Identification of differentially expressed genes between powdery mildew resistant near-isogenic line and susceptible line of cucumber by suppression subtractive hybridization

A population of BC7 near-isogenic cucumber line (NIL210) was made from a cross between the powdery mildew susceptible cultivar (D8) and resistant cultivar (JIN5-508) in order to get powdery mildew resistance genes in cucumber. In this study, suppression subtractive hybridizations (SSHs) were applied to identify differential expressed genes between NIL210 and D8. 166 differentially expressed ESTs were identified from two SSH cDNA libraries including constitutively expressed resistant and susceptible factors. Most of the classified genes belong to four pathogenesis-related categories: ‘disease/defense’, ‘signal transduction’, ‘transcription’ and ‘transporter’, which altogether accounted for 46–53% of the genes classified. Some candidate powdery mildew resistant genes were also identified, such as GT053536 (TIR-NBS-LRR protein) and GT053570 (phenylalanine ammonia-lyase 2). These results will contribute to the better understanding of molecular mechanisms underlying powdery mildew resistance in cucumber.