Detection of a Point Mutation (G143A) in Cyt b of <i>Corynespora cassiicola</i> That Confers Pyraclostrobin Resistance

• Main Authors: Xiuhuan Li, Chengcheng Li, Guixiang Li, Jiamei Zhu, Feng Liu, Lin Jiang, Wei Mu, Xili Liu
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Horticulturae
• Subjects: fungicide resistance; molecular docking; cucumber target spot; QoI
• Online Access: https://www.mdpi.com/2311-7524/7/6/155

Point mutation G143A in the cytochrome b (Cyt b) protein commonly confers resistance to quinone outside inhibitor (QoI) fungicides in phytopathogenic fungi, including <i>Corynespora cassiicola</i>, which causes cucumber target spot disease. However, the effect of G143A on the binding between the QoI fungicide and the Cyt b protein, and the use of LAMP (loop-mediated isothermal amplification) to detect this point mutation had not been reported previously in <i>C. cassiicola</i>. In this study, the sensitivity of 131 <i>C. cassiicola</i> isolates—collected from Shandong province, China in 2019 and 2020—to pyraclostrobin was determined. The EC₅₀ values ranged from 1.67 to 8.82 μg/mL, and sequencing results showed that all <i>C. cassiicola</i> isolates contained the G143A mutation. Molecular docking results suggested that G143A significantly alters the affinity of pyraclostrobin to the Cyt b protein. Following development of three LAMP primer pairs, the best reaction condition for LAMP analysis was 65 °C for 60 min, and the detection limit was 0.01 ng/μL of DNA containing the point mutation. In conclusion, the G143A mutation conferring pyraclostrobin resistance is widespread in <i>C. cassiicola</i> from Shandong province, and the LAMP method can be used to monitor QoI resistance in <i>C. cassiicola</i> caused by the G143A mutation in the field.