Bacterial communities in rhizosphere soil of healthy and diseased cotton (infected by the pathogenic fungus Verticillium dahliae Kleb.) were examined at different plant growth stages using T-RFLP and 16S rDNA clone library. At flowering and bolling, soil samples from the rhizosphere of healthy cotton had the highest richness, whereas the highest evenness was found in the rhizosphere of diseased cotton at boll opening. Acidobacteria and Proteobacteria were the main phyla in the cotton rhizosphere. Other phyla, including WS3, Deinococcus-Thermus, Verrucomicrobia, Firmicutes, Bacteroidetes, Actinobacteria, Thermomicrobia, Gemmatimonadetes, Planctomycetes, Proteobacteria, Cyanobacteria and unclassified bacteria were also found in cotton rhizosphere soils. Deinococcus-Thermus and Firmicutes were only present in diseased cotton rhizospheres. PCA analysis based on the 16S rDNA clone library demonstrated that six sampling resolved three groups of assemblages.
As a consequence of contamination of soil with heavy metals, cadmium accumulation in grain is of great concern worldwide, but especially in southern China. It is important to evaluate the Cd accumulation potential of grain before or when examining and approving new cultivars. An evaluation method and criteria for verifying Cd accumulation potential in rice are proposed, and the Cd accumulation potential of 56 mid-season indica hybrids collected from the provincial cultivar trials in 2016 were investigated. Genotype, environment and their interactions strongly affected the variation in grain Cd accumulation. Two hybrids were identified as slightly Cd accumulating. Hybrids with slight Cd accumulation potential would be suitable for safe grain production on polluted land (total Cd under 2.0 mg$kg-1) in Hunan Province (China) and should be considered for new cultivar evaluation and approval. This evaluation method and criterion could be applied for certifying Cd accumulation potential of rice cultivars.
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