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对从广西28个市、县不同稻区采集的水稻纹枯病株上分离获得的186个类似丝核菌的真菌分离物进行系统研究。根据病原菌的培养性状、菌核大小、菌株生长最适温度和生长速率等形态学方法进行初步分类,然后利用rDNA的PCR-RFLP和序列分析法作进一步鉴定。结果表明,所有供试分离物可分为5个不同菌系,分别为立枯丝核菌(Rhizoctoniasolani AG1-IA)、水稻丝核菌(Rhizoctonia oryzae-sativae)、水稻枯斑丝核菌(Rhizoctonia oryzae)、双核丝核菌的AG-A融合群真菌(Rhizoctoniasp AG-A)、嗜水小核菌(Sclerotium hydrophilum)。其中,Rhizoctonia oryzae、Rhizoctonia sp AG-A、Sclerotium hydrophilum3个菌系在广西为首次报道。致病力测定结果表明,5个菌系均能侵染水稻并引起相似的纹枯病症状,但致病力大小差异较大,其中R. solani AG1-IA是引起广西水稻纹枯病的主要的优势菌系,出现频率最高,致病力最强,其余4个菌系致病力相对比较弱,致病力强弱顺序为R. solani AG1-IA>R. oryzae>R. oryzae-sativae>S. hydrophilum>Rhizoctoniasp AG-A。测定不同菌系对水稻纹枯病防治上几种常规用药的敏感性,表明菌系间的药剂敏感性存在明显差异。研究结果揭示与广西水稻纹枯病相关菌系遗传结构的复杂性,除了常见典型水稻纹枯病菌R.solaniAG1-IA以外,其他不同遗传特性菌系的存在可能是导致该病害难以防治的一个重要原因,在今后水稻生产和病害防治上应引起重视。
A total of 186 fungi isolates from Rhizoctonia solani isolated from rice sheath blight isolates collected from 28 cities and counties in Guangxi were systematically studied. According to the characterization of pathogenic bacteria, sclerotial size, optimum growth temperature and growth rate, the morphological methods were used for preliminary classification and further identification by rDNA PCR-RFLP and sequence analysis. The results showed that all the tested isolates could be divided into five different strains, Rhizoctonia solani (Rhizoctonia solani AG1-IA), Rhizoctonia oryzae-sativae, Rhizoctonia oryzae, Rhizoctonia psoraleae AG-A, Sclerotium hydrophilum. Among them, three strains of Rhizoctonia oryzae, Rhizoctonia sp AG-A and Sclerotium hydrophilum were reported in Guangxi for the first time. The results of pathogenicity test showed that all five bacterial strains could infect rice and cause similar symptoms of sheath blight, but the pathogenicity varied greatly, among which R. solani AG1-IA was the main cause of rice sheath blight in Guangxi Of the dominant strains, the highest frequency of occurrence, the strongest virulence, the other four strains of pathogenicity is relatively weak, the order of the virulence of the pathogenicity of R. solani AG1-IA> R. oryzae> R. oryzae-sativae > S. Hydrophilum> Rhizoctoniasp AG-A. The sensitivity of different strains to the control of several rice sheath blight diseases was determined, indicating that there was a significant difference in drug sensitivity between strains. The results revealed that the genetic structure of rice sheath blight associated with the complexity of Guangxi, in addition to the common typical Rhizoctonia solaniAG1-IA outside, the existence of other genetic characteristics of the strain may lead to the disease is difficult to prevent a Important reason, in the future rice production and disease prevention should pay attention.