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Study on Etiology of Three New Diseases of Dogwood Plants

Author: NiuXiaoRui
Tutor: HuangSiLiang; LiQiQin
School: Guangxi University
Course: Plant Pathology
Keywords: dogwood pathogen identification fungicide screening biologicalcharacteristic
CLC: S435.671
Type: Master's thesis
Year: 2013
Downloads: 4
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Abstract


Dogwood is a valuable medicinal plant in China. Nanyang city, Henan province, is one of the main dogwood-producing areas in China. In recent years, during a survey on dogwood diseases performed in Xixia county, Nanyang city, three new diseases were found on dogwood plants. They are the leaf brown spot disease, the leaf blight disease and the Pestalotiopsis leaf spot disease. The three dogwood diseases occurred in local dogwood plantations, which caused heavy defoliation, fruit drop, and yield loss. Affected leaf samples were collected and used for pathogen isolations. The pathogenicity of the fungal isolates was tested based on Koch’s postulates. The representative isolates were identified based on their morphological characteristics as well as some conservative DNA (rDNA-ITS, β-tubulin gene) sequences, and their biological characters were tested. This study could provide a scientific basis for the management of dogwood diseases. The main results were summarized as follows.1. The causal agent of dogwood brown spot disease was identified as Alternaria alternata (Fr.) Keissler based on its morphological characteristics as well as rDNA-ITS and β-tubulin gene sequences. The pathogen grew well at a pH range of4.0-9.0, with7.0as the optimum; The temperature range for vegetative growth and sporulation of the pathogen was4-34℃, with28℃as the optimum; Of the12utilizable carbon sources and8utilizable nitrogen sources tested, inulin and sodium nitrate or glycine were the best for vegetative growth of the pathogen, while sucrose and carbamide were the best for sporulation. The activities of4extracellular enzymes (amylase, protease, cellulase and pectinase) of the pathogen could be detected on the media containing various enzymatic matrixs, and the activity of cellulase was the strongest among the enzymes tested. The results on the occurrence discipline of dogwood brown spot disease showed that the plant debris was one of the overwintering sites of pathogenic Alternaria alternata. Dogwood brown spot disease occurred in early May, and reached the peak incidence in mid August. The pathogen could infect dogwood healthy leaves with or without wounding.Propiconazole and prochloraz had stronger inhibitory effects against the pathogen in vitro, with the half maximal effective concentrations (EC50) of0.3368mg/L and0.4663mg/L, respectively.2. Based on morphological observation and molecular detection, the causal agent of dogwood leaf blight pathogen was identified as Peyronellaea glomerata (Corda) Goid. ex Togliani. The pathogen grew well at a pH range of2.0-9.5, with growth peaks at pH4and7. Of the12utilizable carbon sources and8utilizable nitrogen sources tested, glucose and carbamide were the best for vegetative growth of the pathogen, while xylose and carbamide were the best for sporulation. Peyronellaea glomerata could grow and produce spores on all of the tested media except the Czapek’s medium. The pathogen could produce protease, cellulase and pectinase on the media containing various matrixs. The activity of amylase could not be detected during the growth of the pathogen.Prochloraz and azoxystrobin had stronger inhibitory effects against the pathogen in vitro, with the EC50values of0.4211mg/L and0.6366mg/L, respectively.3. The causal agent of dogwood Pestalotiopsis leaf spot disease pathogen was identified as Pestalotiopsis foedan (Sacc.&Ellis) Steyaert. The pathogen grew at a pH range of4.0-9.5, with7.0as the optimum. Compared with the alkaline environment, the acidic environment was more suitable for mycelial growth. Pestalotiopsis foedan could not grow at temperatures lower than7℃or higher than34℃, with25℃as the optimum. Of the14utilizable carbon sources and7utilizable nitrogen sources tested, D-mannose and L-histidine were the best for vegetative growth of Pestalotiopsis foedan. The pathogen grew well on several tested media without sporulation. The activities of3extracellular enzymes (amylase, cellulase and pectinase) could be detected during growth of Pestalotiopsis foedan on the media containing various enzymatic matrixes. The activity of protease could not be observed during the growth of the pathogen.Prochloraz and propiconazole had stronger inhibitory effects against the pathogen in vitro, with the EC50values of0.0227mg/L and2.3815mg/L, respectively.

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CLC: > Agricultural Sciences > Plant Protection > Pest and Disease Control > Crop pests and diseases and their prevention > Economic crop pests and diseases > Medicinal crop pests and diseases > Woody crop pests and diseases
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