Efecto antibacteriano in vitro de exudados foliares de tabaco contra dos bacterias fitopatógenas

Abstract

ResumenLos productos naturales son una alternativa para el control de microorganismos que ocasionan enfermedades en los cultivos. Este trabajo tuvo como objetivo evaluar diferentes solventes para la obtención de extractos crudos a partir de exudados foliares de líneas de tabaco, y el efecto in vitro de estos extractos contra dos bacterias fitopatógenas: Xanthomonas campestris (Xc) y Pectobacterium carotovorum (Pc). Se evaluaron solventes con polaridades entre 3.1 y 6.2 (diclorometano, n-butanol, acetato de etilo, metanol y etanol 90 %). El etanol 90 % se seleccionó como mejor solvente y como sustituto del diclorometano por su mayor rendimiento. Los extractos etanólicos crudos se obtuvieron a partir de exudados foliares de diez líneas de tabaco seleccionadas. La diversidad de la composición química de los extractos etanólicos se reveló por cromatografía en capa delgada. La actividad antibacteriana se evaluó por el método de difusión en agar con discos de papel de filtro y la medición del diámetro del halo de inhibición. Se observó inhibición para todos los extractos contra Xc destacándose los correspondientes a las líneas Nic 1061 "TI 1738" y Nic 1016 "Incekara" hasta 5 µg de extracto crudo seco /disco, con un mayor rendimiento para la línea Nic 1061. El extracto de la línea Nic 1015 fue el único con actividad contra Pc hasta 5 µg de extracto crudo seco por disco. Estos resultados sugieren un uso potencial de los extractos crudos de las líneas Nic 1061 y Nic 1015 "TI 1341" como un agente efectivo para la protección de cultivos contra estas bacterias.Palabras clave: fitopatógenos, Nicotiana tabacum, protección de cultivos, solventes, superficie foliar. AbstractNatural products are an alternative to control microorganisms that cause diseases in crops. This work aimed to evaluate different solvents for obtaining crude extracts from tobacco leaf exudates and to determine in vitro effect of these extracts against two phytopathogenic bacteria: Xanthomonas campestris (Xc) and Pectobacterium carotovorum (Pc). Crude extracts from ten tobacco lines using solvents with polarities between 3.1 and 6.2 (dichloromethane, n-butanol, ethyl acetate, methanol and ethanol 90%) were obtained. Ethanol 90% was selected as the best solvent for obtaining extracts from tobacco leaf exudates and as a substitute of dichloromethane due to the best yield. The chemical composition diversity of the ethanolic extracts was revealed by thin-layer chromatography. The antibacterial activity was evaluated by agar disk diffusion method recording the inhibition zones. Growth inhibition was observed for all extracts against Xc, and the better activity corresponded to the lines Nic 1061"TI 1738" and Nic 1016 "Incekara" until a minimal amount of 5 µg/ disc, with higher yield in case of the line Nic1061 . Only the extract of the line Nic 1015 was able to inhibit the growth of Pc until a minimal inhibitory concentration of 5 µg/disc. These results suggest a potential use of crude extracts from lines Nic 1061 and Nic 1015 "TI 1341" as an effective agent for ...

Tobacco Leaf-Surface Extracts: Antimicrobial Potential against Phytopathogenic Fungi and In Vitro Culture Bacterial Contaminants

“…The results in this investigation indicate an antibacterial activity for these non-pathogenic plant bacteria, although with less inhibition than that shown for Xanthomonas campestris and Pectobacterium carotovorum at the same amount of extract (500 µg) [23]. Other ethanolic extracts of Acacia aroma leaves and flowers [37] and other plants [38] showed activity against S. maltophilia.…”

“…Crude extracts were obtained from the leaf surfaces of three plants using a modified method based on Severson [22], employing commercial ethanol produced nationally as the extraction solvent [23]. The whole leaves were individually immersed in commercial ethanol eight times for two seconds in a container, the solvent used was a 90% ethanol and 10% water mixture (v:v).…”

“…It is possible that the extracts cause a thickening of the bacterial cell wall through interference in bacterial cell division, as occurs with terpene compounds that act in this way against a bacterium of the same genus, Bacillus cereus [39]. Kanamycin is one of the commonly used antibiotics for in vitro susceptibility testing assays [23] and gentamicin and ampicillin have been used for S. maltophilia [38]. Other trials that consider the application of these extracts in in vitro culture media should be developed in the future to verify their efficiency in controlling bacterial contamination.…”