Epirrita autumnata induced VOC emission of silver birch differ from emission induced by leaf fungal pathogen

The production of volatile organic compounds (VOCs) through the activation of different signal-transduction pathways may be induced in various biotic and abiotic stress situations having importance e.g. in insect and disease resistance. We compared the emission of VOCs emitted from silver birch Betula pendula Roth (clones 4 and 80) twigs damaged either by larvae of Epirrita autumnata, or infected with pathogenic leaf spot causing fungus Marssonina betulae. We also analysed whether local herbivore damage can systemically induce the release of VOCs from the undamaged top of same sapling. The emissions of methylsalicylate (MeSA), (Z)-ocimene, (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and linalool were induced from the twigs after 72 h feeding damage by E. autumnata larvae. However, 48 h feeding damage did not induce rapid systemic release of VOCs from undamaged top leaves of the same twigs. Pathogen-infected birch twigs had significantly greater emission of (Z)-ocimene and (E)-β-ocimene than intact control twigs. The emission of DMNT was not significantly induced and MeSA was not found at all after pathogen infection, both being significantly different from herbivore damaged twigs. According to our results leaf fungal pathogen induces VOC emission profile differs from that of arthropod herbivore-damaged leaves, suggesting that birch is able to transmit parasite-specific information via VOC emissions to conspecifics and natural enemies of herbivores. Handling editor: Yvan Rahbé     

西北地区苹果褐斑病数学预测模型建立与分析

依据2001～2010年我国西北苹果主产区的气象数据与苹果褐斑病(Marssonina coronaria)病害发生流行数据,构建了平均气温(T)、相对湿度(Hm)、风速(Ws)及地表温度(St)影响下苹果褐斑病的流行趋势预测模型,并利用多元回归分析方法建立了苹果褐斑病预测模型.结果表明环境因素严重影响苹果褐斑病的发生和流行,苹果褐斑病预测模型为:f(T,Hm,Ws,St)=1.317T+0.002Hm+0.047Ws+0.001St-11.885[f(T,Hm,Ws,St)为病情指数].苹果褐斑病发生的T为14℃～15℃,Hm为45%,Ws为13m/s,St为10℃.大发生条件为T为20℃～23℃,Hm在70%～90%之间,Ws为0m/s～2m/s及St为22°.     

Assessment of real-time PCR for quantification of Legionella spp. in spa water

Aim: To identify media and environmental conditions suitable for rapid mycelial growth and sporulation of Diplocarpon mali. Methods and Results: Liquid shake cultures were used to evaluate effects of media and environmental conditions on mycelial growth and conidial production of D. mali. Carrot sucrose broth (CSB), potato and carrot dextrose broth (PCDB) and potato and carrot sucrose broth (PCSB) were most favourable for rapid mycelial growth. PCDB, PCSB, PCB (potato and carrot broth) and carrot dextrose broth (CDB) were favourable for conidial production. All carbon sources tested and peptone favoured for mycelial growth. Carbon and nitrogen sources tested did not significantly stimulate conidial production. The optimum temperature for mycelial growth and conidial production was 25°C. No mycelial growth occurred at 5 or 30°C, but D. mali survived at these temperatures. Active mycelial growth occurred at pH 5–7, and pH 5–8 was favourable for sporulation. Conclusions: PCDB and PCSB incubated at 25°C for 14 day are recommended for mycelial growth and conidial production of D. mali. Significance and Impact of the Study: The information generated in this study will facilitate mycological and pathological research on D. mali and Marssonina leaf blotch of apple caused by D. mali.     

莴笋炭疽病病原鉴定

【背景】2018年7-8月,甘肃省兰州市永登县武胜驿镇种植的莴笋大面积发生炭疽病,约40%的地块发病,绝收面积达10%。【目的】明确莴笋炭疽病的病原。【方法】采用组织分离法进行病原菌分离;通过Koch’s法则明确分出病菌的致病性;采用形态学和分子生物学方法对病原菌进行种类鉴定。【结果】分离得到形态特征一致的真菌菌株3株。在PDA平板上20°C培养7 d,病菌分生孢子无色,单隔,梭形,(10.44-19.40)μm×(2.61-4.48)μm。代表性菌株Lett-11接种莴笋离体叶片可引起与自然发病相似的症状。BLASTn分析结果显示,菌株Lett-11 (GenBank登录号MK252097)的r DNA-ITS序列与莴苣盘二孢菌Marssonina panattoniana strain CBS 163.25 (GenBank登录号MH854831.1)的序列相似性达99%。【结论】引起莴笋炭疽病的病原菌被鉴定为莴苣盘二孢菌Mar. panattoniana [Synonymy:Microdochium panattonianum],这是莴苣盘二孢菌引起莴笋炭疽病在甘肃的首次报道。     

Host effect on genetic variation of Marssonina brunnea pathogenic to poplars

A broad collection was made for 42 isolates of Marssonina brunnea affecting poplar trees from three different sections (Leuce, Aigeiros and Tacamahaca) within the same Populus genus in China. Genetic diversity among these isolates was analyzed for morphological traits, cultural features, pathogenicity, hyphal anastomosis and randomly amplified polymorphic DNA markers (RAPDs). No significant difference was found in conidial morphological features, such as size, shape and septum location. Yet, considerable differences occur in other characteristics, which leads to the classification of the 42 isolates into two distinct groups, M. brunnea f.sp. monogermtubi and M. brunnea f.sp. multigermtubi. Isolates of M. brunnea f.sp. monogermtubi, derived from section Leuce, germinate only one germ tube, grow fast, produce dark-reddish conidiosorus clusters on the PDA medium, and are highly pathogenic to Populus tomentosa of section Leuce. By contrast, isolates of M. brunnea f.sp. multigermtubi, derived from sections Aigeiros and Tacamahaca, germinate 1–5 germ tubes, grow slowly, produce yellow-greenish conidiosorus clusters on PDA medium, and are pathogenic to Populus ×euramericana cv I-45 and Populus canadensis of section Aigeiros. DNA amplification using 11 RAPD primers generate 78 polymorphic bands among isolates. Cluster analyses based on RAPD markers broadly support such a classification by phenotypes, but provide a new insight into the possible origins of M. brunnea. It is proposed that the pathogen co-evolves with the poplars of section Leuce and has been subsequently distributed to the poplars of sections Aigeiros and Tacamahaca. An isolate from Populus adenopoda of section Leuce is placed in the third group, which is most likely a transmission type from M. brunnea f.sp. monogermtubi to M. brunnea f.sp. multigermtubi. Received: 20 May 1999 / Accepted: 30 July 1999