Biology Reference
In-Depth Information
11.2.2.1 Endophytes in Red Algae
The occurrence of epi-endophyte algae in the red algal host
Hymenena falklandica
was recently reported as the first epidemiological study conducted in Argentina
(Gauna et al.
2010
). The green alga
Epicladia heterotricha
revealed a 100%
prevalence of occurrence, particularly in the basal region of the host and low
(14%), moderate (28%), and high (58%) severity degrees of infection were
registered (Gauna et al.
2010
)
.
In contrast, the green epiphyte
Pseudendoclonium
submarinum
exhibited a lower frequency of occurrence, close to 3%. The experi-
mental infection of
H. falklandica
by
E. heterotricha
demonstrated that
E.
heterotricha
initially behaves as epiphytic but with endophytic filaments growing
into the cortex of the host during late infection, while
P. submarinum
was found to
be exclusively epiphytic.
A reassessment of the taxonomy of such green algal epi/endophytes has been
attempted during the recent years using molecular tools. Their assignment to genus
and/or species level has been previously done on the basis of their morphology, but
their growth inside an algal host and their simple growth forms, with relatively few
reliable diagnostic characters, make their taxonomy problematic (Dixon
1963
;White
and Boney
1969
,
1970
;Woelkerling
1971
;Bownetal.
2003
) and strongly impact the
epidemiological studies. Positive identification depends on culturing living isolates to
reveal valuable taxonomic characters that are not always apparent in field collected or
preserved material (Nielsen and McLachlan
1986
; Correa and McLachlan
1991
). The
relationships between isolates belonging to the green algal genus
Acrochaete
and
other chlorophyte taxa were better characterized by the analysis of internal tran-
scribed spacer 2 (ITS2) rDNA sequence variability (Bown et al.
2003
). These
findings indicate that the taxonomy of
Acrochaete
may need major revision and
suggest that species-specific oligonucleotide primers could be used as the basis for a
polymerase chain reaction (PCR) assay to assess endophyte diversity within
populations of
Chondrus
and related host species (Bown et al.
2003
).
11.2.2.2 Endophytes in Brown Algae
Endophyte species of kelps were recently reviewed by Eggert et al. (
2010
). Some of
these endophytes cause only minor changes in their hosts such as tissue darkening,
whereas others are known to produce either degradative losses or tumoral lesions
accompanied by severe thalli deformations (Apt
1988a
; Peters and Schaffelke
1996
). Epidemiological studies in populations of kelps demonstrated that infections
may affect 100% of the host population (Andrews
1977
; Lein et al.
1991
; Peters and
Schaffelke
1996
; Ellertsdottir and Peters
1997
). Recent work on the biology and
ecology of brown algal endophytes has focused on exploring novel interactions
between kelps and brown endophytes in the South-East Pacific Ocean and Antarctic
regions, respectively. Along the Pacific coasts of South America,
Macrocystis
pyrifera
is infected by
Laminariocolax macrocystis
(Burkhardt and Peters
1998
),
