Occurrence of paracrystalloids and their particles in resistant and susceptible carnation plants infected with Fusarium oxysporum f.sp. dianthi race 2

Abstract

Uncommon, opaque particles (of approximately 20-22 nm, referred to as OP), aggregating into paracrystalloids occurred only next to colonized cells in carnation plants of either a susceptible or resistant cultivar (cv.) infected with Fusarium oxysporum f.sp. dianthi. In the susceptible plant, those structures occurred in vessel lumina and host walls, apparently associated with their alterations, but not in parenchyma cells, a situation which was the exact opposite of that observed in resistant plants. In comparison with apparently similar structures reported in other systems, paracrystalloids and their OPs did not seem to have exact counterparts in plants infected with viruses or fungi, although similar paracrystalloids were observed in nematode-infected plants. The OPs were associated in both cvs. with fine opaque matter, often displaying fine filamentous structures, and were in addition connected to fungal cells in the susceptible cv. Similar structures also extended through host walls into adjoining cells; these relations with parenchyma cells in resistant plants were interpreted as if the particles therein were akin to, if not exactly of the same nature as those in susceptible plants. As the opaque matter, the filamentous structures and the OPs were interrelated and associated with pathogen cells, it seemed warranted to assume that the OPs were issued from the pathogen.

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

“…The present observations reinforce the hypothesis, as already expressed for other systems and supported by similar observations (Ouellette and Baayen 2000;Ouellette and Rioux 1993;Ouellette et al 1995Ouellette et al , 1999aOuellette et al , 2004aOuellette et al , 2004bOuellette et al , 2004cOuellette et al , 2004d, that the OM occurrence primarily relates to the pathogen, as: 1) OM, including that of the VWLM, was also connected to fungal cells, and often by means of microfilaments (see also Atstatt 2003, showing some endophyte-like fungal cells with their walls pervaded by similar filamenatous structures); and 2) close similarities noted between OM present in host walls or in periplasmic areas, that of the VWLM, and content of some fungal cells and elements (compare Figs. 6d,7d,8c and element in Fig.…”

“…Observations of the apparent absence of a nuclear envelope in some fungal cells in the present study are also similar to those of O. novo-ulmi and of other F. oxysporum f. spp. (Chamberland and Ouellette 1977a;Charest et al 2004;Ouellette et al 2004c). It is not impossible that the components of high opacity in this OM concealed some structural DNA (see Fig.…”

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

“…Examples of links of this material with OM pervading middle lamellae and with that present in host cell periplasmic spaces have also been provided. These observations corroborate the majority of similar ones that we have made concerning other wilt diseases affecting tomato, carnation, and staghorn sumac (Ouellette et al 2004b(Ouellette et al , 2004c(Ouellette et al , 2004e, 2005b. The matter deposited on vessel walls in plants infected with Verticillium and other fungal wilt pathogens has been defined as coating by other authors Cooper 1983, 1984;Gold et al 1996;Pegg and Brady 2002;Pegg et al 1976;Robb et al 1979aRobb et al , 1979bRobb et al , 1987Robb 2000).…”

“…Particles present in similar matter present in vessel elements or in host walls associated with their alterations have been illustrated in Fusariuminfected susceptible carnation plants (Ouellette and Baayen 2000;Ouellette et al 2004c) and in Dutch elm disease infected elms (see Fig. 7 in Ouellette et al 2004e, andFigs.…”

“…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.…”