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

Abstract

Epiphytism is a major problem world-wide forthe Gracilaria mariculture industry that reduces the productivityof commercial farms. Most of the epiphytesassociated with Gracilaria chilensis belong to the orderCeramiales. Under laboratory conditions we studied theinfection process of Ceramium rubrum rhizoids on G. chilensiscollected from a northern Chilean farm. The rhizoidpenetration was intercellular. The host cell wall and corticalcells adjacent to the epiphyte appeared compressedand disorganized. The rhizoids presented an extensivedynamic complex endomembrane system, mainly representedby a plentiful endoplasmic reticulum (ER) network,dictyosomes, electron dense material surroundedby ER membranes, membrane bodies and vacuolar sacswith fibrillar material. Two types of cell wall depositioncan be suggested: i) one characterized by the direct contactof ER vesicles with the plasmalemma and ii) anotherrepresented by the ER contributing material to the cellwall indirectly through vacuolar sacs. This study providesthe basis for a better understanding of the infection processinvolved in the epiphyte-host interaction.