Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. II. Characteristics of opaque matter associated with extensive host cell and cell wall alterations

Abstract

<jats:title>Abstract</jats:title><jats:p>Light and transmission electron microscopy observations of staghorn sumac plants inoculated or naturally infected with<jats:italic>Fusarium oxysporum</jats:italic>f. sp.<jats:italic>callistephi</jats:italic>are reported. One aspect of infection was the presence of large intercellular masses of opaque matter (OM) in middle lamellae between ray cells and/or fibres, often bypassing several intercellular areas; similar OM confluent with the intercellular OM also occurred in secondary walls and in the periphery of numerous cells. A gradual increase in the abundance of the OM in host tissues vertically from the inoculation point and then radially was noted over infection time and was related to host wall and cell alterations. In the region of recently deposited tissue, the OM was associated with pronounced cell hyperplasia and hypertrophy. The OM was delimited by thin, compact bands, and when it was less compact, displayed opaque particles and other fine structures. No indications were obtained that it contained or had contained intact or altered organelles. The DNA probe bound to OM in middle lamellae and in cell periplasmic areas, and to material of a similar texture lining vessel walls. Samples from<jats:italic>Fusarium</jats:italic>-infected plants, incubated on an agar medium before fixing to determine from which elements the pathogens could develop, displayed bodies as the sole elements present in mature xylem cells and in intercellular areas. These bodies were delimited by membranous structures and profiles of a wall layer and contained opaque particles and areas of fine structures. Certain inter- or intracellular fungal cells in the same tissue frequently had similar content. In the light of these observations it is proposed that the OM is primarily of a pathogen rather than of a host origin.</jats:p>

A Review of Ultrastructural and Ultracytochemical Studies of Infection Processes in Some Plant Wilt Diseases: The Opaque Matter Extensively Involved, Its Links with Pathogen Elements, Insights into Its Nature

“…that initially was not delimited by a wall~see mention in Nicole et al, 1994!, and that mitochondria "followed" later on. filtrates~as referred to above!, from irregular forms growing through Millipore membranes, or from homogeneous, uniform cell content~as shown herein and in some illustrations in Ouellette et al, 2004dOuellette et al, , 2005b!, is indeed a complex question to resolve. VIII!.…”

“…V!. 4B,C,E!, in repeated inoculations of elms, staghorn sumac, and egg-plant~Ouellette, 1978c; Ouellette et al, 2005b;Ouellette & Chamberland, 2006!. 3B-E!.…”

Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. III. Host cell and tissue reactions

“…The observed reacting host cells were often located next to wall alterations in adjacent cells, as in other systems (Ouellette et al 2004a), and likewise associated with opaque matter (Ouellette et al 2005b). An indication that wall ruptures were not attributable to an effect of sample manipulation was that paths of wall alterations, reaching in some cases from one cell to another across their walls, had been sealed off by the deposition of a continuous new wall layer (Ouellette, unpublished observations).…”

Tissue invasion and alteration in eggplant infected with Verticillium dahliae: A light and transmission electron microscopy study

“…In staghorn sumac, OM in host walls and that lining vessel walls was shown to label with a gold-complexed monoclonal antibody to DNA (Ouellette et al 2004e, 2005b) with which such a probe would ordinarily not be expected to bind. A more detailed discussion on the subject is presented in Ouellette et al (2005b). May it be stressed that the OM and related components under study do not appear to simply be degradation or excretion products, and that their occurrence in periplasmic spaces may not necessarily be an expression of host cell reactions (Shi et al 1992).…”

“…We have already described particular modes of pathogen development, of tissue alterations, of host cell reactions and related aspects concerning Dutch elm disease and Fusarium wilts of carnation, tomato and staghorn sumac (Charest et al 2004;Ouellette 1978b;Ouellette et al 1995Ouellette et al , 1999Ouellette et al , 2004aOuellette et al , 2004bOuellette et al , 2004cOuellette et al , 2004dOuellette et al , 2004e, 2005aOuellette et al , 2005b. These works present peculiar characteristics of pathogen structures, of host cell wall and content alterations related to extensive tissue invasion by opaque matter, not ascribable to a host origin, of various host cell reactions and so on, and more than circumstantial evidence was presented to show that most of the material lining vessel walls did not always correspond to the notions of coating as supported by others.…”