（1College of Horticulture，Qingdao Agricultural University，Qingdao 266109，Shandong，China；2Institute of Vegetables and Flowers，Chinese Academy of Agriculture Sciences，Beijing 100081，China）
Abstract：Based on the differences of SdhB gene of Corynespora cassiicola registered in GenBank，specific primers were designed for SdhB-H278Y mutation，and the real-time PCR detection system was established for detecting SdhB-H278Y mutation．The results showed that C. cassiicola carried SdhB-H278Y and SdhB-I280V mutations．The SdhB-H278Y mutants have high resistance to boscalid，the EC50 value of SdhB-H278Y mutants was 21.47 μg·mL-1 or ＞ 30 μg·μL-1．The established standard curve of detection system existed a favorable linear correlation（R2 = 0.992 9）．The detection system can detect the SdhB-H278Y mutation specifically with sensitivity of 3.6 × 10-4 ng·μL-1，which was 10 times of AS-PCR．The expected values were highly correlated with the detected values by verifying genomic DNA carrying different mutation ratios of SdhB-H278Y（R2 = 0.999 7）．The system could also be used to detect the proportion of SdhB-H278Y mutant in the disease spot of corynespora leaf spot of cucumber，and the detection values were 0.12%-2.69% in Shandong．An efficient，sensitive and quantitative real-time PCR system was established for detecting SdhBH278Y mutation，providing technical support for corynespora leaf spot of cucumber controlling．
