In 2020,diseased seedlings of winter oilseed rape(Brassica napus)with cankered taproots as well as abundant sclerotium-like structures in the soil surrounding the roots were found in Longxi County of Gansu province of...In 2020,diseased seedlings of winter oilseed rape(Brassica napus)with cankered taproots as well as abundant sclerotium-like structures in the soil surrounding the roots were found in Longxi County of Gansu province of northwestern China.A fungus with production of pycnidia was isolated from the diseased roots,and it was identified based on morphological characteristics,molecular phylogeny(ITS,LSU)and PCR detection with the specific primers.The fungus was identified as Leptosphaeria sclerotioides Gruyter,Aveskamp&Verkley[anamorph:Phoma sclerotioides(Preuss)ex Sacc.].Re-inoculation of isolates of P9 and P10 of L.sclerotioides on winter oilseed rape(B.napus cultivar‘Zhongshuang No.9’)in Wuhan caused formation of abundant sclerotium-like structures in soil surrounding the roots,but failed to produce root cankers as those observed in Gansu possibly due to lack of long peroid of low-temperature conditioning in Wuhan.In spite of this,plant height,pod number and seed yield of oilseed rape were significantly reduced in the treatment with L.sclerotioides P9 and P10,compared to the control treatment.To the best of our knowledge,this is the first report of L.sclerotioides on B.napus in China and the finding broadened our understanding about the natural distribution of this psychrophilic fungus.展开更多
Leptosphaeria maculans is a serious concern for canola production worldwide.For effective disease management,knowledge of the pathogen’s genetic variability and population structure is a prerequisite.In this study,wh...Leptosphaeria maculans is a serious concern for canola production worldwide.For effective disease management,knowledge of the pathogen’s genetic variability and population structure is a prerequisite.In this study,whole-genome sequencing was performed for 162 of 1590 L.maculans isolates collected in the years 2007e2008 and 2012e2014 in Western Canada.DNA variants in genome-wide and specific regions including avirulence(Avr)genes were characterized.A total of 31,870 high-quality polymorphic DNA variants were used to study L.maculans genetic diversity and population structure.Cluster analysis showed that 150 isolates were clustered into 2 main groups and 4 subgroups by DNA variants located in either Avr or small secreted protein-encoding genes and into 2 main groups and 6 subgroups by genome-wide variants.The analysis of nucleotide diversity and differentiation also confirmed genetic variation within a population and among populations.Principal component analysis with genome-wide variants showed that the isolates collected in 2012e2014 were more genetically diverse than those collected in 2007e2008.Population structure analysis discovered three distinct sub-populations.Although isolates from Saskatchewan and Alberta were of similar genetic composition,Manitoba isolates were highly diverse.Genome-wide association study detected DNA variants in genes AvrLm4-7,Lema_T86300,and Lema_T86310 associated with the years of collection.展开更多
Leptosphaeriaceae is a family in the order Pleosporales comprising economically important plant pathogens.Species may also be endophytes or saprobes on various host plants.In recent classifications Alternariaster,Lept...Leptosphaeriaceae is a family in the order Pleosporales comprising economically important plant pathogens.Species may also be endophytes or saprobes on various host plants.In recent classifications Alternariaster,Leptosphaeria,Neophaeosphaeria,Paraleptosphaeria,Heterospora,Subplenodomus and Plenodomus were included in the family.The taxonomy of genera and species in Leptosphaeriaceae has been problematic due to the lack of understanding of the importance of morphological characters used to distinguish taxa,as well as the lack of reference strains.In order to establish evolutionary relationships and to provide a backbone tree for Leptosphaeria and allied genera,we sequenced the 18S nrDNA,28S nrDNA,ITS,RPB2,TEF and ACT gene regions of Leptosphaeriaceae species and analysed this data.Multi-locus phylogenies together with morphology robustly support the monophyletic nature of Leptosphaeriaceae among the other families in Pleosporales,and the inclusion of the genera Alternariaster,Heterospora,Leptosphaeria,Paraleptosphaeria,Sphaerellopsis,Subplenodomus,Plenodomus and three novel genera Alloleptosphaeria,Neoleptosphaeria and Pseudoleptosphaeria.Five new species,Alternariaster centaureae-diffusae,Leptosphaeria cichorium,Paraleptosphaeria rubi,Plenodomus guttulatus and P.salviae are introduced.An account of sexual morph of Alternariaster centaureae-diffusae is provided,and the sexual morph of Leptosphaeria doliolum is re-described and illustrated using modern concepts from fresh collections.A novel family Neophaeosphaeriaceae is established to accommodate the genus Neophaeosphaeria and its species.展开更多
41 fungal isolates with similar morphological characteristics to Leptosphaeria maculans were obtained by the deep-freezing filter paper method from 2100 seeds of Brassica napus imported from Australia.The isolate 8129...41 fungal isolates with similar morphological characteristics to Leptosphaeria maculans were obtained by the deep-freezing filter paper method from 2100 seeds of Brassica napus imported from Australia.The isolate 8129-5 showed a slower growth on PDA at 20℃with growth rate of 2.8 mm/day.The colonies on PDA at 20℃ had an irregular or regular margin with white or grayish white compact aerial mycelium.No diffusible pigment was produced on PDA at 31℃ or in liquid Czapek-Dox media at 20℃.PCR detection showed that the isolate 8129-5 could be amplified by L.maculans-specific primers LmacF/LmacR and got expected product of 331 bp.The sequence analysis revealed that the ITS sequence of isolate 8129-5 had 99.8% identity with L.maculans.Pathogenicity of the isolate 8129-5 was confirmed on cotyledons of rape seed by artificial inoculation compared with typical symptom of L.maculans.Based on the morphological characteristics,PCR detection and the result of pathogenicity test,the isolate 8129-5 was identified as L.maculans.展开更多
基金supported by the Earmarked Fund for CARS-12 from National Modern Agricultural Technology System.
文摘In 2020,diseased seedlings of winter oilseed rape(Brassica napus)with cankered taproots as well as abundant sclerotium-like structures in the soil surrounding the roots were found in Longxi County of Gansu province of northwestern China.A fungus with production of pycnidia was isolated from the diseased roots,and it was identified based on morphological characteristics,molecular phylogeny(ITS,LSU)and PCR detection with the specific primers.The fungus was identified as Leptosphaeria sclerotioides Gruyter,Aveskamp&Verkley[anamorph:Phoma sclerotioides(Preuss)ex Sacc.].Re-inoculation of isolates of P9 and P10 of L.sclerotioides on winter oilseed rape(B.napus cultivar‘Zhongshuang No.9’)in Wuhan caused formation of abundant sclerotium-like structures in soil surrounding the roots,but failed to produce root cankers as those observed in Gansu possibly due to lack of long peroid of low-temperature conditioning in Wuhan.In spite of this,plant height,pod number and seed yield of oilseed rape were significantly reduced in the treatment with L.sclerotioides P9 and P10,compared to the control treatment.To the best of our knowledge,this is the first report of L.sclerotioides on B.napus in China and the finding broadened our understanding about the natural distribution of this psychrophilic fungus.
文摘Leptosphaeria maculans is a serious concern for canola production worldwide.For effective disease management,knowledge of the pathogen’s genetic variability and population structure is a prerequisite.In this study,whole-genome sequencing was performed for 162 of 1590 L.maculans isolates collected in the years 2007e2008 and 2012e2014 in Western Canada.DNA variants in genome-wide and specific regions including avirulence(Avr)genes were characterized.A total of 31,870 high-quality polymorphic DNA variants were used to study L.maculans genetic diversity and population structure.Cluster analysis showed that 150 isolates were clustered into 2 main groups and 4 subgroups by DNA variants located in either Avr or small secreted protein-encoding genes and into 2 main groups and 6 subgroups by genome-wide variants.The analysis of nucleotide diversity and differentiation also confirmed genetic variation within a population and among populations.Principal component analysis with genome-wide variants showed that the isolates collected in 2012e2014 were more genetically diverse than those collected in 2007e2008.Population structure analysis discovered three distinct sub-populations.Although isolates from Saskatchewan and Alberta were of similar genetic composition,Manitoba isolates were highly diverse.Genome-wide association study detected DNA variants in genes AvrLm4-7,Lema_T86300,and Lema_T86310 associated with the years of collection.
文摘Leptosphaeriaceae is a family in the order Pleosporales comprising economically important plant pathogens.Species may also be endophytes or saprobes on various host plants.In recent classifications Alternariaster,Leptosphaeria,Neophaeosphaeria,Paraleptosphaeria,Heterospora,Subplenodomus and Plenodomus were included in the family.The taxonomy of genera and species in Leptosphaeriaceae has been problematic due to the lack of understanding of the importance of morphological characters used to distinguish taxa,as well as the lack of reference strains.In order to establish evolutionary relationships and to provide a backbone tree for Leptosphaeria and allied genera,we sequenced the 18S nrDNA,28S nrDNA,ITS,RPB2,TEF and ACT gene regions of Leptosphaeriaceae species and analysed this data.Multi-locus phylogenies together with morphology robustly support the monophyletic nature of Leptosphaeriaceae among the other families in Pleosporales,and the inclusion of the genera Alternariaster,Heterospora,Leptosphaeria,Paraleptosphaeria,Sphaerellopsis,Subplenodomus,Plenodomus and three novel genera Alloleptosphaeria,Neoleptosphaeria and Pseudoleptosphaeria.Five new species,Alternariaster centaureae-diffusae,Leptosphaeria cichorium,Paraleptosphaeria rubi,Plenodomus guttulatus and P.salviae are introduced.An account of sexual morph of Alternariaster centaureae-diffusae is provided,and the sexual morph of Leptosphaeria doliolum is re-described and illustrated using modern concepts from fresh collections.A novel family Neophaeosphaeriaceae is established to accommodate the genus Neophaeosphaeria and its species.
文摘41 fungal isolates with similar morphological characteristics to Leptosphaeria maculans were obtained by the deep-freezing filter paper method from 2100 seeds of Brassica napus imported from Australia.The isolate 8129-5 showed a slower growth on PDA at 20℃with growth rate of 2.8 mm/day.The colonies on PDA at 20℃ had an irregular or regular margin with white or grayish white compact aerial mycelium.No diffusible pigment was produced on PDA at 31℃ or in liquid Czapek-Dox media at 20℃.PCR detection showed that the isolate 8129-5 could be amplified by L.maculans-specific primers LmacF/LmacR and got expected product of 331 bp.The sequence analysis revealed that the ITS sequence of isolate 8129-5 had 99.8% identity with L.maculans.Pathogenicity of the isolate 8129-5 was confirmed on cotyledons of rape seed by artificial inoculation compared with typical symptom of L.maculans.Based on the morphological characteristics,PCR detection and the result of pathogenicity test,the isolate 8129-5 was identified as L.maculans.
