| Using the trait of rice allelopathy to develop a kind of safe and environment-friendly technology to control field weeds is one of the current hot topics in agroecology research field. As a quantitative trait, the characteristic of rice allelopathy is easily induced by the external stressful environment conditions, which had been proved by many literatures. However, the research works were done to explore the mechanism in views of plant physiology and molecular biology, and less on soil microbial ecology. At the same time, in the responds of the stress-resistant, rice is sensitive to the drought. Hereby, the study focuses on the functional microbials of allelopathic potential in allelopathic rice rhizosphere by contrasting the microbial divisity in the strong allelopathic rice and weak allelopathic rice at seven leaf stage under dry directly sowing and seedling transplanting conditions from the system biology angle, and modern molecular methods polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE),terminal restrain fragment length polymorphism (T-RFLP) and metaproteomics were applicated to reveal the diversity of the rhizosphere micrbial. The main results were summarized as follows.(1)The results of T-RFLP showed that under dry directly sowing and seedling transplanting conditions, microbial diversity and structure in the different rice soils were significant different. Under dry directly sowing condition, either at the five leaf stage or seven leaf stage, the diversity of microorganisms in allelopathic rice PI312777 rhizosphere were higher than that of the non-allelopathic rice Lemont rhizosphere. And in the development of rice from 5-leaves to 7-leave the number of microbial species of PI312777 range 168 to 424, whereas Lemont range 129 to 169. The range of increase of rhizosphere microorganisms of allelopathic rice accession was greater than non-allelopathic rice accession (252% to 131%). However, the opposite results were showed under seedling transplanting condition. The range of variation of rhizosphere microorganisms of allelopathic rice accession was weaker than non-allelopathic rice accession. Meanwhile, 17 kinds of microbial floras were showed on all test sample in addition to control treatment, accounting for 8% of the total identified species, and of which, majority refer to nitrogen cycle (Frankia.), sulfur cycle (Ectothiorhodospira.), C cycle (Methylomonas.), the utilization of aromatic compounds (Sphingomonas.), the use of glucose to producing acid (Microbacterium., Brevibacillus., Gemella.). Those were indicated that it is high similarity at the decomposition of secondary metabolites, geo-chemistry cycles of micro-organisms under two cultivation conditions.(2)The results of specificity by T-RFLP showed that the dry condition had a strong stimulating effect to rhizosphere microorganisms of allelopathic rice accession. The unique 30 genuses were appeared in PI7. And they could be divided into three functional categories: Myxobacteria, bacteria producing acid & gas and un-detected species. Myxobacteria which seven generas had been showed could decompose polymer, fiber, and dead cells. It suggested that Myxobacteria might play an important role on rice allelopathy through its destruction of weeds seeds in soil seed bank, degradate the seed radicle, embryo that could inhibit the seed germination in soil. The producing acid bacteria and gas contained seven generas which suggested that the soil of allelopathice rice accession was acidic micro-environment.(3)The results of specificity by metaproteimics showed that the diversity of function protein appearing in allelopathic rice accession soil were greater than in non-allelopathic rice accession soil under dry directly sowing condition. There are 9 kinds of functional specific protein in allelopathic rice soil, of which 2 were signal-induced proteins, 5 were the material and energy metabolism-related proteins, 2 were gene transcriptional regulation-related proteins, while functional protein-specific of non-allelopathic rice was only one kind which was a structural protein. The result showed that, the root of allelopathic rice exudates allelochemical to the soil ecosystem,thereby the allelochemical induced the functional microbial to secret protein, which raise campaigns trend, further by some material and energy metabolic enzymes converting to allelochemical which was a sense of secondary metabolites, and the final metabolites affected the target receptor.(4)The results of DGGE showed that, under dry directly sowing condition, the band 16 appeared only in the soil of allelopathy rice accession, further the results of the phylogenetic analysis showed that it was high homology with uncultured Sphingomonas. sp., which was significant different on analysis of the dominance genus level by T-RFLP. The abundance of test sample are 1.1%(PI7),2.1%(PI5),2.1%(PI), non-detection in LE7, 1.6%(LE5)( |
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