Abstract: Differential display reverse transcriptase PCR (DDRT - PCR) method was used to explore thedifferential gene expression in cucumber resistant cultivar‘Dongnong 129’before and after inoculated with Pseudoperonospora cubensis. Four special expressed cDNA segmentswere obtained in the inoculated cucumber leaves, which were named as 49-2, 50-5, 50-7 and 52-14. BLAST analysis revealed that the nucleotide sequence of 50-7 was homologous partly to the lipoxygenase-9 in cucumber, and the others were the unknown sequences of novel genes. Further analysis on expression showed that the 4 fragments were closely related with the infection of P. cubensis. The fragment of 49-2 expressed intensely during the total time of infection; the fragment of 50-5 also had a close relationship with pathogen infection and its expression was delayed than that of 49-2; the fragments of 50-7 and 52-14 only expressed at 24 h after inoculation, which showed the special
relation with the pathogen inoculation. This study provided some useful information for further understanding of the mechanism of resistance to downy mildew in cucumber and isolating the resistance gene for application of molecular breeding.