Land utilization types impacted the species diversity and population distribution of nodulating and non-nodulating rhizobia in the Philippines

Abstract

The influence of three land utilization types (LUT) on the diversity and population of soybean-nodulating rhizobia indicated how human activities affect the ecology of these microorganisms. This report revealed that based on LUT (LUT1-rice-based; LUT2-soybean-based; LUT3-legume-rice), different species of rhizobia can be more abundant than the other species. Targeting the 16S rRNA gene and the 16S-23S rRNA gene ITS region through Polymerase Chain Reaction - Restriction Fragment Length Polymorphisms (PCR-RFLP), it was found out that a majority of the nodulating rhizobia was classified under the genus Bradyrhizobium and the non-nodulating rhizobia was classified under the genus of Sinorhizobium. The species diversity of nodulating rhizobia on the LUT2 showed the lowest at 0.00 whereas the LUT1 showed the highest diversity at 0.87. Similarly, the lowest species diversity of the non-nodulating rhizobia was found on the LUT2 at 0.00 but the highest was obtained from the LUT3 at 0.69. These results suggest that the nodulating rhizobia in this study may have preference with rice-based cropping pattern than with the two cropping systems. On the other hand, the diversity of rhizobia observed on LUT2 indicated that soybean monocropping may have resulted to a lesser diversity of both nodulating and non-nodulating rhizobia.Thus, it can be stated that the change in land utilization even in an agriculture land-use, species diversification and population dominance of certain rhizobia may occur.