Rwt4 , a wheat gene for resistance to Avena isolates of Magnaporthe oryzae , functions as a gene for resistance to Panicum isolates in Japan

Rwt4 (synonym of Rmg1), a temperature-insensitive gene for resistance to Avena isolates of Magnaporthe oryzae, was identified in wheat cultivar Norin 4 in a seedling assay. The significance of Rwt4 was evaluated using flag leaves of wheat cultivars. At high temperature, Norin 4 was completely resistant to Avena isolate Br58, while Chinese Spring, a noncarrier of Rwt4, was susceptible. Genetic analysis of F₂ plants derived from Norin 4 × Chinese Spring indicated that the resistance of flag leaves of Norin 4 to the Avena isolate is conditioned by a single major gene. Segregation analysis of F₃ seedlings derived from the F₂ plants showed that the major gene is actually Rwt4. These results suggest that Rwt4 is effective against Avena isolates throughout the growth stages. Furthermore, screening of Pyricularia isolates from various hosts suggested that Panicum isolates are possible carriers of the corresponding avirulence gene, PWT4. Segregation analyses of F₂ and F₃ seedlings showed that Panicum isolates actually carry PWT4, and, therefore, that Rwt4 is also effective against Panicum isolates. On the other hand, none of the Oryza, Setaria, Triticum, and Lolium isolates tested was a carrier of PWT4. The significance of this finding is discussed from the viewpoint of epidemics of blast disease on wheat.     

EXTRA-ABDOMINAL CHONDROLIPOMA IN A DOG

A 10-year-old male maltise dog was presented for evaluation of a gradual abdominal enlargement, which had developed over 2 years. (On the radiograph of the abdomen, a significant distention of the abdomen with a large accumulation of fat could be seen.) The mass effect was noticeable because of the rightward displacement of the viscera. There was multifocal amorphous mineralization, mostly in the right abdomen. Computed tomography (CT) identified a 13 x 13 x 10 cm mass, most likely an intra-abdominal lipoma, by which the digestive tract had been displaced in the abdomen. It was only during surgery, however, that the mass was found to be located between the peritoneum and transversus abdominis muscles and the rectus abdominus muscle. It was completely resected. Histopathological examination revealed that the mass was chondrolipoma. The amorphous radiopaque lesion on the images corresponded to cartilaginous tissues with calcification. There has been no recurrence for 10 months. This is the first report of an extra-abdominal chondrolipoma in dogs. Cartilaginous metaplasia of lipoma, located in the abdominal area, should be included in the differential diagnosis for multifocal amorphous mineralization.     

Rapid detection of chitosanase activity in chitosanase gene-transformed strains of <Emphasis Type="Italic">Enterobacter cloacae</Emphasis> by lytic infection of specific bacteriophages

 In combination with lytic infection by virulent phages, a simple method for monitoring transgenic strains of Enterobacter cloacae was developed in this study. First, 15 strains of E. cloacae were used as indicator bacteria to isolate virulent phages with different host ranges. Of the phages isolated, five isolates (EcP-22, -35, -45, -55, and -70) were used to construct a set of virulent phages corresponding to all strains of E. cloacae. Using this phage set, a rhizosphere strain (KRM-055E) of E. cloacae was effectively screened from field soil. KRM-055E was transformed with a prokaryotic chitosanase gene csnSM1 and infected with the phage EcP-03, which can lyse the strain most effectively. The lysis of KRM-055E/csn occurred 2 h after inoculation, and the chitosanase activity was simply detected by dropping the lysate onto an agar plate containing glycol chitosan. The positive signal for chitosanase activity was detected in the 2-h lysates, and the signal intensity reached a maximum in the 5-h lysate. The present assay was simple, rapid, inexpensive, easy to perform, and applicable to another strains. Received: August 2, 2002 / Accepted: October 31, 2002 Acknowledgments This work was supported in part by a grant (no. 99L01205) from the “Research for the Future” program of the Japan Society for the Promotion of Science. We are grateful to Dr. M. Sato, National Institute of Agrobiological Science, Dr. H. Okamoto, Fukui Agricultural Experiment Station, and Dr. K. Tsuda, Kyoto Prefectural Institute of Agricultural Biotechnology, for kindly providing E. cloacae strains. We thank Dr. P. Park, Kobe University, for technical support with the electron microscopic observations.     

Genomic analyses of bovine viral diarrhea viruses isolated from cattle imported into Japan between 1991 and 2005

Thirty-one isolates of bovine viral diarrhea virus (BVDV) isolated within the past 15 years from imported cattle by the Japanese Animal Quarantine Service (AQS) were used in this study in which a 5'-untranslated region of each isolate was genetically analyzed. Twenty-six of the 31 isolates were classified as BVDV1 and the remainder as BVDV2. Phylogenetic analysis of the RT-PCR fragments amplified from the isolates showed the presence of viruses belonging to the BVDV1a, BVDV1b, BVDV1c, unclassified BVDV1 genotypes, and BVDV2. From the cattle of Australian origin, 16 of 17 isolates were classified as BVDV1c. This result was in agreement with a report showing that BVDV1c was a predominant subgenotype in Australia. From the cattle of North American origin, BVDV1 and BVDV2 species were both found. BVDV2 from the North American cattle was identified as the same cluster as the BVDV 890 strain, which is the prototype of BVDV2. These results suggest that the BVDVs isolated from exported cattle at the AQS reflect the predominant genotypes of BVDVs found in the exporting countries. The unclassified BVDV1 genotype of Chinese origin was in the same cluster as the ZM-95 strain, which was isolated from pigs in China. In this study, the genomic properties of 31 isolates of BVDV collected in the AQS were investigated. We concluded that isolates are genetically heterogeneous but geographically restricted. The information obtained from this report will be useful when carrying out epidemiological surveys of BVDV isolated in Japan.     

Reduction in aggressiveness among hybrids between host-specific pathotypes of Magnaporthe oryzae is caused by reduced ability to overcome adult resistance at the level of penetration

A genetic cross between a Triticum isolate (pathogenic on wheat) and a Setaria isolate (pathogenic on foxtail millet) of Magnaporthe oryzae yielded several F₁ cultures that were virulent on both wheat and foxtail millet at the primary leaf stage. To estimate whether these cultures survive in nature, they were sprayed onto 1-, 2-, and 3-week-old wheat and foxtail millet. As the age of the inoculated plants increased, the lesion number and size were greatly reduced. The F₁ cultures were almost nonpathogenic on both wheat and foxtail millet at the 3-week-old stage. Cytological analysis revealed that the low pathogenicity of the F₁ cultures on older plants was primarily associated with a reduced ability to penetrate the cuticle. When placed on wounded leaf surfaces, the F₁ cultures produced large lesions on 4-week-old wheat and foxtail millet. These results indicate that hybridization between species-specific pathotypes results in a reduction of aggressiveness. We therefore suggest that, even if such hybrids were produced in nature, they might not survive in the natural environment.     

Re-examination of age and growth of daggertooth pike conger Muraenesox cinereus in the western Seto Inland Sea, Japan

Age determination and growth using otolith rings in Muraenesox cinereus was re-examined in the western Seto Inland Sea, Japan. Previous study in this area indicated that new rings were formed annually from March to May, and then from September to October once individuals had achieved four or five rings. In this study, monthly changes in marginal growth rate indicated that the first ring was formed before November in the year following hatching, and from then on another ring was formed annually in July or August. The birth month was determined to be August based on a peak in monthly change in the gonad somatic index. Estimated von Bertalanffy growth functions were L = 806.6{1 ? exp[? 0.33(t + 0.06)]} and L = 1264.0{1 ? exp[? 0.19(t + 0.15)]} for males and females, respectively. Lengths after 3 years of age in this study were 100 mm longer than those in a previous study for both sexes.