Abstract
Foot and root rot incidence of Strawberry (Fragaria ananassa) was recorded highest in
Mymensingh region (18.5%) followed by Dhaka and Rajshahi regions (3.6%) of Bangladesh. The
incidence was found higher in October in compare to January in all the three areas. Infected
strawberry plant showed a rapid rot of the entire primary root and move up into the foot and
stem tissues. In severe cases, the leaves begin to turn brown, plant wilted and die from the
edges inward. The causal pathogen of this disease was isolated on CMA media amended with
PARP and cultured on PDA and Carrot agar media. Morphological characters of this foot and
root rot pathogen identified and found that the mycelium was hyaline, branched (8-9 µm wide);
sporangia consists of terminal complexes of swollen hyphal branches making globose
structures; Antheridia: typically intercalary; Oogonia: smooth, globose, mostly terminal (22-28
µm dia.); Oospores: highly aplerotic (20-24 µm dia.) with thick walled. Such characters
confirmed that this foot and root rot of strawberry pathogen is Pythium aphanidermatum. An in
vitro experiment revealed that the optimum temperature for growing of this pathogen is
required from 25-30 °C and maximum about 35 °C. Histopathological studies indicating P.
apahnidermatum is localized on rotted roots and collar zone of affected plants that disintegrated
cell wall, cortical cell layers and rotten the endodermis tissues. Molecular characterization of
this pathogen was done using ITS, P-apah species specific primer and COXII markers. PCR
primers of ITS resulted an amplicon size of 800 bp by the isolates of three region but primer pair
Paph54F-ITS2 produced a clear amplicon of the expected size of 200 bp by Mymensingh isolate
only indicating that rest of two isolates may be belongs to other Pythium spp. Further, the COX
II gene of Mymensingh isolates of P. aphanidermatum resulted 512 bp amplicon size. Blast
sequence run in COX II region of this P. aphanidermatum displayed the highest sequence
homology (99%) with P.spinosum over 595 bp, 98% homology with Pythium sp, over 98% with
P. irregulare, 97 % with P. recalcitrans, P. intermedium, P. attrantheridium and P. debaryanum. CoxII
region of this P. aphanidermatum (Mym) is exhibited 91% homology with the findings of P.
aphanidermatum strain P36.3 that produce filamentous sporangia (Clade 1 in Phyllogenic
position) but COX II gene sequence of Mymensingh isolate was found to be related with Clade
2 in Phyllogenic position done by Moralejo et al., (2008) which produce spherical to globose
zoosporangia. Colony growth inhibition assay revealed that Trichoderma harzianum exhibited a
varying levels (90-100%) of antagonism towards P. aphanidermatum and Rhizoctonia. In poison
food technique all three plant extracts (Garlic, Neem and Allamanda) and Mancozeb
significantly reduced the growth of P. apahnidermatumm and Rhizoctonia sp. P. aphanidermatum
appeared to be the most aggressive parasite against strawberry seedlings in pot experiment.
Strawberry production was found very responsive to the different mulching materials where
rice straw mulch resulted lower foot and root rot infection (5.1%) with higher yield (210
g/plant) than the plastic mulches. Strawberry planting on Mid October resulted highest yield
(6.8 t/ha) in compare to November. In both pot and field experiments, biocontrol agents
specially T. harzianum based biopesticide (@64 kg/ha or 100 g/plant) or T. harzianum as foliar
spray (@3% or 108 CFU/ml) showed best performance in reducing of foot and root rot incidence
with highest yield. Strawberry yield was higher in Rajshahi (13.14 t/ha) than Mymensingh
(8.79) in the similar treatments and sowing time. Foot and root rot of strawberry was managed
with higher cost benefit ration where Trichoderma based formulated bio-pesticide (64kg/ha)
used during land preparation and field sprayed with Mancozeb (@0.2%) + T. harzianum (@3% or
108 CFU/ml) as an integrated treatment.