Localization of Pantoea ananatis inside lesions of maize White Spot Disease using transmission electron microscopy and molecular techniques

The etiological agent of maize white spot (MWS) disease has been a subject of controversy and discussion. Initially the disease was described as Phaeosphaeria leaf spot caused by Phaeosphaeria maydis. Other authors have Suggested the existence of different fungal species causing similar symptoms. Recently, a bacterium, Pantoea ananatis, was described as the causal agent of this disease. The purpose of this Study was to offer additional information on the correct etiology of this disease by providing visual evidence of the presence of the bacterium in the interior of the MWS lesions by using transmission electron microscopy (TEM) and molecular techniques. The TEM allowed Visualization of a large amount of bacteria in the intercellular spaces of lesions collected from both artificially and naturally infected plants. Fungal structures were not visualized in young lesions. Bacterial primers for the 16S rRNA and rpoB genes were used in PCR reactions to amplify DNA extracted from water-soaked (young) and necrotic lesions. The universal fungal oligonucleotide ITS4 was also included to identity the possible presence of fungal structures inside lesions. Positive PCR products from water-soaked lesions, both from naturally and artificially inoculated plants, were produced with bacterial primers, whereas no amplification was observed when ITS4 oligonucleotide was used. On the other hand, DNA amplification with ITS4 primer was observed when DNA was isolated from necrotic (old) lesions. These results reinforced previous report of P. ananatis as the primary pathogen and the hypothesis that fungal species may colonize lesions pre-established by P. ananatis.

Ocorrência de Cistos de CLINOSTOMUM MARGINATUM Rudolphi, 1819 "Yellow Spot Disease" em Filé de Jaraqui (SEMAPROCHILODUS INSIGNIS Schomburgk, 1814)

The parasitic inspection of 745 jaraqui fillets (Semaprochilodus insignis Schomburgk, 1814) from the rio Negro, Manaus (AM) - Brazil, show a low prevalence of metacercaria cysts of Clinostomum marginatum Rudolphi, 1819. From the collected samples since 1981 to 1983, only showed the cysts.

Fenneropenaeus indicus is protected from white spot disease by oral administration of inactivated white spot syndrome virus

Fenneropenaeus indicus could be protected from white spot disease (WSD) caused by white spot syndrome virus (WSSV) using a formalin-inactivated viral preparation (IVP) derived from WSSV-infected shrimp tissue. The lowest test quantity of lyophilized IVP coated onto feed at 0.025 g–1 (dry weight) and administered at a rate of 0.035 g feed g–1 body weight d–1 for 7 consecutive days was sufficient to provide protection from WSD for a short period (10 d after cessation of IVP administration). Shrimp that survived challenges on the 5th and 10th days after cessation of IVP administration survived repeated challenges although they were sometimes positive for the presence of WSSV by a polymerase chain reaction (PCR) assay specific for WSSV. These results suggest that F. indicus can be protected from WSD by simple oral administration of IVP

Expression of the Bs2 pepper gene confers resistance to bacterial spot disease in tomato

The Bs2 resistance gene of pepper specifically recognizes and confers resistance to strains of Xanthomonas campestris pv. vesicatoria that contain the corresponding bacterial avirulence gene, avrBs2. The involvement of avrBs2 in pathogen fitness and its prevalence in many X. campestris pathovars suggests that the Bs2 gene may be durable in the field and provide resistance when introduced into other plant species. Employing a positional cloning strategy, the Bs2 locus was isolated and the gene was identified by coexpression with avrBs2 in an Agrobacterium-mediated transient assay. A single candidate gene, predicted to encode motifs characteristic of the nucleotide binding site–leucine-rich repeat class of resistance genes, was identified. This gene specifically controlled the hypersensitive response when transiently expressed in susceptible pepper and tomato lines and in a nonhost species, Nicotiana benthamiana, and was designated as Bs2. Functional expression of Bs2 in stable transgenic tomatoes supports its use as a source of resistance in other Solanaceous plant species.

A new Alternaria leaf-spot disease of cherries...

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Characterizations of the major coral diseases of the Philippines: Ulcerative white spot disease and novel growth anomalies of Porites

Coral reefs are in decline worldwide and coral disease is a significant contributing factor. However, etiologies of coral diseases are still not well understood. In contrast with the Caribbean, extremely little is known about coral diseases in the Philippines. In 2005, off Southeast Negros Island, Philippines, I investigated relationships between environmental parameters and prevalence of the two most common coral diseases, ulcerative white spot (UWS) and massive Porites growth anomalies (MPGAs). Samples were collected along a disease prevalence gradient 40.5 km long. Principal component analyses showed prevalence of MPGAs was positively correlated with water column nitrogen, organic carbon of surface sediments, and colony density. UWS was positively correlated with water column phosphorus. This is the first quantitative evidence linking anthropogenically-impacted water and sediment to a higher prevalence of these diseases. Histological and cytological alterations were investigated by comparing tissues from two distinct types of MPGA lesions (types 1 and 2) and healthy coral using light and electron microscopy. Skeletal abnormalities and sloughing, swelling, thinning, and loss of tissues in MPGAs resembled tissues exposed to bacterial or fungal toxins. Both lesion types had decreases in symbiotic zooxanthellae, which supply nutrients to corals. Notable alterations included migrations of chromophore cells (amoebocytes) (1) nocturnally to outer epithelia to perform wound-healing, including plugging gaps and secreting melanin in degraded tissues, and (2) diurnally to the interior of the tissue possibly to prevent shading zooxanthellae in order to maximize photosynthate production. Depletion of melanin (active in wound healing) in type 2 lesions suggested type 2 tissues were overtaxed and less stable. MPGAs contained an abundance of endolithic fungi and virus-like particles, which may result from higher nutrient levels and play roles in disease development. Swollen cells and mucus frequently blocked gastrovascular canals (GVCs) in MPGAs. Type 1 lesions appeared to compensate for impeded flow of wastes and nutrients through these canals with proliferation of new GVCs, which were responsible for the observed thickened tissues. In contrast, type 2 tissues were thin and more degraded. Dysplasia and putative neoplasia were also observed in MPGAs which may result from the tissue regeneration capacity being overwhelmed.

Characterizations of the Major Coral Diseases of the Philippines: Ulcerative White Spot Disease and Novel Growth Anomalies of Porites

Coral reefs are in decline worldwide and coral disease is a significant contributing factor. However, etiologies of coral diseases are still not well understood. In contrast with the Caribbean, extremely little is known about coral diseases in the Philippines. In 2005, off Southeast Negros Island, Philippines, I investigated relationships between environmental parameters and prevalence of the two most common coral diseases, ulcerative white spot (UWS) and massive Porites growth anomalies (MPGAs). Samples were collected along a disease prevalence gradient 40.5 km long. Principal component analyses showed prevalence of MPGAs was positively correlated with water column nitrogen, organic carbon of surface sediments, and colony density. UWS was positively correlated with water column phosphorus. This is the first quantitative evidence linking anthropogenically-impacted water and sediment to a higher prevalence of these diseases. Histological and cytological alterations were investigated by comparing tissues from two distinct types of MPGA lesions (types 1 and 2) and healthy coral using light and electron microscopy. Skeletal abnormalities and sloughing, swelling, thinning, and loss of tissues in MPGAs resembled tissues exposed to bacterial or fungal toxins. Both lesion types had decreases in symbiotic zooxanthellae, which supply nutrients to corals. Notable alterations included migrations of chromophore cells (amoebocytes) (1) nocturnally to outer epithelia to perform wound-healing, including plugging gaps and secreting melanin in degraded tissues, and (2) diurnally to the interior of the tissue possibly to prevent shading zooxanthellae in order to maximize photosynthate production. Depletion of melanin (active in wound healing) in type 2 lesions suggested type 2 tissues were overtaxed and less stable. MPGAs contained an abundance of endolithic fungi and virus-like particles, which may result from higher nutrient levels and play roles in disease development. Swollen cells and mucus frequently blocked gastrovascular canals (GVCs) in MPGAs. Type 1 lesions appeared to compensate for impeded flow of wastes and nutrients through these canals with proliferation of new GVCs, which were responsible for the observed thickened tissues. In contrast, type 2 tissues were thin and more degraded. Dysplasia and putative neoplasia were also observed in MPGAs which may result from the tissue regeneration capacity being overwhelmed.

Study of white spot disease in four native species in Persian Gulf by histopathology and PCR methods

After serious disease outbreak, caused by new virus (WSV), has been occurring among cultured penaeid shrimps in Asian countries like China since 1993 and then in Latin American countries, during June till July 2002 a rapid and high mortality in cultured Penaeus indicus in Abadan region located in south of Iran with typical signs and symptoms of White Spot Syndrome Virus was confirmed by different studies of Histopathology, PCR, TEM, Virology. This study was conducted for the purpose of determination of prevalence(rate of infection)/ROI and grading severity (SOI) of WSD to five species: 150 samples of captured shrimps and 90 samples of cultured ones; Penaeus indicus, P. semisulcatus, P. merguiensis, Parapenaopsis styliferus, and Metapenaeus affinis in 2005. 136 of 240 samples have shown clinical and macroscopical signs & symptoms including; white spots on carapase (0.5-2 mm), easily removing of cuticule, fragility of hepatopancreas and red color of motility limbs. Histopathological changes like specific intranuclear inclusion bodies (cowdry-type A) were observed in all target tissues (gill, epidermis, haemolymph and midgut) but not in hepatopancreas, among shrimps collected from various farms in the south and captured ones from Persian Gulf, even ones without clinical signs. ROI among species estimated, using the NATIVIDAD & LIGHTNER formula(1992b) and SOI were graded, using a generalized scheme for assigning a numerical qualitative value to severity grade of infection which was provided by LIGHTNER(1996), in consideration to histopathology and counting specific inclusion bodies in different stages(were modified by B. Gholamhoseini). Samples with clinical signs, showed grades more than 2. Most of the P. semisulcatus and M. affinis samples showed grade of 3, in the other hand in most of P. styliferus samples grade of 4 were observed, which can suggest different sensitivity of different species. All samples were tested by Nested PCR method with IQTm 2000 WSSV kit and 183 of 240 samples were positive and 3 1evel of infection which was shown in this PCR confirmed our SOI grades, but they were more specified.

Detection of viral diseases in shrimp Litopenaeus vannamei in Iran with emphasis on white spot disease prevention by using marine alga extract

Nowadays, following was expanded shrimp breeding and culture; viral diseases have been main problem which threatened shrimp industry in the country. Therefore, shrimp samples were obtained from different stages of Litopenaeus vannmei life cycle (larval, post larval, juveniles, adults and broodstocks) based on clinical signs in the breeding center and shrimp farming from Bushehr, Khozestan and Sistan and Baluchestan provinces. Viral diseases were detected by PCR (Polymerase Chain Reaction), histopathology and transmission electron microscopy (TEM) methods. Results of the PCR were indicated present white spot virus (WSV) in juveniles, sub adults and adults shrimp with medium intensity from three provinces, but it was not showed in larval and post larval stages. Histopathological sections were indicated hypertrophy and basophilic Cowdry type A formation in nucleus cells of gill, haematopoietic, lymphoid and epithelial's cuticles and intestinal tissues which was associated with small vacuoles increased in B cells of hepatopancreas tissue of infection shrimps. Transmission electronic microscopic studies were demonstrated that the length and diameter virus was detected, respectively, 300 ± 20 nm and 75 ± 5 nm. Considerable, results of the PCR were only displayed IHHNV in juvenile, adult and broodstock shrimps from breeding and farming center of Bushehr province. The main lesion pathology was formed eosinophilic Cowdry type A in nucleus cells of gill, haematopoietic, lymphoid and epithelial's cuticles and intestinal tissues. Whereas penaeid shrimps are lack specific immune system, hence, in the present study was used of marine alga (Lurensia snideria) collected from along costal Persian Gulf of Bushehr province for viral diseases were prevented. Powder alga extract were added with a ratio of 1 % to shrimp diet. Total haemocyte count (THC) and total protein plasma (TPP) were increased after 5 days of oral administration diets. When shrimps were infected by with spot virus experimentally, THC and TPP gradually were increased in both two groups (shrimps fed with diet containing alga extract and without alga extract) after 48h. Nevertheless; THC, TPP and survival of shrimp fed with diet containing alga extract were more than shrimp control in 15 days. So, oral administration Lurensia snideria extract was capable prevention infected L. vannamei via stimulant specific immune system.

Protection of white leg shrimp (Litopenaeus vannamei) against white spot disease virus using oral recombinant bioencapsulated VP28

Aquaculture, is perceived as having the greatest potential to meet the growing demand for aquatic food. Crustaceans form one of the main value added components in aquaculture and among them, shrimp aquaculture is the predominant one. Industrial shrimp fanning, in combination with poor management in shrimp aquaculture, has quickly led to severe pollution in shrimp ponds, thereby creating a suitable environment for development of bacterial and virus diseases. White spot disease is one of the most deadly diseases that are caused heavy loss in all Penaeid shrimps family. In Iran during 2002 to 2004 in the Kuzestan province and in 2005 in Bushehr province, the most ponds and farms infected with white spot and the entire industry was facing threat of closure. Owing to the impact of WSSV infection to shrimp aquaculture, there is an urgent need to develop suitable strategies to protect cultured shrimps and make aquaculture more sustainable. Therefore, this study aimed to examine the possibility of protecting shrimp against white spot syndrome virus using bioencapsulated Anemia with E. coil containing the recombinant protein VP28, designed. Virus genome was extracted from naturally infected Litopenaeus vannamei in the Choebdch farms and VP28 gene by designed primers was amplified, extracted, purified and cloned in E. coli TGI. Protein expression evaluated and inactivated bacteria containing recombinant protein encapsulated in Artemia nauplii. White shrimp post larvae stage 5 were fed for 5 days with recombinant nauplii and twice on days 7 and 25 after feeding with Artemia nauplii were challenged with white spot virus. The results of the first experiment revealed that cumulative mortality percent in the group receiving the bacteria containing recombinant plasmid (pMal + VP28) was %14.44±1.11 and the relative percent survival %80.30±1.51. In this group the mortality rates in the various repetitions varied from the 13.33% to 16.66% and relative percent survival of 77.27% to 81.81%. in the Non-recombinant plasmid group (pMal) Mean percent mortality was% 33.33±3.84 and the Relative Percent Survival %54.54±5.24 and in the group that received bacteria contained no recombinant plasmid the Mean cumulative mortality percent was%48.88 ± 5.87 and Relative Percent Survival%33.33± 8.01.

In vivo antifungal activity of neem oil and aqueous extracts against leaf spot disease caused by Cercospora abelmoschii on okra

The cercospora leaf spot, caused by Cercospora abelmoschi Ellis and Everhart, is quite common in okra culture. Therefore, this study aimed to evaluate the efficiency of aqueous extracts of neem ( Azadirachta indica A. Juss), citronella ( Cymbopogon nardus (L.) Rendle), eucalyptus ( Eucalyptus grandis L.), ecolife®, A. indica oil and fungicide cercobin 700 PM® in control of cercospora leaf spot on okra in greenhouse. The extracts and neem oil were tested in concentration 10%, the fungicide cercobin 700PM® in dose 2.5 g.l-1, applied 10 days after pathogen inoculation by leaf spray and the citric biomass extract ecolife® in concentration 5.0 ml.l-1, applied 10 days before pathogen inoculation. All treatments, except ecolife®, were effective in controlling cercospora leaf spot and may be recommended as alternatives in agroecological systems.

Identification of common bean resistant sources to angular leaf spot disease in a brazilian germplasm collection.

The aim of this study was to identify sources of resistance in the germplasm collection providing information of potential sources of resistance to introduce in breeding programs.

Les facteurs écologiques influençant la dynamique d'une espèce exotique envahissante, Acer platanoides, et d'un congénère indigène, A. saccharum, dans une forêt urbaine du sud du Québec

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Grouping sunflower genotypes for yield, oil content, and reaction to Alternaria leaf spot using GGE biplot

Abstract:The objective of this work was to evaluate the suitability of the multivariate method of principal component analysis (PCA) using the GGE biplot software for grouping sunflower genotypes for their reaction to Alternaria leaf spot disease (Alternariaster helianthi), and for their yield and oil content. Sixty-nine genotypes were evaluated for disease severity in the field, at the R3 growth stage, in seven growing seasons, in Londrina, in the state of Paraná, Brazil, using a diagrammatic scale developed for this disease. Yield and oil content were also evaluated. Data were standardized using the software Statistica, and GGE biplot was used for PCA and graphical display of data. The first two principal components explained 77.9% of the total variation. According to the polygonal biplot using the first two principal components and three response variables, the genotypes were divided into seven sectors. Genotypes located on sectors 1 and 2 showed high yield and high oil content, respectively, and those located on sector 7 showed tolerance to the disease and high yield, despite the high disease severity. The principal component analysis using GGE biplot is an efficient method for grouping sunflower genotypes based on the studied variables.

Antiviral property of marine actinomycetes against White Spot Syndrome Virus in penaeid shrimps

Aquaculture farms, particularly in Southeast Asia are facing severe crisis due to increasing incidences of White Spot Syndrome Virus (WSSV). Actinomycetes have provided many important bioactive compounds of high prophylactic and therapeutic value and are continually being screened for new compounds. In this communication, the results of a study made to determine the effectiveness of marine actinomycetes against the white spot disease in penaeid shrimps are presented. Twenty-five isolates of actinomycetes were tested for their ability to reduce infection due to WSSV among cultured shrimps. When these actinomycetes were made available as feed additives to the post-larvae of the black tiger shrimp Penaeus monodon for two weeks and challenged with WSSV, the post challenge survival showed variations from 11 to 83%. However, six isolates have shown to be the most potential candidates for further study.