Monacrosporium ellipsosporum, a nematode-trapping fungus, was isolated by baiting with sclerotiaof Sclerotinia sclerotiorum in soil from a tobacco field in Yuxi, Yunnan Province. Colonizationfrequency of the scleroti...Monacrosporium ellipsosporum, a nematode-trapping fungus, was isolated by baiting with sclerotiaof Sclerotinia sclerotiorum in soil from a tobacco field in Yuxi, Yunnan Province. Colonizationfrequency of the sclerotia by the fungus was 18% in natural soil. Reinoculation tests byplacing surface-sterilized sclerotia on fungal cultures for two weeks and then surface-sterilized again led to 32% sclerotia be infected. Dual culture tests in PDA plates did notgive rise to a suppression zone between the colonies of M. ellipsosporum and its counterpartfungi S. sclerotiorum and Rhizoctonia solani, suggesting there was little or no nutritionalcompetition and absent of antifungal compounds. However, M. ellipsosporum could grow overabsent of S. sclerotiorum and R. solani, and significantly inhibited their growth on agarplates. Scanning electron and light microscopic observations showed that hyphae of M. ellipsosporumgrew along and appressed on hypha of S. sclerotiorum and coiled around hyphae of R. solani.Assays of cell wall-degrading enzymes showed that M. ellipsosporum grew well in chitin agarmedia, with clear transparent hydrolysis zones. Activities of total chitinase, exo-chitinase,β-1, 3-glucanase and protease were 140.2±11.9, 82.9±4.1, 111.2±7.6 and 76.1±4.3 U respect-ively, after incubation for 4 days at 30 ℃ in liquid media containing ground sclerotia of S.sclerotiorum as sole nutrient source. These enzymes might be important in the mycoparasiticactivity of M. ellipsosporum.展开更多
A field under rice-wheat rotation was selected near Chengdu, China, to study thepopulation of Rhizoctonia solani anastomosis group 1 (AG-1), pathogen causing ricesheath blight disease, in natural soil ecosystem. Inocu...A field under rice-wheat rotation was selected near Chengdu, China, to study thepopulation of Rhizoctonia solani anastomosis group 1 (AG-1), pathogen causing ricesheath blight disease, in natural soil ecosystem. Inocula of the fungus recovered fromthe field were divided into three types, i.e., sclerotia, free mycelium retained in thesoil passed through a 0.355mm sieve, and colonized plant debris which was subdividedinto small colonized debris retained between 2.00 and 0.355mm sieves and large colonizeddebris retained on 2.00mm sieve after wet screening. Quantitative estimation of thethree types of inocula in one year indicated that small colonized debris was the dominantinoculum type for most of the time. The population peaked in March and September at 1210and 480 colonized debris 100g-1 air-dry soil respectively, and fell down in December andAugust to 0 and 177 colonized debris 100g-1 air-dry soil respectively. Free mycelium wasonly detectable in March, September and October with 1209, 7.9 and 14.5g fresh wtmyceliumg-1 air-dry soil respectively, which corresponded to the two peaks and the secondhighest level of small debris density in the year. Viable sclerotia and large colonizeddebris were rare with populations ranging from 0 to 3 for sclerotia and 0 to 14 for largecolonized debris 100g-1 air-dry soil, but were the main structures to survive overwinter. It was expected that soil temperature was the main factor determining populationdynamics of R.solani AG-1 in natural soil. Optimum temperature for population increasingis predicted to be around 15℃, with a range from 10 to 25℃. Viability tests indicatedthat 60.9% sclerotia could survive after 265d being buried in natural sandy loam in fieldconditions in Beijing, while colonized rice straw debris (0.5-1.0cm long) could notyield the fungus on medium plates after 88d of being buried under the same conditions.展开更多
基金supported by the National High-Tech R&D Proqram(863)of China(2001AA246011).
文摘Monacrosporium ellipsosporum, a nematode-trapping fungus, was isolated by baiting with sclerotiaof Sclerotinia sclerotiorum in soil from a tobacco field in Yuxi, Yunnan Province. Colonizationfrequency of the sclerotia by the fungus was 18% in natural soil. Reinoculation tests byplacing surface-sterilized sclerotia on fungal cultures for two weeks and then surface-sterilized again led to 32% sclerotia be infected. Dual culture tests in PDA plates did notgive rise to a suppression zone between the colonies of M. ellipsosporum and its counterpartfungi S. sclerotiorum and Rhizoctonia solani, suggesting there was little or no nutritionalcompetition and absent of antifungal compounds. However, M. ellipsosporum could grow overabsent of S. sclerotiorum and R. solani, and significantly inhibited their growth on agarplates. Scanning electron and light microscopic observations showed that hyphae of M. ellipsosporumgrew along and appressed on hypha of S. sclerotiorum and coiled around hyphae of R. solani.Assays of cell wall-degrading enzymes showed that M. ellipsosporum grew well in chitin agarmedia, with clear transparent hydrolysis zones. Activities of total chitinase, exo-chitinase,β-1, 3-glucanase and protease were 140.2±11.9, 82.9±4.1, 111.2±7.6 and 76.1±4.3 U respect-ively, after incubation for 4 days at 30 ℃ in liquid media containing ground sclerotia of S.sclerotiorum as sole nutrient source. These enzymes might be important in the mycoparasiticactivity of M. ellipsosporum.
文摘A field under rice-wheat rotation was selected near Chengdu, China, to study thepopulation of Rhizoctonia solani anastomosis group 1 (AG-1), pathogen causing ricesheath blight disease, in natural soil ecosystem. Inocula of the fungus recovered fromthe field were divided into three types, i.e., sclerotia, free mycelium retained in thesoil passed through a 0.355mm sieve, and colonized plant debris which was subdividedinto small colonized debris retained between 2.00 and 0.355mm sieves and large colonizeddebris retained on 2.00mm sieve after wet screening. Quantitative estimation of thethree types of inocula in one year indicated that small colonized debris was the dominantinoculum type for most of the time. The population peaked in March and September at 1210and 480 colonized debris 100g-1 air-dry soil respectively, and fell down in December andAugust to 0 and 177 colonized debris 100g-1 air-dry soil respectively. Free mycelium wasonly detectable in March, September and October with 1209, 7.9 and 14.5g fresh wtmyceliumg-1 air-dry soil respectively, which corresponded to the two peaks and the secondhighest level of small debris density in the year. Viable sclerotia and large colonizeddebris were rare with populations ranging from 0 to 3 for sclerotia and 0 to 14 for largecolonized debris 100g-1 air-dry soil, but were the main structures to survive overwinter. It was expected that soil temperature was the main factor determining populationdynamics of R.solani AG-1 in natural soil. Optimum temperature for population increasingis predicted to be around 15℃, with a range from 10 to 25℃. Viability tests indicatedthat 60.9% sclerotia could survive after 265d being buried in natural sandy loam in fieldconditions in Beijing, while colonized rice straw debris (0.5-1.0cm long) could notyield the fungus on medium plates after 88d of being buried under the same conditions.
