Thyme and suico essential oils: Promising natural tools for potato common scab control

Potato common scab is a worldwide disease mainly caused by Streptomyces scabiei. It seriously affects potato crops by decreasing tuber quality. Essential oils (EO) are natural products with recognised antimicrobial properties. In this research, the antibacterial activities of thyme, oregano, suico and mint EO against S. scabiei were analysed. Infected tubers and soil samples were used for bacterial isolation; the obtained isolates were genetically identified. The chemical composition of the EO was determined by GC-MS. The broth microdilution method was used to analyse antibacterial properties of EO. Thirty-one bacterial isolates were obtained. The isolate chosen for antibacterial assays was morpho-physiologically and genetically identified as S. scabiei. Thyme EO was mainly composed of thymol and o-cymene; suico EO of dihydrotagetone, trans-tagetone and verbenone; oregano EO of trans-sabinene hydrate, thymol and ɣ-terpinene; and mint EO of menthone and menthol. All the EO tested were effective against S. scabiei, but thyme and suico EO were the most successful, with a minimum inhibitory concentration of 0.068 g·l−1 and 0.147 g·l−1, respectively, and a minimum bactericidal concentration of 0.137 g·l−1 and 0.147 g·l−1, respectively. Scanning electron microscopy showed similar damage caused by both thyme and suico EO to the bacterial envelope. Total phenolic content of EO was not related to their antibacterial activity. Thyme and suico EO are effective antibacterial agents against S. scabiei, impeding bacterial viability and disturbing the bacterial cell envelope. These EO are promising tools for control of potato common scab.Fil: Prieto, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Lapaz, M. I.. Universidad de la República Facultad de Química; UruguayFil: Lucini, Enrique Iván. Universidad Nacional de Córdoba; ArgentinaFil: Pianzzola, M. J.. Universidad de la República Facultad de Química; UruguayFil: Grosso, Nelson. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Asensio, Claudia Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin

A novel sensitive method to evaluate potato germplasm for bacterial wilt resistance using a luminescent Ralstonia solanacearum reporter strain

Several breeding programs are under way to introduce resistance to bacterial wilt caused by Ralstonia solanacearum in solanaceous crops. The lack of screening methods allowing easy measurement of pathogen colonization and the inability to detect latent (i.e., symptomless) infections are major limitations when evaluating resistance to this disease in plant germplasm. We describe a new method to study the interaction between R. solanacearum and potato germplasm that overcomes these restrictions. The R. solanacearum UY031 was genetically modified to constitutively generate light from a synthetic luxCDABE operon stably inserted in its chromosome. Colonization of this reporter strain on different potato accessions was followed using life imaging. Bacterial detection in planta by this nondisruptive system correlated with the development of wilting symptoms. In addition, we demonstrated that quantitative detection of the recombinant strain using a luminometer can identify latent infections on symptomless potato plants. We have developed a novel, unsophisticated, and accurate method for high-throughput evaluation of pathogen colonization in plant populations. We applied this method to compare the behavior of potato accessions with contrasting resistance to R. solanacearum. This new system will be especially useful to detect latency in symptomless parental lines before their inclusion in long-term breeding programs for disease resistance

Mecanismos de resistencia a marchitez bacteriana en clones avanzados del Programa de Mejoramiento Genético de papa. [o6*].

El cultivo de papa es uno de los más afectados por Ralstonia solanacearum (Rs), el agente causal de la marchitez bacteriana. Este patógeno es capaz de desarrollar infecciones latentes asintomáticas que facilitan su diseminación. Nuestro grupo trabaja en colaboración con el Programa de Mejoramiento Genético de Papa desarrollado en INIA, en la generación de nuevas variedades con resistencia a esta enfermedad utilizando como fuente de resistencia a la especie silvestre nativa Solanum commersonii. El objetivo de este trabajo es evaluar la interacción planta-patógeno en genotipos de papa con diferentes niveles de resistencia a Rs, seleccionados del programa de mejoramiento de INIA

An engineered two-iron superoxide reductase lacking the [Fe(SCys)(4)] site retains its catalytic properties in vitro and in vivo

Superoxide reductases (SORs) contain a characteristic square-pyramidal [Fe(NHis)(4)(SCys)] active site that catalyzes reduction of superoxide to hydrogen peroxide in several anaerobic bacteria and archaea. Some SORs, referred to as two-iron SORs (2Fe-SORs), also contain a lower-potential [Fe(SCys)(4)] site that is presumed to have an electron transfer function. However, the intra- and inter-subunit distances between [Fe(SCys)(4)] and [Fe(NHis)(4)(SCys)] iron centers within the 2Fe-SOR homodimer seem too long for efficient electron transfer between these sites. The possible role of the [Fe(SCys)(4)] site in 2Fe-SORs was addressed in this work by examination of an engineered Desulfovibrio vulgaris 2Fe-SOR variant, C13S, in which one ligand residue of the [Fe(SCys)(4)] site, cysteine 13, was changed to serine. This single amino acid residue change destroyed the native [Fe(SCys)(4)] site with complete loss of its iron, but left the [Fe(NHis)(4)(SCys)] site and the protein homodimer intact. The spectroscopic, redox and superoxide reactivity properties of the [Fe(NHis)(4)(SCys)] site in the C13S variant were nearly indistinguishable from those of the wild-type 2Fe-SOR. Aerobic growth complementation of a superoxide dismutase (SOD)-deficient Escherichia coli strain showed that the presence of the [Fe(NHis)(4)(SCys)] site in C13S 2Fe-SOR was apparently sufficient to catalyze reduction of the intracellular superoxide to nonlethal levels. As is the case for the wild-type protein, C13S 2Fe-SOR did not show any detectable SOD activity, i.e., destruction of the [Fe(SCys)(4)] site did not unmask latent SOD activity of the [Fe(NHis)(4)(SCys)] site. Possible alternative roles for the [Fe(SCys)(4)] site in 2Fe-SORs are considered