BackgroundSoil microorganisms can mediate the occurrence of plant diseases. Potato common scab (CS) is a refractory disease caused by pathogenic Streptomyces that occurs worldwide, but little is known about the interactions between CS and the soil microbiome. In this study, four soil-root system compartments (geocaulosphere soil (GS), rhizosphere soil (RS), root-zone soil (ZS), and furrow soil (FS)) were analyzed for potato plants with naturally high (H) and low (L) scab severity levels. We aimed to determine the composition and putative function of the soil microbiome associated with potato CS.ResultsThe copy numbers of the scab phytotoxin biosynthetic gene txtAB and the bacterial 16S rRNA gene as well as the diversity and composition of each of the four soil-root system compartments were examined; GS was the only compartment that exhibited significant differences between the H and L groups. Compared to the H group, the L group exhibited a lower txtAB gene copy number, lower bacterial 16S copy number, higher diversity, higher co-occurrence network complexity, and higher community function similarity within the GS microbiome. The community composition and function of the GS samples were further revealed by shotgun metagenomic sequencing. Variovorax, Stenotrophomonas, and Agrobacterium were the most abundant genera that were significantly and positively correlated with the scab severity level, estimated absolute abundance (EAA) of pathogenic Streptomyces, and txtAB gene copy number. In contrast, Geobacillus, Curtobacterium, and unclassified Geodermatophilaceae were significantly negatively correlated with these three parameters. Compared to the function profiles in the L group, several genes involved in “ABC transporters,” the “bacterial secretion system,” “quorum sensing (QS),” “nitrogen metabolism,” and some metabolism by cytochrome P450 were enriched in the H group. In contrast, some antibiotic biosynthesis pathways were enriched in the L group. Based on the differences in community composition and function, a simple model was proposed to explain the putative relationships between the soil microbiome and CS occurrence.ConclusionsThe GS microbiome was closely associated with CS severity in the soil-root system, and the occurrence of CS was accompanied by changes in community composition and function. The differential functions provide new clues to elucidate the mechanism underlying the interaction between CS occurrence and the soil microbiome, and varying community compositions provide novel insights into CS occurrence.Electronic supplementary materialThe online version of this article (10.1186/s40168-019-0629-2) contains supplementary material, which is available to authorized users.

In this study, three polysaccharides including water-soluble polysaccharide (WSP), dilute alkali-soluble polysaccharide (DASP) and concentrated alkali-soluble polysaccharide (CASP) were extracted from purple sweet potatoes and then administered to normal and cyclophosphamide (CTX) treated mice by gavage. The results showed that WSP and CASP could restore the spleen index and immune cytokine (IL-2 and IL-6) levels in CTX treated mice, while DASP could enhance the levels of TNF-α, IL-2 and IL-6. As compared to the normal control group, WSP and CASP treatment groups exhibited increased levels of Bacteroidetes, Lachnospiraceae and Oscillospira, but decreased levels of Firmicutes, Alcaligenaceae and Sutterella in normal mice. When compared with a model control group, all the three polysaccharide treatment groups showed relatively higher abundances of Bacteroidetes, Ruminococcaceae, Lachnospiraceae, Ruminococcus and Oscillospira but lower levels of Firmicutes, Proteobacteria, Alcaligenaceae and Sutterella in CTX treated mice. Moreover, all the polysaccharides could enhance the production of acetic acid, propionic acid and butyric acid in normal mice, while WSP could upregulate the production of these short chain fatty acids in CTX treated mice.

Drip irrigation is the most effective and reliable method for reclaimed water irrigation. The water usually contains a lot of suspended particles, metal salt ions, organisms and microbial communities, which will enhance the possibility of emitter clogging or more complex clogging mechanism. Emitter clogging has become one of the key problems to the application and popularization of the drip irrigation technology. In this paper, we selected four kinds of pressure-compensating emitters and four kinds of non-pressure-compensating emitters, and executed the experiment of drip irrigation with on-site reclaimed water treated with cyclic activated sludge system (CASS). The emitter discharge ratio variation (Dra), coefficient of uniformity (CU) and clogging rate distribution were analyzed to evaluate the emitter clogging characteristics after eliminating the effect of temperature and pressure on the emitter outflow by data correction. The results showed that Dra and CU varied in three periods as system operation. The beginning of experiment was the fluctuated balance period, Dra and CU recurrent fluctuated in 5 %, and the emitters clogged at some spots after the system run 36-48 h. Then the two parameters varied linearly in 60-108 h, tuning into the initiate linear period, as the nonpressure-compensating emitters got an obvious linear change than the pressure-compensating ones with the gradient changed from -0.094 to 0.042 and -0.073 to 0.047, respectively. Some of the emitters have a significant difference on these two parameters at this stage. After the restarting in the second year, Dra and CU decreased sharply. The maximum decrement was, respectively, 9.6 and 10.7 %. Then they varied in line with a greater slope degree as all emitters reached the significant level, the gradient ranges were -0.176 to 0.115 and -0.216 to 0.117, respectively. This stage was called the accelerated linear period. Seriously clogged and completely clogged emitters appeared, and both Dra and CU dropped down to 38.7 and 41.5 %. Various degrees of clogged emitters often emerged in the end part of lateral at first then propelled to the head gradually, the completely clogged emitters in the end accounted for more than 73.0 % when the system run 540 h. Comprehensively considered, the pressure-compensating emitters and cusp-shaped saw-tooth non-pressure-compensating emitters with short flow path are recommended in reclaimed water drip irrigation. These researches are aimed to provide references explaining the emitter clogging mechanism of reclaimed water drip irrigation as well as its technological application and popularization.

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Fifty-one Simmental crossbred steers (357.0±16.5 kg) were used to compare a standard total mix ration (TMR) with variants on animal performance, ruminal fermentation, blood biochemical parameters, and carcass characteristics. Corn grain and cotton seed meal were partially replaced by ensiled mulberry leaves (EML) or sun-dried mulberry fruit pomace (SMFP). Experimental diets had similar amounts of crude protein (CP), acid detergent fiber (ADF), and metabolizable energy (ME). Animals were divided into three groups: control group (CONT), 8% EML group, and 6.3% SMFP group. Performance, including average daily weight gain (ADG), and dry matter intake (DMI), was measured. Blood and rumen samples were collected at the end of the experiment (16 weeks). There were no differences in final body weight (P = 0.743), ADG (P = 0.425), DMI (P = 0.642), or ADG/DMI (P = 0.236) between the groups. There were no differences (P = 0.2024) in rumen pH values; ammonia N was lower (P = 0.0076) in SMFP than in the EML and CONT groups. There were differences in the concentrations of total and individual volatile fatty acids, while no differences were determined in blood biochemical parameters (i.e., plasma glucose, urea concentrations, triglycerides, total protein, insulin, IgG, alanine transaminase, and aspartate aminotransferase, P ≥ 0.098). No differences were observed in carcass characteristics (P ≥ 0.513), tenderness (P = 0.844), adipose and lean color values (P ≥ 0.149), and chemical composition (P ≥ 0.400); however, intramuscular fat was lower in the EML and SMFP groups compared to the CONT animals (P = 0.034). In conclusion, diets supplemented with these two mulberry products in an isocaloric and isonitrogenous manner have similar effects to corn grain and cotton seed meals on steer performance, blood biochemical parameters and carcass characteristics, with the exception of ruminal VFA concentrations and lower intramuscular fat content.

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