Molecular Characterization,Morphology and Pathogenicity of Curvularia pseudobrachyspora,A New Causal Agent of Leaf Spot on Banana

[Objectives]The paper was to study molecular characterization,morphology and pathogenicity of Curvularia pseudobrachyspora,a new causal agent of leaf spot on banana.[Methods]Banana(Musa acuminate)leaves with streaks or long ellipse-shaped lesions were sampled in an orchard of Danzhou City,Hainan Province,China in 2021.Fungus isolates were isolated from the diseased tissues and further identified as C.pseudobrachyspora based on morphological characteristics of colony,conidiophore and spore,phylogenetic analyses of the ITS region,GAPDH and TEF-1αgenes.[Results]In the pathogenicity test,the fungus re-isolated from inoculated leaves with necrotic lesions was identified morphologically and molecularly,fulfilling Koch's postulates.[Conclusions]C.pseudobrachyspora is a new pathogen causing leaf spot of banana in China and the world.

Morphological and Molecular Identification of Alternaria alternata Causing Leaf Spot Disease on Huangdi Banana in China

[Objectives]The paper was to identify Alternaria alternata causing leaf spot disease on Huangdi banana in China.[Methods]Fungal isolates were isolated and identified by morphological features,molecular identification and pathogenicity test.[Results]There were light to dark brown,tiny oval spots on leaves.The causal agent isolated from affected leaves was identified as A.alternata based on the morphological properties,coupled with sequence analyses of the internal transcribed spacer(ITS)region,large subunit ribosomal DNA(LSU rDNA)and the translation elongation factor 1-alpha(TEF-1α)gene.Koch s postulates were fulfilled by successful re-isolation of pathogen from the artificial inoculated leaves.[Conclusions]To our knowledge,this is the first report of leaf spot caused by A.alternata on Huangdi banana in China.The identification of A.alternata as the causal agent of the observed leaf spot disease on Huangdi banana is critical to the prevention and control of this disease in the future.

Characterization of Neopestalotiopsis clavispora , A New Etiological Agent of Leaf Spot Isolated from Banana

[Objectives]The study was to confirm the etiological agent of leaf spot on banana in Yunnan Province of China.[Methods]Fungus isolates were isolated from the diseased tissues,and cultured to observe the morphological characteristics of colony and spore.Furthermore,phylogenetic analyses and pathogenicity test were also conducted to confirm the pathogen.[Results]The fungus isolated from the diseased tissues was identified as Neopestalotiopsis clavispora.[Conclusions]N.clavispora is a new pathogen causing leaf spot of banana.This research provides the first description of N.clavispora as a causal agent on banana in China,and adds new insights related to the host range of N.clavispora.

Morphological and Molecular Identification of Curvularia geniculata Associated with Leaf Spot Disease of Banana in China

[Objectives]The paper was to identify the causal agent of leaf spot of banana in Hainnan,China.[Methods]Fungus isolates were isolated from the diseased tissues,and morphological characteristics of colony and spore were observed.Furthermore,phylogenetic analyses and pathogenicity test were conducted to confirm the pathogen.[Results]The fungus isolates from the diseased tissues was identified as Curvularia geniculata.[Conclusions]C.geniculata is a new pathogen causing leaf spot of banana in Hainan,China.This finding will help to broaden the distribution and host range of C.geniculata,indicating that it poses potential damage to banana in China.

Inhibitory Effects of Six Fungicides against Neocordana musae

[Objective]The paper was to screen effective fungicides to control Cordana leaf spot caused by Neocordana musae.[Method]The toxicities of six fungicides against mycelial growth of N.musae were measured by the method of mycelium growth inhibition.[Result]The average EC50 values of six fungicides against mycelial growth ranged from 0.1029 to 504.065μg/mL.Among them,22.5%picoxystrobin SC and 12.5%epoxiconazole SC showed strong inhibitory activity on mycelial growth,with the average EC50 values of 0.1029 and 0.6851μg/mL,respectively;followed by 50%thiophanate-methyl SC,with an average EC50 value of 1.993.80%Azoxystrobin WG showed a relatively low sensitivity against N.musae,with an average EC50 value of 504.046.[Conclusion]The six fungicides tested have great value in preventing and controlling Cordana leaf spot.22.5%Picoxystrobin SC,12.5%epoxiconazole SC and 50%thiophanate-methyl SC have better inhibitory activities on mycelial growth of N.musae,and can be further used in field trials.

有机工质向心透平变工况特性的数值模拟与极差分析

以R245fa为工质设计向心透平,采用CFD方法对向心透平性能进行全流域三维模拟研究,考察了入口温度、转子转速和膨胀比(进出口压力比)对向心透平工况特性的影响,对主要影响因素进行极差分析。结果表明,向心透平工作转速为设计转速的80%～100%时,输出功率和等熵效率波动较小,工作转速高于设计值时透平性能迅速下降。随入口温度升高,透平输出功率与等熵效率增大;随膨胀比增大,透平输出功率线性增加。透平存在最佳膨胀比使等熵效率最大,且实际运行压比大于最佳膨胀比时,透平等熵效率变化较小。出口压力对向心透平输出功率影响最大,温度的影响最小;转子转速对等熵效率影响最大,入口压力的影响最小。