Identification of Epicoccum sorghinum as the agent of Hydrangea leaf spot and its sensitivity to fungicides

Abstract

AbstractHydrangea macrophylla is an important ornamental plant with a high market value and is widely planted in Guizhou, China. Leaf spot disease in H. macrophylla is common in Shibing County, Guizhou Province, where the estimated disease incidence is 70%–80%, seriously affecting its ornamental value. In this study, we isolated the pathogen from diseased samples of H. macrophylla in Shibing, Guizhou, verified the pathogenicity by Koch's postulates and identified the pathogen by combining the morphological characters with molecular systematics based on DNA sequences of the internal transcribed spacer regions (ITS), partial regions of RNA polymerase II second largest subunit (RPB2), β‐tubulin (TUB), and partial 28S large subunit of the nrRNA gene (LSU). The pathogen causing leaf spot disease was identified as Epicoccum sorghinum. The inhibitory effects of six synthetic fungicides on the pathogen were measured using the poison food technique. In this analysis, 25% pyraclostrobin SC exhibited the strongest inhibitory effect, with an EC50 (concentration producing 50% of the maximal effect) of 0.0208 mg/L, followed by 10% difenoconazole WDG, with an EC50 of 0.0995 mg/L. The results of this study provide a theoretical reference for the prevention and control of leaf spot disease.