Collembolan community dynamics during deciduous forests regeneration in Japan

The structure and feeding group composition of collembolan communities were studied in secondary deciduous forests of different ages to investigate the collembolan community response to environmental changes associated with forest cycles. The study was carried out at eight sites forming a chronosequence (1, 4, 12, 24, 51, 54, 71 and 128 years after clear cutting) of deciduous forest stands in northern Ibaraki (Japan). Total collembolan density and species richness was low at the 1-year-old site, and there was little difference in density among sites over 4 years of age. The density of sucking feeders was especially low at the 1-year-old site. Species richness of trees of a diameter at breast height (DBH)<5 cm positively correlated with the density of fungal feeders. Species richness of total Collembolans and of sucking feeders correlated positively with the water content of the organic layer. Ordination of the collembolan community with Canonical Correspondence Analysis suggested that species richness of larger trees (DBH 5 cm) contributed to the differences in species composition of fungal feeders and sucking feeders. We conclude that total abundance and species richness of collembolans recovered within 4 years after clear-cutting, but species composition of fungal feeders and sucking feeders took longer to recover.     

Biotechnology and apple breeding in Japan

Apple is a fruit crop of significant economic importance, and breeders world wide continue to develop novel cultivars with improved characteristics. The lengthy juvenile period and the large field space required to grow apple populations have imposed major limitations on breeding. Various molecular biological techniques have been employed to make apple breeding easier. Transgenic technology has facilitated the development of apples with resistance to fungal or bacterial diseases, improved fruit quality, or root stocks with better rooting or dwarfing ability. DNA markers for disease resistance (scab, powdery mildew, fire-blight, Alternaria blotch) and fruit skin color have also been developed, and marker-assisted selection (MAS) has been employed in breeding programs. In the last decade, genomic sequences and chromosome maps of various cultivars have become available, allowing the development of large SNP arrays, enabling efficient QTL mapping and genomic selection (GS). In recent years, new technologies for genetic improvement, such as trans-grafting, virus vectors, and genome-editing, have emerged. Using these techniques, no foreign genes are present in the final product, and some of them show considerable promise for application to apple breeding.     

Searching for Myanmar indigenous Bradyrhizobium type C strains that best identify Rj4 genotypes in soybean

Bradyrhizobium species are symbiotic partners of soybean plants. However, some Bradyrhizobium bacteria do not form functional nodules on the roots of Rj₄ genotype soybean cultivars. Our objective was to identify the strains of Bradyrhizobium (i.e., type C strains) that are least competent to form nodules on the roots of this plant genotype. We checked (i) previously isolated type C strains of Myanmar Bradyrhizobium elkanii (MMY6-1, MMY6-2, and MMY6-5), (ii) previously isolated type C strains of Myanmarese Bradyrhizobium spp. (MMY3-5 and MMY3-7), and (iii) strain Is-34 of B. japonicum, for nodule formation when associated with Rj₄ and other Rj genotype soybeans. Strains in groups (i), (ii), and (iii) are known to be incompatible with Rj₄ soybean genotypes. MMY3-5 and MMY3-7 produced functional nodules when associated with Rj₄ and other Rj genotype soybean cultivars, except Hill (Rj₄) cultivar. The ratios of ineffective nodule numbers/total nodule numbers (I/T ratios) for MMY6-1, MMY6-2, MMY6-5, and Is-34 in association with Rj₄ soybean cultivars were > 0.5, demonstrating incompatibility between these bacterial strains and the Rj₄ genotype. Interestingly, the I/T ratios of MMY6-1 and MMY6-2 were higher than that of Is-34 in almost all Rj₄ soybean cultivars. Thus, the nodule-forming abilities of the B. elkanii strains MMY6-1 and MMY6-2 were strongly suppressed in Rj₄ soybean cultivars; these strains may therefore be useful to identify the Rj₄ genotype in soybean cultivars.     

Soybean preference for Bradyrhizobium japonicum for nodulation

For the increase of the occupation ratio of inoculum strain in the competition with indigenous rhizobia, the relationship between Rj-genotypes of soybean and the preference of Rj-cultivars for various types of rhizobia for nodulation was investigated by using the Rj ₂ Rj ₄-genotype of soybean isolated from the cross between the Rj ₂ Rj ₃-cultivar IAC-2 and Rj ₄-one Hill (Ishizuka et al. 1993: Soil Sci. Plant Nutr., 39, 79-86). Firstly, these Rj ₂ Rj ₄-genotypes were found to harbor the Rj ₃-gene. The Rj ₂Rj₃Rj₄-genotypes of soybean were considered to exhibit a more narrow microsymbiont range for nodulation than the Rj ₂ Rj ₃-and Rj₄-cultivars. Therefore, rhizobia were isolated from the nodules of various Rj-genotypes of soybeans grown in soils, and the preference of the Rj ₂ Rj ₃ Rj ₄-genotype for indigenous rhizobia was examined. The nodule occupancy of serotype 110 was significantly higher in the bacteroids of the nodules from the Rj ₂ Rj ₃ Rj ₄-rgenotypes than in those from the other genotypes, non Rj-, Rj ₂ Rj _3-, and Rj ₄-cultivars. These results demonstrated that the Rj ₂ Rj ³ Rj ⁴-genotype prefers more actively serogroup USDA110 to the others of rhizobia. Thus, Rj ₂ Rj ₃ Rj ₄-genotype is superior to non- Rj-, Rj ₂ Rj ₃-, and Rj ₄-genotypes for the formation of efficient nodules for nitrogen fixation.     

Immunohistochemical localization of rainbow trout androgen receptors in the testis

SUMMARY: We examined the distribution of two rainbow trout androgen receptors (rtAR: rtAR-α and rtAR-β) in the testis immunohistochemically using a specific antibody to clarify the target cells of androgen in spermatogenesis. Positive rtAR immunoreactivity in paraffin-embedded sections was revealed using microwave treatment, and was detected in the nuclei of Sertoli cells, Leydig cells, and other interstitial cells. The presence of rtAR in Leydig cells suggested that fish androgens regulate Leydig cell activity in an autocrine fashion similar to mammalian androgens. In addition, we found that not all Leydig cells exhibited rtAR immunoreactivity in the mature testis by double staining using anti-3β-hydroxysteroid dehydrogenase (3β-HSD) antibody. Furthermore, rtAR immunoreactivity was also detected in the nuclei of spermatogonia, spermatocytes, and spermatids. The intensity of rtAR immunoreactivity in the nuclei of spermatogonia seemed to be weaker than those of spermatocytes and spermatids. These results suggested that androgens act directly on both germ cells and somatic cells in the regulation of spermatogenesis in the rainbow trout.     

Genetic analysis of phosphoprotein and matrix protein of rabies viruses isolated in Brazil

To investigate the genetic characteristics of phosphoprotein (P) and matrix protein (M) genes of variable rabies virus (RV) prevalent in Brazil, the authors genetically characterized the P and M genes from 30 Brazilian RV field isolates. Phylogenetic analysis based on the P and M genes revealed the presence of six RV variants that consisted primarily of three insectivorous bats, the vampire bat, dog and fox in Brazil. Specific amino acid substitutions corresponding to these phylogenetic lineages were observed, with Asp(42) and Glu(62) in the P protein found to be characteristic of Brazilian chiroptera- and carnivora-related RVs, respectively. Amino acid sequence motifs predicted to associate with a viral function in the P and M proteins were conserved among Brazilian RV variants.     

Phylogenetic Analysis of Soybean-Nodulating Rhizobia Isolated from Alkaline Soils in Vietnam

In order to analyze the phylogeny of soybean-nodulating bacteria in alkaline soils in Vietnam, indigenous soybean-nodulating bacteria were isolated from root nodules by cultivating three kinds of Rj -soybean cultivars on two alkaline soils in Vietnam. The 120 isolates were classified into two major genera of soybean-nodulating rhizobia, namely Bradyrhizobium and Sinorhizobium genera, based on a growth analysis on medium and PCR-RFLP analyses of 16S rDNA and of the 16S–23S rDNA internal transcribed spacer (ITS) region. Most of the isolates of B. japonicum were extra-slow-growing and their ITS types were similar to that of B. japonicum USDA 135. They were not isolated from the soybean cultivar CNS used as Rj₂Rj₃ genotype. Isolates of Sinorhizobium were divided into two groups, S. fredii and S. sp., based on a PCR-RFLP analysis of 16S rDNA. Furthermore, PCR-RFLP analysis of the 16S–23S rDNA ITS region enabled to separate them into five types, three ITS types associated with S. fredii and two with S. sp. Sinorhizobium was frequently isolated from the three soybean cultivars on two soils. From the isolate ratio, it was suggested that B. japonicum strains similar to B. japonicum USDA 135 and S. fredii predominated in the alkaline soils of Vietnam. Additionally, our findings indicated that the Rj -genotypes affected not only the compatibility, but also the preference for nodulation between the host soybean and rhizobia.     

Effect of sulfate on nitrate transport in volcanic ash soils sampled from the A and the B horizons

Intensive cultivation of crop fields using agricultural chemicals and fertilizers has led to changes in ecological systems, resulting in a high possibility of environmental pollution by contamination, or occasional reactions not only in the soil but also in the water and the atmosphere. Some substances are known to be very toxic to human beings at low concentrations. For example, nitrosamines are believed to be carcinogenic and mutagenic.     

Factors associated with canine skin extensibility in toy poodles

To assess factors for canine skin extensibility, our study investigated associations between the dogs’ skin extension index and the following factors, gender, age, neuter status, weight, coat color and six coat color related gene polymorphisms. Swab samples were collected from 69 toy poodles to extract DNA. The skin extension indices of the lower back and the neck were measured using the following formula: vertical height of the skin fold divided by body length multiplied by 100. The dogs’ age, weight, gender, neuter status and coat color were also recorded, as well as polymorphisms of the following six selected coat color related genes, Melanocortin 1 receptor, Tyrosinase-related protein 1, Melanophilin, Canine β-defensin-1, Major Facilitator Superfamily Domain Containing 12 and Agouti-signaling protein (ASIP). Univariable analysis showed there was a meaningful association between the lower back skin extension index and both gender and age (P<0.001 and P=0.048, respectively). Also, there was a possible association between the lower back skin extension index and ASIP Single nucleotide polymorphism (SNP) (R96C) (P=0.078). Linear model analysis showed there was a significant association between the lower back skin extension index and gender (P<0.001), and there was a tendency of the association between the lower back skin extension index and ASIP SNP (R96C) (P=0.098). In addition, there was an association between gender and age for the skin extension index. (P=0.048). Therefore, these results suggest that a greater risk of skin extensibility in toy poodle could be related to being female and the ASIP SNP (R96C), because these factors were associated with higher lower back skin extension index.