Biotransformation of l‐menthol by twelve isolates of soil‐borne plant pathogenic fungi (Rhizoctonia solani) and classification of fungi

The microbial transformation of l‐menthol ( 1 ) was investigated by using 12 isolates of soil‐borne plant pathogenic fungi, Rhizoctonia solani (AG‐1‐IA Rs24, Joichi‐2, RRG97‐1; AG‐1‐IB TR22, R147, 110.4; AG‐1‐IC F‐1, F‐4, P‐1; AG‐1‐ID RCP‐1, RCP‐3, and RCP‐7) as a biocatalyst. Rhizoctonia solani F‐1, F‐4 and P‐1 showed 89.7–99.9% yields of converted product from 1 , RCP‐1, RCP‐3, and RCP‐7 26.0–26.9% and the other isolates 0.1–12.0%. In the cases of F‐1, F‐4 and P‐1, substrate 1 was converted to (?)‐(1S,3R,4S,6S)‐6‐hydroxymenthol ( 2 ), (?)‐(1S,3R,4S)‐1‐hydroxymenthol ( 3 ) and (+)‐(1S,3R,4R,6S)‐6,8‐dihydroxymenthol ( 4 ), which was a new compound. Substrate 1 was converted to 2 and/or 3 by RRG97‐1, 110.4, RCP‐1, RCP‐3 and RCP‐7. The structures of the metabolic products were elucidated on the basis of their spectral data. In addition, metabolic pathways of the biotransformation of 1 by Rhizoctonia solani are discussed. Finally, from the main component analysis and the differences in the yields of converted product from 1 , the 12 isolates of Rhizoctonia solani were divided into three groups based on an analysis of the metabolites. Copyright © 2003 Society of Chemical Industry     

百菌清及其三氟衍生物对番茄早疫病菌的室内抑菌活性比较

采用生长速率法测定了不同浓度的百菌清及其三氟衍生物对番茄早疫病菌Alternaria solani(Ell,et Mart.)Jones es Gmut的室内杀菌毒力。试验结果表明，百菌清及其三氟衍生物的ED50值分别为6089．89mg／L和156．43mg/L。，前者是后者的38．93倍。百菌清三氟衍生物的毒力明显高于百菌清。     

The Periplasmic Oxidoreductase DsbA Is Required for Virulence of the Phytopathogen Dickeya solani

In bacteria, the DsbA oxidoreductase is a crucial factor responsible for the introduction of disulfide bonds to extracytoplasmic proteins, which include important virulence factors. A lack of proper disulfide bonds frequently leads to instability and/or loss of protein function; therefore, improper disulfide bonding may lead to avirulent phenotypes. The importance of the DsbA function in phytopathogens has not been extensively studied yet. Dickeya solani is a bacterium from the Soft Rot Pectobacteriaceae family which is responsible for very high economic losses mainly in potato. In this work, we constructed a D. solani dsbA mutant and demonstrated that a lack of DsbA caused a loss of virulence. The mutant bacteria showed lower activities of secreted virulence determinants and were unable to develop disease symptoms in a potato plant. The SWATH-MS-based proteomic analysis revealed that the dsbA mutation led to multifaceted effects in the D. solani cells, including not only lower levels of secreted virulence factors, but also the induction of stress responses. Finally, the outer membrane barrier seemed to be disturbed by the mutation. Our results clearly demonstrate that the function played by the DsbA oxidoreductase is crucial for D. solani virulence, and a lack of DsbA significantly disturbs cellular physiology.     

5种杀菌剂对半夏立枯病的室内毒力测定

对半夏立枯病发生特点进行调查,进行了病原菌的分离、培养,选用5种杀菌剂进行了室内筛选试验.结果表明,引起半夏立枯病的病原菌为立枯丝核菌(Rhizoctonia solani Kuhn.).在供试杀菌剂中,80%退菌特WP对半夏立枯菌丝生长有明显抑制作用.     

烯唑醇对水稻重要病原菌的毒力测定及复配研究

烯唑醇对稻纹枯病菌、稻瘟病菌和稻曲病菌具有很强的抑制效果,EC50分别为0.033、0.085和0.147μg/ml。烯唑醇与多菌灵以0.5:10、1.0:10、1.5:10、2.0:10和2.5:10五种比例复配,除1.5:10复配剂对稻瘟病菌的抑制有一定的增效作用外,其他复配剂对稻瘟病菌和纹枯病菌的抑制大都表现为相加作用,而对稻曲病菌的抑制则多为拮抗作用。因此,就增效而言,两者复配对上述三种水稻病害的防治意义不大。     

Phytotoxic and antimicrobial activity of 5,7-dihydroxychromone from peanut shells

A flavonoid decomposition product that is present in peanut (Arachis hypogaea) shells, 5,7-dihydroxychromone (DHC), was found to inhibit the radial growth of cultures of the soil pathogenic fungiRhizoctonia solani andSclerotium rolfsii with I₅₀ (the concentrations of DHC required to inhibit growth 50%) values of 18 and 26µM, respectively. Radicle elongation of velvetleaf, corn, peanut, and wheat was inhibited by DHC with I₅₀ values of 30, 50, 65 and 200µM, respectively. DHC had no effect on the growth ofBradyrhizobium sp. at 10µM in medium containing low (1.0 g/liter) mannitol as the carbon source, although the related flavones luteolin and chrysin each promoted bacterial growth at 10µM 48 hr after inoculation. When tested in high (10.0 g/liter) mannitol medium, DHC initially inhibited growth ofBradyrhizobium sp., but 120 hr after inoculation the growth of all treatments were similar. These results suggest a role for DHC released from peanut shells in suppressing pathogenic fungal infection and competing plant growth but not forBradyrhizobium growth promotion.Mention of firms or products does not imply endorsement by the U.S. Department of Agriculture over other firms or products not mentioned.     

植物生长调节剂与杀菌剂互作对棉花立枯病的影响

采用温室盆栽方法，测定了5种植物生长调节剂分别与7种杀菌剂混用拌种对棉苗立枯病的影响，结果表明：水杨酸 三唑酮、水杨酸 甲基立枯磷、萘乙酸 三唑酮、萘乙酸 烯唑醇、氯化胆碱 甲基立枯磷、氯化胆碱 烯唑醇、油菜素内酯 三唑酮、油菜素内酯 丙环唑、油菜素内酯 多菌灵、多效唑 福美双对棉苗立枯病均有增效作用；水杨酸 福美双有拮抗作用；其它植物生长调节剂与杀菌剂互作为相加作用。     

53．8％可杀得2000DF防治番茄早疫病药效试验

田间试验结果表明，可杀得2000DF对温室内番茄早疫病具有较好的防效，能有效控制病害的扩展蔓延。田间适宜使用浓度为800－1100倍，持效期可达10天以上。