Estimation of nodulation tendency among Rj-genotype soybeans using the bradyrhizobial community isolated from an Andosol

The nodulation tendency of indigenous soybean bradyrhizobia on Rj -genotype soybean cultivars was investigated using approximately 260 bradyrhizobia isolated from an Andosol with 13 soybean cultivars of five Rj -genotypes (non- Rj , Rj ₂ Rj ₃, Rj ₃, Rj ₄ and Rj ₂ Rj ₃ Rj ₄). A dendrogram was constructed based on restriction fragment length polymorphism analysis of the polymerase chain reaction products (PCR-RFLP) of the 16S–23S rDNA internal transcribed spacer (ITS) region. Bradyrhizobium USDA strains were used as a reference. The dendrogram indicated nine clusters based on similarities among the reference strains. The ratio of beta diversity to gamma diversity ( H' _β/ H' _γ), which represents differences in the bradyrhizobial communities by pair-wise comparison between each cultivar, was obtained from Shannon–Wiener diversity indices. The results showed that bradyrhizobial communities among the same Rj -genotype cultivars were similar to each other, whereas bradyrhizobial communities between the Rj ₂-genotype and non- Rj , Rj ₃ or Rj ₄-genotype cultivars were significantly different. These results suggest that the Rj ₂-gene might not only affect the nodulation compatibility between Rj -genotype soybeans and bradyrhizobia, but also the nodulation tendency of the bradyrhizobia.     

Comparison of ratoon yield under high-level cutting in two varieties of forage sugarcane,KRFo93-1, and Shimanoushie

High-level cutting without stubble shaving has been recommended in the cultivation of forage sugarcane, KRFo93-1. However, it is unclear whether this management practice is appropriate for the more recently developed variety Shimanoushie. Therefore, the aim of this study was to compare the dry matter yield of both varieties to high-level cutting. The study included five ratoon crops (RC1–RC5). In KRFo93-1, dry matter yield was higher in HC plots (high-level cutting without stubble shaving plots) than in Control plots (stubble shaving after high-level cutting plots), and the differences were significant for the first three ratoon crops. A similar trend was observed in Shimanoushie; however, the dry matter yield of HC plots was slightly lower than Control plots in RC4 and RC5 owing to a lower stem number. Although the sum of dry matter yield of five ratoon crops was significantly higher in HC plots of both varieties, the influence of high-level cutting was more effective in KRFo93-1 than in Shimanoushie.     

Effects of plastic-hole mulching on effective rainfall and readily available soil moisture under soybean (<Emphasis Type="Italic">Glycine max</Emphasis>) cultivation

Plasticulture is becoming popular to control soil temperature and increase water-use efficiency in rain-fed agriculture. Non-perforated plastic mulching reduces effective rainfall by preventing infiltration, while perforated plastic mulching (plastic-hole mulching) increases effective rainfall by enhancing infiltration; both mulching control soil temperature. The comparative performance of these mulching is not, however, well investigated yet. So, a field experiment was conducted by cultivating soybean (Glycine max) under non-perforated plastic mulching (hereafter denoted by P), plastic-hole mulching (hereafter denoted by PH) and bare soil to investigate soil temperature, effective rainfall, total readily available soil moisture (TRAM), soil-moisture extraction pattern (SMEP) and yield of soybean. The mulching treatments reduced soil temperature by 2 °C at 5 cm depth compared to the bare treatment and created a favorable environment for soybean growth under high air temperature during summer in Japan. The PH treatment increased effective rainfall by as much as 9% of total rainfall compared to the P treatment. The SMEP in the 0- to 30-cm soil profile revealed that soil moisture was consumed, mostly, from the upper soil layer in the bare treatment, while in the P and PH treatments, soil-moisture consumption occurred both from the upper and from the lower soil layers. Consequently, the P and PH treatments provided greater TRAM (57.3 and 54.0 mm) than the bare treatment (48.0 mm), indicating that mulching contributed increasing soil-moisture availability in the root zone. The mulching treatments augmented plant height, number of nodulations per plant, and seed and biomass yields; the PH treatment produced the maximum seed yield.     

Improvements in a simple harmonic analysis of groundwater time series based on error analysis on simulated data of specified lengths

Tidal response method is an efficient technique for investigating hydraulic properties of an aquifer in insular and coastal areas of highly permeable geological settings. The present study extends a simple and straightforward harmonic-analysis technique recently introduced as part of a tidal response method applied to a freshwater-lens aquifer. This simple analysis technique was examined with artificially synthesized time series composed of multiple realistic tidal components. The analysis outputs of major diurnal and semidiurnal components are sufficiently accurate if the analyzed time-series length is appropriately restricted. Limitations of the simple harmonic analysis in the applicable time-series length arise from tidal-component interference that occurs in analyses over a finite length. Definitively recommended simple harmonic-analysis technique with appropriate combinations of time-series lengths and extractable tidal components are convenient for investigating hydraulic properties of an aquifer, such as on a remote island where the freshwater lens is the only freshwater resource.     

National-scale variations in the stable isotopic compositions of irrigation-pond and spring waters across Japan

Paddy and Water Environment - The national-scale variations and regional characteristics of the stable isotopic compositions of irrigation ponds, which are small reservoirs for irrigating paddy...     

Geographical distribution of vampire bat-related cattle rabies in Brazil

Seventy-seven rabies virus (RV) isolates originating from Brazilian cattle were genetically characterized. Partial nucleoprotein gene sequences of these isolates were phylogenetically and geographically analyzed. Cattle isolates, which clustered with the vampire bat-related RV group, were further subdivided into nine genetic subgroups. These subgroups were distributed widely in lowland regions, with some subgroups separated from each other by mountain ranges. In addition, separation of the groups in mountainous regions was correlated with altitude. These results indicate that cattle rabies is derived from several regionally-defined variants, which suggests that its geographical distribution is related to that of the vampire bat population.     

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.     

IgG antibody subclass response against equine herpesvirus type 4 in horses

In this study, IgG subclass responses against equine herpesvirus type 4 (EHV-4) were examined by enzyme-linked immunosorbent assay (ELISA) using a type-specific region of EHV-4 glycoprotein G (gG). ELISA using sera collected from horses experimentally infected with EHV-4 revealed that IgGa and IgGb antibodies were detected at high level, but IgGc and IgG(T) antibody responses were detected at low level or were undetectable. The IgGa antibody response reached its peak on day 10 post-infection, and then dropped. The IgGb antibody response reached its maximum level on day 12 post-infection, and then the level was sustained during at least 28 days after infection. Forty healthy racehorses that had already been infected with EHV-4 possessed antibody against EHV-4. Although IgGa antibodies specific for EHV-4 were not detected in any horses, IgGb antibodies were detected and the levels correlated with total IgG antibodies against EHV-4 gG. The results suggest that EHV-4-specific IgGa and IgGb antibodies are induced in EHV-4-infected horses, and that IgGb antibody, but not IgGa, is long lasting.     

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.