Here, cell and wall modifications in resistant (cv. I) and susceptible (cv. II) carnation inoculated with Fusarium oxysporum are characterized. Samples, of various days after inoculation (dai), were double-fixed and gold-complexed probes used for cellulose, pectin, chitin. In cv. I, mature paratracheal cells contained appositions mostly bound by a cellulose layer over the densely opaque native walls. Middle lamellae of younger cells, many hyperplastic and much distorted, were obliterated, and appositions displayed a mingling of cellulose-labelled and -unlabelled components; adjoining cells contained inner suberin layers. Cell wall modifications in cv. II were limited, but early pathogen invasion was restricted to middle lamellae despite pronounced host cell content alterations. In both cvs, microfilaments linked to often small, thin-walled fungal cells in vessels and in turn to coating on their walls, extended into adjoining cells, seemingly associated in cv. I with cell reactions, and in cv. II excreted as bodies into vacuoles. The present results highlight that extensive cell reactions and wall modifications, including suberin deposition in hyperplastic tissue, are the main initial factors of defence conducive to final pathogen confinement.
- Fungal walls
- Fusarium oxysporum f. sp. dianthi race 2
- Labelled probes
- Microfilamentous structures