© Benaki Phytopathological Institute
Lahuf
2
the description of microconidia provided
by Ichikawa, and Aoki (2000), Zhang
et. al.
(2013) and Kim
et. al.
(2016). Based on these
morphological characteristics, the fungus
was putatively identified as
Fusarium pro-
liferatum
(Matsush.) Nirenberg ex Gerlach
& Nirenberg. To fulfil Koch’s postulates, the
pathogenicity of the isolated fungus was
tested on 20 healthy lucky bamboo plants
growing in 0.5 L containers filled with the
commercial nutrition solution (AgroFiro
®,
Aljoud Company, Iraq). Fifteen plants were
inoculated by adding directly to the nutri-
ent solution five mycelium plugs (each 0.5
cm in diameter) cut from a 7-day old colo-
ny of
F. proliferatum
grown on PDA medium.
The same number of plugs of un-inoculat-
ed PDA was added to the nutrient solution
of the remaining five lucky bamboo plants,
which were used as controls. All plants were
incubated in a growth cabinet at 25 ± 2°C
with 12-h photoperiod and 70% humidity.
After 21 days, stem and root rot symptoms
identical to those observed in the nurser-
ies appeared on 13 out of the 15 inoculated
plants. The control plants were symptom-
less. The fungal pathogen was re-isolat-
ed from the symptomatic plant tissues and
showed the same morphological character-
istics as described above.
To confirm the initial morphological
identification, the internal transcribed spac-
er (ITS) region of ribosomal DNA (rDNA)
from the isolated fungus was sequenced.
Genomic DNA of
F. proliferatum
was extract-
ed from pure cultures using a DNeasy Plant
Mini Kit (Qiagen Inc., Valencia, CA, USA) fol-
lowing the manufacturer’s instructions. The
universal primer pair ITS1/ITS4 was used to
amplify the entire ITS region by PCR (White
et al
., 1990). The 679 bp amplicon was se-
quenced (Macrogen, Korea;
.
macrogen.com/en/main/index.php) using
the same primers used for the PCR ampli-
fication. The sequence was deposited into
the GenBank database and was identified
with the accession number MF099864.1.
Subsequently, BLAST analysis of the isolate
sequence showed >99% identity with sever-
al known sequences of
F. proliferatum
spe-
cies. Phylogenetic analysis was performed
using MEGA 7, utilizing the neighbor-joining
technique (Tamura
et al
., 2013). This analysis
showed that the ITS sequence of the isolate
MF099864.1 was grouped in a clade com-
prising reference isolates of
F. proliferatum
.
The out-group isolates were those of
Fusari-
um oxysporum
(accession No: EU326203.1),
F.
camptoceras
(accession No: KU055634.1) and
F. solani
(accession No: L36632.1, L36634.1,
AY097316.1, AY097317.1 and AY097318.1)
(Fig. 2). Thus, these results support the pre-
liminary morphological identification of the
fungus as
F. proliferatum
(Leslie and Sum-
merell, 2006; Zhang
et. al
., 2013; Aoki
et al
.,
2014).
Numerous fungal pathogens are known
to affect
Dracaena
spp. worldwide. For ex-
ample,
Colletotrichum dracaenophilum
was
reported to cause stem rot on
D. braunii
(syn.
D. sanderiana
) in Bulgaria, USA, Egypt
and Brazil (Bobev
et al.,
2008; Sharma
et al.,
2014; Macedo and Barreto, 2016; Morsy and
Elshahawy, 2016). In Iran,
Fusariumsolani
was
Figure 1
.
Symptoms of stem and root rot on
Dracaena braunii
plants, and cultural and morphological characteristics of the
causal agent,
Fusarium proliferatum
. Stem (A) and roots (B) of
a healthy
D. braunii
plant; rot symptoms on stem (C) and roots
(D) of
D. braunii
plant infected by
F. proliferatum
; (E)-(F): colo-
ny of
F. proliferatum
on PDA medium (E: top surface and F: low-
er surface); (G): micro- and macroconidia of
F. proliferatum
; bar
in (G) = 10 μm.
