[en] This report presents a survey of previous and more recent ultrastructural and cytochemical investigations of disease development in elm, caused by Ophiostoma novo-ulmi, with results of some comparative studies of other wilt diseases caused by f.spp., of Fusarium oxysporum and of Verticillium sp. For cytochemical studies, probes complexed to colloidal gold to detect cellulose, pectin, chitin, and DNA were used. Thus, the formation of tyloses, pit membrane alterations, and the disease effect on parenchyma cells in mature as well as in young tissue were characterized. Vessel lumina in these plants, in diverse situations, contained heterogeneous matter, among which occurred masses of opaque matter and in certain instances pectin fibrils secreted by parenchyma cells and tyloses. Numerous globoid, opaque bodies of regular sizes, which have been mostly overlooked previously, abounded in vessel elements of U. americana and U. glabra, including trees injected with glucose solutions prior to inoculation. Coarser fibrillar material was also noted in vessel lumina, but mostly shortly after inoculation. Other peculiar forms of O. novo-ulmi are also described. The possible role of the components under study is discussed, and a model for DED is proposed in which hindrance to vessel invasion, including downward spread of the pathogen, and reactions of parenchyma cells are complementary and considered to be conducive to defence mechanisms, including compartmentalization of the invaded xylem.

[es] En este informe se presenta una revisi&oacute;n de los m&aacute;s recientes estudios sobre la ultraestructura y la citoqu&iacute;mica del desarrollo infectivo causado por Ophiostoma novo-ulmi en el olmo, y su comparaci&oacute;n con otras enfermedades vasculares causada por hongos como Fusarium oxysporum y Verticillium sp. En los estudios citoqu&iacute;micos se usaron inmunolocalizadores de oro coloidal para la detecci&oacute;n de celulosa, pectina, quitina y ADN. De esta manera se caracteriz&oacute; la formaci&oacute;n de tilosas, las alteraciones en las punteaduras, y los efectos de la infecci&oacute;n en las c&eacute;lulas parenquim&aacute;ticas, tanto en tejidos adultos como j&oacute;venes. En estas plantas, el interior de los elementos conductores contiene, en diversas ocasiones, sustancias heterog&eacute;neas en las que aparecen masas de sustancias opacas, as&iacute; como, en ciertas ocasiones, fibrillas de pectina segregadas por c&eacute;lulas parenquim&aacute;ticas y por tilosas. Numerosos cuerpos opacos globulares de tama&ntilde;o medio, que previamente hab&iacute;an pasado en gran medida inadvertidos, eran abundantes en los elementos conductores de U. americana y U. glabra, incluyendo &aacute;rboles a los que se inyect&oacute; soluciones de glucosa antes de la inoculaci&oacute;n. Tambi&eacute;n se detect&oacute; la presencia, en el interior de los vasos, de material fibrilar de mayor di&aacute;metro, sobre todo al poco de la inoculaci&oacute;n. Tambi&eacute;n se describen otras formas peculiares de O. novo-ulmi. Se discute el posible papel de los componentes en estudio, y se propone un modelo para la grafiosis en el cual los obst&aacute;culos para la invasi&oacute;n del vaso, incluidas la transmisi&oacute;n corriente abajo del pat&oacute;geno y la reacci&oacute;n de c&eacute;lulas parenquim&aacute;ticas, son complementarios, consider&aacute;ndose que son conducentes a la aparici&oacute;n de mecanismos de defensa, incluida la compartimentaci&oacute;n del xilema invadido.