First Report of Alternaria alternata and Fusarium spp. Causing Brown Apical Necrosis in Walnut Fruit in Southern Chile

This is the first report of Alternaria alternata and Fusarium spp. causing brown apical necrosis (BAN) in walnut fruit in southern Chile. English walnut (Juglans regia L.) is the second most widely grown fruit in Chile. The bacterial pathogen Xanthomonas arboricola pv. juglandis affects walnut production in Chile and has been associated with apical necrosis symptom and premature fruit drop; this research focused on determining if fungal pathogens were associated with this damage. The presence of BAN in commercial walnut orchards in southern Chile reveals the need for improved phytosanitary programs to control this disease.

Biological role of EPS from Pseudomonas syringae pv. syringae UMAF0158 extracellular matrix, focusing on a Psl-like polysaccharide

Pseudomonas syringae is a phytopathogenic model bacterium that is used worldwide to study plant–bacteria interactions and biofilm formation in association with a plant host. Within this species, the syringae pathovar is the most studied due to its wide host range, affecting both, woody and herbaceous plants. In particular, Pseudomonas syringae pv. syringae (Pss) has been previously described as the causal agent of bacterial apical necrosis on mango trees. Pss exhibits major epiphytic traits and virulence factors that improve its epiphytic survival and pathogenicity in mango trees. The cellulose exopolysaccharide has been described as a key component in the development of the biofilm lifestyle of the P. syringae pv. syringae UMAF0158 strain (PssUMAF0158). PssUMAF0158 contains two additional genomic regions that putatively encode for exopolysaccharides such as alginate and a Psl-like polysaccharide. To date, the Psl polysaccharide has only been studied in Pseudomonas aeruginosa, in which it plays an important role during biofilm development. However, its function in plant-associated bacteria is still unknown. To understand how these exopolysaccharides contribute to the biofilm matrix of PssUMAF0158, knockout mutants of genes encoding these putative exopolysaccharides were constructed. Flow-cell chamber experiments revealed that cellulose and the Psl-like polysaccharide constitute a basic scaffold for biofilm architecture in this bacterium. Curiously, the Psl-like polysaccharide of PssUMAF0158 plays a role in virulence similar to what has been described for cellulose. Finally, the impaired swarming motility of the Psl-like exopolysaccharide mutant suggests that this exopolysaccharide may play a role in the motility of PssUMAF0158 over the mango plant surface.

A Volatile Signal Controls Virulence in the Plant Pathogen Pseudomonas syringae pv. syringae and a Strategy for Infection Control in Organic Farming

Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the antimetabolite toxin mangotoxin. The production of this toxin was shown to be regulated by a self-produced signaling molecule. In this study, we determined the structure of the Pss signal molecule belonging to the recently described family of diazeniumdiolate communication molecules. Employing a targeted mass spectrometry-based approach, we provide experimental evidence that the major signal produced by Pss is the volatile compound leudiazen, which controls mangotoxin production and virulence in a detached tomato leaflet infection model. Experimental results demonstrate that KMnO4 solution inactivates leudiazen and that treatment of infected leaves with KMnO4 abolishes necrosis. This strategy represents the first example of chemically degrading a signaling molecule to interfere with bacterial communication. The application of KMnO4 solution, which is regulatorily approved in organic farming, may constitute an environmentally friendly strategy to control Pss infections.

A Volatile Signal Controls Virulence in the Plant Pathogen Pseudomonas syringae pv. syringae and a Strategy for Infection Control in Organic Farming

<div><div><div><p>Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the antimetabolite toxin mangotoxin. The production of this toxin was shown to be regulated by a self-produced signaling molecule. In this study, we determined the structure of the Pss signal molecule belonging to the recently described family of diazeniumdiolate communication molecules. Employing a targeted mass spectrometry-based approach, we provide experimental evidence that the major signal produced by Pss is the volatile compound leudiazen, which controls mangotoxin production and virulence in a detached tomato leaflet infection model. Experimental results demonstrate that KMnO4 solution inactivates leudiazen and that treatment of infected leaves with KMnO₄ abolishes necrosis. This strategy represents the first example of chemically degrading a signaling molecule to interfere with bacterial communication. The application of KMnO4 solution, which is regulatorily approved in organic farming, may constitute an environmentally friendly strategy to control Pss infections.</p></div></div></div>

A Volatile Signal Controls Virulence in the Plant Pathogen Pseudomonas syringae pv. syringae and a Strategy for Infection Control in Organic Farming

<div><div><div><p>Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the antimetabolite toxin mangotoxin. The production of this toxin was shown to be regulated by a self-produced signaling molecule. In this study, we determined the structure of the Pss signal molecule belonging to the recently described family of diazeniumdiolate communication molecules. Employing a targeted mass spectrometry-based approach, we provide experimental evidence that the major signal produced by Pss is the volatile compound leudiazen, which controls mangotoxin production and virulence in a detached tomato leaflet infection model. Experimental results demonstrate that KMnO4 solution inactivates leudiazen and that treatment of infected leaves with KMnO₄ abolishes necrosis. This strategy represents the first example of chemically degrading a signaling molecule to interfere with bacterial communication. The application of KMnO4 solution, which is regulatorily approved in organic farming, may constitute an environmentally friendly strategy to control Pss infections.</p></div></div></div>

THE EFFECT OF VITAMINS A AND E ON THE STRUCTURE OF THE SMALL INTESTINE OF RATS AFTER TWO WEEKS AND THEN THREE MONTHS FOLLOWING EXPOSURE TO SINGLE-WALLED CARBON NANOTUBES

Introduction. Currently, there is a number of works aimed at studying the effect of carbon nanotubes (UNT), including single-walled (oUNT), on the body and there are studies to find means to reduce their toxic effects, such as compounds with antioxidant properties. Material and methods. In fifteen groups of animals there were studied intragastric effects of two weeks with the count at doses of 0.05 and 0.5 mg/kg and a single dose of 5mg/kg, as well as complex with vitamins A and E (AE) at a dose of 25.3 mg / kg on the small intestine of male Wistar rats, and in the same batch of animals three months later. Results. In a two-week experiment under the influence of oUNT in doses of 0.05 and 0.5 mg/kg there was shown the dose dependence on indices of reducing the number of normal villi with an increase in the number of destructured ones, whereas three months later among the destructured villi were increased in number with apical necrosis. After a single exposure of oUNT at a dose of 5mg/kg three months later, there also was increased the number of villi with apical necrosis. Two-weeks exposure of AE reduced the number of normal villi, increasing the number of degraded forms, and three months later the number of villi with apical necrosis increased. Two-weeks complex exposure of AE and oUN at doses of 0.05 and 0.5 mg/kg reduced the number of normal villi with an increasing number of destructured ones; three months later, as well as with other effects, the pathology developed, increasing the number of villi with apical necrosis. Conclusion. The toxic effect of oUNT and AE on the small intestine of rats with the separate and complex applications, increasing in the recovery period, was proved.

Histopathological and ultrastructural findings induced by heat-inactivated Lactobacillus plantarum and the culture supernatant on the intestinal mucosa of piglets: an ex vivo approach

ABSTRACT In the present study, histological, morphometrical and ultrastructural analysis were performed to investigate intestinal mucosa changes in piglets jejunal explants exposed to two concentration of heat-inactivated Lactobacillus plantarum and their respective culture supernatants. Jejunal explants were incubated for 4 hours in DMEM culture medium with a) only culture medium (control group), b) heat-inactivated Lactobacillus plantarum strain1 - LP1 (1.1 x 108CFU/ml), c) heat-inactivated Lactobacillus plantarum strain2 - LP2 (2.0 x 109CFU/ml), d) heat-inactivated Lactobacillus plantarum strain1 culture supernatant (CS1), and e) heat-inactivated Lactobacillus plantarum strain2 culture supernatant (CS2). Explants exposed to heat-inactivated L. plantarum strain 1 and 2 showed multifocal to difuse villi atrophy, villi apical necrosis and enterocyte flattening. Morphological assessment revealed similar results with bacterial adhesion to mucus and intestinal epithelial cells and, morphometric analysis showed a decreased villi height compared to the control group. Alterations in explants treated with the culture supernatant of both strains include mild villi atrophy and mild enterocyte apical necrosis. Morphological assesment reveled numerous well delineated villi and, morphometric analysis showed a significant increase in villi height compared to the control group. In general, exposure to the culture supernatants improved the intestinal morphology.

Pantoea agglomerans as a New Etiological Agent of a Bacterial Necrotic Disease of Mango Trees

Bacterial apical necrosis of mango trees, a disease elicited by Pseudomonas syringae pv. syringae, is a primary limiting factor of mango crop production in the Mediterranean region. In this study, a collection of bacterial isolates associated with necrotic symptoms in mango trees similar to those produced by bacterial apical necrosis disease were isolated over five consecutive years in orchards from the Canary Islands. The bacterial isolates were characterized and identified as Pantoea agglomerans. Pathogenicity tests conducted on onion bulbs and mango plants confirmed that P. agglomerans strains isolated from mango trees are a new etiological agent of a bacterial necrotic disease in the Canary Islands. Pathogenicity plasmids of the pPATH family have been previously reported in P. agglomerans. The majority of putatively pathogenic (n = 23) and pathogenic (n = 4) P. agglomerans strains isolated from mango trees harbored four plasmids, one of which was close in size to the 135-kb pPATH pathogenicity plasmid. The analysis of the presence of two major genes in pPATH plasmids (repA and hrpJ) was undertaken in P. agglomerans strains isolated from mango trees. The hrpJ gene was detected in the 140-kb plasmid of pathogenic P. agglomerans strains isolated from mango trees but it showed differences in nucleotide sequences compared with other pathogenic strains. In contrast, the repA gene was not detected in any of the putatively pathogenic and pathogenic P. agglomerans strains isolated from mango trees. Finally, genetic characterization and phylogenetic analysis using the hrpJ gene and the housekeeping genes gyrB and rpoB showed that almost all P. agglomerans strains that were putatively pathogenic and pathogenic on mango trees clustered together, forming a differentiated phylogroup with respect to the other pathogenic P. agglomerans strains described from other hosts.

Diseases and Pests Associated to Tomato Cultivation in the Locality of Daloa (Côte d’Ivoire)

This study aims at identifying the major tomato pests and diseases in the locality of Daloa. To achieve this goal, surveys were conducted among tomato farmers in the city, the outskirts and the villages of Daloa. They consisted in questioning farmers about their identity, the cropping practices and the problems encountered in the practice of tomato cultivation. Then another step consisted in monitoring tomato farms for observing diseases and pests associated to tomato. The results of the study showed that tomato cultivation is concentrated in rural areas and is carried out by men with a very low level of education. The most cultivated varieties are petromech and cobra because of their resistance to certain pests. Several tomato diseases have been identified, however the most significant were seedling damping-off (Pythium sp, Fusarium sp, Rhizoctonia solani), plant wilting (Fusarium oxyporum and Ralstonia solanacerum), fruit anthracnose (Colletotrichum sp.), apical necrosis and root-knot nematode (Meloidogyne sp.). The main pests observed on tomato in the locality were Helicoverpa armigera (Lepidoptera), Bemisia tabaci (Homoptera), Dysdercus sp. (Hemiptera). This study provides a pathway from which further studies including mapping the different diseases could be conducted so as to better monitor and protect tomato cultivation.