Evaluation of Bacillus-fortified organic fertilizer for controlling tobacco bacterial wilt in greenhouse and field experiments

Bacterial wilt caused by Ralstonia solanacearum is one of the most serious tobacco diseases worldwide, and no effective control measures are available to date. Three Bacillus isolates (Bacillus amyloliquefaciens SQR-7 and SQR-101 and Bacillus methylotrophicus SQR-29) were obtained from the rhizosphere soil of tobacco. These bacilli exhibited strong inhibition against R. solanacearum and produced indole acetic acid and siderophores. The three antagonistic strains were used to fortify organic fertilizers to produce bioorganic fertilizers (BOFs named for each isolate) for the control of tobacco bacterial wilt. The application of BOFs delayed wilt development and effectively decreased the disease incidence under both greenhouse and field conditions. The tobacco bacterial wilt control efficacy was 44.3%, 70.5%, and 85.1% using BOF101, BOF29, and BOF7 in the greenhouse. Although the control efficacies in the field were lower, the application of BOF7 still achieved 58.0% and 56.2% control efficacies in two years field experiments. The application of bioorganic fertilizer significantly (p < 0.001) repressed the pathogen R. solanacearum in soil in both pot and field experiments, though the abundance of R. solanacearum increased as during the growth period of the tobacco plants. In general, the populations of the antagonistic bacterial strains declined after soil application and as the tobacco plants grew; however, the density of SQR-7 and SQR-29 in the rhizosphere soil remained at a high level (≥10⁶ cfu/g) in the later growth stages. Additionally, the application of bioorganic fertilizers promoted tobacco growth and increased the leaf yield.     

微生物有机肥结合土壤改良剂防治烟草青枯病

盆栽试验设置了五个处理:对照(T1)、施用普通有机肥(T2)、施用SQY-7号微生物有机肥(T3)、石灰处理土壤后施用SQY-7号微生物有机肥(T4)、石灰和碳铵处理土壤后施用SQY-7号微生物有机肥(T5),用DGGE和平板计数法研究了根际土壤微生物群落的多样性,旨在探讨微生物有机肥及微生物有机肥结合土壤改良剂对烟草青枯病的防治效果和对烟草根际土壤细菌群落多样性的影响.结果表明:连作土壤中,施用普通有机肥(T2)不仅不能防治烟草青枯病,还提高了烟草青枯病的病情指数,而施用微生物有机肥处理(T3、T4和T5)对烟草青枯病的防治效果达66.7％～87.9％;施用微生物有机肥可显著改变根际微生物区系结构:T2处理的根际土壤细菌和放线菌数量较T1处理略有增加,真菌数量则较T1处理增加了1.1倍;T3和T4处理的根际土壤细菌分别较T1处理增加了3.5倍和6.1倍,同时,放线菌数量分别增加了3.7倍和3.5倍,而真菌数量分别下降了66.2％和70.1％;T5处理的根际土壤细菌和放线菌数量较T1处理分别增加了13.6倍和5.1倍,真菌数量下降了75.0％;各处理的细菌群落多样性均较T1处理增加.初步研究表明,连作病害土壤用石灰和碳铵预处理后再施用SQY-7号微生物有机肥能有效防控烟草青枯病和减缓连作生物障碍,其作用机制主要通过改变微生物区系和降低病原菌数量实现.     

Tobacco bacterial wilt can be biologically controlled by the application of antagonistic strains in combination with organic fertilizer

Bacterial wilt caused by Ralstonia solanacearum is one of the most serious tobacco diseases worldwide. Brevibacillus brevis (L-25) and Streptomyces rochei (L-9) with strong inhibitory effects on R. solanacearum in vitro were isolated from the rhizosphere of a healthy tobacco plant in a severely wilt-diseased field. Pot and field experiments were conducted to evaluate the biocontrol effect of the isolated antagonists alone and in combination with organic fertilizer. In pot experiment, the control efficacy was 92.3–100 % in the treatments applied with L-25 and L-9 alone or together with organic fertilizers. When bioorganic fertilizer containing L-9 and L-25 was applied to the soil in field condition, the control efficacies were 95.4 and 30.0 in the Anhui and Guizhou field plots, respectively. The counts of bacteria and actinomycetes in rhizosphere soil were significantly increased (p?≤?0.05) under all antagonist applications compared with CK (P_R). In contrast, fungal and R. solanacearum densities in the rhizosphere soil applied with antagonists were much lower than the CK (P_R) rhizosphere. Combined application of the two antagonists had better effect than single antagonist treatments. The antagonists were more effective when they were combined with organic fertilizer as compared with the antagonistic strains only. These results allow us to conclude that a combination of the biocontrol agents, L-25 and L-9, together with organic fertilizers can effectively control bacterial wilt by affecting soil microbial structure.     

Rhizobacterium Bacillus amyloliquefaciens Strain SQRT3-Mediated Induced Systemic Resistance Controls Bacterial Wilt of Tomato

Tomato bacterial wilt caused by Ralstonia solanacearum seriously threats tomato growth in tropical and temperate regions around the world. This study reported an antagonistic bacterial strain, Bacillus amyloliquefaciens strain SQRT3, isolated from the rhizosphere soil of tomato plants, which strongly inhibited in vitro growth of pathogenic R. solanacearum. The suppression of tomato bacterial wilt by strain SQRT3 was demonstrated under greenhouse conditions. Additionally, induced systemic resistance (ISR) in tomato as one of the potential disease suppression mechanisms was investigated in the plants inoculated with the isolated bacterial strain SQRT3. The results showed that strain SQRT3 applied with R. solanacearum by drenching significantly reduced tomato bacterial wilt by 68.1% biocontrol efficiency (BE) and suppressed the R. solanacearum populations in the rhizosphere soil compared to the control only drenched with R. solanacearum. The BE of the isolated bacterial strain SQRT3 against tomato wilt increased to 84.1% by root-dipping. Tomato plants treated with both strain SQRT3 and R. solanacearum showed increases in activities of peroxidase and polyphenol oxidase compared with other treatments. The application of strain SQRT3 reduced membrane lipid peroxidation in tomato leaves. The expressions of marker genes for jasmonic acid-and salicylic acid-dependent signaling pathways were faster and stronger in tomato plants treated with both strain SQRT3 and R. solanacearum than in plants treated with either R. solanacearum or strain SQRT3 alone. Collectively, the findings indicated that strain SQRT3 can effectively control tomato wilt.     

生物有机肥对田间蔬菜根际土壤中病原菌和功能菌组成的影响

利用实时荧光定量PCR方法对田间条件下连作番茄和辣椒施用生物有机肥(BOF)和常规施肥(CK)的根际土壤微生物中青枯病原菌和功能菌群(固氮菌和荧光假单胞菌)的数量进行定量研究.结果表明:与CK相比,BOF处理的番茄和辣椒产量分别提高了26.0％和19.9％,青枯病发病率分别降低了41.5％和44.7％,番茄和辣椒植株根际土壤固氮菌数量分别增加了23.5％和25.8％、荧光假单胞菌数量分别增加了29.5％和20.2％、病原菌数量分别减少了73.2％和90.1％.生物有机肥能够调控根际微生物区系的组成,降低土传病害的发病率,促进作物健康生长;实时荧光定量PCR方法能够快速准确地检测根际土壤中功能微生物种群数量变化.     

Control of tomato bacterial wilt and root-knot diseases by Bacillus thuringiensis CR-371 and Streptomyces avermectinius NBRC14893

Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.     

产脂肽菌株发酵生物有机肥的生物防治与促生作用研究

选取对番茄青枯菌有明显抑制作用的产脂肽菌株XZ-173,与有机肥混合发酵制成生物有机肥。通过温室盆栽试验,评价了该生物有机肥对番茄青枯病的防治效果及对番茄的促生效用。结果表明,生物有机肥能够显著降低青枯病发病率,相对防效达56.8%。与施用化肥和未添加XZ-173的有机肥处理相比,施用该生物有机肥能显著提高番茄植株叶绿素含量、番茄地上部和地下部生物量、根际土壤细菌和放线菌数量,显著降低根际土壤中真菌数量。生物有机肥的有益效果使其在作物种植中具有广阔的应用前景。     

The rhizosphere soil of diseased tomato plants as a source for novel microorganisms to control bacterial wilt

Plant growth promoting rhizobacteria (PGPRs) are used for biocontrol of bacterial wilt caused by Ralstonia solanacearum. They are commonly isolated from the rhizosphere of healthy plants and are scarce in the rhizosphere of diseased plants. We hypothesized that a pathogen-prevalent environment, such as the rhizosphere of infected plants, would be a good or better source for isolating PGPRs than the rhizosphere of healthy plants. In order for these PGPRs to survive successfully in a pathogen-prevalent environment, they must have particularly well-developed survival strategies under the stresses exerted by pathogen activities, which would be of value for their use as biocontrol agents. To test this hypothesis, R. solanacearum-antagonistic bacteria were screened from the rhizospheres of diseased and healthy tomato plants. In total, 110 rhizobacteria were isolated, 18 of which showed antagonism to R. solanacearum in vitro. Among the 18 antagonistic strains, 11 (out of 60) were from the rhizosphere of diseased plants, with inhibition diameter zones ranging from 11.2 to 15.2 mm, whereas 7 (out of 50) were from the rhizosphere of healthy plants, with inhibition diameter zones ranging from 11.5 to 30.5 mm. Strains WR4, WR21, and WR42 from diseased plants rhizosphere, and HR61, HR62, and HR92 from healthy plants rhizosphere, were chosen to investigate their biocontrol efficacies (BCEs) in greenhouse condition. Results showed that WR-isolates performed better in reducing disease incidence (DI) than those HR-isolates. Population densities of R. solanacearum in the rhizosphere soil and crown section of tomato plants were lower in WR-isolate treatments than those in HR-isolate treatments. The best biocontrol effect was achieved by inoculating the strain WR21, followed by WR4, WR42, HR92, HR62, and HR61. Root colonization test showed WR21 had the highest root-colonizing capacity compared with 5 other antagonists. BCEs were positively (r = 0.747) correlated with root-colonizing capacities, but were negatively (r = −0.797) correlated with inhibition zones. In conclusion, the rhizosphere of diseased tomato plants is a good reservoir of biocontrol bacteria.     

Suppression of Ralstonia solanacearum in soil following colonization by other strains of R. solanacearum

The effect of prior colonization of a sterile loam soil and a sterile clay loam soil by individual soil bacteria on the subsequent growth of a bacterial wilt pathogen Ralstonia solanacearum YU1Rif43 (tRNA type III: Seal et al. 1992: Appl. Environ. Microbiol., 58, 3759–3761) was investigated. Various strains, belonging to the same type, the same species, the same genus, Gram-negative, Grampositive, or fungi, were used. The degree of suppression of the growth of R. solanacearum YU1Rif43 was markedly different depending on the species that had previously colonized the soil, hereafter referred to as priorcolonists. All the strains belonging to R. solanacearum type III suppressed the growth of R. solanacearum YU1Rif43 markedly, while strains of R. solanacearum type I and type II showed a moderate suppressive effect on R. solanacearum YU1Rif43. The suppressive effect of the strains belonging to species other than R. solanacearum, including fungal strains, was relatively limited, or some strains did not show any suppressive effect. The production of bacteriocin did not appear to be related to the strong suppressive effect of the R. solanacearum type III strains. Possible mechanisms for the suppressive effect of priorcolonists on R. solanacearum YU1Rif43 are discussed in relation to nutrients and physical sites in soil available for growth.     

抑制烟草青枯病型生物有机肥的田间防效研究

【目的】烟草青枯病是影响烟叶生产最主要的土传病害之一,生物防控烟草青枯病是近年来的研究热点。为验证抑制烟草青枯病型生物有机肥对生防青枯病的影响,进行2年田间试验研究其防效及其对土壤微生物的影响。【方法】本试验采用从烟草根际原位土壤分离得到的烟草青枯病拮抗菌株L-25和L-9,利用有机肥二次固体发酵技术,制成烟草青枯病拮抗生物有机肥。连续两年在安徽进行田间试验,分别在烟草移栽后50天和105天调查生物防控率,探求生物有机肥对青枯病的田间防效和对烟叶产量的影响;利用平板计数法、Biolog特征性碳源法和梯度变性凝胶电泳法摸索生物有机肥施用后根际土壤微生物数量、群落功能多样性和结构多样性的变化,揭示生物有机肥对青枯病的防控机理。【结果】 1）第一年和第二年施用生物有机肥处理移栽50天后烟草青枯病的生物防控率分别为82.2%和96.2%,105天后烟草青枯病的生物防控率分别达到75.2%和95.4%; 2）生物有机肥处理第一年和第二年烟叶产量分别为2212.5 kg/hm2、1475.5 kg/hm2,是对照的2.4和2.6倍; 3）两年生物有机肥处理的根际土壤可培养细菌、放线菌数量均显著高于对照,真菌数量显著低于对照（P＜0.05）,其中第一年生物有机肥处理50天和105天拮抗菌数量分别为对照的241.8倍和13.4倍,病原菌数量仅为对照的19.7%和56.6%,第二年生物有机肥处理50天和105天拮抗菌数量分别是对照的111.0倍和26.7倍,病原菌数量仅为对照的9.1%和31.4%; 4）两年生物有机肥处理50天和105天根际土壤的微生物群落功能多样性,即Shannon指数、Simpson指数和Mclntosh指数均显著高于对照（P＜0.05）; 5）生物有机肥处理与对照土壤微生物群落结构也不相同,细菌和真菌梯度变性凝胶电泳图谱明显不同,分别属于不同的聚簇,生物有机肥处理的细菌种类较对照有所增加,同时真菌的种类有所减少。【结论】在烟草青枯病发病较为严重的烟田施用生物有机肥,可以显著降低青枯病发病率,增加烟草产量。生物有机肥可以显著提高拮抗菌数量,抑制根际土壤病原菌的数量,提高土壤微生物群落功能多样性,改善微生物种群和组成,丰富土壤微生物群落结构,使土壤保持健康的微生物生态平衡。     

Effect of Ralstonia solanacearum on Mineral Nutrients and Infrared Temperatures in Two Tomato Cultivars

ABSTRACT

The objective of this study was to determine how the responses of two tomato cultivars to Ralstonia solanacearum relate to their leaf infrared temperature and acquiring of nutrients from soil. Tomato (Solanum lycopersicum L.) cultivars of disease susceptible-‘FL 47’ and resistant-‘H 7998’ were grown in soil inoculated with R. solanacearum. Bacterial wilt incidence, leaf infrared temperatures, and uptake of nutrients were measured for 28 d. In bacterial wilt-resistant cultivar ‘H 7998’, concentration of sulfur (S; +77%), calcium (Ca; +66%), boron (B; +60%) were found higher and nitrogen (N; ?26%) were found lower, compared with susceptible ‘FL 47’. Infrared temperatures were correlated with wilt percentage at 14 d, but not at 7 d. These results provide evidence that there is a correlation between bacterial wilt resistance and translocation of some nutrients in the shoots. Additionally, data indicates that the infrared thermometer could only detect wilting after obvious symptoms were visibly incited by R. solanacearum in tomato.     

生物质炭载体联合有益菌防控番茄土传青枯病的效果研究

土传青枯病是由青枯菌（Ralstonia solanacearum）引起的一种细菌性病害。根际有益细菌在青枯病的防控中发挥着重要作用,其在根际有效定殖是发挥生防作用的前提。以玉米秸秆、木块（松木）和稻壳为原料制成的3种生物质炭为有益菌Bacillus amyloliquefaciens T-5的载体,探究生物质炭对有益菌防控番茄土传青枯病效果的影响,并利用室内模拟试验探究生物质炭对青枯菌的吸附、固持以及对根系分泌物的吸附作用,旨在阐述施用生物质炭提升有益菌T-5抑制病原青枯菌能力的可能机制。温室试验结果表明：单独施用3种生物质炭均显著降低青枯病的发病率和根际青枯菌的数量,其中具有高比表面积的木块生物质炭的防控效率达到60.56%。3种生物质炭作为有益菌T-5的载体均能够显著提升有益菌T-5的根际定殖数量及其防病效率,其中木块生物质炭的提升效果最好。与仅接种青枯菌的对照相比,木块生物质炭与有益菌T-5组合处理的根际青枯菌数量降幅达97.42%;与单独有益菌T-5处理相比,有益菌T-5以木块生物质炭为载体使其根际定殖数量提高了5.71倍。进一步研究发现,木块生物质炭能够有效吸附青枯菌,吸附...     

Effect of fertilizers, lime, and inoculation with rhizobia and mycorrhizal fungi on the growth of four leguminous tree species in a low-fertility soil

The aim of this study was to evaluate the effects of lime, fertilizers, mycorrhizal fungi, and selected rhizobia strains on the growth of four woody legume species, Albizia lebbeck (L.) Benth., Enterolobium contortisiliquum (Vell.) Morong., Leucaena leucocephala (Lam.) de Wit, and Sesbania virgata (Cav.) Pers. in a low-fertility soil. The experiment was conducted under greenhouse condition in plastic pots (4 kg). Eight treatments and eight replicates per treatment were performed in a completely randomized design. The treatments were: (1) complete treatment (C) (NPK fertilization?+?micronutrients?+?liming?+?MR that is inoculation with mycorrhizal fungi and rhizobia); (2) C minus N (C???N that is as C without the addition of N); (3) C???N???M (as C???N without inoculation with arbuscular mycorrhizal fungi (AMF)); (4) C???N??R (as C???N without inoculation of rhizobia); (5) C???N???liming (as C???N without liming); (6) C???N???micro (as C???N without addition of micronutrients); (7) C???N???P (as C???N without addition of P); (8) control without fertilization, liming, and without inoculation with AMF and rhizobia. After 4 months of growth, we determined the yield of individual plants, nodulation, mycorrhizal colonization, and nutrient contents. Phosphorus was the most limiting nutrient for plant growth, followed by nitrogen. L. leucocephala and S. virgata had the most robust response to the addition of micronutrients and liming, showing an increase in nutrient content, plant height, and root and shoot dry matter. When compared to the single inoculation, the dual inoculation increased growth of all plants, except that of A. lebbeck, which did not respond to either rhizobia or mycorrhizal fungi inoculation.     

Suppression of rice blast,cabbage black leaf spot,and tomato bacterial wilt diseases by Meyerozyma guilliermondii TA-2 and the nature of protection

This study was conducted to evaluate the efficacy of yeast strain TA-2 for controlling rice blast, cabbage black leaf spot, and tomato bacterial wilt diseases. Microscopic and phylogenetic analyses based on rDNA-internal transcribed region (ITS) and rDNA-D1/D2 sequences indicated that yeast strain TA-2 is Meyerozyma guilliermondii. Pretreatment with TA-2 by soil drenching significantly reduced the severity of black leaf spot disease caused by Alternaria brassicicola and leaf blast disease caused by Magnaporthe oryzae. Symptom development of tomato bacterial wilt caused by Ralstonia solanacearum in both soil drench and needle inoculation tests was significantly reduced in TA-2-pretreated plants under soil drenching. Disease severity and R. solanacearum growth were significantly reduced in tomato plants pretreated with yeast culture, cell suspension, or culture filtrate of TA-2 under soil drenching. TA-2 does not produce antibiotics. The present study indicates that disease suppression is systemic, as the roots were treated with TA-2 and the pathogens were inoculated onto leaves or stems, thereby separating the two spatially. M. guilliermondii TA-2 could become a promising natural antimicrobial agent against rice blast, cabbage black leaf spot, and tomato bacterial wilt diseases and might be useful as an eco-friendly control measure, contributing to sustainable agriculture.     

病原青枯菌土壤存活的影响因素研究进展

土传青枯病是一种毁灭性的细菌性病害,广泛分布于热带、亚热带和温带地区,严重威胁世界粮食安全。病原青枯菌主要从土壤中侵染作物根系,其在土壤中存活能力强,因此防治极为困难。明确病原青枯菌土壤存活的关键影响因素有助于开发高效阻控土传青枯病的措施。国内外学者在青枯菌的土壤存活方面开展了大量研究,但由于影响青枯菌土壤存活的因素复杂,而相关研究多围绕单一因素展开,缺乏针对青枯菌土壤存活规律和影响因素的系统性认识。本文系统梳理了青枯菌的自身特性（基因、行为和代谢产物）及土壤生物、非生物因素对其在土壤中存活的影响,阐明了青枯菌在寄主存在时土体存活、向寄主根表方向运动迁移时根际存活以及入侵寄主根系时根表存活的主要影响因子,以期为土传青枯病的系统阻控提供参考。     

Response of the bacterial diversity and soil enzyme activity in particle-size fractions of Mollisol after different fertilization in a long-term experiment

Particle-size soils were fractionated for evaluating changes in the composition of bacterial community and enzyme activity in response to 13 years of fertilization. This study focused on Mollisol and its particle-size fractions of 200–2,000 μm (coarse sand sized), 63 to 200 μm (fine sand sized), 2 to 63 μm (silt sized), and 0.1 to 2 to μm (clay-sized). Long-term chemical fertilization lowered the pH of all particle fractions, whereas organic fertilizer application mitigated soil acidification. Nutrient concentrations depended on both fertilizer treatment and particle fractions and enzymes were unevenly active throughout the soil. Generally, the highest enzyme activities were observed in the silt and clay fractions of control soil and the soil treated with chemical fertilizer (N, P, and K (NPK)) and in the sand-sized fraction of soil treated with manure and chemical fertilizer (MNPK). Except for acid phosphomonoesterase, the other tested enzyme activities in coarse-sized fractions of MNPK soil were significantly higher than those of the control and NPK soils. Fertilization and soil fraction interactively (p?<?0.05) affected the enzyme activity. Denaturing gradient gel electrophoresis analysis showed that the bacterial community structure significantly differed in different particle sizes with a higher bacterial diversity in small-sized than in coarse-sized fractions. Dominant bands were excised and sequenced. We have found the following bacterial groups: Actinobacteria, γ-proteobacteria, and Acidobacteria. In addition, enrichment of organic matter in coarser fractions was related to greater bacterial diversity than any other treatment. Principal component analysis showed a smaller variability among fractions of the organic amended treatment. Redundancy analysis showed that the tested properties significantly affected the composition of bacterial community with the exception of C/N and available P. No significant correlation between enzyme activity and bacterial community composition was detected, whereas positive correlations between other soil properties and enzyme activities were observed to various extents. Probably, enzyme activities might be affected by specific functional bacterial communities rather than by the overall bacterial community. We concluded that the long-term application of organic manures contributed to the increase of soil organic matter content of particles higher than 200 mm, with higher bacterial diversity and increases in most of the enzyme activities.     

根际施用微生物有机肥防治连作西瓜枯萎病研究

为了探讨西瓜专用微生物有机肥料(BOF)对西瓜植株枯萎病的防治效果,采用盆栽试验研究了西瓜专用BOF对连作土壤上西瓜植株生长和枯萎病的防治效果以及西瓜枯萎病致病菌的数量分布的影响。结果表明:1）营养钵育苗和移栽土壤中都施用BOF的处理,未发现西瓜枯萎病植株,而对照植株则完全发病;2）施用BOF处理的致病菌（尖孢镰刀菌西瓜专化型）数量在根际土壤中为0.7×103 cfu/g,在土体土壤中为2.7×103 cfu/g,都控制在104 cfu/g数量级以下,而对照处理的数量分别达到了1.17×105 cfu/g和1.1×105 cfu/g;3）与对照比较,营养钵育苗时施用1%的BOF,西瓜苗期（播种后17 d）生物量都显著增加,根系生物量比地上部生物量提高了16.7个百分点（以鲜重计）和24.8个百分点(以干重计);营养钵育苗和移栽土壤中均施用BOF的处理,西瓜植株（生长67 d）生物量（干重）是对照的1.83倍;在营养钵育苗或移栽时施用BOF的处理,西瓜植株干重两者差异不大,分别是对照的1.28倍和1.27倍。采用营养钵育苗和移栽时都施用BOF的方法种植西瓜,能有效地促进西瓜植株生长,防止西瓜枯萎病发生,克服西瓜连作障碍。     

Antagonist Bacillus subtilis HJ5 controls Verticillium wilt of cotton by root colonization and biofilm formation

Cotton plants that are continuously subjected to monoculture suffer greatly from Verticillium wilt disease. The application of a novel bioorganic fertilizer (BOF) consisting of organic fertilizer combined with the antagonistic Bacillus subtilis strain HJ5 significantly suppressed Verticillium wilt of cotton. The disease incidence rates in soils that were treated with BOF (1 %, w/w) in the nursery stage, in the transplanted soil stage or in both stages, decreased by 42.9 %, 57.1 %, and 88.0 %, respectively, compared with controls. B. subtilis HJ5 was tagged with a plasmid-borne gfp gene encoding the green fluorescent protein to investigate its colonization behavior on cotton root surfaces. The results indicated that B. subtilis HJ5 predominantly colonizes the elongation and differentiation zones of the roots and forms micro-colonies in hydroponic and soil systems. The population of B. subtilis HJ5 in the rhizosphere and on cotton roots was also monitored. The number of B. subtilis HJ5 cells on the root surface reached a peak value of approximately 10⁷ cfu per gram of roots 3 days after exposure of the cotton seedlings to the bacteria. Probably the colonization of B. subtilis HJ5 on cotton roots is one of the mechanisms involved in protecting cotton plants from fungal infection.     

Pig manure vermicompost (PMVC) can improve phytoremediation of Cd and PAHs co-contaminated soil by Sedum alfredii

Purpose

A major challenge to phytoremediation of co-contaminated soils is developing strategies for efficient and simultaneous removal of multiple pollutants. A pot experiment was conducted to investigate the potential for enhanced phytoextraction of cadmium (Cd) by Sedum alfredii and dissipation of polycyclic aromatic hydrocarbons (PAHs) in co-contaminated soil by application of pig manure vermicompost (PMVC).

Materials and methods

Soil contaminated by Cd (5.53?mg?kg^?1 DW) was spiked with phenanthrene, anthracene, and pyrene together (250?mg?kg^?1 DW for each PAH). A pot experiment was conducted in a greenhouse with four treatments: (1) soil without plants and PMVC (Control), (2) soil planted with S. alfredii (Plant), (3) soil amended with PMVC at 5?% (w/w) (PMVC), and (4) treatment 2?+?3 (Plant?+?PMVC). After 90?days, shoot and root biomass of plants, Cd concentrations in plant and soil, and PAH concentrations in soil were determined. Abundance of PAH degraders in soil, soil bacterial community structure and diversity, and soil enzyme activities and microbial biomass carbon were measured.

Results and discussion

Application of PMVC to co-contaminated soil increased the shoot and root dry biomass of S. alfredii by 2.27- and 3.93-fold, respectively, and simultaneously increased Cd phytoextraction without inhibiting soil microbial population and enzyme activities. The highest dissipation rate of PAHs was observed in Plant?+?PMVC treatment. However, neither S. alfredii nor PMVC enhanced PAH dissipation when applied separately. Abundance of PAH degraders in soil was not significantly related to PAH dissipation rate. Plant?+?PMVC treatment significantly influenced the bacterial community structure. Enhanced PAH dissipation in the Plant?+?PMVC treatment could be due to the improvement of plant root growth, which may result in increased root exudates, and subsequently change bacterial community structure to be favorable for PAH dissipation.

Conclusions

This study demonstrated that remediation of Cd and PAHs co-contaminated soil by S. alfredii can be enhanced by simultaneous application of PMVC. Long-term evaluation of this strategy in co-contaminated field sites is needed.     

Long-term and legacy effects of manure application on soil microbial community composition

We analyzed soil prokaryotic and fungal community composition in soils with varying histories of cattle manure application. The manure treatments were (i) annual application for 43 years (MF), (ii) annual application for 14 years followed by 29 years without application (MF14), and (iii) annual application for 30 years followed by 13 years without application (MF30). An annual application of chemical nitrogen (N) fertilizer (CNF) and a non-amended control (Con) were also included. Soil prokaryotic evenness and diversity significantly decreased in MF relative to other treatments in fall, but were similar to the other fertilizer treatments in spring and summer. Distinct prokaryotic and fungal community composition was observed in MF compared to other treatments across fall, spring, and summer seasons. The MF treatment significantly increased the relative abundance of Firmicutes, Gammaproteobacteria, and Gemmatimonadetes, but significantly decreased the relative abundance of Acidobacteria. In fall, the soil prokaryotic and fungal community composition with MF30 was significantly different than the other fertilization treatments. Overall, the study showed that annual manure application (MF) led to a different microbial community composition than the other fertilizer treatments. Soil without manure application for 13 years (MF30) had a significantly different microbial community composition from other fertilizer treatments in fall, while the soil without manure application for 29 years (MF14) resembled a microbial community that had never received manure.