Baseline sensitivity of Bipolaris maydis to the novel succinate dehydrogenase inhibitor benzovindiflupyr and its efficacy

Abstract

Benzovindiflupyr is a novel member of succinate dehydrogenase inhibitor (SDHI) fungicides. The filamentous fungus Bipolaris maydis Nisik. et Miyake was the causal agent of southern corn leaf blight (SCLB). Here, baseline sensitivity of B. maydis to benzovindiflupyr was established by mycelial growth and conidium germination methods using 96 B. maydis isolates collected from various places of Jiangsu Province of China, and EC50 values ranged from 0.0321 to 0.9149 μg/ml with the mean value of 0.3446 (±0.2248) μg/ml for mycelial growth, and 0.1864 to 0.964 μg/ml with the mean value of 0.5060 (±0.2094) μg/ml for conidium germination respectively. Treated with benzovindiflupyr, the distribution of nuclei and septum of hyphae did not change, but hyphae of offshoot and conidial production of B. maydis decreased significantly, the cell membrane permeability increased. The result of transmission electron microscope showed that the cross section of hypha was out of shape, the cell wall became thin and sparse, the cell membrane were distinctly damaged, organelles dissolved and vacuolated, and the cell nearly broke up. The results suggested that benzovindiflupyr had strong activity against mycelial growth and conidial production of B. maydis by damaging cell wall, membrane and organelles. The protective and curative activity assays for benzovindiflupyr indicated that benzovindiflupyr exhibited excellent suppression of B. maydis development on detached corn leaves. In protective activity assay with application of benzovindiflupyr at 10 μg/ml, the control efficacy reached to 100%. In curative activity assay with application of benzovindiflupyr at 50 μg/ml, the control efficacy reached to 90.72%. This is the first report of baseline sensitivity of B. maydis to benzovindiflupyr and its biological activity against B. maydis. It is recommended that benzovindiflupyr is a excellent candidate for controlling SCLB.