International Journal of Horticulture, 2017,Vol.7, No.2, 7-19
8
effective control. There are several reports regarding their life cycle and control by using some insecticides,
biorationals, botanicals etc.(Das et al., 2002; Liu et al.,2003; Karunaratne and Arukwatta, 2009; Sharma and
Sexena, 2012; Rajagopal and Trivedi, 1989; Abbas and Nakamura, 1985; Otsu et al., 2003) but their host
preference in terms of their feeding dynamics, survivability and population parameters on the three host plants are
unknown.The present study will give the basic knowledge about their nutritional ecology and population
dynamics including different demographic parameters on different host plants for developing sustainable
agricultural tactics towards integrated pest management (IPM) during the crop cultivation.
1 Result
1.1 Phytochemicals
The biochemical constituents of the three host plants,
S. melongena
, S
. nigrum
and
M. cochinchinensis
, are
presented in Table 1. The primary metabolites i.e., total carbohydrates, proteins and lipids including amino acids
content was higher in
S. melongena
leaves (94.947±1.444, 10.470±0.110, 9.400±0.216 and 1.857±0.049 µg/mg
dry wt., respectively) and varied significantly with
S. nigrum
and
M. cochinchinensis
leaves (
F
2,6
= 154.885,
15.257, 47.209 and 26.753, respectively,
P
< 0.005) (Table 1). The moisture content were higher in
S. nigrum
(79.333±0.561%) relative to the other hosts and significantly differed (
F
2,6
=45.692,
P
>0.0001)(Table 1). Among
the secondary metabolites, total phenolics, flavonoids, tannin, saponin and phytate concentrations were higher in
M. cochinchinensis
(10.177±0.180, 8.233±0.203, 7.843±0.067, 11.620±0.061 and 7.470±0.112 µg/mg dry wt.,
respectively) and varied significantly with
S. nigrum
and
S. melongena
(
F
2,6
= 115.697, 16.851, 239.295, 162.685
and 192.103, respectively,
P
< 0.005) (Table 1). On the other hand, alkanes and fatty acids contents were highest in
S. melongena
(0.680±0.023 and 0.570±0.026, µg/mg dry wt., respectively) relative to
S. nigrum
and
M.
cochinchinensis
with highly significant differences (
F
2,6
=29.115 and 16.363, respectively,
P
< 0.005) (Table 1).
Thus, the nutritional factors (primary metabolites including moisture content) relative to the anti-nutritional
factors (Secondary metabolites) in
S. melongena
leaves were always higher followed by
S. nigrum
and
M.
cochinchinensis
leaves.
Table 1 A phytochemical variation of
Solanum melongena
,
S. nigrum
and
Momordica cochinchinensis
leaves
Phytochemicals (µg/mg dry wt.)
S. melongena
S. nigrum
M. cochinchinensis
F
(
df
=2,6)
P
Total Carbohydrates
94.947 ±1.444
a
74.100 ±1.000
b
62.117 ±1.504
c
154.885
0.001
Total proteins
10.470 ±0.110
a
11.177 ±0.466
a
8.790 ±0.257
b
15.257
0.004
Total Lipids
9.400 ±0.216
a
7.543 ±0.257
b
6.203 ±0.226
c
47.209
0.001
Total Aminoacids
1.857 ±0.049
a
1.657 ±0.066
a
1.277 ±0.055
b
26.753
0.001
Moisture %
76.913 ±0.773
a
79.333 ±0.561
a
70.267 ±0.731
b
45.692
0.001
Total phenolics
6.397 ±0.093
a
7.250 ±0.247
b
10.177 ±0.180
c
115.697
0.001
Total Flavonoids
6.580 ±0.091
a
7.800 ±0.231
b
8.233 ±0.203
bc
16.851
0.003
Tanin
5.410 ±0.121
a
7.350 ±0.040
b
7.843 ±0.067
c
239.295
0.001
Saponin
8.307 ±0.093
a
10.327 ±0.198
b
11.620 ±0.061
c
162.685
0.001
Phytate
4.597 ±0.130
a
6.420 ±0.061
b
7.470 ±0.112
c
192.103
0.001
Alkanes
0.680 ±0.023
a
0.523 ±0.026
b
0.430 ±0.021
bc
29.115
0.001
Fatty acids
0.570 ±0.026
a
0.437 ±0.027
b
0.380 ±0.017
bc
16.363
0.004
Note: Different letters with in the rows indicate the means (Mean ± SE of 3 observations) are significantly different (
P
< 0.05,
Tukey’s HSD) with
F
and
P
values (ANOVA) while comparing one type of host plant with the other
1.2 Feeding dynamics
The life cycle and food utilization indices of this epilachna beetle,
E. vigintioctopunctata
were investigated in the
laboratory condition by providing three host leaves separately and showed four distinct stages with four larval
instars (i.e., egg, larva, pupa, and adult) (Supplementary material: Figure 1). Adult beetles are spherical and pale
brown in colour with 28 black spots on their elytra. Yellowish cigar shaped eggs are laid in masses attached to
ventral surface of leaves in batches of 20-35 eggs. Grubs (larvae) are yellowish with spines all over the body. The
larvae pupate on the abaxial leaf surface and they are yellow with the anterior devoid of spines. As both, adult and
larval stages feed on the epidermal tissues of leaves by scrapping the green matter (chlorophyll) (Supplementary
material: Figure 2), the food utilization indices were relevant only for these stages which lead to the variation in
overalllife history along with their population parameters.
