Page 19 - Volume 4, Issue 2, July 2011
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© Benaki Phytopathological Institute
Karamaouna
et al.
48
kept in a growth room at 28 ± 1
o
C and L16:D8
h until the mealybugs became mummified.
The mummies were collected, measured (tip
of the head to the end of the abdomen) and
kept individually in 0.5 ml Eppendorf tubes,
under the aforementioned conditions of tem-
perature and light until parasitoid emergence.
A binocular stereo-microscope (Χ 5 – Χ 50)
with a linear scale graticule fitted in one of
its lenses was used for all the necessary meas-
urements of the host and the parasitoid.
Proportion of mealybugs mummified
out of the total number in each size class of
the host (index of host size preference) as
well as the sex, development time and size
(headwidth) of the parasitoid offspring were
recorded (body size is usually a good predic-
tor of fecundity in parasitoids).
Data analysis
The four host size classes, offered simul-
taneously to the parasitoid in each Petri dish,
were the treatments. Each Petri-dish was
considered as one experimental unit – repli-
cation of the experiment. Fifty experimental
units were set but parasitism was observed
only in 34 Petri dishes in the two larger class-
es of the host. Because observations of host
size classes within the same experimental
unit were not independent, the 34 observa-
tions were divided into two groups and data
on development time and headwidth of one
parasitized host size class from one group
were compared with the respective data of
the other size class from the second group
using ANOVA (α = 0.05) in MINITAB (Release
10.51 Xtra). Data on parasitism rate were sub-
jected to angular transformation to fulfill the
assumptions of normality and homogeneity
of variance before ANOVA.
Results
Molecular identification of A. sp.near
pseudococci
The employment of a PCR-based meth-
od in the identification of the
Anagyrus
spe-
cies, through either BLAST or phylogenetic
tree contruction yielded a similar outcome.
BLAST indicated a high similarity of the 818
bp long sequence with
Anagyrus
sp. near
pseudococci
sequences, whereas it was less
similar with the sequences of
A. pseudococ-
ci
and
A. dactylopii.
Furthermore, the dis-
tance-based calculation of the phylogenet-
ic tree clustered the sequences in the clade
of the
A
. sp.near
pseudococci
sequences ob-
tained from the NCBI GeneBank, supporting
this clade with high bootstrap value (Boot-
strap Value: 100%) whereas sequences from
A
.
pseudococci
individuals were separately
clustered into another distinct monophylet-
ic clade (Figure 1).
Host size preference of the parasitoid A.
sp.near pseudococci
The evaluation of host size preference
was based on the rate of parasitized mealy-
bugs (mummies) in each size class. No para-
sitism was observed in the smaller host size
classes (0.5-0.9 mm and 1-1.5 mm). The rate
of parasitism in the larger size classes was
0.18-0.22 and did not statistically differ be-
tween them. (ANOVA,
F
1, 48
= 0,37,
P
= 0,544)
(Table 1).
Effect of host size of P. ficus on develop-
ment time and size of the parasitoid off-
spring A. sp. near pseudococci
The mean development time of female
and male offspring of
A.
sp. near
pseudococ-
ci
in female adults did not significantly dif-
fer between the size classes ‘1.6-2.3 mm’ and
‘>2.3 mm’ (females: ANOVA,
F
1,15
= 0.02,
P
=
0.877; males: ANOVA,
F
1,20
= 0.94,
P
= 0.344)
(Table 2). No significant difference was
found in development time of female and
male parasitoids, when the pooled data of
the two size classes were analysed (ANOVA,
F
1, 37
= 2.06,
P
= 0.160) (Table 2).
The mean size (headwidth) of female
and male offspring of the parasitoid
A.
sp.
near
pseudococci
in female adults (1.6-2.3
mm and >2.3 mm) of
P. ficus
did not signif-
icantly differ significantly between the size
classes (females: ANOVA,
F
1,10
= 0.92,
P
=
0.360; males:
F
1,30
= 0.01,
P
= 0.932) (Table 2).
Female parasitoids were larger (headwidth)
than male parasitoids based on the pooled
