Oxidative foliar photo-necrosis produced by the bacteria Pseudomonas cedrina

BACKGROUND: Although bioactive metabolites capable of causing oxidative photo-necrosis in plant tissues have been identified in fungi, little is known about this type of mechanism in bacteria. These metabolites act as photosensitizers that generate reactive oxygen species (ROS) capable of causing damage to cells. In addition, these metabolites can pass into an energetically excited state when they receive some luminous stimulus, a condition in which they interact with other molecules present in the environment, such as molecular oxygen (O2), also known as triplet oxygen (3 O2), generating ROS. RESULTS: The suspension of the bacterial culture of Pseudomonas cedrina was shown to produce foliar necrosis in papaya leaves (Carica papaya L.) only in the presence of sunlight, which is evidence of photosensitizing mechanisms that generate singlet oxygen (1 O2). From the chemical study of extracts obtained from this bacteria, 3-(4-(2-carboxipropyl) phenyl) but-2-enoic acid (1) was isolated. This compound, in the presence of light and triplet oxygen (3 O2), was able to oxidize ergosterol to its peroxide, since it acted as a photosensitizer producing 1 O2, with which it was corroborated that a photosensitization reaction occurs, mechanism by which this bacterium could prove to cause oxidative foliar photo-necrosis. CONCLUSIONS: P. cedrina was able to induce oxidative foliar photo-necrosis because of its potential ability to produce photosensitizing metabolites that generate singlet oxygen in the plants it colonizes. Based on the above, it can be proposed that some bacteria can cause oxidative foliar photo-necrosis as an important mechanism in the pathogenesis of host species.

Efecto de la biofertilización y los biorreguladores en la germinación y el crecimiento de carica papaya L / Effect of biofertilization and bioregulators on germination and growth of carica papaya L

Con el objetivo de incrementar y acelerar el proceso de germinación de las semillas y obtener una alta producción y homogeneidad de plántulas de Carica papaya variedad Maradol en vivero, se evaluó el efecto de tres biofertilizantes aplicados solos o en combinación (Azotobacter chroococcum, Azospirillum brasilense y Glomus intraradices), y un biorregulador del crecimiento vegetal, el ácido giberélico (AG3), en la germinación y el crecimiento vegetal. Se realizó un experimento bajo un diseño completamente al azar con ocho tratamientos y tres repeticiones. A las semillas se les aplicó un pretratamiento germinativo con alternancia de temperatura para superar la dormancia. Los tratamientos simples con A. chroococcum y A. brasilense, incrementaron el porcentaje de germinación a 90,28 y 88,89% respectivamente. Además, con la aplicación de los biofertilizantes y el AG3, la velocidad de germinación se incrementó y el tiempo medio de germinación se redujo. La doble aplicación en semillas y foliar de los biofertilizantes y el AG3 en plántulas mejoró el crecimiento vegetal. La población de A. chroococcum fue mayor cuando se inoculó en combinación con G. intraradices. La prevalencia de colonización de las plántulas inoculadas con G. intraradices varió de 18,53 a 26,67%, con el mayor valor registrado para el tratamiento combinado con A. brasilense. Finalmente, aplicando esta metodología se logró acelerar la germinación, obteniéndose una mayor homogeneidad en la emergencia de las plántulas, disminuyendo así el tiempo de permanencia en el vivero.

In order to increase and accelerate the process of seed germination and obtain a high yield and homogeneity of papaya seedlings cv. Maradol in nurseries, we evaluated the effect of three biofertilizers applied single or in combination (Azotobacter chroococcum, Azospirillum brasilense and Glomus intraradices) and a plant growth bioregulator, the gibberellic acid 3 (AG3), on the germination and subsequent growth of papaya seedlings. An experimental design completely random with eight treatments and three replications were used. The application of a pre-germinal treatment with alternating temperature had to be applied to seeds to overcome dormancy. Single biofertilization with A. chroococcum and A. brasilense, promoted the germination percentage 90.28 y 88.89% respectively. Germination rate could be enhanced and the mean germination time was reduced with the application of biofertilizer and AG3. Both applications on seeds and leaves of biofertilizers and AG3, had a positive effect on plant growth. The population of A. chroococcum was higher in the combined inoculation with G. intraradices. The prevalence of colonization of plants inoculated with G. intraradices ranged from 18.53 to 26.67%, with the greatest values recorded for the treatment involving combined inoculation with A. brasilense. Finally, with the application of this methodology the seed germination rate was improved, as well as the uniformity of seedlings emergence...

Detecção de Listeria spp. e Salmonella spp. em superfícies de melão (Cucumis melo), melancia (Citrullus vulgaris) e mamão (Carica papaya), pelo método imunoenzimático TECRA VIA e procedimentos de cultura / Detection of Listeria spp. and Salmonella spp. in melon (Cucumis melo), watermelon (Citrullus vulgaris) and papaya (Carica papaya), by immunoenzyme TECRA VIA method and procedures for culture

Neste trabalho, foram avaliadas a incidência de Salmonella spp. e Listeria spp. em superfície de frutas, melões (Cucumis melo), melancias (Citrullus vulgaris) e mamões (Carica papaya), coletadas em feira livre e na central de abastecimento (CEASA) em Campinas-São Paulo, Brasil. De um total de 120 frutas 42 amostras foram analisadas simultaneamente pelo método imunoenzimático TECRA-VIA e BAM modificado para presença de Salmonella e por um método canadense Health Protection Branch e TECRA-VIA para detecção de Listeria. As 78 amostras restantes foram analisadas somente pelos métodos de cultura. Salmonella spp. não foi encontrada em nenhuma das 42 amostras analisadas por ambas metodologias sendo que o método TECRA VIA apresentou um falso positivo. Contudo Listeria spp. foi detectada em 1 (2.38 por cento ) das amostras analisadas e apresentou 2 resultados falsos positivos quando utilizado o método TECRA – VIA. Salmonella spp. também não foi constatada nas 78 amostras analisadas apenas pelo método BAM modificado. Contudo, Listeria spp. foi detectada em 9 (7.50 por cento) das amostras analisadas, sendo que L. innocua e L. grayii foram isoladas e L. welshimeri de melão quando utilizado o método canadense Health Protection Branch. As amostras coletadas em feira livre mostraram uma freqüência maior de Listeria quando comparadas com as obtidas no CEASA.