Abstract

DIVERSITY OF THE BACTERIAL COMMUNITY IN RICE STRAW RESIDUES IN SOIL UNDERGOING RICE-MONOCULTURE VERSUS CROP ROTATION SYSTEMS IN THE MEKONG DELTA OF VIETNAM

Dr. Tran Van Dung, Prof. Dr. Cao Ngoc Diep* and Prof. Dr. Dirk Springael

ABSTRACT

In this study, the influence of crop rotation on the structure of the bacterial community, as a catalytic agent of degradation of crop residues, was investigated over 2 crops. The studied crop rotation systems were rice-rice-rice (CRS1), baby corn -rice-mungbean (CRS2). Litter bags containing rice stems were inserted into the soil and recollected at different time points for analysing of the structure of the bacterial community colonizing the rice straw means of 16S rRNA gene based Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA gene clone library sequence analysis.The results showed that, during the cultivation of two crops, the bbacterial community colonizing rice straw residues were significantly different in phylum in the baby corn-rice-mungbean rotation system (CRS2) compared to those in the other systems. The analysis of the 16S rRNA gene libraries constructed from selected samples of rotation systems CRS1 and CRS2 during growth of the two crops confirmed this results. During growth of crop I, the bacterial community colonizing the rice straw residue in crop rotation system CRS1 was mainly composed of bacteria belonging to the Firmicutes phylum while the community colonizing rice straw in crop rotation system CRS2 was mainly composed of bacteria belonging to the Actinobacteria and Proteobacteria. During growth of crop II, in the CRS1 system bacteria belonging to the Firmicutes group still remained dominant. In the CRS2 system the Proteobacteria became the largest fraction although bacteria belonging to the Fimicutes phylum started to propagate. Our data indicate that applied crop rotation systems affect the composition of the bacterial community colonizing rice straw residues.

Keywords: 16S rRNA Gene Sequence, bacterial communication, crop rotation systems, Mekong Delta, Vietnam, rice mono-culturing system.