The continuous cropping of cucumber in the same potting soils may result in reduction of yield and quality of the crop,a phenomenon described as soil sickness.The changes of soil microbial communities as affected by continuous cropping and the link between these changes and soil sickness of cucumber are still not clear.In this experiment,cucumber was cropped in pots under greenhouse conditions for nine successive cropping cycles.Structures and sizes of rhizosphere fungal and Fusarium (Ascomycota,Fungi)communities,both ubiquitous and ecologically important in soils,were analyzed with PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative reverse transcription PCR (qRT-PCR),respectively.Cucumber showed a growth retard in the seventh cropping cycle.The RNA-and DNA-based fungal community structures derived from the same sample differed from each other,and the active soil fungal communities were more sensitive to be influenced by the continuous cropping.The RNA-based fungal and Fusarium community sizes were larger in the seventh cropping cycle than in the other cropping cycles.