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Abstract

Platypus cylindrus is a pest that since the 80’s of the last century has been considered a cork oak mortality agent in Portugal. It is an ambrosia beetle that establishes complex symbioses with fungi whose role in the insect-fungus-host interaction has not been completely clarified. In order to characterize P. cylindrus associated micoflora in Portugal, fungi were isolated from different beetle organs and from its galleries in cork oak trees. Fungi of the genera Acremonium, Aspergillus, Beauveria, Botrytis, Chaetomium, Fusarium, Geotrichum, Gliocladium, Nodulisporium, Paecilomyces, Penicillium, Raffaelea, Scytalidium, Trichoderma and of the order Mucoraleswere identified. An actinomycete of the genus Streptomyces was also identified. Some of these genera were related for the first time to this interaction. In the present work the isolated fungi are characterized and their contribution for beetle population establishment and tree weakness is discussed.
FUNGI ASSOCIATED TO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) IN CORK OAK
FUNGOS ASSOCIADOS AO INSECTO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) EM SOBREIRO
JOANA HENRIQUES, MARIA DE LURDES INÁCIO, EDMUNDO SOUSA
ABSTRACT
Platypus cylindrus is a pest that since the
80’s of the last century has been considered
a cork oak mortality agent in Portugal. It
is an ambrosia beetle that establishes com-
plex symbioses with fungi whose role in the
insect-fungus-host interaction has not been
completely claried. In order to characterize
P. cylindrus associated micoora in Portugal,
fungi were isolated from different beetle or-
gans and from its galleries in cork oak trees.
Fungi of the genera Acremonium, Aspergillus,
Beauveria, Botrytis, Chaetomium, Fusarium,
Geotrichum, Gliocladium, Nodulisporium,
Paecilomyces, Penicillium, Raffaelea, Scyta-
lidium, Trichoderma and of the order Muco-
rales were identied. An actinomycete of the
genus Streptomyces was also identied. Some
of these genera were related for the rst time
to this interaction. In the present work the iso-
lated fungi are characterized and their contri-
bution for beetle population establishment and
tree weakness is discussed.
Key-words: ambrosia beetle, decline, inte-
raction, mycoora, Quercus suber.
RESUMO
Platypus cylindrus é uma praga que desde
os anos 80 do século passado tem sido refe-
rida como agente de mortalidade do sobrei-
ro em Portugal. É um insecto ambrósia que
estabelece simbioses complexas com fungos
cujo papel não está completamente esclare-
cido na interacção insecto-fungo-sobreiro.
Com o objectivo de caracterizar a micoora
associada a P. cylindrus em Portugal foram
efectuados isolamentos a partir de diferen-
tes órgãos do insecto e suas galerias em so-
breiro. Identicaram-se fungos dos géneros
Acremonium, Aspergillus, Beauveria, Bo-
trytis, Chaetomium, Fusarium, Geotrichum,
Gliocladium, Nodulisporium, Paecilomyces,
Penicillium, Raffaelea, Scytalidium, Tricho-
derma e da ordem Mucorales. Foi igualmen-
te identicado um actinomiceta do género
Streptomyces. Alguns destes géneros são
referidos pela primeira vez nesta interacção.
No presente trabalho caracterizam-se os fun-
gos isolados e discute-se a sua contribuição
para o estabelecimento das populações do
insecto e enfraquecimento das árvores.
Palavras-chave: insecto ambrósia, declínio,
interacção, micoora, Quercus suber.
INTRODUÇÃO
Scolytidae and Platypodidae are among the
most successful wood-inhabiting beetles cau-
sing damage of economic signicance to tre-
es and timber (Cassier et al., 1996). Platypus
cylindrus Fab. is a cork oak (Quercus suber L.)
pest that has come to assume an increasing im-
portance in Portugal and Mediterranean basin
Instituto Nacional de Recursos Biológicos, I.P.
Edifício da ex-Estação Florestal Nacional,
Quinta do Marquês, 2780-159 Oeiras
joana.henriques@efn.com.pt; lurdes.inacio@efn.
com.pt; edmundo.sousa@efn.com.pt
Recepção/Reception: 2009.01.15
Aceitação/Acception: 2009.05.14
57
FUNGI ASSOCIATED TO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) IN CORK OAK
countries (Ferreira & Ferreira, 1989; Chakali
et al., 2002; Riziero et al., 2002; Sousa et al.,
2005). Until recently, damages produced by
this insect were limited to dead or weakened
trees. The understanding of recent population
outbreaks, mainly in Portuguese cork oak
stands, can be based on three assumptions: (i)
gradual changes of the cork oak stand dyna-
mics, (ii) development of more specic host
colonization mechanisms and (iii) changes on
the insects and their natural enemies’ popula-
tion dynamics (Sousa & Inácio, 2005). Within
the host colonization strategies, it’s essential
to consider the fungal symbiosis that may
contribute to the host weakness and create bet-
ter conditions for the establishment of insects
(Henriques et al., 2006).
In deed, P. cylindrus, as almost all members
of the Platypodidae, is denominated an am-
brosia beetle because larvae and adults feed
mainly on fungi (ambrosia fungi) that cover
the gallery walls (Batra, 1963). This insect-
fungi relation is expressed in an ectosymbio-
sis in which the fungi live outside the insects’
body but are temporarily stored in special ec-
todermical organs for dissemination purposes
(Francke-Grosmann, 1967). Insects carry via-
ble inoculum in sac-like structures, called my-
cangia, located in the prothorax; the inoculum
is protected from desiccation during the entire
life of the beetle and is disseminated into new
breeding sites at the time of tunnel excavation
(Batra, 1963; Sousa & Inácio, 2005).
Ambrosia fungi denition includes a set
of concepts whose interception allows the
classication of several fungi as ambrosia: i)
direct participation in insect feeding; ii) pre-
sence inside insect galleries in the host; iii)
dimorphism, meaning ability to grow both
as yeast and mycelia; iv) possible specicity
in the insect-fungi-host relationship (Batra,
1963; Beaver, 1989).
Batra (1985) grouped ambrosia fungi as
primary and auxiliary. Primary ambrosia fun-
gi are highly insect species specic and their
distribution correspond to those of insect
symbionts. They are present and dominant
in the tunnels and isolated regularly from the
mycangia of the beetles in the ight stage or
when excavating tunnels. Auxiliary ambrosia
fungi are transitory, non-specic with respect
to symbiont insect and may appear after in-
sect development. They may not be present
in larval cradles or in adult beetles; and their
habitat and distribution range are unrestric-
ted and unrelated to that of the ambrosia be-
etles.
Several fungi have already been isolated
from P. cylindrus and from galleries in Quer-
cus spp. (Baker, 1963; Cassier et al., 1996;
Sousa et al., 1997; Morelet, 1998; Henriques
et al., 2006). Their constant presence asso-
ciated to the insect allows us to presume that
they play an important role in the symbiosis.
Besides the implication in insect feeding, am-
brosia fungi might also be involved in other
processes such as host weakness, through
pathogenic action; decomposition of ligno-
cellulolitic compounds, which helps gallery
construction and enables fungi colonization;
and/or antagonism that controls the growth
of other fungi (Sousa & Inácio, 2005; Henri-
ques et al., 2006).
The aim of the present work is to charac-
terize the micoora associated to P. cylindrus
and discuss its contribution for beetle popu-
lations’ establishment and host weakness.
MATERIAL AND METHODS
Four infested logs of cork oak trees exhi-
biting decline symptoms were collected from
three of the main Portuguese cork oak produc-
tive regions: Chamusca (Ribatejo province),
Montemor and Grândola (Alentejo province).
The logs were maintained in the laboratory in
order to capture 100 P. cylindrus insects, males
and females, as they emerged. Samplings were
repeated during 2005, 2006 and 2007. The in-
sects were aseptically dissected in mycangia,
intestine and parts of the exoskeleton (elytra).
The logs were cut in order to identify the diffe-
rent insect gallery sections: cork, inner-bark,
pre-parental section, larval section and gallery
end. One complete gallery was observed from
each log and six samples (fragments with 1
cm2) of each section were collected.
REVISTA DE CIÊNCIAS AGRÁRIAS
58
The samples were surface sterilized with
a sodium hypochlorite solution (1%) for 1
min, rinsed with distilled sterilized water and
then plated in malt extract agar (MEA, Dif-
co, USA) added with streptomycin (500 mg/l)
and MEA added with cycloheximide (500
mg/l). The cultures were incubated at 24±1ºC
in darkness. Pure cultures of each fungi isolate
were obtained and identied as genus based
on morphological features according to Ellis
(1971, 1976), Lanier et al. (1978), Kiffer &
Morelet (1997) and Barnett & Hunter (1998).
Cultural description of colonies was made on
potato dextrose agar (PDA, Difco, USA).
RESULTS
Fifteen genera were isolated from the di-
fferent insect parts and from all cork oak gal-
lery sections (Table 1). The identied fungi
are classied in very distinct orders including
the Ascomycota (Eurotiales, Heliotioales,
Hypocreales, Ophiostomatales, Saccharomy-
cetales, Sordiales and a genus not assigned
to any order) and Basidiomycota (Xylariales)
although all the obtained genera, except Cha-
etomium, were isolated in the mitosporic sta-
te. Also, an actinomycete was isolated from
the insect (Streptomycetales).
Table 1 – Genera isolated from Platypus cylindrus intestine, exoskeleton and mycangia and from the different
sections of insects galleries on cork oak.
* Streptomyces (order Actinomycetales) is an actinomycete, the other genera described belong to Fungi.
The isolated genera were described ac-
cording to the morphological features ba-
sed on optical microscopic observations
and literature guides. In table 2 the main
cultural features for all isolated genera are
described.
From the genus Aspergillus several individu-
als with different cultural characteristics were
isolated, probably belonging to different spe-
cies. Their microscopic features are: hyphae
septate and branched, conidiophores macro-
nematous, mononematous, erect, simple, often
with a foot cell, with a terminal vesicle bearing
short branches or phialides radiating from the
entire surface. When present, the branches are
in one or several series and the terminal ones
59
Table 2 – Cultural characteristics on PDA of the isolated genera.
always bear phialides. Conidiogenic cells mo-
nophialidic, discrete, several arising together
at the end of terminal branches or over the sur-
face of the vesicles, mostly determinate, rarely
percurrent, ampulliform or lageniform, colla-
rettes sometimes present. Conidia are phialos-
poric, unicellular, dry, smooth, rugose, echinu-
late, globose and hyaline but colored in mass,
disposed in long basiptal chains (Figure 1a).
Penicillium produces conidiophores ma-
cronematous, mononematous, simple or
branched, penicilated, ending in a group of
phialides. The walls of conidiophores may be
smooth and thin or variously roughened, with
aerial portions appearing delicately echinula-
te, granular or asperulate. The penicillus co-
vers all the branching system and can be mo-
noverticillate or biverticillate, symmetrical
FUNGI ASSOCIATED TO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) IN CORK OAK
REVISTA DE CIÊNCIAS AGRÁRIAS
60
or asymmetrical. Conidia are phialosporic,
unicellular, dry, globose or ovoid, hyaline to
green (Figure 1b).
Paecilomyces produces conidiophores
macronematous, mononematous, arising as
upright branches from hyphal ropes or ae-
rial mycelium, smooth-walled, usually with
several stages of irregular branching, and
frequently bearing secondary branches, with
divergent penicilated phialides, cylindrical to
ellipsoidal in the lower part, usually narro-
wing abruptly into a long cylindrical neck.
Conidia phialosporic, unicellular, hyaline,
ovoid, smooth-walled, highly variable in size
produced in long, strongly divergent chains
(Figure 1c).
Several Raffaelea isolates were obtained
showing a great macro and microscopic va-
riability, probably corresponding to different
species. This genus produces hyphae hyali-
ne and septate that bound together forming
compact hyphae ropes. Supercial sporodo-
chia, effuse, white to brownish. Conidiopho-
res are macronematous and mononematous,
erect, septate, slender with a tapered apex,
producing simpodulosporic conidiae that
leave cicatricial scars in the conidiogenous
cells. Conidiae are unicellular and hyaline,
with variable forms (triangular, oval, allan-
toid, fusiform or truncated claviform) and
dimensions (Figure 1d).
Fusarium produces conidiophores macro-
nematous and mononematous, variable, slen-
der, and simple or stout, short, septate and
branched that originates phialosporic coni-
dia, hyaline, canoe-shaped, with 5 to 6 trans-
versal septa and collected in a slimy drop. No
microconidia were observed (Figure 1e).
Trichoderma conidiophores macronema-
tous and mononematous, hyaline and highly
ramied, disposed in pyramidal structures
with inserted phialides in 90º angles. Conidia
are phialosporic, enteroblastic and monoblas-
tic, unicellular, green, globose to subglobose
and remain grouped in the top of the phiali-
des (Figure 1f).
Beauveria produces conidiophores micro-
nematous and mononematous, simple, irre-
gularly grouped, inated in the base and ta-
pered in the apical fertile portion that appears
sinusoidal after conidia production. Conidia
are simpodulosporic, unicellular, dry, hyali-
nes and ovoid with small denticles, giving
the conidiogenous cells a spiny appearance
(Figure 1g).
Gliocladium presents conidiophores ma-
cronematous and mononematous, erect, sep-
tate and branched, ending in a branched sys-
tem of phialides disposed in tight penicilate
structure with three phialides per metulae.
Phialides narrowly cylindrical to sub-ulate,
taper slightly towards the tip, smooth-walled.
Conidia are phialosporic, unicellular, hyali-
ne, ovoid or cylindrical and aggregated in
conidial masses, slimy to watery, whitish or
light-yellow, never forming imbricate chains
(Figure 1i).
Acremonium produces hyphae hyaline sep-
tate that sometimes bound together by anas-
tomoses. Conidiophores are macronematous
and mononematous, erect, solitary to weakly
branched, straight, tapered to the apex, with
basal septum to separate the conidiopho-
re from the vegetative hyphae. Conidia are
phialosporic, unicellular and ovoid, aggrega-
ted in a slimy drop (Figure 1k).
Geotrichum produces conidiophores mi-
cronematous and mononematous producing
arthrosporic conidiae, hyaline, unicellular,
dry, smooth, short cylindrical with truncated
bases, resulting from fragmentation of undi-
fferentiated hyphae by ssion through dou-
ble septum, (Figure 1l).
Botrytis has conidiophores macronema-
tous, mononematous, straight or exuous,
smooth, brown, slender, irregularly bran-
ched with enlarged apical polyblastic cells
where botryoblatosporic conidia are produ-
ced simultaneously; conidia solitary, simple,
smooth, hyaline to grey in mass, unicellular,
ovoid with a denticule. Mycelium immersed
or supercial, with brownish course hyphae.
Sclerotia frequently present (Figure 1h).
Chaetomium produces supercial perithe-
cia, brown, single, globose, covered with
different sized brown laments; asci clavate,
61
pedunculate with evanescent walls. Ascospo-
res unicellular, light olive-brown and lemo-
niform, smooth, often pushed out of ostiole
in a cirrhus (Figure 1j).
Streptomyces produces laments that ori-
ginate very small spores by fragmentation
that remain disposed in helical chains (Figu-
re 1m).
Nodulisporium produces mycelium partly
immersed and partly supercial, conidio-
phores macronematous and mononematous,
arising laterally from the brownish vegetati-
ve hyphae, with principal axis erect, septate,
branched, hyaline to light brown, slightly
rugouse, conidiogenic cells poliblastic and
sympodial, slender or short and thick, ver-
ticilated. Conidiae sympodulosporic, acro-
pleurogenous, unicellular, hyaline or bro-
wn to olive in mass, ellipsoidal or obovoid,
smooth or roughened, with a small frill when
detached (Figure 1n).
Scytalidium produces sparse thick
hyphae, septate, hardly branched, hyaline or
light-brown, disposed in parallel; conidio-
phores micronematous and mononematous
with terminal conidiogenic cell originating
arthroconidiae by holothalic fragmentation.
Conidia are catenulated, schizogenous, uni
or bicellular, hyaline, rectangular. It also
forms terminal or interpolate chlamydospo-
res, with thick wall, brown and ellipsoidal
(Figure 1o).
Figure 1 – Reproductive structures of isolated genus: a) Aspergillus (x1000); b) Penicillium (x1000);
c) Paecilomyces (x600); d) Raffaelea (x600); e) Fusarium (x600); f) Trichoderma (x600); g) Beauveria (x1000);
h) Botrytis (x600); i) Gliocladium (x400); j) Chaetomium (x1000); k) Acremonium (x600); l) Geotrichum;
m) Streptomyces (x1000); n) Nodulisporium (x600); o) Scytalidium (x600).
a
b
e
g h
k
lmn
o
i
i
df
c
In P. cylindrus galleries on cork oak, gre-
ater fungi variety were presented than in the
insects’ body. In both cases were isolated
cosmopolite fungi and others more specic
for insect-fungi relation. Concerning isola-
tes from insects, it was in the exoskeleton
that was found the major diversity of genus,
followed by mycangia and then intestine.
Among sexes, no relevant differences were
observed. Penicillium, Raffaelea and Asper-
gillus were the most frequent genus in the
three sampled organs and for both sexes.
Beauveria and Streptomyces were only iso-
lated from the insect, the former only from
the exoskeleton.
Along P. cylindrus galleries in cork oak,
the majority of the isolated genera were
found in all sections and, in general, in si-
FUNGI ASSOCIATED TO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) IN CORK OAK
REVISTA DE CIÊNCIAS AGRÁRIAS
62
milar proportions, highlighting cosmopolite
and saprophytic fungi such as Penicillium,
Trichoderma, Gliocladium and Scytalidium,
but also Raffaelea was isolated in a conside-
rable percentage in all sections. Botrytis, Fu-
sarium, Geotrichum and Chaetomium were
isolated only from the galleries but in very
low percentages and distribution.
In Figures 2 and 3 are represented the dis-
tribution of the isolated fungi both in P. cylin-
drus body and along its galleries in cork oak,
respectively.
Figure 2 – Percentage of isolated genera in the different body parts (intestine, exoskeleton and mycangia) of
Platypus cylindrus females (F) and males (M).
Figure 3Percentage of isolated genera from the different Platypus cylindrus galleries on cork oak (cork, inner
bark, pre-parental section, larval section and gallery end).
%
Intestine
Exoskeleton
Mycangia
0
10
20
30
40
50
0
10
20
30
40
50
0
10
20
30
40
50
Acremonium
Aspergillus
Beauveria
Gliocladium
Nodulisporium
Paecilomyces
Penicillium
Raffaelea
Scytalidium
Streptomyces
Trichoderma
Ge nus
F M
%
Intestine
Exoskeleton
Mycangia
0
10
20
30
40
50
0
10
20
30
40
50
0
10
20
30
40
50
Acremonium
Aspergillus
Beauveria
Gliocladium
Nodulisporium
Paecilomyces
Penicillium
Raffaelea
Scytalidium
Streptomyces
Trichoderma
Ge nus
F M
63
DISCUSSION
From all isolated genera, Raffaelea is hi-
ghlighted because of its known importance
as ambrosia fungi and both its frequency
and distribution (Beaver, 1989). This genus
includes twelve species, the majority asso-
ciated with ambrosia beetles (Kubono & Ito,
2002; Bisby et al., 2006). Two species (R.
ambrosiae and R. montetyi) are identied as
P. cylindrus primary ambrosia fungi (Arx &
Hennebert, 1965; Morelet, 1998) and have
been isolated both from the insect organs
and from its galleries in the host (Sousa et
al., 1997; Morelet, 1998). Although Raffa-
elea sexual state is lacking, observations
of conidial development support its place-
ment within the Ophiostomatales (Gebhardt
& Oberwinkler, 2005) and, 18S ribosomal
DNA sequence analysis, shows a monophy-
letic lineage which forms a sister group to
species of the genus Ophiostoma (Jones &
Blackwell, 1998). The Ophiostomatales are
economically important sapstaining fungi
occurring world-wide on hardwoods and
commercially produced pines, and are in
some cases, already known as pathogenic to
oaks (Degreef, 1992). The effect of Raffaelea
spp. on cork oak remains unknown, but in Ja-
pan, R. quercivora involved in an interaction
with P. quercivorus has proven pathogenici-
ty to several oak trees (Kubono & Ito, 2002;
Kinnura & Kobayashi, 2006).
Other isolated fungi were already related
to P. cylindrus. Sousa et al. (1997) isolated
A. carbonarius from mycangia and cork oak
galleries. Pa. variotii has been isolated from
galleries in cork oak and other oaks (Baker,
1963). Also Penicillium was found both on
the insect and in oak galleries (Baker, 1963;
Cassier et al., 1996; Sousa et al., 1997). Bo-
trytis was isolated from galleries in oak, as
well as Acremonium and Fusarium (Baker,
1963). Acremonium sp. and F. solani, Glio-
cladium roseum and G. solani has also been
isolated by Sousa et al. (1997) from P. cylin-
drus organs and galleries in cork oak. Cas-
sier et al. (1996) isolated Trichoderma from
the insect and T. viride was isolated from
galleries on cork oak and other oaks (Baker,
1963; Sousa et al., 1997). Nodulisporium and
Scytalidium were found in mycangia and gal-
leries on cork oak, the last one only in the
host (Sousa et al., 1997).
Four genera were newly associated with
this interaction: Beauveria, Geotrichum,
Chaetomium and Streptomyces. Beauveria is
an entomopathogenic fungus and two species
(B. bassiana and B. brongniartii) are alrea-
dy known as harmful to Platypus spp. (Glare
et al., 2002). Several species of Geotrichum
have been identied in association with in-
sects (Suh & Blackwell, 2006) and the genus
Streptomyces act as an antimicrobial defense
in the termite-fungi association (Mueller &
Gerardo, 2002). Chaetomium is a very com-
mon genus in soil and plant debris, in par-
ticular in wood (Hawksworth, 1995) and it
might be a Scytalidium teleomorph (Halin,
1997).
The role of each isolated genus in the in-
sect-fungi-host interaction is discussed. Most
of them are considered cosmopolite and sa-
prophytic fungi (Hawksworth et al., 1995;
Kiffer & Morelet, 1997) which can be invol-
ved just in a commensalistic relation or might
play some other action due to their isolation
frequency and distribution among samples.
Following P. cylindrus host colonization
process, symbiotic fungi may start to act as
wood degrading, thus facilitating galleries’
excavation. Trichoderma, as a great extroli-
te producer such as lignocellulolictic enzy-
mes, might be an active intervenient in that
process (Samuels, 1996). Then, to overco-
me host defense reaction, the insect might
inoculate phytopathogenic fungi. Nodulis-
porium might be relevant in this part as the
ITS rDNA analysis proved that it is a Bis-
cogniauxia mediterranea anamorph, which
is responsible for cork oak charcoal disease
(Collado et al., 2001). Other isolated gene-
ra might also interfere in this phase: Acre-
monium which might be Nectria anamorph,
thus being a potential pathogenic to several
woody plants and Fusarium also pathoge-
nic to several plant organs (Kiffer & Mo-
relet, 1997). Within the galleries, fungi that
FUNGI ASSOCIATED TO PLATYPUS CYLINDRUS FAB.
(COLEOPTERA: PLATYPODIDAE) IN CORK OAK
REVISTA DE CIÊNCIAS AGRÁRIAS
64
will be nourishment for larvae develop in
a controlled manner by the permanent care
of parental insects but probably also due to
the antagonistic action of fungi over others.
Gliocladium and Trichoderma are known
by their antagonistic activity being used as
biocontrol agents (Papavizas, 1985). Strep-
tomyces and Scytalidium might act in the
fungi colonies management within the gal-
leries. Also in the insect body this manage-
ment might be essential to achieve ambrosia
fungi transport. The nal role of the isola-
ted fungi, which is the base of this insect-
fungi interaction, is the larvae nourishment.
According to denition, ambrosia fungi are
eaten by the insects and thus are the ones
found in their intestine. Nevertheless, whe-
reas larvae eat exclusively ambrosia fungi,
the adults might also eat wood, which ex-
plains all the cosmopolite and saprophytic
fungi found in their intestine that were alre-
ady contaminating tree wood. Also, in my-
cangia, where specic fungi for this inte-
raction are transported, ambrosia fungi are
expected to be present. In both cases, intes-
tine and mycangia, Raffaelea was the most
frequent genus, which supports the fact that
some species of this genus are P. cylindrus
primary ambrosia fungi. The other isolated
fungi might be considered auxiliary ambro-
sia fungi as sustained by Batra (1985) or
simply be worldwide saprobes that are fre-
quently present in host tissues.
In conclusion, there is a vast diversity of
fungi associated to P. cylindrus-cork oak
interaction. Some could be determinant
to the success of the insect colonization,
mainly Raffaelea which is its principal am-
brosia fungi and also might be pathogenic
to host trees.
Acknowledgments
The authors wish to thank to Professor
Arlindo Lima (Departamento de Protecção
de Plantas e Fitoecologia, Instituto Superior
de Agronomia) for critical comments on the
manuscript.
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... and these have a commensal relationship (Cassier et al., 1996;Inàcio et al., 2008). The presence of these fungi associated with the insect indicates their importance in symbiosis, such as cellulose decomposers and/or antagonists that inhibits the growth of other fungi (Henriques et al., 2009). Penicillium and Aspergillus sp. were also found in the adults intestinal contents. ...
... Ophiostoma sp. with three unidentified isolates and Raffaelea sp. with two isolates identified on the basis of the morphological appearance (Raffaelea montetyi and Raffaelea Canadensislike). These species have been considered as fungi of nutritional interest (ambrosia fungi) and studied by different authors (Henriques et al., 2009). The study conducted by Inàcio et al. (2010) confirms the pathogenicity of the species Raffaelea montetyi on cork oak in Portugal. ...
... The most frequent fungi isolated from P. cylindrus and its galleries belong to Raffaelea genus. It has been obtained in particular from intestinal contents and mycangia, about 30% and 40% of all fungi isolated, in both organs, respectively of the females and males, respectively (Henriques, 2009). ...
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... Several fungi have already been isolated from Platypus cylindrus and its galleries in Quercus spp. (Baker ,1963;Cassier et al. ,1996;Sousa et al., 1997;Morelet, 1998;Henriques et al., 2006Henriques et al., , 2009Belhoucine et al., 2011bBelhoucine et al., , 2012Belhoucine ,2013, among others); in Algeria only a study is reported Belhoucine et al. (2011b). The beetles and their fungi are intimately associated in a mutualistic relationship (Batra, 1963) causing damage of economic significance to trees and timber (Nakashima, 1975;Cassier et al., 1996). ...
... The beetles and their fungi are intimately associated in a mutualistic relationship (Batra, 1963) causing damage of economic significance to trees and timber (Nakashima, 1975;Cassier et al., 1996). Besides the implication in insect feeding, ambrosia fungi might also be involved in other processes such as host weakness, through pathogenic action; decomposition of lignocellulolitic compounds, which helps gallery construction and enables fungi colonization; and/or antagonism that controls the growth of other fungi (Sousa & Inácio, 2005;Henriques et al., 2006Henriques et al., , 2009). ...
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... Although insects can produce endogenous cellulases (Watanabe and Tokuda 2010;Shelomi et al. 2014;Pothula et al. 2019), the polysaccharide hydrolysis is mainly performed by extracellular enzymes produced by microorganisms that colonize the digestive tracts of the insects, especially by fungi like Aspergillus Micheli ex Haller, Fusarium Link and Penicillium Link (Rojas-Jiménez and Hernández 2015). Several filamentous fungi, such as Cladosporium Link, Penicillium, and Trichoderma Persoon, have been found in the guts of Coleoptera and Diptera such as Silvanidae (Coleoptera) (David et al. 1974), Tenebrionidae (Coleoptera) (Prabha et al. 2011), Platypodidae (Coleoptera) (Henriques et al. 2009) and Culicidae (Diptera) (Fonseca et al. 2008;Pereira et al. 2009;Maketon et al. 2014). However, the evolution and dynamics of microorganism communities and their insect hosts are not yet fully understood (Bobay and Raymann 2019). ...
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... ambrosia beetles (particularly Platypus cylindrus), longhorn beetles (Cerambyx cerdo and Phymatodes testaceus) and buprestids of the genus Coraebus (Ferreira & Ferreira 1991, Villemant & Fraval 1991, Romanyk & Cadahia 1992. Ambrosia beetles are xylomycetophagous, coping with many genera of endosimbiotic fungi which will feed their larvae inside galleries in the wood, therefore acting as a vector for fungal diseases (Sousa et al. 1997, Sousa & Debouzie 2002, Henriques et al. 2009, Inácio et al. 2011. ...
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... Three main groups of wood-boring insects attack cork and holm oak trees: ambrosia beetles (particularly Platypus cylindrus), longhorn beetles (Cerambyx cerdo and Phymatodes testaceus) and buprestids of the genus Coraebus (Ferreira and Ferreira 1991; Villemant and Fraval 1991; Romanyk and Cadahia 1992). Ambrosia beetles are xylomycetophagous, coping with many genera of endosymbiotic fungi which will feed their larvae inside galleries in the wood, therefore acting as a vector for fungal diseases (Sousa et al. 1997; Sousa and Debouzie 2002; Henriques et al. 2009; Inácio et al. 2011). Longhorn beetles are considered secondary pests, however they open outsized holes in trees which can act as entryways for fungal infection (Soria et al. 1994a; Martín et al. 2005). ...
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