P oc. 6 h Con . EFPP 2002, P ague. Plan P o ec . Sci., 38 (Special Issue 2), 2002: 429–431 429
Plan P o ec ion Science – 2002
INTRODUCTION
Colle o ichum spp. cause an h acnose disease o
lea bligh on all signi ican ag icul u al c ops and
o namen al plan s a ound he wo ld, being one o he
mos des uc i e disease on s awbe y. In ac se e al
species o Colle o ichum ha e been epo ed om
majo a eas o s awbe ies p oduc ion c op in a la ge
amoun o coun ies. Colle o ichum acu a um J. H.
Simmonds a acks ae ial pa s o he plan inducing
high losses o seedlings and ui s. Spain is he i s
p oduce , o esh ma ke , a e Uni ed S a es. Huel a
in Andalucia, Sou h-wes e n Spain, con ibu es wi h
mo e han 90% o he na ional p oduc ion (DE LOS
SANTOS & ROMERO MUÑOZ 1999).
In ui ing ields in Huel a C. acu a um cause c own
o and plan dea h, ui o , owe bligh and lesions
on pe ioles, s olons and lea es, which a e ligh -b own
wi h eddish colo in ma gins (DE LOS SANTOS &
ROMERO MUÑOZ 1999) and a e di e en o black lea
spo caused by C. aga iae and C. gloeospo ioides
desc ibed by HOWARD and ALBREGTS (1983) in he
summe nu se y. Lesions on olia issue a e no e y
equen and se e al s udies ha e sugges ed ha can
de elop quiescen in ec ions on s awbe y plan s
ha ing a epidemiological ole p io o coloniza ion
o ui s and ano he issues.
The ini ial s ages o Colle o ichum in ec ion is
well s udied and gene ally include conidia adhe e
o, and ge mina i e on plan su aces, p oduce
ge m- ubes which di e en ia e o o m melanized
app esso ia (VAN DYKE & MIMS 1991; BYRNE e
al. 1997). On symp omless s awbe y lea es has
been epo ed p oduc ion o seconda y conidia o
mic ocyclic conidia ion by C. acu a um and may
be a signi ican sou ce o inoculum o in ec ions
(LEANDRO e al. 2001).
The in ec ion p ocess o Colle o ichum species
causing la en in ec ion on cowpea lea es e eals ha
ungus colonized he mesophyll by in e cellula hyphae,
wi hou ini ially isible symp oms (LATUNDE-DADA
e al. 1999). Assymp oma ic s ages in some in ec ed
plan issues di icul s he knowledge o he p ocess o
pa hogenesis. This wo k p e ends o con ibu e o he
cla i ica ion o he la ency phase o C. acu a um in he
olia issue o he s awbe y plan s h oughou he
De elopmen o Colle o ichum acu a um in he Folia Tissue
o S awbe y Plan s
F. T. ARROYO1*, F. J. MORENO2, P. DAZA2, J. TORREBLANCA2, G. GARCÍA-HERDUGO2,
B. DE LOS SANTOS1, C. BARRAU1, C. BLANCO1, M. PORRAS1 and F. ROMERO1
1C.I.F.A. Las To es- omejil, Alcalá del Río, 41200. Se illa, Spain; 2Depa amen o
de Biología Celula , Uni e sidad de Se illa, 41012 Se illa, Spain
*E-mail: [email p o ec ed]
Abs ac
S awbe y an h acnose, caused by Colle o ichum acu a um, is one o he mos des uc i e disease o his c op h oughou
he wo ld. Assymp oma ic s ages in he plan ha e been he aim o his wo k. Inocula ed lea es samples we e aken a
di e en imes and hey we e p ocessed o scanne elec on mic oscopy (SEM) and ansmission elec on mic oscopy
(TEM). Conidial de elopmen on bo h su aces lea es was de e mined. The ul as uc u al s udy o ungus pene a ion
in o plan cell was cha ac e ized by he o ma ion o esicles o e he ungus pe iphe y and is a mo phological pa am-
e e o he in ense memb anes a ic, also could be a e idence o a ansc ip ional ac i i y and enzyma ic cell sec e ion.
Di e ences o symp oms on bo h su aces o lea es we e obse ed.
Keywo ds: an h acnose; Colle o ichum acu a um; la en in ec ion; ul as uc u e
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Plan P o ec ion Science – 2002 Vol. 38, Special Issue 2: 429–431
s udy o he conidium de elopmen and ul as uc u al
in he ela ionship hos -pa hogen.
MATERIALS AND METHODS
Suscep ible c . Cama osa lea es, we e inocula ed
wi h 100 µl d ops o a conidial suspension (106 conidia
pe ml dis illed s e il wa e ) o C. acu a um CECT
20240 (ARROYO e al. 2001). Plan s we e incuba ed
a 25°C, 100% RH and 16 h ligh pho ope iod in
a g ow h chambe . Fo he s udy o he conidium
de elopmen on he olia su ace using scaning
elec onic mic oscopy (SEM), 1 cm2 pieces o lea
we e sampled a 4, 8, 12, 16, 20, 24, 36, 48, 72,
96, and 120 hou s a e -inocula ion (hpi), hen hey
we e ixed in glu a aldehyde, dehyd a ed and d ied
up by means o he c i ical poin d ying echnique.
The s udy o he in ec ion p ocess a ul as uc u al
le el using ansmission elec onic mic oscopy (TEM)
was ca ied ou in s ips o issue ob ained a 24, 48
and 120 hpi. Samples we e ixed in glu a aldehyde
and pos ixed in OsO4 , dehyd a ed wi h ace one and
embedded in Epon 812 esin.
RESULTS
Conidia o C. acu a um we e le adhe ed on o-
lia su ace h ough ma ix ex acellula sec e ed by
hemsel es. Ge mina ion on bo h, uppe and down
olia su aces began wi hin 4 hpi.
A 8 hpi some app esso ia we e obse ed in bo h
shee s o he lea su ace ha g ew om ge mina i e
ubes, gene ally sho ubes o sessile on he uppe
lea su ace and longe on he lowe one (Figu es 1A
and 1B, espec i ely). A his ime i was also app e-
cia ed o ma ion o seconda y conidia (mic ocyclic
conidia ion) o igina ed om conidiogenes s uc u es
ep esen ed by hypha and conidia phialide (Figu es
1C and 1D).
Anas omoses o bo h hypha and p ima y conidia
we e de ec ed and hey became o make accumula ions
un il 100 µm. F om his s uc u es we e also obse ed
p ocesses o conidiogenesis (Figu e 1E).
A 72 hpi was pe cei ed on he uppe lea su ace
a collapse and lysis o ungi s uc u es ha i was
inc eased a 120 hpi (Figu e 1F).
Pene a ion o cu icle om app esso ium was ob-
se ed a 24 hpi, no being a synch onous p ocess
(Figu e 2A). In ec ion in acellula was also mani-
es ed in he lowe lea su ace a 24 hpi whe eas in
he uppe one i could only be de ec ed hypha inside
cell wall (Figu es 2B and 2C, espec i ely).
Mac oscopics symp oms on lea es e eals a di e -
en ial answe be ween bo h olia su aces, nec o ic
spo s o se e al mm in he lowe lea su ace and
symp omless in he uppe one. Obse a ion o hese
small spo s in he lowe lea su ace seems o be co -
Figu es 1. Conidial de elopmen on he lea su ace. A and B, app esso ia on he uppe and lowe lea su aces esp. a
8 hpi. C and D, hypha and conidia phialide a 72 hpi. E, anas omoses on he lowe one a 120 hpi. F, ungi collapse on
uppe one a 120 hpi
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Plan P o ec ion Science – 2002 Vol. 38, Special Issue 2: 429–431
ela ed wi h a educed numbe o cells died by hypha
in acellula , mainly in eins bu also in he shee
(Figu es 3A and 3B). In he uppe lea su ace his
pa hogen appea s o su i e inside epide mic cell wall
whe e is conside ed an in ense ac i i y o enzyma ic
sec e ion, mani es ed by a la ge amoun o endo- and
exocy osis esicles and he deg ada ion o wall in his
a ea, can exis .
The eco e y o he pa hogen is 100% in bo h lea
su aces a 120 hpi.
Conclusions
The in ec ion and de elopmen o pa hogen in he
olia issue o s awbe y plan s shows he capaci y
o i o be loca ed and o emain asymp oma ic, being
able o con ibu e o he disease dispe sion h ough
c op ields.
Re e ences
ARROYO F.T., MORENO F.J., GARCÍA-HERDUGO G.,
ROMERO F. (2001): Respues a di e encial de Colle o-
ichum acu a um y del ejido olia en plan as de e-
sa. In: IV Sem. Cien í ico In . P o ección de Plan as,
41ª Reunión Anual de la Sociedad de Fi opa ología de
Amé ica-Di isión Ca ibe (APS-CD). Va ade o, Cuba.
BYRNE J.M., HAUSBECK M.K., HAMMERSCHMIDT R.
(1997): Conidial ge mina ion and app esso ium o ma-
ion o Colle o ichum coccodes on oma o oliage. Plan
Dis., 81: 715–718.
DE LOS SANTOS B., ROMERO MUÑOZ F. (1999): Occu -
ence o Colle o ichum acu a um, causal o ganism o
s awbe y an h acnose in sou hwes e n Spain. Plan
Dis., 83: 301.
HOWARD C.M., ALBREGTS E.E. (1983): Black lea spo
phase o s awbe y an h acnose caused by C. gloeo-
spo ioides. Plan Dis., 67: 1144–1146.
LATUNDE-DADA A.O., O’CONNELL R.J., NASH C., LUCAS
J.A. (1999): S oma al pene a ion o cowpea (Vigna
unguicula a) lea es by a Colle o ichum species causing
la en an h acnose. Plan Pa hol., 48: 777–785.
LEANDRO L.F.S., GLEASON M.L., NUTTER F.W., WEGULO
S.N., DIXON P.M. (2001): Ge mina ion and spo ula ion
o Colle o ichum acu a um on symp omless s awbe y
lea es. Phy opa hology, 91: 659–664.
VAN DYKE C.G., MIMS C.W. (1991): Ul as uc u e o
conidia, conidium ge mina ion, and app esso ium de e-
lopmen in he plan pa hogenic ungus Colle o ichum
unca um. Can. J. Bo ., 69: 2455–2467.
Figu es 2. T ansmission elec on mic og aphs o in e ac ion be ween C. acu aum and s awbe y lea es. A, app esso ium
on he uppe lea su ace a 24 hpi, which is o ming a pene a ion peg. B, in acellula hypha in he lowe one a 24 hpi.
C, ungi inside epide mic cell wall wi h shows a la ge amoun o esicles, i is obse ed deg ada ion o cell wall
Figu es 3. A and B, mac o-
scopic symp oms on he
lowe lea su ace