Effects of a novel SDHI fungicide pyraziflumid on the biology of the plant pathogenic fungi Bipolaris maydis

Pyraziflumid is a novel member of succinate dehydrogenase inhibitor (SDHI) fungicide. Southern corn leaf blight (SCLB) caused by Bipolaris maydis is an important foliar disease of maize crop. In this study, baseline sensitivity of B. maydis to pyraziflumid was determined using 100 strains of B. maydis collected from different geographical regions in Jiangsu Province of China during 2015 and 2016, and EC50 values ranged from 0.0309 to 0.8856 μg/ml with the average value of 0.2780 ± 0.2012 μg/ml for mycelial growth, and 0.032 to 0.9592 μg/ml with the average value of 0.3492 ± 0.2450 μg/ml for conidium germination. After treatment with pyraziflumid, the distribution of cell nucleus and septum of mycelium was not changed, but hyphae of offshoot and conidia production decreased, cell secretion decreased, the cell membrane was damaged, mycelium electrolyte leakage increased, and organelles in mycelial cell dissolved and vacuolated. The protective and curative activity test of pyraziflumid suggested that pyraziflumid had great control efficiency against B. maydis on detached corn leaves. In protective activity assay with application of pyraziflumid at 5 μg/ml and 10 μg/ml, the control efficacy reached to 87.32% and 100% respectively. In curative activity assay with application of pyraziflumid at 20 μg/ml and 50 μg/ml, the control efficacy reached to 82.10% and 100% respectively. [Display omitted] •Confirmed the sensitivity distribution of B. maydis 100 strains to pyraziflumid•Analyzed the effects of pyraziflumid on morphology and physiology of B. maydis•Investigated protective and curative activity of pyraziflumid on leaves of corn