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The role of root exudates in mediating plant–microbe interactions has been well documented. However, the function of volatile organic compounds (VOCs) emitted by plant roots has only recently begun to attract attention. This newly recognized relevance of belowground VOCs has so far mostly been tested using systems limited to a two-compartment Petri-dish design. Furthermore, many of the plant–microbe interaction studies have only investigated the effects of microbial VOCs on plant growth. Here, we go two steps further. First we investigated the volatile profile of healthy and pathogen (Fusarium oxysporum) infected tomato roots grown in soil. We then used a unique soil-based olfactometer-choice assay to compare the migration pattern of four beneficial bacteria (Bacillus spp.) towards the roots of the tomato plants. We demonstrate that the blend of root-emitted VOCs differs between healthy and diseased plants. Our results show that VOCs are involved in attracting bacteria to plant roots. [ABSTRACT FROM AUTHOR]

Fire blight is one of the most devastating plant diseases in the world. This paper proposes a Filippov fire-blight model incorporating cutting off infected branches and replanting susceptible trees. The Filippov-type model is formulated by considering that no control strategy is taken if the number of infected trees is less than an infected threshold level I c ; further, we cut off infected branches once the number of infected trees exceeds I c ; meanwhile, we replant trees if the number of susceptible trees is less than a susceptible threshold level S c . The global dynamical behaviour of the Filippov system is investigated. It is shown that model solutions ultimately converge to the positive equilibrium that lies in the region above I c , or below I c , or on I = I c , as we vary the susceptible and infected threshold values S c and I c . Our results indicate that proper combinations of the susceptible and infected threshold values based on the threshold policy can lead the number of infected trees to an acceptable level, when complete eradication is not economically desirable. [ABSTRACT FROM AUTHOR]

Background: Reed plants are widely distributed in Iraq and responsible to invade irrigation channels and drainage systems. Aim: The present study was designed to identify and characterize the causal agent of reed wilt disease. Methods: Disease symptoms, characteristics and growth pattern of causal agent were investigated. Results: Reed wilt disease has been observed during the survey which was held at the end of October 2016. The percent of natural infection of this disease was found in the range of 7-18%, the causal agent was identified as Marasmiellus palmivorus based on macro and microscopic characteristics. Microscopic observation of M. palmivorus revealed the engendered white cottony mycelia turned to creamy with clamp connection. Radial growth of this fungus was greatly varied according to the type of additives supplemented in the growth media and results were as following: M. oleifera (7.8 cm) > wheat (7.7cm) > Reed (7.4 cm) > millet (6.8 cm) > Caladium (6.7 cm) > PDA (5.86 cm) > onion (2.94 cm). Conclusion: The results of present study concluded that M. palmivorus was recorded as the causal agent of wilt disease on reed plant for the first time in Iraq and possibly for other countries as far as we know. Also, this fungus could be act as bio-herbicidal against reed plants, but more attention should be paid to this point. [ABSTRACT FROM AUTHOR]

Okra (Abelmoschus esculentus) is an economically important plant in China which is widely used in food, medicine and manufacturing. In September 2014, diseased samples of okra were collected in Yanqing District, Beijing City, China. Symptoms were brown to brownish black, sunken cavities on the leaves and fruits. The disease occurred on okra plants with an incidence of 35–55% in different fields. According to morphological and cultural characteristics, and sequence analysis of the internal transcribed spacer (ITS) and actin (ACT) regions, the pathogen was identified asBoeremia exigua(Desm.) Aveskamp, Gruyter & Verkley. Pathogenicity of the isolated fungus was conducted on okra fruits and on potted plants. Symptoms similar to those occurring in the field were reproduced. This is the first report of Boeremia spot of okra caused byBoeremia exiguain China. [ABSTRACT FROM PUBLISHER]

Computers have been used for mechanization and automation in different applications of agriculture/horticulture. The critical decision on the agricultural yield and plant protection is done with the development of expert system (decision support system) using computer vision techniques. One of the areas considered in the present work is the processing of images of plant diseases affecting agriculture/horticulture crops. The first symptoms of plant disease have to be correctly detected, identified, and quantified in the initial stages. The color and texture features have been used in order to work with the sample images of plant diseases. Algorithms for extraction of color and texture features have been developed, which are in turn used to train support vector machine (SVM) and artificial neural network (ANN) classifiers. The study has presented a reduced feature set based approach for recognition and classification of images of plant diseases. The results reveal that SVM classifier is more suitable for identification and classification of plant diseases affecting agriculture/horticulture crops. [ABSTRACT FROM AUTHOR]

Plant germplasm resources with natural resistance against globally important toxigenic Fusarium are inadequate. CWP2, a Fusarium genus-specific antibody, confers durable resistance to different Fusarium pathogens that infect cereals and other crops, producing mycotoxins. However, the nature of the CWP2 target is not known. Thus, investigation of the gene coding for the CWP2 antibody target will likely provide critical insights into the mechanism underlying the resistance mediated by this disease-resistance antibody., Immunoblots and mass spectrometry analysis of two-dimensional electrophoresis gels containing cell wall proteins from Fusarium graminearum ( Fg) revealed that a glyoxal oxidase ( GLX) is the CWP2 antigen. Cellular localization studies showed that GLX is localized to the plasma membrane., This GLX efficiently catalyzes hydrogen peroxide production; this enzymatic activity was specifically inhibited by the CWP2 antibody. GLX-deletion strains of Fg, F. verticillioides ( Fv) and F. oxysporum had significantly reduced virulence on plants. The GLX-deletion Fg and Fv strains had markedly reduced mycotoxin accumulation, and the expression of key genes in mycotoxin metabolism was downregulated., This study reveals a single gene-encoded and highly conserved cellular surface antigen that is specifically recognized by the disease-resistance antibody CWP2 and regulates both virulence and mycotoxin biosynthesis in Fusarium species. [ABSTRACT FROM AUTHOR]

The analysis of the spatial distribution of plant diseases requires the availability of trustworthy geostatistical methods. The mean distance tests (MDT) are here proposed as a series of permutation and randomization tests to assess the spatial distribution of plant diseases when the variable of phytopathological interest is categorical. A user-friendly software to perform the tests is provided. Estimates of power and type 1 error, obtained with Monte Carlo simulations, showed the reliability of the MDT (power > 0.80: type I error < 0.05). A biological validation on the spatial distribution of spores of two fungal pathogens causing root rot on conifers was successfully performed by verifying the consistency between the MDT responses and previously published data. An application of the MDT was carried out to analyze the relation between the plantation density and the distribution of the infection of Gnomoniopsis castanea. an emerging fungal pathogen causing nut rot on sweet chestnut. Trees carrying nuts infected by the pathogen were randomly distributed in areas with different plantation densities, suggesting that the distribution of G. castanea was not related to the plantation density. The MDT could be used to analyze the spatial distribution of plant diseases both in agricultural and natural ecosystems. [ABSTRACT FROM AUTHOR]

Plant diseases are often thought to be caused by one species or even by a specific strain. Microbes in nature, however, mostly occur as part of complex communities and this has been noted since the time of van Leeuwenhoek. Interestingly, most laboratory studies focus on single microbial strains grown in pure culture; we were therefore unaware of possible interspecies and/or inter-kingdom interactions of pathogenic microbes in the wild. In human and animal infections, it is now being recognized that many diseases are the result of multispecies synergistic interactions. This increases the complexity of the disease and has to be taken into consideration in the development of more effective control measures. On the other hand, there are only a few reports of synergistic pathogen-pathogen interactions in plant diseases and the mechanisms of interactions are currently unknown. Here we review some of these reports of synergism between different plant pathogens and their possible implications in crop health. Finally, we briefly highlight the recent technological advances in diagnostics as these are beginning to provide important insights into the microbial communities associated with complex plant diseases. These examples of synergistic interactions of plant pathogens that lead to disease complexes might prove to be more common than expected and understanding the underlying mechanisms might have important implications in plant disease epidemiology and management. [ABSTRACT FROM AUTHOR]

Several questions remain unanswered on escape mechanism of lentil against Fusarium wilt caused by Fusarium oxysporum f. sp. Lentis. Consequently, this study was designed with few parameters including inoculum density, temporal sowing (associated with soil temperature) and its thermal effect with the pathogen. Increased amount of inoculum resulted higher number of diseased plants. However, increased inoculum was proved to be ineffective under cooler condition. Increase in inoculum density numerically enhanced disease incidence at each sowing time (temporal sowing); however, significant difference (p<0.05) increase in disease incidence was detected in the October sown batch. Early sowing associated with high soil temperature (22.6°C) rendered maximum wilt incidence (97.2%), which is complemented in the laboratory test exhibited by maximum radial growth of the fungus at higher temperature (27°C). This report suggests development of late sown variety could be a good option to suppress this disease. [ABSTRACT FROM AUTHOR]

Guava ( Psidium guajava) wilt, caused by Nalanthamala psidii, has been a destructive disease in Taiwan, Thailand, Malaysia and South Africa since it was first reported in guava in 1926. However, the primary infection site of the pathogen remains controversial. This study was conducted to elucidate the importance of root infection by N. psidii in guava orchards in Taiwan. During 2010-2012, a total of 23 guava trees were sampled from three orchards and the isolation frequency of N. psidii from wounded twigs and roots was analysed. The overall isolation frequency of N. psidii was significantly higher ( P < 0·01) from roots than trimmed and pruned twigs. Nalanthamala psidii was detected in 53·5% of the root samples from a guava tree showing mild symptoms of wilt and in 0·9% of the root samples from another guava tree without visible symptoms of wilt; however, no N. psidii was detected in the tissues of the trimming and pruning wounds in either tree. Cross sections of diseased guava branches showed that N. psidii colonized the lower part more heavily than the upper part of the branch. When guava trees were inoculated by applying N. psidii-infested soil to injured roots, wilt symptoms developed within 6-13 months. Furthermore, N. psidii infection of guava seedlings via root contact with wilted guava trunks was recorded for the first time in Taiwan, demonstrating the importance of root infection in guava wilt disease. [ABSTRACT FROM AUTHOR]

Phacidiopycnis washingtonensis is the cause of speck rot, a recently reported postharvest fruit rot disease of apple. The pathogen is believed to incite infections in the field, and disease symptoms become evident only during storage. To determine the timing of apple fruit infection in relation to development of speck rot in storage, 'Red Delicious' and 'Fuji' apple fruit were inoculated in the orchard with P. washingtonensis at different times during the growing season, harvested, and monitored for decay development during storage at 0°C. Fruit inoculated in both field and laboratory also were used to identify the infection courts and mode of apple fruit penetration by P. washingtonensis. In all 3 years, stem-end speck rot and calyx-end speck rot developed during cold storage on fruit inoculated during the growing season, regardless of inoculation time; and the incidence of total speck rot in storage increased as the fruit inoculation time approached harvest. On fruit floral parts, the pathogen colonized sepals at higher rates than stamens. Availability of naturally occurring necrotic tissues favored the colonization of the fungus on sepals. Histological studies indicated that infection occurred through micro-cracks on the surfaces of pedicels and sepals of the fruit, and invasion of these tissues was restricted between the cuticle and epidermis. Findings of this study will assist in the development of effective control strategies for speck rot. [ABSTRACT FROM AUTHOR]

The plant-parasitic nematode Pratylenchus penetrans is a major constraint to the production of red raspberry. To determine whether several popular raspberry cultivars in Washington State differ in susceptibility to P penetrans and whether post-plant nematicides treatments are warranted, five independent, multiyear trials were conducted. Trials in existing plantings of 'Cascade Bounty', 'Chemainus', 'Meeker' (two trials), and 'Saanich' raspberry were established in northwest Washington. Treated plots were protected from P. penetrans by applying nematicides over a 3-year period, while nontreated plots received no nematicides. P. penetrans population densities in soil and root samples were assessed spring and fall of each year. In addition, impact of P. penetrans on raspberry yield, fruit composition, cane production, and root biomass was measured several times in each cultivar during the 3-year study. P. penetrans root population densities in nematicide-treated plots were consistently lower than those in nontreated plots at all the samplings. There were few consistent treatment differences in fine root biomass, the preferred feeding sites for P. penetrans. However, a complete root system sampling of one of the cultivars did show greater fine root biomass in treated plants compared with nontreated plants. When differences were observed aboveground, treated plants yielded less than corresponding nontreated plants, indicating that the nematicides may have been phytotoxic to some of the cultivars. This study suggests that post-plant nematicide applications are of limited benefit because, at least during the 3-year time period of this study, there were few observable benefits of protecting these raspberry cultivars from P. penetrans. [ABSTRACT FROM AUTHOR]

Although Botrytis cinerea is known for its ability to produce high amounts of spores on diseased plants, enabling it to complete rapidly numerous developmental cycles in favorable environments, population genetics studies of this fungus indicate enormous diversity and limited clonal spread. Here, we report an exception to this situation in the settings of commercial tomato greenhouses. The genotypic characterization of 712 isolates collected from the air and from diseased plants, following the development of gray mold epidemics in four greenhouses in southern France, revealed the presence of a few predominant genotypes in a background of highly diverse populations. The comparison of genotypic profiles for isolates collected in the air or on the plants was compatible with the hypothesis of an entry in the greenhouse of substantial amounts of inoculum from the outside environment but it also highlighted the importance of secondary inoculum produced within the crop. The overall results of this work suggest that sporulation could be an important target for disease management strategies in the greenhouse. [ABSTRACT FROM AUTHOR]

Recently, a new disease was reported on greenhouse tomato plants in both Quebec, Canada and Maine, United States. Symptomatic plants bore brown lesions at graft points and pruning sites, resulting in expanding cankers with clearly delineated margins. Diseased plants eventually wilted and died within a few weeks following the appearance of the first symptoms. The symptoms are reminiscent of infection by Fusarium oxysporum f. sp. radicis-lycopersici, with the notable difference of a discoloration of the pith area rather than the vascular tissues. A homothallic Fusarium sp. was consistently recovered from these lesions. Sequencing of the internal transcribed spacer and the partial translation elongation factor 1-a gene identified the species as F. striatum. Pathogenicity tests with F. striatum isolates from diseased tissues reproduced disease symptoms in tomato similar to those observed on tomato plants in the greenhouses. Specific detection of F. striatum from mycelia and diseased and disease-free plant tissues was achieved by developing a polymerase chain reaction-based test. These results establish, for the first time, that the species F. striatum is the cause of crown and stem rot affecting tomato in North America. In addition F. striatum was detected from all sampled tissues of plants delivered by the nursery common to both growers, suggesting that the transplants would be the source of the inoculum. [ABSTRACT FROM AUTHOR]

Genes encoding plant nucleotide-binding leucine-rich repeat (NB-LRR) proteins confer dominant resistance to diverse pathogens. The wild-type potato NB-LRR protein Rx confers resistance against a single strain of potato virus X (PVX), whereas LRR mutants protect against both a second PVX strain and the distantly related poplar mosaic virus (PopMV). In one of the Rx mutants there was a cost to the broad-spectrum resistance because the response to PopMV was transformed from a mild disease on plants carrying wild-type Rx to a trailing necrosis that killed the plant. To explore the use of secondary mutagenesis to eliminate this cost of broad-spectrum resistance, we performed random mutagenesis of the N-terminal domains of this broad-recognition version of Rx and isolated four mutants with a stronger response against the PopMV coat protein due to enhanced activation sensitivity. These mutations are located close to the nucleotide-binding pocket, a highly conserved structure that likely controls the "switch" between active and inactive NB-LRR conformations. Stable transgenic plants expressing one of these versions of Rx are resistant to the strains of PVX and the PopMV that previously caused trailing necrosis. We conclude from this work that artificial evolution of NB-LRR disease resistance genes in crops can be enhanced by modification of both activation and recognition phases, to both accentuate the positive and eliminate the negative aspects of disease resistance. [ABSTRACT FROM AUTHOR]

The use of bacteriophages as an effective phage therapy strategy faces significant challenges for controlling plant diseases in the phyllosphere. A number of factors must be taken into account when considering phage therapy for bacterial plant pathogens. Given that effective mitigation requires high populations of phage be present in close proximity to the pathogen at critical times in the disease cycle, the single biggest impediment that affects the efficacy of bacteriophages is their inability to persist on plant surfaces over time due to environmental factors. inactivation by UV light is the biggest factor reducing bacteriophage persistence on plant surfaces. Therefore, designing strategies that minimize this effect are critical. For instance, application timing can be altered: instead of morning or afternoon application, phages can be applied late in the day to minimize the adverse effects of Uv and extend the time high populations of phage persist on leaf surfaces. Protective formulations have been identified which prolong phage viability on the leaf surface, however, Uv inactivation continues to be the major limiting factor in developing more effective bacteriophage treatments for bacterial plant pathogens. Other strategies, which have been developed to potentially increase persistence of phages on leaf surfaces, rely on establishing non-pathogenic or attenuated bacterial strains in the phyllosphere that are sensitive to the phage(s) specific to the target bacterium. we have also learned that selecting the correct phages for disease control is critical. This requires careful monitoring of bacterial strains in the field to minimize development of bacterial strains with resistance to the deployed bacteriophages. we also have data that indicate that selecting the phages based on in vivo assays may also be important when developing use for field application. Although bacteriophages have potential in biological control for plant disease control, there are major obstacles, which must be considered. [ABSTRACT FROM AUTHOR]

Yellowish lesions with downy, gray growth developed on the leaves of carnations ( Dianthus caryophyllus) in a greenhouse in Hokkaido Prefecture, Japan, in March 2011. We identified the fungus on diseased plants as Peronospora dianthicola on the basis of the morphologies of the conidia, conidiophores, and oospores. To confirm pathogenicity of the fungus, we inoculated healthy plants with a conidial suspension of the fungus, and the plants developed the same signs and symptoms as the naturally infected plants. We then reidentified P. dianthicola from the diseased lesions. This is the first report of downy mildew of carnation in Japan. [ABSTRACT FROM AUTHOR]

Bacterial blight, caused by the phytopathogen Pseudomonas cannabina pv. alisalensis, is an emerging disease afflicting important members of the Brassicaceae family. The disease is often misdiagnosed as pepper spot, a much less severe disease caused by the related pathogen Pseudomonas syringae pv. maculicola. We have developed a phage-based diagnostic that can both identify and detect the causative agent of bacterial blight and differentiate the two pathogens. A recombinant "light"-tagged reporter phage was generated by integrating bacterial luxAB genes encoding luciferase into the genome of P. cannabina pv. alisalensis phage PBSPCA1. The PBSPCA1::luxAB reporter phage is viable and stable and retains properties similar to those of the wild-type phage. PBSPCA1::luxAB rapidly and sensitively detects P. cannabina pv. alisalensis by conferring a bioluminescent signal response to cultured cells. Detection is dependent on cell viability. Other bacterial pathogens of Brassica species such as P. syringae pv. maculicola, Pseudomonas marginalis, Pectobacterium carotovorum, Xanthomonas campestris pv. campestris, and X. campestris pv. raphani either do not produce a response or produce significantly attenuated signals with the reporter phage. Importantly, the reporter phage detects P. cannabina pv. alisalensis on diseased plant specimens, indicating its potential for disease diagnosis. [ABSTRACT FROM AUTHOR]

Compartmental models have become the dominant theoretical paradigm in mechanistic modeling of plant disease and offer well-known advantages in terms of analytic tractability, ease of simulation, and extensibility. However, underlying assumptions of constant rates of infection and of exponentially distributed latent and infectious periods are difficult to justify. Although alternative approaches, including van der Plank's seminal discrete time model and models based on the integro-differential formulation of Kermack and McKendrick's model, have been suggested for plant disease and relax these unrealistic assumptions, they are challenging to implement and to analyze. Here. we propose an extension to the susceptible, exposed, infected, and removed (SEIR) compartmental model, splitting the latent and infection compartments and thereby allowing time-varying infection rates and more realistic distributions of latent and infectious periods to be represented. Although the model is, in fact, more general, we specifically target plant disease by demonstrating how it can represent both the van der Plank model and the most commonly used variant of the Kermack and McKendrick (K & M) model (in which the infectivity response is delay Gamma distributed). We show how our reformulation retains the numeric and analytic tractability of SEIR models, and how it can be used to replicate earlier analyses of the van der Plank and K & M models. Our reformulation has the advantage of using elementary mathematical techniques, making implementation easier for the nonspecialist. We show a practical implication of these results for disease control. By taking advantage of the easy extensibility characteristic of compartmental models, we also investigate the effects of including additional biological realism. As an example, we show how the more realistic infection responses we consider interact with host demography and lead to divergent invasion thresholds when compared with the "standard" SEIR model. An ever-increasing number of analyses purportedly extract more biologically realistic invasion thresholds by adding additional biological detail to the SEIR model framework: we contend that our results demonstrate that extending a model that has such a simplistic representation of the infection dynamics may not, in fact, lead to more accurate results. Therefore, we suggest that modelers should carefully consider the underlying assumptions of the simplest compartmental models in their future work. [ABSTRACT FROM AUTHOR]

Background: Setosphaeria turcica is a fungal pathogen that causes northern corn leaf blight (NCLB) which is a serious foliar disease in maize. In order to unravel the genetic architecture of the resistance against this disease, a vast association mapping panel comprising 1487 European maize inbred lines was used to (i) identify chromosomal regions affecting flowering time (FT) and northern corn leaf blight (NCLB) resistance, (ii) examine the epistatic interactions of the identified chromosomal regions with the genetic background on an individual molecular marker basis, and (iii) dissect the correlation between NCLB resistance and FT. Results: The single marker analyses performed for 8 244 single nucleotide polymorphism (SNP) markers revealed seven, four, and four SNP markers significantly (α = 0.05, amplicon wise Bonferroni correction) associated with FT, NCLB, and NCLB resistance corrected for FT, respectively. These markers explained individually between 0.36 and 14.29% of the genetic variance of the corresponding trait. Conclusions: The very well interpretable pattern of SNP associations observed for FT suggested that data from applied plant breeding programs can be used to dissect polygenic traits. This in turn indicates that the associations identified for NCLB resistance might be successfully used in marker-assisted selection programs. Furthermore, the associated genes are also of interest for further research concerning the mechanism of resistance to NCLB and plant diseases in general, because some of the associated genes have not been mentioned in this context so far. [ABSTRACT FROM AUTHOR]

Celastrol, a natural substance isolated from plant extracts used in traditional Chinese medicine, has been extensively investigated as a possible drug for treatment of cancer, autoimmune diseases, and protein misfolding disorders. Although studies focusing on celastrol's effects in specific cellular pathways have revealed a considerable number of targets in a diverse array of in vitro models there is an essential need for investigations that can provide a global view of its effects. To assess cellular effects of celastrol and to identify target proteins as biomarkers for monitoring treatment regimes, we performed large-scale quantitative proteomics in cultured human lymphoblastoid cells, a cell type that can be readily prepared from human blood samples. Celastrol substantially modified the proteome composition and 158 of the close to 1800 proteins with robust quantitation showed at least a 1.5 fold change in protein levels. Up-regulated proteins play key roles in cytoprotection with a prominent group involved in quality control and processing of proteins traversing the endoplasmic reticulum. Increased levels of proteins essential for the cellular protection against oxidative stress including heme oxygenase 1, several peroxiredoxins and thioredoxins as well as proteins involved in the control of iron homeostasis were also observed. Specific analysis of the mitochondrial proteome strongly indicated that the mitochondrial association of certain antioxidant defense and apoptosis-regulating proteins increased in cells exposed to celastrol. Analysis of selected mRNA transcripts showed that celastrol activated several different stress response pathways and dose response studies furthermore showed that continuous exposure to sub-micromolar concentrations of celastrol is associated with reduced cellular viability and proliferation. The extensive catalog of regulated proteins presented here identifies numerous cellular effects of celastrol and constitutes a valuable biomarker tool for the development and monitoration of disease treatment strategies. [ABSTRACT FROM AUTHOR]

This review focuses on the detection of diseased plants by analysis of volatile organic compound (VOC) emissions. It includes an overview of studies that report on the impact of infectious and noninfectious diseases on these emissions and discusses the specificity of disease-induced emissions. The review also provides an overview of processes that affect the gas balance of plant volatiles, including their loss processes. These processes are considered as important because they contribute to the time-dynamic concentration profiles of plant-emitted volatiles. In addition, we describe the most popular techniques currently in use to measure volatiles emitted from plants, with emphasis on agricultural application. Dynamic sampling coupled with gas chromatography and followed by an appropriate detector is considered as the most appropriate method for application in agriculture. It is recommended to evaluate the state-of-the-art in the fields concerned with this method and to explore the development of a new instrument based on the specific needs for application in agricultural practice. However, to apply such an instrument in agriculture remains a challenge, mainly due to high costs. [ABSTRACT FROM AUTHOR]

Arabidopsis (Arabidopsis thaliana) NON-RACE-SPECIFIC DISEASE RESISTANCE1 (NDR1), a plasma membrane-localized protein, plays an essential role in resistance mediated by the coiled-coil-nucleotide-binding site-leucine-rich repeat class of resistance (R) proteins, which includes RESISTANCE TO PSEUDOMONAS SYRINGAE2 (RPS2), RESISTANCE TO PSEUDOMONAS SYRINGAE PV MACULICOLA1, and RPS5. Infection with Pseudomonas syringae pv tomato DC3000 expressing the bacterial effector proteins AvrRpt2, AvrB, and AvrPphB activates resistance by the aforementioned R proteins. Whereas the genetic requirement for NDR1 in plant disease resistance signaling has been detailed, our study focuses on determining a global, physiological role for NDR1. Through the use of homology modeling and structure threading, NDR1 was predicted to have a high degree of structural similarity to Arabidopsis LATE EMBRYOGENESIS ABUNDANT14, a protein implicated in abiotic stress responses. Specific protein motifs also point to a degree of homology with mammalian integrins, well-characterized proteins involved in adhesion and signaling. This structural homology led us to examine a physiological role for NDR1 in preventing fluid loss and maintaining cell integrity through plasma membrane-cell wall adhesions. Our results show a substantial alteration in induced (i.e. pathogen-inoculated) electrolyte leakage and a compromised pathogen-associated molecular pattern-triggered immune response in ndr1-1 mutant plants. As an extension of these analyses, using a combination of genetic and cell biology-based approaches, we have identified a role for NDR1 in mediating plasma membrane-cell wall adhesions. Taken together, our data point to a broad role for NDR1 both in mediating primary cellular functions in Arabidopsis through maintaining the integrity of the cell wall-plasma membrane connection and as a key signaling component of these responses during pathogen infection. [ABSTRACT FROM AUTHOR]

Colonization of potato (Solanum tuberosum) tissue, including roots, stolons, and above and below ground stems, by Colletotrichum coccodes, the causal agent of black dot, was evaluated following soil infestation, inoculation of seed tubers and foliage, and every combination thereof, in field trials over two growing seasons in North Dakota and Minnesota. A total of 107,520 isolations for C. coccodes performed across four site-years allowed for an extensive comparison of fungal colonization of the host plant and disease severity. The black dot pathogen was detected in potato stems at the first sampling date in all four site-years, as early as 14 days prior to emergence. Colonization of above and below ground stems occurred at a higher frequency than in roots and stolons in all four site-years, resulting in significantly higher relative area under the colonization progress curves (RAUCPCs) (α = 0.05). Although fungal colonization and disease incidence were higher in inoculated and/or infested treatments, sufficient natural inoculum was present to result in substantial levels of disease in noninoculated and noninfested plots. However, noninoculated and noninfested plots displayed the lowest RAUCPC values across three of four site-years and those treatments with multiple inoculation events tended to have higher RAUCPC values. Isolates belonging to vegetative compatibility group (VCG)2 and -5 were recovered from plants sampled in 2004 more frequently than isolates belonging to VCG1 and -3. A significant difference in disease incidence on stems was observed only in North Dakota in 2004 and Minnesota in 2003 (α = 0.05). Noninoculated and noninfested plots displayed the lowest disease incidence, whereas those treatments with more than one inoculation and/or infestation event tended to have higher disease incidence. Results of this study, including the disease severity and yield data, provide a better understanding of colonization of potato plants by C. coccodes and its impact. [ABSTRACT FROM AUTHOR]

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is the most devastating wheat disease in China. Although pathogens oversummering and overwintering in many regions of southwestern China have been studied, spore exchange among these regions is largely unknown. It is especially important to study the role of Sichuan, Yunnan, and Guizhou provinces in southwestern China in contributing to regional disease outbreaks in the major wheat-growing areas of China. Long-distance transport of P. striiformis f. sp. tritici urediniospores after oversummering and overwintering in Sichuan, Yunnan, and Guizhou was investigated using the HYSPLIT-4 model based on meteorological data. Results suggest that the pathogen spores can interchange frequently among Sichuan, Yunnan, and Guizhou in both spring and autumn. The sources of inoculum in Sichuan, Yunnan, and Guizhou have a high probability of impacting the epidemics in northern, northwestern, and southwestern China. In particular, disease epidemics in Guizhou can be affected not only by local inoculum but also by that from Yunnan in the spring. [ABSTRACT FROM AUTHOR]

Diatrypaceous fungi have been isolated from cankered wood of grapevines (Vitis vinifera) in California. However, the pathogenicity of these fungi and their potential to cause diseases in grapevine was unknown. A series of pathogenicity tests were conducted to determine if these fungi were grapevine pathogens. In all experiments, species of the family Diatrypaceae were re-isolated from the margins of developing lesions, although frequency of re-isolation and average length of vascular discolorations varied among isolates. Cryptovalsa ampelina, Diatrype stigma, and Eutypa leptoplaca were capable of colonizing dormant canes and causing vascular necrosis. Cryptosphaeria pullmanensis, C. ampelina, D. stigma, Diatrype whitmanensis, and E. leptoplaca infected and caused lesions in green shoots of the new vegetative growth. Diatrype oregonensis and Diatrypella verrucaeformis isolates did not produce lesions that were significantly different from those produced in the control shoots and canes. This suggests that D. oregonensis and D. verrucaeformis fungi may be saprophytic rather than pathogenic to grapevine. [ABSTRACT FROM AUTHOR]

In 2009, a previously undescribed disease was found on the nonnative invasive annual grass Microstegium vimineum (Japanese stiltgrass). Diseased plants exhibited foliar lesions, wilting, and in some cases, death of entire plants. We identified the causal agent as a Bipolaris sp. similar to B. zeicola. We observed spores and associated structures characteristic of Bipolaris spp. growing from leaf lesions on field collected plants. Pure cultures of the fungus were made and spore suspensions were applied to laboratory-reared M. vimineum seedlings in growth chamber and greenhouse experiments. Initial symptoms appeared on seedlings in the growth chamber experiment within 72 h of inoculation, and seedlings exhibited characteristic lesions within 10 days. The fungus was reisolated from lesions, and the internal transcribed spacer (ITS) region was sequenced to confirm its identity. In the greenhouse experiment, inoculated plants displayed characteristic lesions, and relatively greater spore loads increased disease incidence. Disease reduced seed head production by 40% compared to controls. This is the first report of a Bipolaris sp. causing disease on invasive M. vimineum. Following further analysis, including assays with co-occurring native species, this Bipolaris sp. may be considered as a biocontrol agent for invasive M. vimineum. [ABSTRACT FROM AUTHOR]

Foliar wilt as well as crown and root rot with sclerotia formation has affected potted liver leaf ( Hepatica nobilis var. japonica f. magna) in Ojiya, Niigata Prefecture, Japan, since 2006. Apothecia developed from the sclerotia on soil surface of pots with the diseased plants in March. A fungus forming the apothecia was identified as Dumontinia tuberosa (Sclerotiniaceae) based on its morphology and demonstrated to cause the disease. We coined the name “Dumontinia root rot (Dumontinia-negusare-byo in Japanese) of liver leaf” for the new disease. [ABSTRACT FROM AUTHOR]

The means by which European mountain ash ringspot-associated virus (EMARaV), a minus-strand ssRNA virus and the type member of the genus Emaravirus, is naturally spread, is unknown. In attempts to identify an EMARaV vector, galls induced by the eriophyid mite Phytoptus pyri were frequently found on infected leaves. By immunofluorescence microscopy, the presence of EMARaV nucleocapsid protein P3 was demonstrated in P. pyri individuals collected from diseased plants. Furthermore, RT-PCR analysis of entire P. pyri individuals revealed the presence of both viral genomic ss(−)RNAs and antigenomic ss(+)RNAs, suggesting that P. pyri might be a candidate vector of EMARaV. [ABSTRACT FROM AUTHOR]

A diagrammatic scale with six levels of disease severity: 1.6; 3.2; 6.4; 12.6; 23.1 and 38.6% was developed and validated to assess rice brown spot, caused by Bipolaris oryzae. The scale was developed considering the maximum limit of disease severity observed in the field and the intermediate values followed logarithmic increases according to the "Stimulus Law by Weber-Fechner". Initially, the estimatives of severity were performed without the use of the scale in 30 leaves with different levels of severity by eight people without previous experience in assessing diseases severity. Then, the same people estimated the severity of leaves using the proposed diagrammatic scale. Assessments with the diagrammatic scale were of great precision for all raters and did not presented systematic errors in over- or underestimating the disease severity. The proposed diagrammatic scale was considered adequate to estimate rice brown spot severity. [ABSTRACT FROM AUTHOR]

The exploration of new source materials and the use of alternative isolation and identification methods have led to rapid expansion in the knowledge of diversity; in Lysobacter, 11 new species having been described since 2005, and in Stenotrophomonas with six new species since 2000. The new species of Lysobacter, isolated by dilution and direct plating on standard media, differ in several key phenotypic properties from those obtained by enrichment on complex polysaccharides in the original description of the genus. Revision of the definition of the genus will be required. Both culture-dependent and culture-independent methods to assess community structure, in a variety of host and nonhost environments, have established that some species of Lysobacter are a dominant component of the microflora, where previously their presence had not been suspected. Culture-independent studies have generally not added new information on the occurrence and distribution of Stenotrophomonas maltophilia and other members of the genus, which are readily isolated on standard media from source materials. Lysobacter enzymogenes and Sten. maltophilia produce similar antibiotics and share some enzyme activities which, subject to safety considerations, may make them attractive candidates for use in biological control of plant diseases and of nematodes. [ABSTRACT FROM AUTHOR]

A leaf curl disease was observed on croton (Codiaeum variegatum L.), a popular ornamental plant in botanical, home, and office gardens in and around Bengaluru, South India. Diseased plants showed typical symptoms of vein thickening, severe inward curling and a reduction in leaf size, and stunting. The pathogen responsible was transmitted to healthy croton plants by grafting of infected scions, and through the whitefly vector, Bemisia tabaci, suggesting that the disease was caused by a begomovirus. The association of a begomovirus with the disease was further confirmed by the amplification of viral DNA fragments of ca. 520 bp and 575 bp derived from the coat protein (CP) gene of DNA-A using degenerate primers and total DNA extracted from infected, but not from healthy croton plants. The 575 bp fragment corresponding to the core region of the CP gene was cloned and sequenced. Phylogenetic analysis of the core CP sequence grouped the croton-infecting begomovirus, which we tentatively called croton leaf curl virus (CrLCuV), with Ageratum yellow vein virus (AJ810825), with which it shared the highest nucleotide identity (95%). The core CP sequence was similar (90 - 95%) to many other begomoviruses from the Indian sub-continent that infect tomato, tobacco, cotton, and papaya. Thus, its precise taxonomic denomination will require sequencing of the complete ssDNA viral genome. [ABSTRACT FROM AUTHOR]

Recent studies on plant immunity have suggested that a pathogen should suppress induced plant defense in order to infect a plant species, which otherwise would have been a nonhost to the pathogen. For this purpose, pathogens exploit effector molecules to interfere with different layers of plant defense responses. In this review, we summarize the latest findings on plant factors that are activated by pathogen effectors to suppress plant immunity. By looking from a different point of view into host and nonhost resistance, we propose a novel breeding strategy: disabling plant disease susceptibility genes (S-genes) to achieve durable and broad-spectrum resistance. [ABSTRACT FROM AUTHOR]

Phytophthora capsici is the oomycete that causes root rot and wilting of jalapeño pepper in the South Central region of Chihuahua State. The zoosporangia release zoospores which can spread by water surface movement, resulting in pathogen dispersion in places where it was not present yet. Therefore, the spatio-temporal distribution of wilting on jalapeño pepper was studied in 2002 and 2003 in the municipalities of Camargo and Delicias, Chih. The spatio-temporal distribution was determined by the Poisson distribution and the spatial autocorrelation analysis. These studies revealed that the disease continuously spreads from a single infected plant up to ten nearest neighboring plants within the row (4.5m), and up to four continuous neighboring plants across the row (2m), this may indicate that the pathogen's dispersal followed the furrow irrigation path and aggregates manly in the waterlogged spots due to a lack of land leveling in the field. Gompertz was the model that best described the progress of the disease, reaching apparent intensity rates from 0,008 to 0,016 gompitz day-1 (R² = 0,75 to 0,95). In order to determine the causal agent of the jalapeñño pepper wilt the pathogen was isolated from diseased plants and by pathogenicity test. The isolates were identified as P. capsici throughout morphological characteristics, and sequencing of 796 bp of the internal transcribed spacers (ITS) of the rDNA. The representative isolate sequence was deposited in GenBank with the accession number EF660564. Compatibility types A1 and A2 were detected among the isolates, and they were sensitive to mefenoxam. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to evaluate the impact of different N-rich animal wastes on the composting of ligno-cellulosic wastes by a range of classical and novel methods, with particular emphasis on microbial community composition. Two composting mixtures were prepared by adding to a mixture of cotton carding wastes and wheat straw: (i) meat and bone meal and (ii) blood meal and horn and hoof meal. Composts were analyzed using physico–chemical and biochemical properties, as well as nucleic acid microarrays. Results showed that physico–chemical and biochemical parameters differentiated composts depending on their degree of stability, while microarray hybridization discriminated compost samples according to the starting materials used in the compost production. Microarray analysis indicated not only the presence in the composts of bacteria involved in N2 fixation and plant disease suppression, but also the presence of Acinetobacter calcoaceticus that is suspected to trigger an autoimmune response related to bovine spongiform encephalopathy. The present work highlights the importance of using parameters addressing different properties of the composting matrix for a proper evaluation of the process performance. [Copyright &y& Elsevier]

The advent of Precision Agriculture has made possible the analysis of complex spatial patterns of plant disease epidemiology considering statements of integrated disease management. The objective of this work was to use geostatistics, statistics and geographical information systems to characterize the structure and magnitude of spatial dependency of rust ( Hemileia vastatrix) and brown eye spot ( Cercospora coffeicola) incidence and severity in coffee agroecosystem cultivated with Catuai Vermelho IAC-99 ( Coffea arabica L.). Evaluations of incidence and severity of rust and brown eye spot were accomplished at 67 georeferenced points arranged in 6.6202 ha of coffee crop, in the years of 2005, 2006 and 2007. Exponential models of covariance enabled the characterization of the magnitude and structure of rust and brown eye spot spatial variability in the evaluated dates. Ordinary block kriging presented satisfactory performance to map rust and brown eye spot outbreaks based on kriging error coefficients. Kriged maps enabled the visualization of intensity of rust and brown eye spot in each evaluation date. Assessments of incidence and severity presented highly statistical correlation based on linear regression models, also confirmed by the spatial variability of kriging maps. Kriging maps of rust and brown eye spot enabled to observe that intensity of disease was dispersed in foci patterns along the coffee plantation, indicating that the current strategy of disease control based in total area may be replaced by site specific disease management, with less environmental impact and sustainability of coffee crop, according to statements of integrated disease management and precision agriculture. [ABSTRACT FROM AUTHOR]

This study describes an image-processing based method that identifies the visual symptoms of plant diseases, from an analysis of coloured images. The processing algorithm developed starts by converting the RGB image of the diseased plant or leaf, into the H, I3a and I3b colour transformations. The I3a and I3b transformations are developed from a modification of the original I1I2I3 colour transformation to meet the requirements of the plant disease data set. The transformed image is then segmented by analysing the distribution of intensities in a histogram. Rather than using the traditional approach of selecting the local minimum as the threshold cut-off, the set of local maximums are located and the threshold cut-off value is determined according to their position in the histogram. This technique is particularly useful when the target in the image data set is one with a large distribution of intensities. In tests, once the image was segmented, the extracted region was post-processed to remove pixel regions not considered part of the target region. This procedure was accomplished by analysing the neighbourhood of each pixel and the gradient of change between them. To test the accuracy of the algorithm, manually segmented images were compared with those segmented automatically. Results showed that the developed algorithm was able to identify a diseased region even when that region was represented by a wide range of intensities. [Copyright &y& Elsevier]

The article discusses the regulation of the pcol/pcoR quorom-sensing system in Pseudomonas fluorescens 2P24 by the PhoP/PhoO two-component system. It is said that pcol/pcoR is involved in the regulation of root colonization and plant disease-suppressive ability. Furthermore, PhoO is a sensor protein of the regulatory system PhoP/PhoO, which regulates virulence in Salmonella typhimurium and antimicrobial peptide resistance in Pseudomonas aeruginosa. It is cited that through deletion mutagenesis and complementation experiments, the transcription of pcol was demonstrated.

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Gram-positive bacterium BRF-1 isolated from the rhizosphere of root-rotten diseased soybean plants shows strong antifungal activity on plates. In the present study, the ability of BRF-1 to control brown stem rot disease and to promote plant growth was examined using soybean plants grown in pots. Brown stem rot is a severe soil-borne disease of soybean that is caused by the pathogenic fungus Phialophora gregata. Eighteen-day-old soybean seedlings were grown in a mixture of soil (40 mL) and BRF-1 suspension (10 mL) and were dipped in a suspension of P. gregata (106 c.f.u. mL−1), and the severity of the disease was judged 62 days after the fungal inoculation. Inoculation with BRF-1 at 107 and 108 c.f.u. mL−1 significantly lowered the severity of the disease. Soybean seeds incubated in 100 mL of the BRF-1 suspension (2 × 106 c.f.u. mL−1) were sown in pots filled with sand, and plants were collected 7 days after emergence. The dry weight increase in shoots and roots and mineral absorption were significantly stimulated by the inoculation. These results suggest that BRF-1 might be an effective biocontrol agent to manage brown stem rot disease in soybean. The 16S rDNA sequence of BRF-1 showed high homology with sequences of Paenibacillus polymyxa strains (e.g. 99.7% identity with P.  polymyxa strain WY110). [ABSTRACT FROM AUTHOR]

Common scab caused by Streptomyces scabies is a major bacterial disease of potato (Solanum tuberosum). Its best known symptom is superficial lesions on the surface of progeny potato tubers, observed at harvesting. In this study, effects of S. scabies on space occupancy by underground organs and on structural complexity of root systems are investigated during growth via computed tomography (CT) scanning. Two groups of potato plants were grown in a greenhouse in middle-sized plastic pots. Using a high-resolution X-ray CT scanner formerly used for medical applications, their underground organs and surrounding medium (sieved and autoclaved homogeneous sand) were submitted to CT scanning 4, 6, and 8 weeks after planting. For one group, sand was inoculated with the common scab-inducing pathogen (S. scabies EF-35) at potting. Space occupancy by underground organs was estimated via curve fitting applied to histograms of CT scan data, while three-dimensional skeletal images were used for fractal analysis. Root systems of diseased plants were found to be less complex than those of healthy plants 4 weeks after planting, and the relative growth rates derived from space occupancy measures were of different sign between the two groups from week 4 to week 8. [ABSTRACT FROM AUTHOR]

Fire blight incidence and spread of the shoot blight phase of the disease was studied in four apple cultivars in replicated blocks over 4 years (1994 to 1997). Cv. York was highly susceptible, followed by 'Fuji' and 'Golden Delicious,' which were moderately susceptible, and 'Liberty,' which was least susceptible. On York, the first appearance of shoot blight was within 48 h of its predicted appearance according to the Maryblyt model in 3 of the 4 years studied. Shoot blight epidemics in York in 1995 and 1996, and Fuji in 1995, were best described with a logistic model that showed apparent infection rates ranging from 0.05 to 0.20, indicating a low to moderately high rate of disease increase. The spatial positions (row and column) of all infected plants in each subplot were recorded on plot maps on each sampling date. The binomial and β-binomial distributions were fit to the data to test for spatial aggregation of disease incidence for each cultivar plot. Maximum likelihood estimation was possible for 92 (43.6%) of the 211 data sets subjected to this analysis. Of these, 35 data sets were better fit by the β-binomial distribution than the binomial distribution. The binary power law was used to characterize the relationship between the variance among quadrats within each plot to the variance expected for that plot given the observed level of disease incidence. The binary power law provided an excellent fit to the full data set and to nearly all of the subsets and, with b > 1, indicated that heterogeneity changed systematically with disease incidence. A covariance analysis was conducted to determine the effect of the factors 'year,' 'cultivar,' 'orchard plot,' and 'observation date' on the intercept and slope parameters of the binary power law. In general, plot followed by year had the greatest impact on parameter estimates and is an indication that location and seasonal factors impact heterogeneity of disease, although the specifics could not be ascertained from this study. Ordinary runs analysis was used to analyze the pattern of diseased trees within rows and detected significant nonrandom patterns of disease incidence in 63.5% of the orchard plots over the 4-year study. From these data sets, 68.7% had significantly fewer runs, particularly at disease incidences greater than 0.1. The fewer-than-expected runs at incidences greater than 0.10 provides strong evidence of localized spread. [ABSTRACT FROM AUTHOR]

Based on the number of new reports during the last two decades, bacterial blight of onion (A ilium cepa) is considered an emerging disease. The causal agent, Xanthomonas axonopodis pv. ailii, is pathogenic to several A ilium species after inoculation, but outbreaks worldwide have been primarily reported on onion. We describe a unique epidemiological situation in Reunion Island, France, with concomitant outbreaks on three A ilium species, onion, leek (A. porrum), and garlic (A. sativum). There was no host specialization within Alhum spp. among strains associated with the three host species. Based on amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism, strains associated with these outbreaks in Reunion Island were highly related genetically to strains isolated from diseased plant samples and contaminated seed lots in the neighboring island of Mauritius, where the disease has occurred since 1984. All AFLP haplotypes were identified as X. axonopodis pv. allu based on polymerase chain reaction analysis using specific primers, biochemical tests, and/or pathogenicity tests. Two genetically related groups of strains (A and B) that can be distinguished by AFLP, differential utilization of three carbon sources, and xanthomonadin pigment production were detected initially after establishment of the pathogen. In less than 10 years after the establishment of the pathogen there was nearly an extinction of group A strains in Reunion Island, suggesting differences in fitness between strains in the two groups. [ABSTRACT FROM AUTHOR]