Occurrence of Fusarium fujikuroi Causing Fusarium Wilt on Carthusian Pink in China.

Carthusian pink (Dianthus carthusianorum) is native to Europe and is widely grown in China for landscaping. In September 2022, wilting symptoms of carthusian pink were found in Xixia City (33°18'31″ N, 111°29'45″ E), Henan Province, China, with a disease incidence of 65%. Approximately 100 plants were surveyed on the landscaping lawns of the park. Initial symptoms were yellow to brown lesions on the base of stems and leaves. Later, the lesions spread throughout the plants, turning leaves yellow, and leading to root and leaf rot. Eventually, the plants shriveled and died (Figure S1a). Thirty diseased tissues isolated from the roots and leaves were cut into 5×5 mm pieces, which were surface sterilized with 75% ethanol solution for 30 seconds and 1% NaClO solution for 1 minute, rinsed three times in sterilized water, placed on potato dextrose agar (PDA) plates supplemented with 50 µg ml-1 streptomycin, and incubated at 28°C for five days. A total of 25 purified fungal strains with similar phenotypic features were obtained. Three representative strains named OSZ-P1, OSZ-P2, and OSZ-P3 were selected for identification. Fungal colonies developed an abundant aerial mycelium, initially white, which subsequently developed red to purple pigments (Figure S1b). Macroconidia were slender, straight, and measured 12.74 to 49.39 × 2.07 to 4.39 µm (n=50), with two to five septa. Microconidia were clavate and measured 6.31 to 11.61 × 2.15 to 4.02 µm (n=50) (Figure S1c). These morphological characteristics were consistent with Fusarium spp.. The rDNA internal transcribed spacer (ITS), ß-tubulin gene (tub2), translation elongation factor 1-alpha gene (tef1), calmodulin (cmdA), RNA polymerase largest subunit (rpb1), and RNA polymerase II second largest subunit (rpb2) were amplified with primers ITS1/ITS4, BT-2a/BT-2b, EF1/EF2, CL1/CL2A, Fa/G2R, and 5F2/7Cr, respectively, for further identification (Yilmaz et al. 2021, O'Donnell et al. 2022). ITS (OQ726389, OQ726390, OQ726391), tub2 (OQ730191, OQ789645, OQ789646), tef1 (OR088904, OR088905, OR088906), cmdA (OR133730, OR133731, OR133732), rpb1 (OR088907, OR088908, OR133729), and rpb2 (OR133733, OR133734, OR133735) nucleotide sequences of the strains OSZ-P1, OSZ-P2, and OSZ-P3 were submitted to GenBank. BLASTn analysis of OSZ-P1 sequences exhibited 99 to 100% similarity with Fusarium fujikuroi sequences (strains Augusto2, I1.3, and CSV1) CP023096, CP023108, CP023084 of cmdA, CP023089, CP023077 of rpb1, and CP023093, CP023105, CP023081 of rpb2. A Phylogenetic tree was constructed of combined genes (tub2, tef1, cmdA, rpb1, rpb2) of sequences, alongside the sequences of the type strains by the neighbor-joining method. The three strains formed a clade with the type strains CBS257.52 and Augusto2 of F. fujikuroi in phylogenetic trees, being clearly separated from other Fusarium spp. (Figure S2). The morphological features and molecular analyses supported the strains as members of F. fujikuroi. To verify the pathogenicity, aboveground parts of the plants of five healthy six-month-old potted plants were sprayed with 100 µl of conidial suspension per pot (106 conidia ml-1), and five similar plants were sprayed with sterilized water as a control. All plants were placed in a climate incubator at 28°C and 90% relative humidity. Seven days after inoculation, withered and yellowed lesions were observed, similar to the natural lesions (Figure S1e). No symptoms were observed on the control plants. The whole pathogenicity tests were performed thrice. Reisolation resulted in cultures that were morphologically and molecularly identical to the original isolates, fulfilling Koch's postulates. Fusarium wilt disease has been reported on other plants of the genus Dianthus. Vascular wilt on Dianthus caryophyllus (carnation) caused by Fusarium oxysporum is the most destructive disease of carnation crops worldwide (Ardila et al. 2014). Fusarium acuminatum causing Dianthus chinensis root rot and foliage blight has recently been reported in Nanjing, China (Xu et al. 2022). To our knowledge, this is the first report of F. fujikuroi causing Fusarium wilt on carthusian pink worldwide. The host range of F. fujikuroi still needs to be clarified for accurate disease management in the selection of plant species for landscape.

Plant organ- and growth stage-diversity of endophytic bacteria with potential as biofertilisers isolated from wheat (Triticum aestivum L.).

BACKGROUND: Chemical fertilisers are extensively used for crop production, which may cause soil deterioration and water pollution. Endophytic bacteria with plant-growth-promoting (PGP) activities may provide a solution to sustainably improve crop yields, including in-demand staples such as wheat. However, the diversity of the PGP endophytic bacteria in wheat across plant organs and growth stages has not been thoroughly characterised. RESULTS: Here, we report the isolation of endophytic bacteria from root, stem, leaf and seed of three winter wheat varieties at tillering, jointing, heading and seed-filling growth stages that were identified via 16S rRNA gene sequence analysis. Strains were screened for indole-3-acetic acid (IAA) production, potassium and phosphate solubilisation and the ability to grow on a nitrogen-free medium. Strain's capacity to stimulate various plant growth parameters, such as dry root weight, dry above-ground parts weight and plant height, was evaluated in pot trials. A total of 127 strains were randomly selected from 610 isolated endophytic bacterial cultures, representing ten genera and 22 taxa. Some taxa were organ-specific; others were growth-stage-specific. Bacillus aryabhattai, B. stratosphericus, Leclercia adecarboxylata and Pseudomonas oryzihabitans were detected as wheat endophytes for the first time. The IAA production, inorganic phosphorous solubilisation, organic phosphorus solubilisation, potassium solubilisation and growth on N-free medium were detected in 45%, 29%, 37%, 2.4% and 37.8% of the 127 strains, respectively. In pot trials, each strain showed variable effects on inoculated wheat plants regarding the evaluated growth parameters. CONCLUSIONS: Wheat endophytic bacteria showed organ- and growth-stage diversity, which may reflect their adaptations to different plant tissues and seasonal variations, and differed in their PGP abilities. Bacillus was the most predominant bacterial taxa isolated from winter wheat plants. Our study confirmed wheat root as the best reservoir for screening endophytic bacteria with potential as biofertilisers.

Gray Blight Disease on Euonymus japonicas Caused by Pestalotiopsis disseminata in China.

Euonymus japonicas is widely planted as an important landscape species throughout China. In June 2021, a serious gray blight disease was detected on E. japonicas in Henan Province (32°30'58" N, 112°19'44" E), causing severe defoliation of infected trees with a foliar disease incidence of 52 to 70% (n = 100). Gray spots initially appeared on leaves, gradually expanded into irregular white blotches with dark brown borders, eventually leading to wilting and death of the leaves. The junctions between the lesion and healthy tissue of infected leaves were cut into 3 × 3-mm pieces, surface sterilized with 1% NaClO solution for 1 min, rinsed in sterile water, and placed on PDA plates with 50 µg/ml of streptomycin. Three isolates (HY94, HY95, and HY98) were selected for subsequent experiments. The colonies reached 80-85 mm diam after 7 days at 25°C, with undulated margins, white to pale in color, with moderate aerial mycelium on the surface. Conidiomata were globose, solitary, and dark black. Conidia were ellipsoid, straight to slightly curved, 4-septate, 19 to 26.4 × 5 to 7.5 µm (n=100). The apical cell was cylindrical and hyaline, with 2 to 3 tubular apical appendages, unbranched, filiform, 2.5 to 3.5 µm in length. The basal appendage was single, unbranched, centric, 1.5 to 3 µm long. The characteristics were close to those of Pestalotiopsis spp. (Maharachchikumbura et al. 2013). The genomic DNA was extracted, and the rDNA internal transcribed spacer (ITS), the ß-tubulin gene (TUB), and the translation elongation factor 1-alpha gene (TEF1) were amplified by primers ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R, respectively (Carbone and Kohn, 1999). Sequences were submitted to GenBank with accession numbers OL840327-OL840329(ITS), OL961454-OL961456(TUB), and OL961448-OL961450 (TEF1). BLASTn analyses of ITS, TUB, and TEF1 sequences exhibited 99.46, 99.05, and 96.53% similarity to the sequences of Pestalotiopsis disseminata strain MEAN1166 (ITS, 548/551 bp; MT374688) (Silva et al. 2020), PSH2000I-066 (TUB, 418/422 bp; DQ333575), and TAP29O082 (TEF1, 250/259 bp; AB453850), respectively in GenBank. The three isolates formed a clade with the type strains, MEAN 1166 and MAFF238347 of P. disseminata in phylogenetic trees, being clearly seperated from other Pestalotiopsis spp. Based on morphological and molecular evidence, the pathogen was identified as P. disseminata (Maharachchikumbura et al. 2011). To fulfill Koch's postulates, pathogenicity was tested with three isolates. Ten healthy leaves of 5-year-old intact plants were used per isolate and inoculated with mycelial plugs on both nonwounded and wounded leaves. Control leaves were inoculated with agar plugs. The inoculated plants were placed at 28°C in a greenhouse (90% relative humidity). Distinct lesions were observed after 10 days. The pathogen reisolated was identical to that of the original cultures according to phenotype and ITS sequences. The control leaves showed no obvious symptoms. P. disseminata is known to cause disease on several important plants in China, such as Camellia japonica (Zhang et al. 2012), Pinus armandii (Hu et al. 2007), and Tripterygium wilfordii (Kumar et al. 2004). This is the first report of gray blight disease caused by P. disseminata on E. japonicas in China and worldwide. The fungal pathogen identification will provide valuable information for prevention and management of gray blight disease associated with E. japonicas.

Leaf Spot Disease on Punica granatum Caused by Alternaria alternata in China.

Pomegranate (Punica granatum L.), which is native to central Asia, is considered as one of the most renowned commercial fruit trees in the world. The planting area in China is roughly 120 thousand hectares. In June 2020, symptoms of leaf spot on P. granatum appeared in Nanyang City (32º40´34˝N, 111º44´20˝E), Henan Province, with an incidence rate of 35% in several 3.3-hectare orchards. Initially, the lesions showed as round or subrounded brown spots on affected leaves. The spots then progressively developed into irregular lesions with distinct yellow halos surrounding them. Parts of the lesions were weakly zonate, which finally led to leaf withering and falling off. Diseased tissues were cut into 5×5 mm2 pieces, which were surface sterilized with 75% ethanol solution for 30 s, washed 3 times in sterilized water, and put on potato dextrose agar (PDA) plates supplemented with 50 µg ml-1 streptomycin. A total of 16 purified fungal isolates with similar phenotypic features were obtained. Three randomly chosen isolates SLY11, SLY24, and SLY25 were utilized for the investigation. Fungal colonies on PDA were first white to gray and later mycelium became olive green to blackish brown. To examine the morphological properties of conidia, we utilized potato carrot agar (PCA) culture medium and incubated it at 23°C under a 12-hour light/dark alternation. Conidia were obclavate or spheroidal, dark brown, with 3 to 5 transverse septa and 1 to 4 longitudinal septa. Conidiophores were septate, solitary, and measured 22.7 (±4.64) × 10.6 (±2.15) µm (n=50), with a conical beak length of 0 to 5.5 µm. The rDNA internal transcribed spacer (ITS), translation elongation factor 1-alpha gene (TEF1), ß-tubulin gene (TUB), and glyceraldehyde 3-phosphate dehydrogenase gene (GAPDH) were amplified using primer pairs ITS1/ITS4, EF1-728F/EF1-986R, Bt2a/Bt2b, and GDF1/GDF2 from genomic DNA. Sequences were submitted to GenBank with accession numbers OL840230, OL840231, OL840232 for ITS, OL982540, OL982541, OL982542 for TEF1, OL982543, OL982544, OL982545 for TUB, OL862608, OL862609, OL862610 for GAPDH sequences of isolates SLY11, SLY24, and SLY25, respectively. BLASTn analysis of ITS (OL840230), TEF1 (OL982540), TUB (OL982543), GAPDH (OL862608) sequences indicated 100, 99.59, 99.68, and 100% similarity to the sequences of Alternaria alternata strain HC-2 (MT644140), BJFA-1 (MK895958), CS36-5 (KY814630), and ag1 (KP057228) in GenBank. Isolates SLY11, SLY24, and SLY25 formed a clade with the type strains CBS 130265 and CBS 130258 of A. alternata in phylogenetic trees established, clearly seperating from other Alternaria spp. The morphological features and molecular analyses supported the isolates as members of A. alternata. To validate the pathogenicity of the isolates, ten healthy leaves of 3-year-old potted pomegranate trees were utilized for testing and inoculated with conidial suspension (106 conidia ml-1), 20 µl each leaf. Control plants were inoculated with sterilized water. An additional pathogenicity test was repeated on wounded leaves. The inoculated plants were placed at 28°C in a greenhouse (12 h light per day and 90% relative humidity) for 5 days. The pathogenicity testing was conducted three times. Distinct lesions were found on the nonwounded and wounded leaves of inoculated plants after 3 to 5 days. The morphology and ITS sequences of the fungi that were reisolated from each of the inoculated plants were similar to that of the inocula, fulfilling Koch's postulates. Fruit rot of pomegranate induced by A. alternata was not identified in our investigation. A. alternata is reported to induce leaf spot disease on P. granatum in India (Zakir et al. 2009), Israel (Ezra et al. 2010), Spain (Garcia-Jimenez et al. 2014). To our knowledge, this is the first report of A. alternata causing leaf spot disease on P. granatum in China. Severe leaf disease caused by A. alternata can lead to reduced pomegranate yields in the harvest stages. This note will aid in pathogen identification and disease control.

Ottowia caeni sp. nov., a novel phenylacetic acid degrading bacterium isolated from sludge.

A novel bacterium, designated BD-1T, was isolated from a sludge sample. Cells of the novel Gram-stain-negative strain were identified to be facultative anaerobic, non-motile and short rod-shaped. Growth occurred at 15-37 °C (optimum, 30 °C), pH 5.0-10.0 (pH 7.0) and in 0-4.0  % NaCl (2.0 %, w/v). The 16S rRNA gene sequence of strain BD-1T showed the highest sequence similarity to Ottowia thiooxydans DSM 14619T (97.0 %), followed by Ottowia pentelensis DSM 21699T (96.3 %) and less than 96 % to other related strains. The phylogenetic trees revealed that strain BD-1T clustered within the genus Ottowia. Summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c, 48.2 %), C16 : 0 (23.2 %) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c, 8.6 %) were the major fatty acids (>5 %), and ubiquinone-8 was the respiratory quinone. Phosphatidylethanolamine, phosphatidylmethylethanolamine and phosphatidylglycerol were identified as the major polar lipids. Meanwhile, the G+C content of the DNA was 63.6 mol% based on the draft genome analysis. The average nucleotide identity and digital DNA-DNA hybridization values between strain BD-1T and DSM 14619T were 74.5 and 21.4  %, respectively. In addition, the novel strain completely degraded 500 mg l-1 phenylacetic acid within 72 h under the condition of 3 % NaCl. Given the results of genomic, phylogenetic, phenotypic and chemotaxonomic analyses, strain BD-1T was considered to represent a novel species of the genus Ottowia, for which the name Ottowia caeni sp. nov. is proposed. The strain is a potential resource for the bioremediation of phenylacetic acid contaminated water. The type strain is BD-1T (=CGMCC 1.18541T=KCTC 82183T).

First Report of Soft Rot Caused by Aspergillus niger sensu lato on Mother-in-law's Tongue in China.

"Mother-in-law's tongue" (MLT) [Dracaena trifasciata (Prain) Mabb. (syn. Sansevieria trifasciata Prain.)], also known as "Saint George's sword", "snake plant", "tiger's tail orchid", etc., is an evergreen perennial ornamental plant grown worldwide. In September 2016, severe soft rot occurred on the leaves of MLT in a flower market in Nanyang city (32º56´N, 112º32´E), Henan province, China with 25% disease incidence (n=100). Water-soaked spots initially appeared on the leaf margin, enlarged rapidly, and became soft rot under excessively watered conditions. A blight zone was visualized at the margin of a developing lesion in backlit conditions. Severely affected leaves folded down from the lesions. Lesion expansion stopped under dry conditions. Grey or dark brown mycelia were frequently seen on the lesions. Tissue pieces (4×4 mm2) at the margin of lesions were cut out, treated with 75% ethanol for 10 s, followed by 70 s in 0.1% HgCl2, rinsed eight times with sterile water, and plated on potato dextrose agar (PDA) medium. Pure Aspergillus cultures were obtained from the surface-disinfected lesions after 4 days of incubation at 26°C. Two single-spore-derived isolates (An-1 and An-2) were randomly selected and used for morphological and molecular identifications as well as pathogenicity tests. The isolates formed round dark brown colonies with a large number of conidia after 5 days of incubation on PDA at 28°C. Conidia were subsphaeroidal or oblate, unicellular, dark brown, 2.9-4.2(3.5) × 1.9-3.4(2.7) µm in size (n=100), developed from a two-series of strigmata born on a conidial head, with ridge or stab-shaped prominences. For pathogenicity tests, the two isolates were separately grown on oatmeal agar and incubated at 30°C for 6 days. Mycelial plugs (5 mm diam.) were inoculated on the scalpel incision X-shaped wounds of surface-disinfected leaves of MLT. The inoculated leaves were kept on a two-layer of wet napkin in a steel basin covered with a plastic film. Soft rot symptoms developed from the wounds 6 days after incubation, similar to those observed on naturally affected leaves. The An-1- and An-2-inoculated unwounded leaves remained symptomless during the pathogenicity tests. Fungal cultures with the same phenotypes as the inocula were consistently reisolated from the lesions of the leaves inoculated by each of the two isolates, verifying the isolates as the causal agent of the disease based on Koch's postulates. Both ß-tubulin gene and rDNA-ITS (internal transcribed spacer) sequences of the two isolates were separately amplified and sequenced. Sequences were submitted to GenBank with accession numbers MN259522 and MN259523 for the ß-tubulin gene sequences, and accession numbers MN227322 and MN227324 for the rDNA-ITS sequences of An-1 and An-2, respectively. Both An-1 and An-2 were clustered with members of Aspergillus niger van Tieghem in the phylogenetic tree of rDNA-ITS, clearly separated from other Aspergillus spp. In the phylogenetic tree of ß-tublin gene, both An-1 and An-2 formed a subclade inside a large clade consisting of members of A. niger in strict sense. Based on the molecular and morphological results, both An-1 and An-2 clearly separated from other Aspergillus spp. and can be considered as A. niger sensu lato. Foliar diseases of MLT are known to be caused by a few fungal species such as Chaetomella spp. (Li et al. 2014) and Colletotrichum sansevieriae (Nakamura et al. 2006). This is the first report of A. niger sensu lato causing soft rot on MLT in China.

[Polyamine-producing Bacteria Regulated the Community Structure of Rhizosphere Bacteria and Reduced the Absorption of Cd in Wheat].

Some functional microorganisms in the soil immobilize heavy metals by adsorption and precipitation, prevent the absorption of heavy metals by crops, and play an important role in the passivation and remediation of medium and mild heavy metal-contaminated soil. A pot experiment was conducted to study the effects of the exogenous polyamine-producing bacterium Bacillus sp. N3 on Cd uptake and the bacterial community composition and function in the rhizosphere soil. The results showed that strain N3 significantly reduced the contents of Cd (64.7%) in wheat grain and DTPA-Cd (50.1%) in rhizosphere soil and increased the pH (from 6.84 to 6.97) and polyamine content. High-throughput sequencing results showed that inoculation of strain N3 reduced the diversity of the bacterial community; however, it increased the relative abundances of ß-Proteobacteria, Bacteroidetes, and Firmicutes in wheat rhizosphere soil. Meanwhile, strain N3 also increased the relative abundances of heavy metal-immobilizing bacteria and plant growth-promoting bacteria (Bacillus, Arthrobacter, Brevundimonas, Ensifer, Pedobacter, Rhizobium, Pseudomonas, Enterobacter, and Serratia) in wheat rhizosphere soil. The PICRUSt function prediction showed that strain N3 increased the copy number of genes involved in antioxidant capacity, hormone synthesis, and sulfur metabolism in wheat rhizosphere soil. These results indicated that the polyamine-producing bacteria N3 reduced the DTPA-Cd content by increasing the pH; the polyamine contents; the abundances of bacteria with heavy metal-immobilizing or plant growth-promoting traits; and the metabolic pathway involved in antioxidant capacity, hormone synthesis, and sulfur metabolism in wheat rhizosphere soil, thus inhibiting the absorption of Cd by wheat. The results provide theoretical basis and technical support for restoring farmland with excessive heavy metals and ensuring the safe production of wheat.

[High-Throughput Sequencing Combined with Metabonomics to Analyze the Effect of Heavy Metal Contamination on Farmland Soil Microbial Community and Function].

Heavy metal contamination affects microbial composition and diversity. The interaction between heavy metal contamination and soil microorganisms has been a hot topic in ecological research. Battery manufacturing has been going on for over six decades in Xinxiang City, resulting in severe soil heavy metal contamination due to battery wastewater runoff. Few studies have investigated the effect of heavy metal contamination due to long-term battery wastewater runoff on microbial diversity and metabolomics in Xinxiang City. In this study, we collected samples from three heavy metal contaminated sites in Xinxiang City and found that Cd and Pb exceeded the recommended thresholds by 34-66 fold and 1.5-2.32 fold, respectively. High-throughput sequencing showed that Bacillus, Arthrobacter, Sphingomonas, and Streptomyces were the dominant bacteria genera, while Olpidium, Plectosphaerella, and Gibellulopsis were the dominant fungi genera, indicating that heavy metal contaminated soil in Xinxiang City was rich in heavy metal tolerant bacteria and fungi due to the long-term heavy metal stress. Correlation analysis showed that total Cu, DTPA extract Cu, and water soluble Pb were significant factors in bacterial diversity, while total Cd, total Ni, total Pb, total Zn, DTPA extract Cu, and water soluble Pb were significant factors in fungal diversity. To better understand the effect of heavy metal contamination on the metabolism of soil microorganisms, we conducted non-targeted metabolomic profiling, which showed significant differences in metabolites across the samples. Pathway enrichment analysis showed that these differential metabolites were involved in pathways such as metabolism, environmental information processing, and genetic Information Processing, which may play a role in heavy metal stress mitigation and environmental adaptation.

Characterization of a novel chitinolytic Serratia marcescens strain TC-1 with broad insecticidal spectrum.

The Gram-negative rod-shaped bacterium Serratia marcescens is an opportunistic pathogen of many organisms, including insects. We report the identification and optimal in vitro chitinase production conditions of a novel chitinolytic S. marcescens strain TC-1 isolated from a naturally infected white grub (Anomala corpulenta) collected from a peanut field at Nanyang city, Henan province, China. Strain identification was conducted by morphological, physiological, biochemical and molecular analyses. The amplified 16S rRNA gene of TC-1 showed a similarity greater than 99% with multiple strains of S. marcescens. Based on Neighbor-joining phylogenetic tree analysis of bacterial 16S rRNA gene sequences, TC-1 formed a clade with S. marcescens, clearly separated from other Serratia spp. The strain TC-1 showed larvicidal activities against five insect species (A. corpulenta, Plutella xylostella, Spodoptera exigua, Helicoverpa armigera, Bombyx mori) and the nematode Caenorhabditis elegans, but not against S. litura. The operating parameters of chitinase production by TC-1 were optimized by response surface methodology using a three-factor, three-level Box-Behnken experimental design. The effects of three independent variables i.e. colloidal chitin concentration (7-13 g l-1), incubation time (24-72 h) and incubation temperature (24-32 °C) on chitinase production by TC-1 were investigated. A regression model was proposed to correlate the independent variables for an optimal chitinase activity predicted as 20.946 U ml-1, using a combination of colloidal chitin concentration, incubation time and incubation temperature of 9.06 g l-1, 63.83 h and 28.12 °C, respectively. The latter agreed well with a mean chitinase activity of 20.761 ± 0.102 U ml-1 measured in the culture supernatants of TC-1 grown under similar conditions with a colloidal chitin concentration, incubation time and incubation temperature of 9 g l-1, 64 h and 28 °C, respectively. Our study revealed the S. marcescens strain TC-1 with potential as a biocontrol agent of insect pests and nematodes and demonstrated the proposed regression model's potential to guide chitinase production by this strain.

[Functional Stability and Applicability of Heavy Metal Passivators in Reducing Cd Uptake by Lettuce].

The use of heavy metal passivators to prevent vegetables from absorbing heavy metals is an important measure to control heavy metal-polluted vegetable fields and to ensure the safe production of vegetables. A pot experiment of planting three times in succession was conducted to study the effects of Bacillus megaterium N3 (N3), rice husk biochar (BC), sheep manure organic fertilizer (SM), strain N3 combined with biochar (BC+N3), and strain N3 combined with sheep manure (SM+N3) on Cd uptake and the functional stability of lettuce using a heavy metal passivator only at the first planting. The comprehensive applicability of the passivation materials was evaluated by the dynamic weighted comprehensive function. The results showed that when lettuce was planted for the first time, compared with the control, all the heavy metal passivators could significantly reduce (61.2%-81%) the Cd content in the edible part of the lettuce. However, in the third cultivation of lettuce, only SM+N3 could significantly reduce the Cd uptake by lettuce, which indicated that SM+N3 had the best functional stability. The dynamic weighted comprehensive function was used to evaluate the Cd content in the edible part of fresh lettuce, available Cd content in the soil, yield, and remediation cost. The results showed that the comprehensive applicability of SM+N3 was the best, followed by that of SM, BC+N3, and BC, and the comprehensive evaluation effect of strain N3 was the worst. The results of this study provide a theoretical basis and technical support for remediation of heavy metal-contaminated vegetable fields.

[Community Structure and Predictive Functional Analysis of Surface Water Bacterioplankton in the Danjiangkou Reservoir].

Bacterioplankton are important components of aquatic ecosystems, and play a crucial role in the global biogeochemical cycle of nitrogen. In this study, surface-water samples were collected from Kuxin (the center of Danjiangkou Reservoir) and Qushou (the Middle Route of the South-to-North Water Diversion Project's canal head) in the Danjiangkou Reservoir in May 2016. Total DNA was isolated, and high-throughput sequencing was performed to analyze the community structure and diversity of bacteria. Phylogenetic analyses of 16S rDNA sequences showed that bacterial communities included species from 12 major phylogenetic groups. The predominant phylogenetic groups included Proteobacteria, Bacteroidetes, Firmicutes, Cyanobacteria, and Verrucomicrobia. The microbial biodiversity of Danjiangkou Reservoir bacterioplankton was greater in water samples from Qushou than in those from Kuxin. PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) was used to determine the metabolic and functional abilities of the observed bacterial communities. Our results revealed a wide genetic diversity of organisms involved in various essential processes, such as Amino acid transport and metabolism, Transcription, Energy production and conversion, and Carbohydrate transport and metabolism. Thirty-five metabolic pathways involving nitrogen were detected. Key genes impacting the nitrogen cycle were detected in both the Kuxin and Qushou samples, and these encoded enzymes involved in nitrogen fixation (nifH), nitrification (hao), denitrification (narG、nirK、norB、nosZ), and assimilatory and dissimilatory nitrogen reduction to ammonia (nasA、narB、napA、nirA、nirB、nrfA). Copy numbers of 16S rRNA genes of each detected phylotype of Danjiangkou Reservoir bacterioplankton were uniformly higher in water samples from Kuxin than in water samples from Qushou. Our analyses of differences in nitrogen abatement potential between water samples, based on bacterial community composition and function, provide a foundation for setting water environmental protection policies in the Danjiangkou Reservoir.

[Composition and Predictive Functional Analysis of Rhizosphere Bacterial Communities in Riparian Buffer Strips in the Danjiangkou Reservoir, China].

Microbial communities play crucial roles in the global biogeochemical nitrogen cycle. To our knowledge, the compositions and functions of rhizosphere communities in riparian buffer strips have not been reported. In this study, rhizosphere soil samples were collected from herbs (Vetiveria zizanioides and Phragmites australis), trees (Pyrus betulifolia), and shrubs (Discocleidion rufescens) in the Danjiangkou Reservoir in June 2017. High-throughput sequencing was performed to analyze the community structure and diversity of bacteria. Phylogenetic analysis based on 16S rDNA sequences shows that the bacterial communities can be divided into 31 major phylogenetic groups. The dominant phylogenetic groups include Proteobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes, and Acidobacteria. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) was used to determine the metabolic and functional abilities of the observed bacterial communities. Our results reveal a wide genetic diversity of organisms involved in various essential processes such as biosynthesis of other secondary metabolites, transcription, Glycan biosynthesis and metabolism, cell growth and death, and carbohydrate metabolism. Based on the 16S rRNA gene copy number of the detected phylotype, the bacterial rhizospheres of plants in riparian buffer strips can be ranked as follows:Discocleidion rufescens > Phragmites australis > Vetiveria zizanioides > Pyrus betulifolia. We analyzed the differences of different plants from the perspective of bacterial community composition and function and provide a foundation for vegetation construction and water environmental protection in riparian buffer strips of the Danjiangkou Reservoir.

Biocontrol Agents for Controlling Wheat Rust.

Bacterial endophytes are potential biocontrol agents of wheat rusts. Apart from disease control, these bacterial endophytes have growth-promoting efficacies which differ significantly from one isolate to another. Here, we describe the procedure for isolation, screening, and identification of endophytic bacterial isolates with high capacities to suppress strip rust infection and better ability to enhance wheat yields.