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Soil microbial community structure in cucumber rhizosphere of different resistance cultivars to fusarium wilt

Zhejiang Provincial Key Laboratory of Subtropic Soil and Plant Nutrition, Zhejiang University, Hangzhou, China.
FEMS Microbiology Ecology (Impact Factor: 3.88). 03/2010; 72(3):456-63. DOI: 10.1111/j.1574-6941.2010.00859.x
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ABSTRACT Cucumber fusarium wilt is a common soil-borne disease. We hypothesize that there is a relationship between the severity of disease and soil microbial ecology. In this work, culturable microbial populations, lipid fatty acid and community-level physiological profiles (CLPP) from rhizosphere soils of four different cucumber cultivars were investigated. Comparatively higher actinomycetes, mycorrhizal colonization and higher ratios of bacteria to fungi were found in the two resistant cultivars compared with the two susceptible cultivars. CLPP analysis showed that catabolic diversity indices were higher in the presence of two resistant cultivars. Phospholipid fatty acid (PLFA) profiles suggested that fungal (18:2omega6,9c) PLFA was enriched in the rhizosphere soils of the two susceptible cultivars, but some bacterial (16:0 and 15:0a) PLFAs were found in a lower relative abundance in these soils. The neutral lipid fatty acid 16:1omega5, which is an indicator of arbuscular mycorrhizal fungi, was enriched in the rhizosphere soils of the two resistant cultivars. All the three methods suggested that plant genotype had a significant impact on the soil microbial community composition and activity, and the differences in the rhizosphere microbial community may result in the differences in the resistance to fusarium wilt.

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Available from: Huaiying Yao, Oct 29, 2014
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    • "Rhizosphere bacteria are affected not only by the plant species but also by the cultivar (Germida and Siciliano 2001). Yao and Wu (2010) suggested that in cucumber cultivars, the level of resistance to Fusarium wilt had a significant effect on the soil microbial community and activity. These findings indicate that plants dramatically select their microflora (Hartmann et al. 2009). "
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    ABSTRACT: The colonization of rhizosphere by microorganisms is directly associated with bacterial growth, chemotaxis, biofilm formation, and the interaction with host plant root exudates. In this study, the responses of Ralstonia solanacearum to the root exudates from two tobacco cultivars (Hongda, susceptible; K326, resistant) were determined. The results showed that the population of R. solanacearum was much higher in the rhizosphere soil of Hongda than in the rhizosphere soil of K326, resulting in a higher disease index for the Hongda treatments (92.73 %). The attraction of R. solanacearum to Hongda root exudates (HRE) was stronger than the response to K326 root exudates (KRE). Four organic acids, oxalic acid, malic acid, citric acid, and succinic acid, from the root exudates were identified and subsequently evaluated. The amount of oxalic acid from HRE was significantly higher than that from KRE. The results also showed that oxalic acid could both significantly induce the chemotactic response and increase the biofilm biomass of R. solanacearum. Both malic acid and citric acid could significantly increase the chemotaxis ability in vitro and the recruitment of R. solanacearum to tobacco root under gnotobiotic conditions. Overall, these data suggested that the colonization of tobacco rhizosphere by pathogenic bacterial strains was influenced by the organic acids secreted from the roots. The results expand our understanding of the roles of root exudates in plant-microbe interactions and will be useful for screening and applying beneficial bacteria for better control of plant wilt diseases.
    European Journal of Plant Pathology 12/2014; 141(4). DOI:10.1007/s10658-014-0569-4 · 1.71 Impact Factor
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    • "As an important indicator for the soil microbial ecology, the ratio of F/B has been used to indicate the shift of soil microbial community structure under environmental stress (Kaur et al., 2005; Yao and Wu, 2010). It has been reported that F/B ratio was positively correlated with soil fertility quality, but negatively with pollution level (Liu and Herbert, 2002; Zhang et al., 2012). "
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    • "Such suppressiveness is typically dependent upon the activity of resident beneficial or antagonistic microbes (Weller et al. 2002) with increasing microbial biomass and/or diversity (Larkin and Honeycutt 2006; Postma et al. 2008). Evenness of the rhizosphere microbiome is an important factor for soil suppression (Crowder et al. 2010; Yao and Wu 2010) ensuring that no individual microbial taxum is dominant. A diverse and even microbiome maximizes niche overlap between pathogens and other community members in the rhizosphere limiting empty niche space for potential invaders and new comers (Hillebrand et al. 2008). "
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    ABSTRACT: It was hypothesized that disruption of the root–microbiome association creates empty rhizosphere niches that could be filled by both soilborne pathogens and beneficial microbes. The effect of de-coupling root–microbiome associations related to improve soil suppressiveness was investigated in cucumber using the pathogen Fusarium oxysporum f. sp. Cucumerinum (FOC) and its antagonist Bacillus amyloliquefaciens SQR9 (SQR9) system. The root–soil microbiome association of cucumber was disrupted by applying the fungicide carbendazim to the soil, and then FOC or/and its antagonist SQR9 were inoculated in the rhizosphere. In the fungicide treatment, the FOC wilt disease incidence was significantly increased by 13.3 % on average compared to the FOC treatment without fungicide. However, when the fungicide treatment was applied to the soil with SQR9 and FOC, the SQR9 effectively reduced the disease incidence, and improved cucumber plant growth compared to a no fungicide control. These results indicate that de-coupling of root–microbiome associations followed by antagonist inoculation can improve rhizosphere soil suppressiveness, which may help to develop strategies for efficient application of rhizosphere beneficial microbes in agriculture.
    Biology and Fertility of Soils 02/2014; 50(2). DOI:10.1007/s00374-013-0835-1 · 3.40 Impact Factor
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