Effects of rice allelochemicals on the microbial community of flooded paddy soil

Allelopathic rice roots release the allelochemicals in soil at significant rates to interact with soil microorganisms, but their impact on microbial community structure of flooded paddy soil has not been studied yet. In this study, phospholipid fatty acid (PLFA) analysis was used to evaluate the entire microbial community of soil incubated with rice allelochemicals (5,7,4′-trihydroxy-3′,5′-dimethoxyflavone and benzoic acid) and root exudates under flooded condition. It appeared from the results showed that the total PLFAs, bacteria and fungi all showed the largest increase in root exudates amendment at day 1, benzoic acid at day 3 and the flavone at day 5, respectively. Anaerobic bacteria increased more in allelopathic root exudates than in non-allelopathic root exudates. Benzoic acid was less stimulatory to anaerobes than flavone. There was a clear separation among the different treatments by principal component analysis (PCA). The PC1 and PC2 components together accounted for 62.8% of the variation (PC1=40.4%, PC2=22.4%) in data. Besides, the stepwise discriminating analysis showed DF1 and DF2 accounted for 70.5% and 21.1% of the variance, respectively. For the correlations of 8 selected fatty acids with the two DFs, i15:0, a15:0, 10Me16:0 and 10Me18:0 were correlated with DF1, whereas 16:1ω7c, 18:2ω6c 18:1ω9c and cy19:0 were correlated with DF2. These results suggested that allelopathic rice could modify microbial community structure in flooded paddy soil to their advantage through release of allelochemicals.