Pigmented algal endophytes of Chondrus crispus Stackhouse: Host specificity, fine structure, and effects on host performance in infections by Acrochaete operculata Correa & Nielsen and Acrochaete heteroclada Correa & Nielsen.
Date
1990
Authors
Correa, Juan Alberto.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The present study was undertaken to elucidate various aspects of the symbiosis established between the rhodophyte Chondrus crispus and its green algal endophytes Acrochaete operculata and A. heteroclada. The three main aspects investigated were (a) host specificity, (b) fine structure of the infections and (c) effects of the infections on the performance of C. crispus in culture.
Acrochaete operculata is a highly selective endophyte whose specificity is determined by the polysaccharide fraction of the host cell wall. It was demonstrated that only hosts producing carrageenan of the lambda family were susceptible, regardless of species. Sporophytic fronds of Iridaea cordata and C. crispus, both $\lambda$-carrageenophytes, displayed similar patterns of infections. The gametophytic, $\kappa$-carrageenophytes, fronds of I. cordata were not infected and those of C. crispus displayed light infection which did not spread throughout the frond. Fine structural observations indicate that A. operculata breaches the outer cell wall of C. crispus, apparently by enzymatic means, reaches the cortex and spreads throughout the frond embedded in the intercellular matrix. Only minor host-cell damage occurs at this stage, whereas subsequent maturation of the endophyte, followed by zoospore release, causes massive host-cell destruction accompanied by disruption of the outer cell wall. This permits secondary bacterial infection, which accelerates the decay of the host tissue. Cellular destruction in infected fronds results in low biomass accumulation, poor or suppressed regenerative capacity and tissue softening. Furthermore, infected C. crispus becomes a preferred item when offered to crustacean grazers.
Acrochaete heteroclada was not host specific and infected various carrageenophytic, agarophytic and other hosts. Penetration of the host outer cell wall, which appears to be mechanical, is followed by development of endophytic filaments within the inner portion of the outer cell wall. No host-cell damage was observed at this stage, while subsequent penetration of the cortex of C. crispus resulted in massive cell destruction. Effects of infection on host performance were similar to those observed after infection by A. operculata, although A. heteroclada affected the two life-history phases of C. crispus.
The results of this study lead to the conclusion that A. operculata and A. heteroclada are pathogens, with potentially negative effects on both wild and cultivated C. crispus.
Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
Acrochaete operculata is a highly selective endophyte whose specificity is determined by the polysaccharide fraction of the host cell wall. It was demonstrated that only hosts producing carrageenan of the lambda family were susceptible, regardless of species. Sporophytic fronds of Iridaea cordata and C. crispus, both $\lambda$-carrageenophytes, displayed similar patterns of infections. The gametophytic, $\kappa$-carrageenophytes, fronds of I. cordata were not infected and those of C. crispus displayed light infection which did not spread throughout the frond. Fine structural observations indicate that A. operculata breaches the outer cell wall of C. crispus, apparently by enzymatic means, reaches the cortex and spreads throughout the frond embedded in the intercellular matrix. Only minor host-cell damage occurs at this stage, whereas subsequent maturation of the endophyte, followed by zoospore release, causes massive host-cell destruction accompanied by disruption of the outer cell wall. This permits secondary bacterial infection, which accelerates the decay of the host tissue. Cellular destruction in infected fronds results in low biomass accumulation, poor or suppressed regenerative capacity and tissue softening. Furthermore, infected C. crispus becomes a preferred item when offered to crustacean grazers.
Acrochaete heteroclada was not host specific and infected various carrageenophytic, agarophytic and other hosts. Penetration of the host outer cell wall, which appears to be mechanical, is followed by development of endophytic filaments within the inner portion of the outer cell wall. No host-cell damage was observed at this stage, while subsequent penetration of the cortex of C. crispus resulted in massive cell destruction. Effects of infection on host performance were similar to those observed after infection by A. operculata, although A. heteroclada affected the two life-history phases of C. crispus.
The results of this study lead to the conclusion that A. operculata and A. heteroclada are pathogens, with potentially negative effects on both wild and cultivated C. crispus.
Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
Keywords
Agriculture, Plant Pathology.