Resumo

HERNANDEZ, Y.; MARINO, N.; TRUJILLO, G.  e  URBINA DE NAVARRO, C.. Invasión de Ralstonia solanacearum en tejidos de tallos de tomate (Lycopersicon esculentum Mill). Rev. Fac. Agron. [online]. 2005, vol.22, n.2, pp.185-194. ISSN 0378-7818.

Abstract In Venezuela Ralstonia solanacearum has been reported as a pathogen affecting growing crop of Solanaceae. In order to determine the pattern of the bacterium invasion on the tissue stem of tomato (Lycopersicom esculentum), a study was carried out by using optic and electronic microscope. Tomato plants in the variety ´Río Grande`, which were 45 days old, were selected and wounded on the base of the stem and roots. They were then inoculated with a bacterial suspension adjusted to 10⁹ cel/ml, which was applied directly on the soil. Control plants were treated with sterile distilled water. Samples from half of the stem were taken from eight up to 12 days after the inoculation. For optical microscopy observations sections of stem were fixed in FAA solution. Sectioning was performed by hand and the tissue was stained with toluidine and blue aniline. For electronic microscopy the samples were fixed in glutaric aldehyde and osmium tetraoxyde. A dehydration in series of ethanol was carried out and samples were embedded in resin, then sectioning was performed by using a ultramicrotome and specimens were stained with acetate uranide and lead citrate. The results under the optical microscopy showed the bacterial invasion on the xylem and phloem. The invasion takes place mainly on the vessels of most diameter. Observations with electronic microscopy showed that the invasion also occurs on the parenchyma cells around the conductive vessels, at this region, thyllos were also observed, this could be interpreted as a plant response to the bacteria attack.

Palavras-chave : Ralstonia solanacearum; invasion; Lycopersicon esculentum.