Expression of Special Genes Resistant to Powdery Mildew (Blumeria graminis f. sp. tritici) in Wheat Germplasm N9436

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important fungal diseases in common wheat (Triticum aestivum L.) worldwide. Wheat germplasm N9436 is resistant to powdery mildew. In the present study, a suppression subtraction hybridization (SSH) cDNA library was constructed with cDNA from N9436 leaves inoculated with Blumeria graminis as the tester and cDNA from uninoculated N9436 leaves as the driver. A total of 140 positive clones were randomly chosen from the SSH-cDNA library. Amplification using primers sp6 and t7 indicated that the sizes of the inserts ranged from 200 to 1000 bp with an average of 238 bp. Among the 140 clones, 32.86% showed redundant and repeated sequences. The most frequent sequence was glutathione transferase followed by ribulose-1,5-bisphosphate carboxylase/oxygenase small/large subunit. After screening the repeated and redundant sequences, 94 expressed sequence tags (ESTs) were acquired. Nucleic acid and protein homology search were performed using the basic local alignment search tool (BLAST) program with the default settings at NCBI website. BlastX results in nr-protein database revealed that 49 ESTs were highly homologous with known proteins involved in the disease resistance and defense reactions, energy metabolism, cell structure, protein synthesis and processing, and transport and signal transduction. BlastNr results showed that 69 and 20 ESTs had high identities with known Unigene and function-unknown ESTs, respectively, and 5 ESTs matched none in the nr-database. Thirty-three ESTs were both in the nucleic acid and protein databases, including 22 ESTs associated with powdery mildew resistance. Among them, 6 were responsible for signal transduction, 2 for hypersensitive necrosis reaction system, and 14 for systemic acquired resistance system, respectively.