Infection process of Ceramium rubrum (Rhodophyta, Ceramiales) on the agarophyte Gracilaria chilensis (Rhodophyta, Gracilariales)

摘要

Epiphytism is a major problem world-wide for the Gracilaria mariculture industry that reduces the productivity of commercial farms. Most of the epiphytes associated with Gracilaria chilensis belong to the order Ceramiales. Under laboratory conditions we studied the infection process of Ceramium rubrum rhizoids on G. chilensis collected from a northern Chilean farm. The rhizoid penetration was intercellular. The host cell wall and cortical cells adjacent to the epiphyte appeared compressed and disorganized. The rhizoids presented an extensive dynamic complex endomembrane system, mainly represented by a plentiful endoplasmic reticulum (ER) network, dictyosomes, electron dense material surrounded by ER membranes, membrane bodies and vacuolar sacs with fibrillar material. Two types of cell wall deposition can be suggested: i) one characterized by the direct contact of ER vesicles with the plasmalemma and ii) another represented by the ER contributing material to the cell wall indirectly through vacuolar sacs. This study provides the basis for a better understanding of the infection process involved in the epiphyte-host interaction.