Article

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
Source: PubMed

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.

Full-text

Available from: Huaiying Yao, Oct 29, 2014
0 Followers
 · 
102 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Evaluation of the soil rhizosphere has been limited by the lack of robust assessments that can explore the vast complex structure and diversity of soil microbial communities. Our objective was to combine fatty acid methyl ester (FAME) and pyrosequencing techniques to evaluate soil microbial community structure and diversity. In addition, we evaluated biogeochemical functionality of the microbial communities via enzymatic activities of nutrient cycling. Samples were taken from a silt loam at 0–10 and 10–20 cm in an organic farm under lettuce (Lactuca sativa), potato (Solanum tuberosum), onion (Allium cepa L), broccoli (Brassica oleracea var. botrytis) and Tall fescue pasture grass (Festuca arundinacea). Several FAMEs (a15:0, i15:0, i15:1, i16:0, a17:0, i17:0, 10Me17:0, cy17:0, 16:1ω5c and 18:1ω9c) varied among the crop rhizospheres. FAME profiles of the soil microbial community under pasture showed a higher fungal:bacterial ratio compared to the soil under lettuce, potato, onion, and broccoli. Soil under potato showed higher sum of fungal FAME indicators compared to broccoli, onion and lettuce. Microbial biomass C and enzyme activities associated with pasture and potato were higher than the other rhizospheres. The lowest soil microbial biomass C and enzyme activities were found under onion. Pyrosequencing revealed significant differences regarding the maximum operational taxonomic units (OTU) at 3% dissimilarity level (roughly corresponding to the bacterial species level) at 0–10 cm (581.7–770.0) compared to 10–20 cm OPEN ACCESS Diversity 2011, 3 309 (563.3–727.7) soil depths. The lowest OTUs detected at 0–10 cm were under broccoli (581.7); whereas the lowest OTUs found at 10–20 cm were under potato (563.3). The predominant phyla (85%) in this soil at both depths were Bacteroidetes (i.e., Flavobacteria, Sphingobacteria), and Proteobacteria. Flavobacteriaceae and Xanthomonadaceae were predominant under broccoli. Rhizobiaceae, Hyphomicrobiaceae, and Acidobacteriaceae were more abundant under pasture compared to the cultivated soils under broccoli, potato, onion and lettuce. This study found significant differences in microbial community structure and diversity, and enzyme activities of nutrient cycling in this organic farming system under different rhizospheres, which can have implications in soil health and metabolic functioning, and the yield and nutritional value of each crop.
    Diversity 12/2011; 3(4). DOI:10.3390/d3030308
  • [Show abstract] [Hide abstract]
    ABSTRACT: Urea [(NH(2))(2)CO] applied in the seed row can damage seedlings and affect soil microorganisms. A field study was conducted in five site-years to compare the effects of seed-placed and side-banded N applied to barley (Hordeum vulgare L.) at 0 to 120 kg ha(-1) on rhizosphere and bulk-soil microbial biomass carbon (MBC) and functional diversity (H.), and to investigate if increasing barley seeding rate (200-400 seeds m(-2)) would modify the N effects. Nitrogen rate affected MBC in four and one site-years in barley rhizosphere and bulk soil, respectively. Two of the four responses in the rhizosphere were quadratic, and the other two were a linear decrease and a cubic response. The response in bulk soil was a linear decrease. One of the two responses in the rhizosphere depended on N placement. Responses of H. to N rate, which were mostly cubic and depended on N placement, were observed in three and four site-years in the rhizosphere and bulk soil, respectively. Increasing barley seeding rate increased MBC in one and three site-years in the rhizosphere and bulk soil, respectively, and increased H. in one and two site-years, respectively. In two of the three cases in bulk soil, seeding rate increased MBC only when N was banded. Banded N up to 60 kg ha(-1) had minimal adverse effects on soil microorganisms, but only 30 kg N ha(-1) or less of seed-placed N was relatively harmless. Increasing seeding rate did not usually alleviate the negative effects of seed-placed N applied at high rates.
    Agronomy journal 07/2011; 103(4):1064. DOI:10.2134/agronj2010.0334 · 1.54 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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