic seeds and applied thiophanate-methyl and azoxystrobin during the reproductive growth of soybeans. The isolation frequency of resistant strains increased more than 99% by thiophanate-methyl but was not significantly increased by azoxystrobin. In amplified fragment length polymorphism (AFLP) DNA fingerprinting, genotypic diversity was significantly decreased by thiophanate-methyl but was not affected by azoxystrobin. In addition, the similarity of the AFLP genotype structure was increased by thiophanate-methyl but not by azoxystrobin. These results suggest that thiophanate-methyl selectively inhibited the proliferation of sensitive strains, which resulted in a small number of genotypes, most of which were resistant strains. Azoxystrobin was found to nonselectively inhibit proliferation of the pathogen, which retained a large number of genotypes including thiophanate-methyl-sensitive or thiophanate-methyl-resistant strains or both. The nucleotide sequence data for the cytochrome b gene are available in the DDBJ/EMBL/GenBank databases under accession number AB231863.