Istituto Regionale per la Floricoltura
Via Carducci, 12 - 18038 Sanremo - IM - Italia
tel. +39 0184 53 51 49 - www.regflor.it
Root and basal stem rot caused by
Phytophthora nicotianae on thyme in Liguria
Patrizia Martini*, Santa Olga Cacciola**, Simona Savona*, Giorgio Bozzano***
*Regional Institute of Floriculture, Via Carducci 12, 18038 Sanremo (IM), Italy
**Department S.En.Fi.Mi.Zo., University of Palermo, Viale delle Scienze 2, 90128 Palermo, Italy
* * * Te c h n i c a l S e r v i c e o f C o o p e r a t i v a L ' O r t o f r u t t i c o l a , V i a D a l m a z i a 1 6 9 , 1 7 0 3 1 A l b e n g a ( S V ) , I t a l y
R o o t a n d b a s a l s t e m r o t c a u s e d b y t h e s o i l - b o r n e p a t h o g e n P h y t o p h t h o r a n i c o t i a n a e v. B r e d a d e H a a n w a s
r e c e n t l y o b s e r v e d o n b o t h T h y m u s v u l g a r i s L . a n d T. x c i t r i o d o r u s ( P e r s . ) S c h r e b . e x S c h w e i . ( c v B e r t r a m
A n d e r s o n , D o o n e Va l l e y, S i l v e r K i n g a n d S i l v e r Q u e e n ) , s p e c i e s t h a t i n L i g u r i a a r e u s u a l l y g r o w n i n p o t
and used as ornamental as well as officinal plants.
The symptoms of the disease are collar and root rot, progressive withering of the branches and wilting of
the entire plant.
A
B1
B2
A - Symptoms of the disease on potted
plants of Thymus spp. grown outdoors
in a commercial farm near Albenga.
B 1 - B 2 - Plants of Thymus x citriodorus
cv Silver Queen and cv Bertam Anderson
affected by Phytophthora root rot.
C1-C2 - P a p i l l a t e , o v o i d s p o r a n g i u m o f
C1
C2
The pathogen was obtained by isolation on a selective medium
and identified by morphological, biochemical, and molecular
characters. Oospores (mean diameter of 25 µm) were produced
in dual cultures with reference strains of P. nicotianae of A1 and
A2 mating type; they were thick-walled, smooth, spherical.
Sporangia (18-70 x 14-39 µm) were usually with a single
prominent papilla. Chlamydospores (14 to 60 µm in diameter)
were spherical to ovoid. Cardinal temperatures were 10-12°C
minimum, 24-30°C optimum, and 36°C maximum. Electrophoretic
patterns of total mycelial proteins and isozymes of the isolates
from Thymus spp. were very similar to those of reference isolates
of P. nicotianae from different hosts, but clearly distinct from
those of reference isolates of other species included in
Waterhouse's taxonomic group II. Sequences of internal transcribed
spacer (ITS) regions of rDNA confirmed the identification as P.
nicotianae. Pathogenicity tests and re-isolation of P. nicotianae
were carried out to fulfil Koch's postulates.
Phytophthora nicotianae on the left
and a group of chlamydospores on the
right (400x).
Panel A. Polyacr ylamide gel electrophoresis of total mycelium proteins
stained with Coomassie Blue. Lanes 1 to 4: Thymus isolates of Phytophthora
nicotianae; lane 5: reference isolate of P. nicotianae.
P a n e l B . Ar yl esterase zymograms on polyacr ylamide slab gel. Lanes 2-3:
Thymus isolates of Phytophthora nicotianae; lanes 1, 4, 5, 6, 7: isolates
of other papillate Phytophthora species.
Lavoro svolto nell'ambito del Progetto Operativo "Realizzazione del Laboratorio Regionale di Analisi Fitopatologica" in attuazione della Misura 14.2 del Piano di Sviluppo Rurale 2000-2006 della Regione
Liguria ai sensi del Reg. CE n°a1 1257/99.