Modeling the flowering sensitivity of five accessions of wild soybean (Glycine soja) to temperature and photoperiod, and its latitudinal cline.

The introgression from genetically modified soybean (Glycine max (L)) to wild soybean (Glycine soja Sieb. et Zucc.) could be threat the genetic diversity of wild soybean. Flowering synchrony is essential to the occurrence of outcrossing, but the flowering phenology of wild soybean is less well researched than that of cultivated soybean. We developed models to predict flowering initiation of wild soybean, based on the flowering initiation dates of wild soybean five accessions from different latitudes (31.4°N to 42.6°N) in growth chambers in which temperature and day length varied. Our proposed models predicted the flowering initiation date of wild soybean in the natural habitat well; the averaged difference from observed date in 5 areas was -1.8 days (-8 to +5). In the long day condition, there was a clear latitudinal cline of photoperiodic sensitivity throughout Japan. Accessions in southern part of Japan archipelago required higher temperature even under the short-day conditions and northern accessions were less-sensitive to long-day conditions. Our result showed the possibility of predicting the flowering initiation of wild soybean, corresponding to latitudes.

A new method for evaluating flowering synchrony to support the temporal isolation of genetically modified crops from their wild relatives.

Hybridization between crops and their wild relatives potentially threatens the genetic identity of the wild plants, particularly in the case of genetically modified crops. Only a few studies have examined the use of temporal isolation to prevent hybridization, and the indices used in those studies, (e.g., the days of flowering overlap), are not precise to evaluate the degree of synchrony in flowering. Here we propose a flowering similarity index that can compare the degree of flowering synchrony between two relevant species and measure the efficiency of temporal isolation. The results showed that the flowering similarity index predicts the likelihood of hybridization much better than the number of flowering-overlap days, regardless of different flowering patterns among cultivars. Thus, temporal isolation of flowering or flowering asynchrony is the most effective means in preventing hybridization between crops and their wild relatives.

Combined analyses of bacterial, fungal and nematode communities in andosolic agricultural soils in Japan.

We simultaneously examined the bacteria, fungi and nematode communities in Andosols from four agro-geographical sites in Japan using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and statistical analyses to test the effects of environmental factors including soil properties on these communities depending on geographical sites. Statistical analyses such as Principal component analysis (PCA) and Redundancy analysis (RDA) revealed that the compositions of the three soil biota communities were strongly affected by geographical sites, which were in turn strongly associated with soil characteristics such as total C (TC), total N (TN), C/N ratio and annual mean soil temperature (ST). In particular, the TC, TN and C/N ratio had stronger effects on bacterial and fungal communities than on the nematode community. Additionally, two-way cluster analysis using the combined DGGE profile also indicated that all soil samples were classified into four clusters corresponding to the four sites, showing high site specificity of soil samples, and all DNA bands were classified into four clusters, showing the coexistence of specific DGGE bands of bacteria, fungi and nematodes in Andosol fields. The results of this study suggest that geography relative to soil properties has a simultaneous impact on soil microbial and nematode community compositions. This is the first combined profile analysis of bacteria, fungi and nematodes at different sites with agricultural Andosols.

Hybridization between GM soybean (Glycine max (L.) Merr.) and wild soybean (Glycine soja Sieb. et Zucc.) under field conditions in Japan.

Accumulation of information about natural hybridization between GM soybean (Glycine max) and wild soybean (Glycine soja) is required for risk assessment evaluation and to establish biosafety regulations in Japan. This is particularly important in areas where wild relatives of cultivated soybean are grown (i.e. East Asia including Japan). To collect information on temporal and spatial factors affecting variation in hybridization between wild and GM soybean, a two year hybridization experiment was established that included one wild soybean and five GM soybean cultivars with different maturity dates. Hybridization frequencies ranged from 0 to 0.097%. The maximum hybridization frequency (0.097%) was obtained from wild soybean crossed with GM soybean cv. AG6702RR, which were adjacently cultivated with wild soybean, with 25 hybrids out of 25 741 seedlings tested. Cultivar AG6702RR had the most synchronous flowering period with wild soybean. Ten hybrids out of 25 741 were produced by crossing with cv. AG5905RR, which had the second most synchronous flowering period with wild soybean. Most hybrids were found where GM and wild soybeans were adjacently cultivated, whereas only one hybrid was detected from wild soybean plants at 2 m, 4 m and 6 m from a pollen source (GM soybean). Differences in flowering phenology, isolation distance and presence of buffer plants accounted for half of the variation in hybridization frequency in this study. Temporal and spatial isolation will be effective strategies to minimize hybridization between GM and wild soybean.