Phytopathology. 2006 Jul;96(7):751-62. doi: 10.1094/PHYTO-96-0751.
ABSTRACT Strains of Pseudomonas fluorescens producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) are biocontrol agents which play a key role in the suppressiveness of some soils against soilborne pathogens. We evaluated the effect of the host plant genotype on rhizosphere colonization by both indigenous and introduced 2,4-DAPG-producing P. fluorescens. First, population densities of indigenous 2,4-DAPG producers in the rhizospheres of alfalfa, barley, bean, flax, lentil, lupine, oat, pea, and wheat grown in a Fusarium wilt-suppressive Puget silt loam were determined. Population densities differed among the various crops and among pea cultivars, with lentil and oat supporting the highest and lowest densities of 2,4-DAPG producers, respectively. Second, to determine the interactions among 2,4-DAPG producers in the rhizosphere, a Shano sandy loam was inoculated individually and with all possible combinations of P. fluorescens Q8r1-96 (genotype D), F113 (genotype K), and MVP1-4 (genotype P) and sown to wheat or pea, and the rhizosphere population dynamics of each strain was monitored. All three strains were similar in ability to colonize the rhizosphere of wheat and pea when introduced alone into the soil; however, when introduced together in equal densities, the outcome of the interactions differed according to the host crop. In the wheat rhizosphere, the population density of strain F113 was significantly greater than that of Q8r1-96 in the mixed inoculation studies, but no significant differences were observed on pea. The population density of strain Q8r1-96 was greater than that of MVP1-4 in the mixed inoculation on wheat, but the opposite occurred on pea. In the wheat rhizosphere, the population of MVP1-4 dropped below the detection limit (log 3.26 CFU g(-1) of root) in the presence of F113; however, on pea, the population density of MVP1-4 was higher than that of F113. When all three strains were present together, F113 had the greatest density in the wheat rhizosphere, but MVP1-4 was dominant in the pea rhizosphere. Finally, eight pea cultivars were grown in soil inoculated with either MVP1-4 or Q8r1-96. The effect of the pea cultivar on rhizosphere colonization was dependent on the bacterial strain inoculated. Rhizosphere population densities of MVP1-4 did not differ significantly among pea cultivars, whereas population densities of Q8r1-96 did. We conclude from these studies that the host crop plays a key role in modulating both rhizosphere colonization by 2,4-DAPG-producing P. fluorescens and the interactions among different genotypes present in the same rhizosphere.
摘要 产生抗生素 2,4-二乙酰基间苯三酚（2,4-DAPG）的荧光假单胞菌菌株是生物防治剂，在一些土壤对土传病原体的抑制中起着关键作用。我们评估了宿主植物基因型对土著和引入的 2,4-DAPG 产生荧光假单胞菌在根际定殖的影响。首先，在弗雷泽枯萎病抑制性普吉特粉壤土中种植紫花苜蓿、大麦、豆类、亚麻、小扁豆、羽扇豆、燕麦、豌豆和小麦时，确定了根际中土著 2,4-DAPG 生产者的种群密度。不同作物和豌豆品种之间的种群密度存在差异，小扁豆和燕麦的 2,4-DAPG 生产者密度最高和最低。其次，为了确定根际中 2,4-DAPG 生产者之间的相互作用，用沙诺沙壤土单独接种和接种荧光假单胞菌 Q8r1-96（基因型 D）、F113（基因型 K）和 MVP1-4（基因型 P）的所有可能组合，并播种到小麦或豌豆中，监测每种菌株在根际中的种群动态。当单独引入土壤时，所有三种菌株在定殖小麦和豌豆根际方面的能力相似；然而，当以相等的密度引入时，根据宿主作物的不同，相互作用的结果也不同。在小麦根际中，混合接种研究中 F113 的种群密度明显大于 Q8r1-96，但在豌豆上未观察到显著差异。在小麦混合接种中，Q8r1-96 的种群密度大于 MVP1-4，但在豌豆上则相反。在小麦根际中，F113 的存在使 MVP1-4 的种群数量降至检测限以下（根的 log 3.26 CFU g(-1)）；然而，在豌豆上，MVP1-4 的种群密度高于 F113。当所有三种菌株同时存在时，F113 在小麦根际中密度最大，但 MVP1-4 在豌豆根际中占优势。最后，在接种 MVP1-4 或 Q8r1-96 的土壤中种植了 8 个豌豆品种。豌豆品种对根际定殖的影响取决于接种的细菌菌株。MVP1-4 的根际种群密度在豌豆品种之间没有显著差异，而 Q8r1-96 的种群密度则有显著差异。从这些研究中我们得出结论，宿主作物在调节产生 2,4-DAPG 的荧光假单胞菌在根际中的定殖以及同一根际中不同基因型之间的相互作用方面起着关键作用。
