Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada.
Can J Microbiol. 2010 Nov;56(11):896-905. doi: 10.1139/w10-076.
Three composts (Ball, dairy, and greenhouse) were tested for the ability to suppress the development of Fusarium root and stem rot (caused by Fusarium oxysporum f. sp. radicis-cucumerinum) on greenhouse cucumber. Dairy and greenhouse composts significantly reduced disease severity (P = 0.05), while Ball compost had no effect. Assessment of total culturable microbes in the composts showed a positive relationship between disease suppressive ability and total population levels of pseudomonads. In vitro antagonism assays between compost-isolated bacterial strains and the pathogen showed that strains of Pseudomonas aeruginosa exhibited the greatest antagonism. In growth room trials, strains of P. aeruginosa and nonantagonistic Pseudomonas maculicola, plus 2 biocontrol strains of Pseudomonas fluorescens, were tested for their ability to reduce (i) survival of F. oxysporum, (ii) colonization of plants by the pathogen, and (iii) disease severity. Cucumber seedlings grown in compost receiving P. aeruginosa and P. fluorescens had reduced disease severity index scores after 8 weeks compared with control plants without bacteria. Internal stem colonization by F. oxysporum was significantly reduced by P. aeruginosa. The bacteria colonized plant roots at 1.9 × 10(6) ± 0.73 × 10(6) CFU·(g root tissue)-1 and survival was >107 CFU·(g compost)-1 after 6 weeks. The locus for 2,4-diacetylphloroglucinol production was detected by Southern blot analysis and confirmed by PCR. The production of the antibiotic 2,4-diacetylphloroglucinol in liquid culture by P. aeruginosa was confirmed by thin layer chromatography. These results demonstrate that composts containing antibiotic-producing P. aeruginosa have the potential to suppress diseases caused by Fusarium species.
三种堆肥（球肥、奶牛场肥和温室肥）被用于测试其抑制温室黄瓜枯萎病（由尖孢镰刀菌黄瓜专化型引起）发展的能力。奶牛场肥和温室肥显著降低了病害严重度（P=0.05），而球肥则没有效果。对堆肥中可培养微生物总量的评估表明，病害抑制能力与假单胞菌总种群水平之间呈正相关。在体外拮抗测定中，堆肥分离的细菌菌株与病原菌之间的关系表明，铜绿假单胞菌表现出最大的拮抗作用。在生长室试验中，测试了铜绿假单胞菌和非拮抗假单胞菌斑点亚种，以及 2 种荧光假单胞菌生物防治菌株，以评估它们降低（i）尖孢镰刀菌存活、（ii）病原菌对植物的定殖和（iii）病害严重度的能力。与没有细菌的对照植物相比，在接收到铜绿假单胞菌和荧光假单胞菌的堆肥中生长的黄瓜幼苗在 8 周后其病害严重度指数得分降低。铜绿假单胞菌显著降低了内部茎尖孢镰刀菌的定殖。细菌在植物根部定殖，在 6 周后达到 1.9×10(6)±0.73×10(6)CFU·(g 根组织)-1，存活量>107 CFU·(g 堆肥)-1。通过 Southern blot 分析检测到 2,4-二乙酰基间苯三酚产生的基因座，并通过 PCR 进行了确认。通过薄层层析确认了铜绿假单胞菌在液体培养中产生抗生素 2,4-二乙酰基间苯三酚。这些结果表明，含有产生抗生素的铜绿假单胞菌的堆肥具有抑制尖孢镰刀菌属引起的病害的潜力。
