Efficacy of combined applications of antagonist bacteria and chemical resistance inducers for the management of Fusarium solani causing root rot in Withania somnifera

Application of Thiosalicylic acid+Bacillus cereus; O-Acetylsalicylic acid+Pseudomonas fluorescens reduced root rot severity by 85 and 88% and enhanced root yields by 358 and 419%, respectively, against Fusarium solani induced root rot disease in Withania somnifera. Reduction in disease severity was correlated with defence-related enzymes peroxidase, polyphenol oxidase and phenyl ammonium lyase.     

Induced systemic resistance (ISR) against pathogens in the context of induced plant defences

Induced systemic resistance (ISR) of plants against pathogens is a widespread phenomenon that has been intensively investigated with respect to the underlying signalling pathways as well as to its potential use in plant protection. Elicited by a local infection, plants respond with a salicylic-dependent signalling cascade that leads to the systemic expression of a broad spectrum and long-lasting disease resistance that is efficient against fungi, bacteria and viruses. Changes in cell wall composition, de novo production of pathogenesis-related-proteins such as chitinases and glucanases, and synthesis of phytoalexins are associated with resistance, although further defensive compounds are likely to exist but remain to be identified. In this Botanical Briefing we focus on interactions between ISR and induced resistance against herbivores that is mediated by jasmonic acid as a central signalling molecule. While many studies report cross-resistance, others have found trade-offs, i.e. inhibition of one resistance pathway by the other. Here we propose a framework that explains many of the thus far contradictory results. We regard elicitation separately from signalling and from production, i.e. the synthesis of defensive compounds. Interactions on all three levels can act independently from each other.     

Salt tolerant Methylobacterium mesophilicum showed viable colonization abilities in the plant rhizosphere

The source of infection has always been considered as an important factor in epidemiology and mostly linked to environmental source such as surface water, soil, plants and also animals. The activity of the opportunistic pathogens associated with plant root, their adaptation and survival under hostile environmental condition is poorly understood. In this study the salt tolerance ability of Methylobacterium mesophilicum and its colonization in the root and shoot of plants under severe drought and salt stress conditions were investigated. The colonization of plant by M. mesophilicum was investigated in a gnotobiotic sand system, and their survival in pots with saline soil. Bacterial strain was found to colonize rhizosphere of cucumber, tomato and paprika grown under normal and salt stress condition and reached up to 6.4 × 10⁴ and 2.6 × 10⁴ CFU/g root. The strain was resistant to Gentamicin, Ampicillin, Amoxicillin plus Clavulanic acid, Cefotaxime, neomycin, penicillin and was also tolerant to salinity stress (up to 6% NaCl). These abilities play important roles in enabling persistent colonization of the plant surface by M. mesophilicum strains. In conclusion, this study provides background information on the behaviour of opportunistic pathogen M. mesophilicum on plants and their survival in harsh environmental conditions.     

GSNOR-mediated de-nitrosylation in the plant defence response

A key feature of the plant defence response is the transient engagement of a nitrosative burst, resulting in the synthesis of reactive nitrogen intermediates (RNIs). Specific, highly reactive cysteine (Cys) residues of low pK_a are a major site of action for these intermediates. The addition of an NO moiety to a Cys thiol to form an S-nitrosothiol (SNO), is termed S-nitrosylation. This redox-based post-translational modification is emerging as a key regulator of protein function in plant immunity. Here we highlight recent advances in our understanding of de-nitrosylation, the mechanism that depletes protein SNOs, with a focus on S-nitrosoglutathione reductase (GSNOR). This enzyme controls total cellular S-nitrosylation indirectly during the defence response by turning over S-nitrosoglutathione (GSNO), a major cache of NO bioactivity.     

外源抗虫基因与植物自身抗虫防御体系的互作

外源抗虫基因的导入将导致植株本身生理代谢等方面发生改变,从而对植物原有抗虫防御体系产生影响。本文综述了外源基因导入对植株外部形态结构、内在生化抗性以及诱导抗性的影响,为外源、内源抗虫体系的相互利用以及抗性植物的研制与推广提供参考依据。     

Interpreting phenotypic variation in plant allelochemistry: problems with the use of concentrations

Ecologists often use concentrations of defensive compounds as measures of plant allocation to defence and/or allelochemical production. I demonstrate that this practice may lead to erroneous conclusions because plants produce and allocate molecules (quantities) of compounds whereas concentrations reflect the distribution of these quantities in plant tissues and are, therefore, functions of plant biomass. As a tool for distinguishing between shifts in allelochemical production versus changes in plant biomass in determining allelochemical concentrations, I suggest using a technique known as graphical vector analysis (GVA) which has been developed for diagnosing nutrient limitations in forest stands, but has seldom been applied by researchers studying plant allelochemicals. I used data from several published studies to demonstrate how GVA can be applied to interpret ontogenetic and environmental effects on allelochemical levels and to compare the results obtained for different allelochemical types, plant species, treatments and experiments. These examples show that changes in plant biomass per se are an important source of variation in allelochemical concentrations and, therefore, concentration data can be easily misinterpreted if changes in absolute content and plant biomass are not considered simultaneously. Because studies reporting variation in allelochemical concentrations have been considered as tests for general theories of plant chemical defence, evidence in support of or against these theories should be re-examined using multivariate techniques such as analysis of covariance, allometric analysis and GVA. Received: 16 September 1998 / Accepted: 4 March 1999     

Molecular and biochemical basis of the interaction between tomato and its fungal pathogen Cladosporium fulvum

The interaction between the biotrophic fungal pathogen Cladosporium fulvum and tomato complies with the genefor-gene model. Resistance, expressed as a hypersensitive response (HR) followed by other defence responses, is based on recognition of products of avirulence genes from C. fulvum (race-specific elicitors) by receptors (putative products of resistance genes) in the host plant tomato. The AVR9 elicitor is a 28 amino acid (aa) peptide and the AVR4 elicitor a 106 aa peptide which both induce HR in tomato plants carrying the complementary resistance genes Cf9 and Cf4, respectively. The 3-D structure of the AVR9 peptide, as determined by 1H NMR, revealed that AVR9 belongs to a family of peptides with a cystine knot motif. This motif occurs in channel blockers, peptidase inhibitors and growth factors. The Cf9 resistance gene encodes a membrane-anchored extracellular glycoprotein which contains leucine-rich repeats (LRRs). 125I labeled AVR9 peptide shows the same affinity for plasma membranes of Cf9+ and Cf9- tomato leaves. Membranes of solanaceous plants tested so far all contain homologs of the Cf9 gene and show similar affinities for AVR9. It is assumed that for induction of HR, at least two plant proteins (presumably CF9 and one of his homologs) interact directly or indirectly with the AVR9 peptide which possibly initiates modulation and dimerisation of the receptor, and activation of various other proteins involved in downstream events eventually leading to HR. We have created several mutants of the Avr9 gene, expressed them in the potato virus X (PVX) expression system and tested their biological activity on Cf9 genotypes of tomato. A positive correlation was observed between the biological activity of the mutant AVR9 peptides and their affinity for tomato plasma membranes. Recent results on structure and biological activity of AVR4 peptides encoded by avirulent and virulent alleles of the Avr4 gene (based on expression studies in PVX) are also discussed as well as early defence responses induced by elicitors in tomato leaves and tomato cell suspensions.     

Proteomic dissection of plant responses to various pathogens

During their growth and development, plants are vulnerable to the effects of a variety of pathogens. Proteomics technology plays an important role in research studies of plant defense mechanisms by mining the expression changes of proteins in response to various biotic stresses. This review article provides a comprehensive overview of the latest developments in international proteomic research on plant biotic stress. It summarizes the methods commonly used in plant proteomic research to investigate biotic stress, analyze the protein responses of plants in adverse conditions, and reviews the applications of proteomics combined with transgenic technology in plant protection.     

Ecological costs of biotrophic versus necrotrophic pathogen resistance, the hypersensitive response and signal transduction

Recent advances along numerous research avenues show that plant interactions with biotrophic and necrotrophic pathogens use similar pathways with opposing effects. The hypersensitive response is associated with increased biotroph resistance but decreased necrotroph resistance. In plant/herbivore interactions, opposing effects of defenses against specialist versus generalist herbivores are controlled by plant secondary metabolites, where a metabolite that provides resistance to generalist herbivores may stimulate specialist herbivores. This multi-trophic interaction is presented as an ecological cost of plant resistance, but similar concepts are rarely applied to plant interactions with different classes of pathogens. In this review, we begin to describe how necrotrophic pathogens may place an ecological cost upon plant resistance to biotrophic pathogens. We separate these potential ecological costs into three concepts: (1) the local cost of the hypersensitive response, (2) organismal cost of having machinery for a hypersensitive response and (3) antagonism between salicylate and jasmonate signaling. We describe the literature supporting these concepts and some predictions that they generate.     

Phenotypic and genetic patterns of resistance to the pathogen Phakopsora pachyrhizi in populations of Glycine canescens

Summary Phenotypic patterns of resistance to nine races of the pathogen Phakopsora pachyrhizi (soybean rust) in two natural populations of Glycine canescens were determined. In both populations there was considerable variability both within and between different host lines in their resistance or susceptibility to the nine different pathogen races. The genetic basis of these patterns of resistance was analyzed through an extensive series of crosses. In both host populations resistance was conditioned by single dominant genes with major phenotypic effects. One, two or three such genes were present in each host line. Using the principles of the gene-for-gene hypothesis, knowledge about the number of resistance genes present in each host line and by cross comparison of the phenotypic patterns of disease resistance detected in each line, estimates were made of the number of resistance genes or alleles present in each population of G. canescens. The two populations contained a minimum of 10 and 12 resistance genes. The relevance of these results to agriculture is discussed briefly.     

Genetically-based plant resistance traits affect arthropods,fungi, and birds

We examine how the distribution of a leafgalling aphid (Pemphigus betae) affects other species associated with natural stands of hybrid cottonwoods (Populus angustifolia x P. fremontii). Aphid transfers on common-garden clones and RFLP analysis show that resistance to aphids in cottonwoods is affected by plant genotype. Because susceptible trees typically support thousands of galls, while adjacent resistant trees have few or none, plant resistance traits that affect the distribution of this abundant herbivore may directly and/or indirectly affect other species. We found that the arthropod community of aphid-susceptible trees had 31% greater species richness and 26% greater relative abundance than aphid-resistant trees. To examine direct and indirect effects of plant resistance traits on other organisms, we experimentally excluded aphids and found that abundances and/or foraging behavior of arthropods, fungi, and birds were altered. First, exclusion of gall aphids on susceptible trees resulted in a 24% decrease in species richness and a 28% decrease in relative abundance of the arthropod community. Second, exclusion of aphids also caused a 2- to 3-fold decrease in foraging and/or presence of three taxa of aphid enemies: birds, fungi, and insects. Lastly, aphidexclussion resulted in a 2-fold increase in inquilines (animals who live in abodes properly belonging to another). We also found that fungi and birds responded to variation in gall density at the branch level. We conclude plant resistance traits affect diverse species from three trophic levels supporting a bottom-up influence of plants on community structure.     

Synergies and trade-offs between insect and pathogen resistance in maize leaves and roots

Determining links between plant defence strategies is important to understand plant evolution and to optimize crop breeding strategies. Although several examples of synergies and trade-offs between defence traits are known for plants that are under attack by multiple organisms, few studies have attempted to measure correlations of defensive strategies using specific single attackers. Such links are hard to detect in natural populations because they are inherently confounded by the evolutionary history of different ecotypes. We therefore used a range of 20 maize inbred lines with considerable differences in resistance traits to determine if correlations exist between leaf and root resistance against pathogens and insects. Aboveground resistance against insects was positively correlated with the plant's capacity to produce volatiles in response to insect attack. Resistance to herbivores and resistance to a pathogen, on the other hand, were negatively correlated. Our results also give first insights into the intraspecific variability of root volatiles release in maize and its positive correlation with leaf volatile production. We show that the breeding history of the different genotypes (dent versus flint) has influenced several defensive parameters. Taken together, our study demonstrates the importance of genetically determined synergies and trade-offs for plant resistance against insects and pathogens.     

2009年度宁波市妇儿医院主要病原菌的临床分布及耐药性分析

目的了解宁波市妇儿医院主要病原菌的临床分布及耐药性分析。方法血液培养采用法国生物梅里埃公司的BacT/Alert3D,菌株鉴定采用法国生物梅里埃公司的VITEK 60分析仪,药敏试验采用K-B法,纸片扩散确证试验检测ESBLs。结果前10位细菌构成比依次是大肠埃希菌(13.4%)、白色念珠菌(8.7%)、阴道加德纳菌(7.8%)、表皮葡萄球菌(6.9%)、金黄色葡萄球菌(5.6%)、肺炎克雷伯菌(4.9%)、鲍曼复合醋酸钙不动杆菌(3.9%)、粪肠球菌(D群)(3.1%)、铜绿假单胞菌(2.7%)和溶血葡萄球菌(2.0%)。大肠埃希菌539株中产ESBLs阳性率为52.5%,肺炎克雷伯菌195株中产ESBLs阳性率为45.2%。大肠埃希菌主要分离于尿液,其次是脓液/切口。肺炎克雷伯菌在痰及咽拭子中所占比例最高。46株铜绿假单胞菌和11株鲍曼复合醋酸钙不动杆菌对亚胺培南耐药。结论对产ESBLs的肺炎克雷伯菌和大肠埃希菌、耐甲氧西林金黄色葡萄球菌(MRSA)和耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)、耐亚胺培南的鲍曼复合醋酸钙不动杆菌和铜绿假单胞菌,应加强隔离预防,控制在医院内的扩散,减少耐药菌株产生。     

Engineering bacteriocin‐mediated resistance against the plant pathogen Pseudomonas syringae

The plant pathogen, Pseudomonas syringae (Ps), together with related Ps species, infects and attacks a wide range of agronomically important crops, including tomato, kiwifruit, pepper, olive and soybean, causing economic losses. Currently, chemicals and introduced resistance genes are used to protect plants against these pathogens but have limited success and may have adverse environmental impacts. Consequently, there is a pressing need to develop alternative strategies to combat bacterial disease in crops. One such strategy involves using narrow‐spectrum protein antibiotics (so‐called bacteriocins), which diverse bacteria use to compete against closely related species. Here, we demonstrate that one bacteriocin, putidacin L1 (PL1), can be expressed in an active form at high levels in Arabidopsis and in Nicotiana benthamiana in planta to provide effective resistance against diverse pathovars of Ps. Furthermore, we find that Ps strains that mutate to acquire tolerance to PL1 lose their O‐antigen, exhibit reduced motility and still cannot induce disease symptoms in PL1‐transgenic Arabidopsis. Our results provide proof‐of‐principle that the transgene‐mediated expression of a bacteriocin in planta can provide effective disease resistance to bacterial pathogens. Thus, the expression of bacteriocins in crops might offer an effective strategy for managing bacterial disease, in the same way that the genetic modification of crops to express insecticidal proteins has proven to be an extremely successful strategy for pest management. Crucially, nearly all genera of bacteria, including many plant pathogenic species, produce bacteriocins, providing an extensive source of these antimicrobial agents.     

孕产妇产后感染病原菌的构成及耐药性分析

目的 了解孕产妇产后感染病原菌的分布及耐药现状,为临床抗感染治疗提供依据。方法 采用法国生物梅里埃VITEK-2全自动细菌鉴定分析仪进行鉴定和药敏试验,采用WHONET 5.6软件进行数据统计分析。结果 2012年1月至2015年12月我院产科病房孕产妇共60 229例,产后感染336例,感染主要部位为宫腔、切口、血液和尿液。主要病原菌依次为大肠埃希菌、粪肠球菌、B型链球菌和金黄色葡萄球菌。大肠埃希菌对头孢他啶、头孢吡肟、妥布霉素、阿米卡星、头孢替坦、哌拉西林/他唑巴坦、头孢哌酮/舒巴坦、亚胺培南耐药率均<15.00%;粪肠球菌和无乳链球菌对氨苄西林、青霉素耐药率为0.00%,耐甲氧西林金黄色葡萄球菌（MRSA）耐药率高达19.05%。结论 我院产科病房感染主要部位为宫腔（43.18%）,减少剖宫产率可以降低产后感染发生率,感染的主要病原菌为大肠埃希菌和粪肠球菌（63.23%）,在预防用药的选择上应选择对大肠埃希菌和粪肠球菌均有效的抗生素以减少产后感染的发生率,同时了解孕产妇产后感染病原菌的构成和耐药性,有助于临床更快速有效地治疗产后感染。     

Molecular dialogues between Trichoderma and roots: Role of the fungal secretome

Trichoderma species are opportunistic fungi residing primarily in soil, tree bark and on wild mushrooms. Trichoderma is capable of killing other fungi and penetrating plant roots, and is commonly used as both a biofungicide and inducer of plant defence against pathogens. These fungi also exert other beneficial effects on plants including growth promotion and tolerance to abiotic stresses, primarily mediated by their intimate interactions with roots. In root–microbe interactions (both beneficial and harmful), fungal secreted proteins play a crucial role in establishing contact with the roots, fungal attachment, root penetration and triggering of plant responses. In Trichoderma–root interactions, the sucrose present in root exudates has been demonstrated to be important in fungal attraction. Attachment to roots is mediated by hydrophobin-like proteins, and secreted swollenins and plant cell wall degrading enzymes facilitate internalization of the fungal hyphae. During the early stage of penetration, suppression of plant defence is vital to successful initial root colonisation; this is mediated by small soluble cysteine-rich secreted proteins (effector-like proteins). Up to this stage, Trichoderma's behaviour is similar to that of a plant pathogen invading root structures. However, subsequent events like oxidative bursts, the synthesis of salicylic acid by the plants, and secretion of elicitor-like proteins by Trichoderma spp. differentiate this fungus from pathogens. These processes induce immunity in plants that help counter subsequent invasion by plant pathogens and insects. In this review, we present an inventory of soluble secreted proteins from Trichoderma that might play an active role in beneficial Trichoderma–plant interactions, and review the function of such proteins where known.     

Direct trade-off between cyanogenesis and resistance to a fungal pathogen in lima bean (Phaseolus lunatus L.)

1.  Plants are simultaneously attacked by multiple herbivores and pathogens. While some plant defences act synergistically, others trade-off against each other. Such trade-offs among resistances to herbivores and pathogens are usually explained by the costs of resistance, i.e. resource limitations compromising a plant's overall defence.
2.  Here, we demonstrate that trade-offs can also result from direct negative interactions among defensive traits. We studied cyanogenesis (release of HCN) of lima bean (Fabaceae: Phaseolus lunatus ) and effects of this efficient anti-herbivore defence on resistance to a fungal pathogen (Melanconiaceae: Colletotrichum gloeosporioides ).
3.  Leaf tissue destruction by fungal growth was significantly higher on high cyanogenic (HC) lima bean accessions than on low cyanogenic (LC) plants. The susceptibility of HC accessions to the fungal pathogen was strongly correlated to reduced activity of resistance-associated polyphenol oxidases (PPOs) in leaves of these plants. LC accessions, in contrast, showed high PPO activity, which was correlated with distinct resistance to C. gloeosporioides .
4.  Experimentally applied, gaseous HCN reduced PPO activity and significantly increased the size of lesions caused by C. gloeosporioides in LC leaves.
5.  Field observations of a wild lima bean population in Mexico revealed a higher infection rate of HC compared to LC plant individuals. The types of lesions observed on the different cyanogenic plants in nature were similar to those observed on HC and LC plants in the laboratory.
6.   Synthesis. We suggest that cyanogenesis of lima bean directly trades off with plant defence against fungal pathogens and that the causal mechanism is the inhibition of PPOs by HCN. Our findings provide a functional explanation for the observed phenomenon of the low resistance of HC lima beans in nature.     

The effect of protein supplied in the growth medium on plant pathogen resistance

Externally supplied protein (bovine serum albumin, BSA) affects root development of Arabidopsis, increasing root biomass, root hair length, and root thickness. While these changes in root morphology may enhance access to soil microenvironments rich in organic matter, we show here that the presence of protein in the growth medium increases the plant''s resilience to the root pathogen Cylindrocladium sp.