| Camellia oleifera is an important edible woody oil plant (family Theaceae) in southern China, which has high economic value and oil content. It is one of the most famous and endemic oil plants in China. In recent years, a serious disease with Camellia oleifera Anthracnose has been outbreaking in Hubei province, which resulted in great economic losses. The objectives of work were to figure out the pathogen of Camellia oleifera Anthracnose and its biological characteristics, and to find suitable control methods for the disease.Several Colletotrichum sp. isolated were obtained from diseased leaves and fruits of Camellia oleifera in nursery of Hongan county, Macheng city and Yangxin city, Hubei province. The pathogenicity tests were performed using conidial suspension or mycelial of Colletotrichum sp. on young and healthy leaves of Camellia oleifera, and the Colletotrichum sp. Isolates were confirmed to pathogenic to Camellia oleifera Anthracnose. Isolations were transferred onto PDA plates and showed circular colonies. These were first colourless, and turned grey or sandy beige on the upper surface after5days of incubations on PDA. Conidia were clavate, single cell, colorless,9to18×3to5.5um in size with oil bubble. Acervulus were130-295um in diameter, with black bristles around. ITS sequences from three isolates were compared with sequences in NCBI, and shared the highest homology with Colletotrichum gloeosporioides and Glomerella cingulata. By neighbor-joining method, the phylogenetic tree of the ITS1-5.8S-ITS2sequences from Colletotrichum species was constructed. Colletotrichum gloeosporioides (FJ550213.1, HQ645073.1and AF203450), G. cingulata (AB042315.1and GQ410773.1) and isolates YX-1, MC-8were grouped together. C. gloeosporioides (FJ459929.1) and HA-7were grouped together. Based on culture characteristics, and results of ITS sequencing, these three isolates was identified as C. gloeosporioides Penz..The casual agent grew on PDA plates nommally with or without light. The24h light was the most favorable condition for mycelial growth, and condition of1h/1h light/dark was the best for conidial germination. The temperature of30℃was the most suitable for conidial germination and. mycelial growth Mycelia could grow on PDA of which pH was from3.0to11.0, and the optimal pH was6.0. And the conidia germination shared the similar pH feature. For testing utilization of carbon and nitrogen sources, soluble starch carbon and urea nitrate were the best for mycelial growth. Mannitol carbon and glycine nitrate were the most favorable for sporulation. The lethal temperatures for mycelia and conidia were both55℃,10min.Overwinter survival test indicated that C. gloeosporioides mainly infected latently in receptacles, young fruit, disease tissues and diseased plant debris of Camellia oleifera by, and mycelia became the primary source for infection. Conidia could also survive in the diseased plant debris of Camellia oleifera in winter, however, detected rate of spores in diseased spots on leaves was very low.In2011, occurrence of Camellia oleifera Anthracnose was first observed on the newborn leaves in late April and on the fruits in early May. At the early stage, brown spots appeared on a few newborn leaves and fruits with slow-growing disease severity. During early June and early September, disease increased significantly and symptom of brown spots was observed on a large number of leaves and fruits.The inhibition of ten fundicides to mycelia growth was tested.40%Flusilazole EC,10%Difenoconazole WG,25%Propiconazole EC and12.5%Tebuconazole WP showed the highest inhibitory efficiacy with the EC50at0.1011mg/L,0.1680mg/L,0.2425mg/L and0.3014mg/L while80%Mancozeb WP was the lowest one with EC50at389.5424mg/L. In2011, field trials for disease control were set up and the results indicated that the best control efficacy was observed with40%Flusilazole EC2000x and10%Difenoconazole WG4500x while the worst control efficacy was found on treatment of12.5%Tebuconazole WP3000x. |
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