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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING CHEMICAL, PHYSICAL, AND BIOLOGICAL PROPERTIES OF DEGRADED SANDY SOILS FOR ENVIRONMENTALLY SUSTAINABLE PRODUCTION

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Genetic diversity and geographical distribution of indigenous soybean-nodulating Bradyrhizobia in the United States

Authors
item Shiro, Sokichi -
item Matsuura, Syoto -
item Saiki, Rina -
item Sigua, Gilbert
item Yamamoto, Akihiro -
item Umehara, Yosuke -
item Hayashi, Masaki -
item Saeki, Yuichi -

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2013
Publication Date: May 29, 2013
Citation: Shiro, S., Matsuura, S., Saiki, R., Sigua, G.C., Yamamoto, A., Umehara, Y., Hayashi, M., Saeki, Y. 2013. Genetic diversity and geographical distribution of indigenous soybean-nodulating Bradyrhizobia in the United States. Applied and Environmental Microbiology. 79(12):3610-3618.

Interpretive Summary: Inoculation of the bradyrhizobia in soybean had shown a high ability for nitrogen fixation, resulted in increase of soybean yield. However, the efficiency of inoculum in soybean with high nitrogen fixation ability is poor because the inoculum cannot compete with indigenous soybean-nodulating rhizobia in the soil. To solve this problem, it is very important to understand the ecology of indigenous soybean-nodulating rhizobia in terms of the genetic diversity, geographical distribution, compatibility with the host soybean, and environmental factors associated with its localization and dominance in the soil. The objectives of this study were 1) to investigate the genetic diversity, community structure and field allocation by PCR-RFLP analysis of 16S-23S rRNA gene ITS region; and 2) to estimate the soybean-nodulating bradyrhizobial community structure and geographical distribution using some mathematical ecology analyses. The major clusters were Bj123 in northern region and Bradyrhizobium elkanii in the middle to southern regions. Generally, the occupancy of cluster belonging to B. elkanii was larger than the cluster belonging to Bradyrhizobium japonicum. The indigenous soybean-nodulating bradyrhizobial community structure in the USA indicated a high correlation in the northern latitude, suggesting that indigenous soybean-nodulating bradyrhizobial community in America varies according to geographical location. The investigation of geographical distribution of soybean-nodulation rhizobia appears to be beneficial to better understand the bradyrhizobial ecology, thus further improving inoculation techniques of soybean-nodulating rhizobia with high nitrogen fixing ability.

Technical Abstract: The relationship of indigenous soybean-nodulating bradyrhizobial genetic diversity and geographical distribution in the United States of America (USA) were investigated using soil isolates from eight states (Michigan, Ohio, Kentucky, North Carolina, Alabama, Georgia, Florida and Louisiana) with three Rj genotype soybeans (non-Rj, Rj2Rj3 and Rj4). The genetic diversity and community structure were analyzed by PCR-RFLP using the 16S-23S rRNA gene internal transcribed spacer region with eleven Bradyrhizobium USDA strains. Furthermore, some mathematical ecology analyses such as diversity analysis, multi-dimensional scaling analysis based on Bray-Curtis index and polar ordination analysis were also conducted to estimate the soybean-nodulating bradyrhizobial community structure and geographical distribution. Indigenous soybean-nodulating bradyrhizobial communities in America vary according to geographical location. The major clusters were Bj123 in northern region and Bradyrhizobium elkanii in the middle to southern regions. Generally, the occupancy of cluster belonging to B. elkanii was larger than the cluster belonging to Bradyrhizobium japonicum. The indigenous soybean-nodulating bradyrhizobial community structure in the USA indicated a high correlation in the northern latitude with R2 = 0.82. The investigation of geographical distribution of soybean-nodulation rhizobia appears to be beneficial to better understand the bradyrhizobial ecology, thus further improving inoculation techniques of soybean-nodulating rhizobia with high nitrogen fixing ability.

Last Modified: 4/21/2014
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