Vermicompost has become a promising alternative to chemical pesticide because of its disease suppression effect during these decades. However, the mechanisms by which vermicompost suppress plant disease are not well-u...Vermicompost has become a promising alternative to chemical pesticide because of its disease suppression effect during these decades. However, the mechanisms by which vermicompost suppress plant disease are not well-understood. Antifungal compounds, which are released by beneficial organisms in the vermicompost, may play an important role in inhibiting plant pathogens;however, these mechanisms have not been widely examined. In this study, Sterilized Water Extracts of bamboo vermicompost (SWE), using a 0.22-μm cellulose acetate filter, significantly (P < 0.05) inhibited the mycelium growth of Rhizoctonia solani AG1-IB on a Potato Dextrose Agar (PDA) plate. This suggests that antifungal compounds are present in bamboo vermicompost. The ethanol acetate (EtOAc) crude extracts of bamboo vermicompost showing antifungal activity were further separated. Two compounds were isolated from the EtOAc fraction of bamboo vermicompost and characterized as ergosterol peroxide (1) and (22E, 24R)-5α,8α-epidioxyergosta-6,9(11),22-trien-3β-ol (2). Their chemical structures and mass spectra were determined by nuclear magnetic resonance and mass spectrometry analyses. Ergosterol peroxide tested at 150, 300, 600, and 900 μg showed 13%, 22%, 34%, and 53% mycelial growth inhibition against R. solani AG1-IB, respectively. Because EtOAc crude extracts of the initial substrate materials of bamboo vermicompost did not inhibit mycelium growth of R. solani AG1-IB, antifungal compounds in the vermicompost may be released by microbes but not from the original substrates during vermicomposting.展开更多
【目的】明确中国南方水稻纹枯病菌不同地理群体的遗传结构,为研究该病害的流行规律提供信息。【方法】采用8个SSR荧光标记对收集自中国南方8省(自治区)的188个水稻纹枯病菌进行检测。利用POPGENE version 1.31软件计算各项遗传多样性参...【目的】明确中国南方水稻纹枯病菌不同地理群体的遗传结构,为研究该病害的流行规律提供信息。【方法】采用8个SSR荧光标记对收集自中国南方8省(自治区)的188个水稻纹枯病菌进行检测。利用POPGENE version 1.31软件计算各项遗传多样性参数,近交系数由FSTAT 2.9.3软件估算。基于马尔可夫链模型,采用GENEPOP 4.2软件以卡方检验估计Hardy-Weinberg平衡。应用Arlequin 3.1软件进行分子方差变异分析,并通过遗传分化系数计算基因流。基于Nei’s遗传距离,利用MEGA5.0软件构建UPGMA树状图。使用STRUCTURE 2.3.3软件的贝叶斯聚类法进行群体遗传结构分析,并估计群体间遗传混杂程度。采用Mantel test检测遗传距离与地理距离的相关性。【结果】8个地理群体的平均观测等位基因数和有效等位基因数分别为4.025和2.071。Shannon’s信息指数为0.659—1.088,平均为0.859。等位基因丰富度为2.500—5.152,平均为3.858。观测杂合度为0.425—0.619,平均为0.506。期望杂合度为0.399—0.546,平均为0.472。总群体水平的近交系数(FIS=-0.069)为负值,表明总群体内杂合子过剩(纯合子缺失)。Hardy-Weinberg平衡检验表明,在6个群体中存在因杂合子的缺失或过剩引起的平衡偏离,暗示了水稻纹枯病菌同时具有克隆生长和有性繁殖,两种繁殖方式间的平衡因群体而异。AMOVA分析结果显示,有88.14%的遗传变异来自群体内部的个体间,表明遗传变异主要发生在群体内。Mantel检测发现,遗传距离与其地理距离之间呈显著正相关(r=0.422,P=0.025)。UPGMA聚类表明,所有群体可被划分为遗传分化明显的两个亚群(FST=0.209—0.624),其中位于珠江沿岸的广宁和长塘群体为一个组群,而位于长江沿岸的6个群体为另一组群,与遗传结构分析结果一致。位于长江沿岸的群体遗传混杂明显,基因交流水平高(Nm=2.525—8.447),群体分化程度较低(FST=0.029—0.094)。【结论】中国南方水稻纹枯病菌分布范围广泛、可能的混合繁殖模式以及菌核或菌丝具有远距离传播特性,是导致其遗传多样性水平较高的原因。长江亚群内部个体在不同群体之间的迁移所形成的基因流动,在一定程度上阻止了群体间的遗传分化。而长江亚群和珠江亚群之间存在明显的遗传分化,推测病原菌有限的长距离迁移可能是群体遗传变异空间结构形成的主要原因。展开更多
文摘Vermicompost has become a promising alternative to chemical pesticide because of its disease suppression effect during these decades. However, the mechanisms by which vermicompost suppress plant disease are not well-understood. Antifungal compounds, which are released by beneficial organisms in the vermicompost, may play an important role in inhibiting plant pathogens;however, these mechanisms have not been widely examined. In this study, Sterilized Water Extracts of bamboo vermicompost (SWE), using a 0.22-μm cellulose acetate filter, significantly (P < 0.05) inhibited the mycelium growth of Rhizoctonia solani AG1-IB on a Potato Dextrose Agar (PDA) plate. This suggests that antifungal compounds are present in bamboo vermicompost. The ethanol acetate (EtOAc) crude extracts of bamboo vermicompost showing antifungal activity were further separated. Two compounds were isolated from the EtOAc fraction of bamboo vermicompost and characterized as ergosterol peroxide (1) and (22E, 24R)-5α,8α-epidioxyergosta-6,9(11),22-trien-3β-ol (2). Their chemical structures and mass spectra were determined by nuclear magnetic resonance and mass spectrometry analyses. Ergosterol peroxide tested at 150, 300, 600, and 900 μg showed 13%, 22%, 34%, and 53% mycelial growth inhibition against R. solani AG1-IB, respectively. Because EtOAc crude extracts of the initial substrate materials of bamboo vermicompost did not inhibit mycelium growth of R. solani AG1-IB, antifungal compounds in the vermicompost may be released by microbes but not from the original substrates during vermicomposting.
