Suppression of root-knot disease by Pseudomonas fluorescens CHA0 in tomato:: importance of bacterial secondary metabolite, 2,4-diacetylpholoroglucinol
Suppression of root-knot disease by Pseudomonas fluorescens CHA0 in tomato:: importance of bacterial secondary metabolite, 2,4-diacetylpholoroglucinol
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DOI：
10.1016/j.soilbio.2003.08.006
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发表时间：
2003-12-01
影响因子：
9.7
通讯作者：
Shaukat, SS
中科院分区：
文献类型：
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作者：
Siddiqui, MA;Shaukat, SS
抗菌代谢产物2,4-二乙酰间苯三酚（2,4- dapg）和pyoluteorin有助于荧光假单胞菌菌株CHA0控制土传病原体引起的植物疾病。研究了荧光假单胞菌（P. fluorescens）菌株CHA0及其衍生物CHA89（抗生素缺乏）和CHA0/pME3424（抗生素过量）作为根结线虫的潜在生物防治剂。在体外条件下，将根结线虫暴露于荧光假单胞菌培养滤液中，可显著降低其卵的孵化率，并导致爪哇假单胞菌幼虫的大量死亡。添加2% （w/v）葡萄糖或1 mM EDTA的营养肉汤酵母浸膏（NBY）培养基可显著抑制菌株CHA0的孵化活性，但对CHA0/pME3424和CHA89的孵化抑制活性无显著影响。另一方面，添加葡萄糖的NBY培养基显著增强了菌株CHA0/pME3424的杀线虫活性。葡萄糖和EDTA对菌株CHA0和CHA89的杀线虫活性均无影响。在体外条件下，抗生素过量菌株CHA0/pME3424和CHA0表达了phl'-'lacZ报告基因，而菌株CHA89则不表达。报告基因的表达反映了DAPG的实际生产。总的来说，CHA0/pME3424比其野生型对应体CHA0更大程度地表达报告基因。无论哪种菌株，在NBY培养基中添加葡萄糖后，报告基因的表达均显著增强，而EDTA则无此作用。体外实验还发现，phl'-'lacZ报告基因表达量与幼鱼死亡程度呈正相关。菌株CHA0在含有明胶的mm培养基上产生4 ~ 6 mm的区，而菌株CHA0/pME3424和CHA89则没有。当含有明胶的MM培养基中加入2%的葡萄糖I MM EDTA时，菌株CHA0产生的光晕尺寸减小到2mm。在温室条件下，不同接种量(10(7)、10(8)或10（9)cfu ml(-1)）下，菌株CHA0或CHA0/pNIE3424的细胞悬液显著降低了根结的发育。当应用于10(9)cfu ml（-1）时，CHA89显着减少了磨损。为了更好地了解线虫抑制的机制，进行了劈裂根生物测定。裂根试验保证了诱导剂和挑战病原体的空间分离，结果表明，用CHA0或CHA0/pME3424细胞悬悬液对一半根系进行土壤处理，产生了显著的系统诱导抗性，导致未消毒的线虫对一半番茄根系的javanica感染减少。结果表明，荧光假单胞菌（P. fluorescens CHA0）中的抗生素2,4- dapg是番茄根系系统抗性的诱导剂。在第一次和第四次收获期间（接种后0-21天），CHA0及其衍生物的种群数量逐渐下降10倍。然而，细菌数量在最后收获时（施用后28天）有所增加。(C) 2003 Elsevier Ltd.版权所有。
The antimicrobial metabolites 2,4-diacetylphloroglucinol (2,4-DAPG) and pyoluteorin contribute to the ability of Pseudomonas fluorescens strain CHA0 to control plant diseases caused by soil-borne pathogens. P. fluorescens strain CHA0 and its derivatives CHA89 (antibiotics-deficient) and CHA0/pME3424 (antibiotics overproducing) were investigated as potential biocontrol agents against Meloidogyne javanica the root-knot nematode. Exposure of root-knot nematode to culture filtrates of P. fluorescens under in vitro conditions significantly reduced egg hatch and caused substantial mortality of M. javanica juveniles. Nutrient broth yeast extract (NBY) medium amended with 2% (w/v) glucose or 1 mM EDTA markedly repressed hatch inhibition activity of the strain CHA0 but not that of CHA0/pME3424 or CHA89. On the other hand, NBY medium amended with glucose significantly enhanced nematicidal activity of the strain CHA0/pME3424. Neither glucose nor EDTA had an influence on the nematicidal activity of the strains CHA0 and CHA89. Under in vitro conditions, antibiotic overproducing strain CHA0/pME3424 and CHA0 expressed phl'-'lacZ reporter gene but strain CHA89 did not. Expression of the reporter gene reflects actual production of DAPG. In general, CHA0/pME3424 expressed reporter gene to a greater extent compared to its wild type counterpart CHA0. Regardless of the bacterial strains, reporter gene expression was markedly enhanced when NBY medium was amended with glucose but EDTA had no such effect. A positive correlation between the degree of juvenile mortality and extent of phl'-'lacZ reporter gene expression was also observed in vitro. Strain CHA0 produced zones of 4-6 mm on MM medium containing gelatin while strain CHA0/pME3424 and CHA89 did not. When MM medium containing gelatin was amended with 2% glucose of I mM EDTA size of haloes produced by the strain CHA0 reduced to 2 mm. Under glasshouse conditions aqueous cell suspension of the strains CHA0 or CHA0/pNIE3424 at various inoculum levels (10(7), 10(8) or 10(9) cfu ml(-1)) significantly reduced root-knot development. CHA89 caused significant reduction in galling when applied at 10(9) cfu ml(-1). To better understand the mechanism of nematode suppression, split root bioassay was performed. Split-root experiments, that guarantee a spatial separation of inducing agent and a challenging pathogen, showed that soil treatment of one half of the root system with cell suspension of CHA0 or CHA0/pME3424 resulted in a significant systemic induced resistance leading to reduction of M. javanica infection of tomato roots in the non-baterized nematode treated half. The results clearly suggest that the antibiotic 2,4-DAPG from P. fluorescens CHA0 act as the inducing agents of systemic resistance in tomato roots. Populations of CHA0 and its derivatives declined progressively by 10-fold between first and fourth harvests (0-21 days after inoculation). However, bacterial populations increased at final harvest (28 days after application). (C) 2003 Elsevier Ltd. All rights reserved.