Impact Of Lower Phosphorus Supplies On Rhizospheric Microbial Diversity Of Different Allelopathic Rice

In order to explore the relationship of the rice allelopathic potential and microbe, allelopathic rice PI312777 and non allelopathic rice Lemont were employed as test materials which cultured with branyardgrass (Echinochloa crus galli L.) in hydroponic by different phosphorus supplies. The aquatic microbe of culture solution was collected to analyze the microbe function and diversity by BIOLOG ECO and Terminal Restriction Fragment Length Polymorphism (T-RFLP) technique, respectively. The results were as follow:(1) The results of allelopathic potential showed that the root length, plant height, dry weight inhibition rate of barnyardgrass by allelopathic rice PI312777 under normal phosphorus treatment were 44.05%, 29.32%, and 33.33%, respectively. But, under low phosphorus treatment, there were 56.51%, 38.49%, and 43.14%, respectively. Further, under normal phosphorus treatment, the root length, plant height, dry weight inhibition rate of barnyardgrass by non allelopathic rice Lemont were 13.43%, 7.96%, and 0.78%, respectively. But, under low phosphorus treatment, there were 8.59%, 5.59%, and 7.84%, respectively. The results suggested that the allelopathic potential of allelopathic rice PI312777 was enhanced and significantly higher than non allelopathic rice Lemont after lower phosphorus stress.(2) Microbial population analysis indicated that the number of bacteria and fungi in the culture solution of allelopathic rice PI312777 were significantly increased under lower phosphorus stress. As the results showed that the the number of bacteria and fungi was increased from 3.56×103 to 5.19×103CFU/mL, 1.24×101 to 2.31×101 CFU/mL, respectively. However, there were not significantly changed in the culture solution of non allelopathic rice Lemont under different phosphorus treatment.(3) The results of BIOLOG showed that comparing with non allelopathic rice Lemont, allelopathic rice PI312777 could significantly enhance the growth of microbial flora feeding on phenolic acid and carboxylic acid as carbon sources after lower phosphorus treatment. Principal component analysis indicated that three components related to carbon sources accounted for 62.436%, 32.710% and 4.852% of the data variation, respectively. Correlation analysis of principal component and different carbon sources indicated that the carbon source of phenolic acids and carboxylic acid made a mainly contribution to the separation of three principal components. Correlation analysis of allelopathic potential and different microbial suggested that the allelopathic potential was positively correlated with the number of bacteria. Especially, the bacteria existed with phenolic acid, carbohydrate, carboxylic acid and fatty acids. But the change of total bacteria was mainly dued to the increased of bacteria existed with phenolic acid. Because, the bacteria existed with phenolic acid could activate the bacteria existed with carbohydrate, Carboxylic acid and fatty acids. So, the results suggested that enhanced allelopathic potential was mainly dued to the increased of bacteria existed with phenolic acid, especially under lower phosphorus treatment.The results of T-RFLP analysis showed that the microbe varieties from the culture solution of allelopathic rice PI312777 were significantly higher than those of Lemont, especially under lower phosphorus stress. The correlation analysis between allelopathic potential and microbic T-RFs showed that there were 17 microbic T-RFs, which significantly correlated with allelopathic potentail. 10 of the 17 microbic varieties derived from PI31777 were significantly increased under lower phosphorus stress, comparing to normal phosphorus. Analysis the function of microbial indicated that 21 microbial were detected and 10 of 21 were pathogenic bacteria. All the suggested that the enhanced allelopathic potential of allelopathic rice PI312777 under lower phosphorus stress not only dued to increased of phenolic acid secondary metabolite, but also dued to the contributed of pathogenic bacteria which maybe feeding on phenolic acid.