Effect of Certain Cucumber Varieties on the Biology of Aphis gossypii

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Effect of Certain Cucumber Varieties on the Biology of Aphis gossypii (Homoptera :
Aphididae).
By
Nashat A. Hafiz Ali
Abstract. Development, reproduction, and population growth parameters of the melon aphid,
Aphis gossypii (Glover), on seven cucumber varieties were evaluated under greenhouse
conditions. Melon aphids had faster nymphal development on Tamra 761, Rawa- F1- RS and F1hybrid Beit alpha MR (5.2, 5.4 and 5.4 d) respectively, compared with the other varieties (5.8 6.1 d). Aphids reared on Rawa- F1- RS had the highest fecundity (59.3 offspring/aphid) and daily
reproduction (3.8 offspring/aphid/day). The net reproductive rate (50.4
offspring/aphid/generation) on Rawa- F1- RS was 18 %, 25 %, 38 %, 10 %, 35 %, and 47 %
higher and the population doubling time (2.31d) was 7 %, 25 %, 15 %, 15 %, 10 %, and 11 %
faster than those parameters on Beit alpha MR, F1- hybrid Beit alpha MR, Beth alpha MR, Beth
alpha MR hybrid, Hezera 480, and Tamra 761, respectively. The intrinsic rate of increase
indicated that a population of 10 females of A. gossypii could increase to become 59, 66, 66, 59,
53, and 77 individuals on Beth alpha MR, Tamra 761, Hezera 480, Beth alpha MR hybrid, Beit
alpha MR, F1- hybrid Beit alpha MR, and Rawa- F1- RS, respectively.
Key words: melon aphid, life table, population growth, cucurbits
The melon aphid, Aphis gossypii (Glover), is a serious pest of cucumber plants in Egypt. This
aphid causes economic damage to cucumber plants by direct injury to the plants and vectors viral
diseases, such as CMV. At present, insecticides are relied upon for control of aphids in cucumber.
The use of insect resistant varieties has been a major successful control tactic against vegetable
pests, often resorted to because of the difficulty of using pesticides on these edible plants
(Chambliss and Jones, 1966; Da Costa and Jones, 1971a; Hafiz and Hagag, 1997; Howe et al.,
1976; Kooistra, 1971). Knowledge of host plant effects on the biological parameters of the melon
aphid is essential for population dynamics studies. Consequently, experiments were conducted to
examine the effects of seven cucumber varieties on the development, longevity, and reproduction
of melon aphid collected in Assuit, Egypt.
Materials and Methods
Aphid source. Laboratory colonies of melon aphid were established with field-collected aphids
from cucumber and cotton plants. The colonies were maintained on potted seedlings of cucumber
plants in an environmental chamber (maintained at 25 ± 2 0C and 70 ± 5% RH) at the A.R.E.
Egypt, Assuit, Insect Research Laboratory.
Experimental procedures. Seven cucumber varieties, Cucumis sativus L., were used for the
experiments: F1- hybrid Beit alpha MR, Beit alpha MR, Beth alpha MR F1- hybrid, Beth alpha
MR, Rawa- F1- RS, Hezera 480, and Tamra 761.
The cucumber varieties were grown under controlled conditions in the greenhouse at 25 ± 2 0C
and 70 ± 5% RH. Each plant was grown in a 15-cm-diameter plastic pot in a mixture of loam,
sand, peat, and fertilizer. The pots were watered on alternate days. The soil was fertilized every
two weeks with a standard dilution of fertilizer 15-30-15 (NPK). Five apterous adult melon
aphids were transferred from the stock colonies (maintained on each cucumber variety for at least
two generations) to one seedling and were allowed to reproduce for 6 hr. The adult aphids and all
but one newborn nymph were then removed. Each seedling with one newborn nymph was placed
in a pot (9 cm × 6 cm). The pots were placed at 25 ± 1 0C, 60-80 % RH, and photoperiod of 14:10
(L:D) h. The seedlings were replaced every 3 d. Individual nymphs were observed daily for
molting and survival. The presence of exuviae was used to determine molting. After the
immatures became adult, they were observed daily for reproduction and survival, and all newborn
nymphs were removed. Observations continued until all of the aphids were dead. Development
times for each nymphal instar, duration of adult pre-reproductive, reproductive, and postreproductive periods, lifetime fecundity, and average daily reproduction were calculated for each
aphid. Thirty aphids were tested for each cucumber variety, but only those individuals that
completed development to the adult stage were included in nymphal development time
calculations, and individual adults that escaped or were damaged during transfer were excluded
from reproduction and survival rate analyses.
Data analysis and statistics. Effects of host plant on population growth of melon aphid were
assessed by constructing a life table, using age-specific survival rates (Lx) and fecundity (mx) for
each age interval (x) per day (Andrewartha and Birch 1954). Growth reproductive rate (GRR) =∑
Lxmx, the number of times a population will multiply per generation, was measured in
offspring/aphid/generation. Intrinsic rate of increase (rm) describes the growth potential of a
population under a given set of environmental condition and was calculated by iteratively solving
the equation ∑e-rmx Lxmx =1. Finite capacity for increase (λ) = erm, the number of times the
population will multiply itself per unit of time, was measured in offspring/aphid/d). Mean
generation time (T) = ln R0/rm, the mean time required for a given population to finish one
generation, was measured in days. Doubling time (DT) (days) = ln 2/rm, the time required for a
given population to double its numbers, was measured in days. Data on nymphal development
times, adult life spans, fecundity, and daily reproduction for seven cucumber variety-treatment
cohorts were analyzed by analysis of variance (ANOVA) and treatment differences were
determined by t-test.
Results and Discussion
Total development time of nymphs showed significant differences within the group of cucumber
varieties tested, although the differences for each instar were not always significant. Nymphal
development on Tamra 761, Rawa- F1- RS, and F1- hybrid Beit alpha MR was ≈ 1 d shorter
compared with that on Hezera 480 and Beth alpha MR. Pre-reproductive period and postreproductive periods of adults were not significantly different among the seven cucumber
varieties. However, total adult longevity varied significantly between cucumber varieties, and the
aphids reared on Rawa-F1- RS had the longest adult longevity. Both daily reproduction and total
fecundity of A. gossypii were significantly different among the tested cucumber varieties, and
were highest on Rawa-F1- RS followed by F1- hybrid Beit alpha MR, Beit alpha MR, Hezera 480,
Tamra 761, Beth alpha MR, and Beth alpha MR hybrid (Table 1).
Cucumber varieties influenced melon aphid population growth parameters (Table 2). Overall
population growth rates of melon aphid were highest on Rawa-F1- RS followed by Beit alpha
MR, F1- hybrid Beit alpha MR, Beth alpha MR, Beth alpha MR hybrid, Hezera 480, and Tamra
761. The net reproductive rate (R0) on Rawa-F1-Rs was 18 %, 25 %, 38 %, 10 %, 35 %, and 47 %
higher and population doubling time (DT) was 7 %, 25 %, 15 %, 15 %, 10 %, and 11 % shorter
than these of Beit alpha MR, F1- hybrid Beit alpha MR, Beth alpha MR, Beth alpha MR hybrid,
Hezera 480, and Tamra 761, respectively.
The values of rm increased markedly more on all the tested varieties than on Beth alpha MR
(Table 2). The intrinsic rate of increase (rm) was used in a comparative manner to estimate the
degree of fitness of various genotypes to their environment (Ayaia, 1968; Birch et al., 1963;
Ohba, 1987). When the values of intrinsic rate of increase (rm) were converted into finite rate of
increase (λ) it was clear that the population of A. gossypii had the capacity to multiply about 1.32,
1.27, 1.29, 1.29, 1.34, 1.31, and 1.31 per day on tested varieties (Table 2). This finding indicated
that a population of 10 females of A. gossypii could increase in a week to become 69, 53, 59, 59,
77, 66, and 66 individuals (Table 2).
Cucumber varieties had a significant effect on melon aphid development and reproduction. RawaF1- RS, Beit alpha MR and Tamra 761 were more suitable for melon aphid than other cucumber
varieties with respect to development time, adult longevity, reproduction, and population growth.
From the obtained results it could be concluded that the length of the pre-reproductive period of
aphids and their reduced fecundity may be attributed to the presence of antibiosis in Beth alpha F1
variety (Table 2). Similar results on the turnip aphid have been reported (Kennedy and AbouGhadir 1979). They stated that the population of the turnip aphid Lipaphis erysimi (Kaltenbach)
reared on PTWG (susceptible turnip cultivar) was three times larger than that on ‘Shogoin’
(resistant turnip cultivar). The greenhouse studies indicated that this difference was due primarily
to reduced reproduction by turnip aphid on ‘Shogoin’, although a significantly longer prereproduction period on the resistant variety also was involved. The presence of cucurbitacins has
been associated with the toxic effect of cucumber leaves, which proved that cucurbitacins
evolved in wild cucurbits as a mechanism to protect them from generalized herbivores such as
Tetranychus urticae (Koch) (Andeweg and De Bruyin, 1959; Da Costa and Jones, 1971b).
Table 1: Average development and reproduction of A. gossypii on seven cucumber varieties under greenhouse conditions.
Beit alpha
MR
Nymph
1st instar
2nd instar
3rd instar
4th instar
Total
Adult
Pre-reproductive period
Reproductive period
Post-Reproductive period
Longevity
F1- hybrid Beit
alpha MR
Beth alpha
MR
Beth alpha MR
hybrid
Rawa F1-Rs
Hezera 480
Tamra 761
Development time (days ± SE)*
1.7 ± 0.6a
1.5 ± 0.6a
1.4 ± 0.6a
1.5 ± 0.7a
5.9 ± 1.2ab
1.7 ± 0.6a
1.5 ± 0.6a
1.2 ± 0.6c
1.1 ± 0.6b
5.4 ±0.9a
1.6 ± 0.6a
1.7 ± 0.6ab
1.6 ± 0.7a
1.2 ± 0.4b
6.0 ± 1.0b
1.5 ± 0.6ab
1.4 ± 0.6a
1.6 ± 0.6a
1.3 ± 0.6b
5.8 ± 0.9ab
1.4 ± 0.6b
1.3 ± 0.5a
1.4 ± 0.6a
1.3 ± 0.4b
5.4 ± 0.9a
1.6 ± 0.6a
1.8 ± 0.6b
1.8 ± 0.6b
1.6 ± 0.6a
6.1 ± 1.2ab
1.2 ± 0.4c
1.4 ± 0.4a
1.0 ± 0.4c
1.3 ± 0.4b
5.2 ± 0.9a
1.1 ± 0.7a
16.4 ± 0.9a
0.9 ± 0.1a
18.4 ± 0.1a
1.6 ± 0.6b
15.8 ± 0.1a
1.0 ± 0.8a
18.4 ± 0.1b
1.2 ± 0.1a
9.9 ± 0.8b
1.0 ± 0.8a
12.1 ± 0.1c
0.9 ± 0.1a
16.2 ± 0.1a
1.0 ± 0.1a
18.1 ± 0.1a
0.7 ± 0.6a
15.6 ± 0.8a
0.8 ± 0.1a
17.1 ± 0.1a
0.7 ± 0.6a
14.5 ± 0.1a
0.9 ± 0.1a
16.1 ± 0.9ab
0.8 ± 0.1a
15.2 ± 0.1a
1.0 ± 0.1a
17.0 ± 0.1ab
40.6 ± 2.6b
3.3 ± 0.1b
40.2 ± 3.1b
2.6 ± 0.1a
Reproduction (offspring/female ± SE)*
Total fecundity
Daily reproduction
52.5 ± 2.4a
3.2 ± 0.1a
47.4 ± 2.1a
3.0 ± 0.1a
42.5 ± 2.9b
3.6 ± 0.1a
50.5 ± 3.2c
3.4 ± 0.1a
59.3 ± 2.8b
3.8 ± 0.1b
* Mean within a row sharing the same letter are not significantly different (α = 0.05, t-test).
Table 2: Life table parameters of A. gossypii reared on seven cucumber varieties under greenhouse conditions.
Varieties
Parameters
Growth reproduction rate (GRR)
Net reproductive rate (R0)
Generation time (T)
Doubling time (DT)
Intrinsic rate of increase (rm)
Finite capacity for increase (λ)
Population increase of 10 females
in 1 week
Beit alpha
MR
F1- hybrid
Beit alpha
Beth alpha
MR
Beth alpha
MR hybrid
Rawa F1-Rs
Hezera
480
Tamra
761
52.5
42.6
13.4
2.48
0.28
1.32
69
47.4
40.2
15.4
2.89
0.24
1.27
53
42.5
36.5
13.8
2.67
0.26
1.29
59
50.5
45.6
14.7
2.67
0.26
1.29
59
59.3
50.4
13.06
2.31
0.30
1.34
77
40.6
37.3
13.4
2.56
0.27
1.31
66
40.2
34.2
13.08
2.57
0.27
1.31
66
Hafiz- cucurbits- oral- Entomology- GFC.
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Nashat, Hafiz, Plant Protection Research Institute, Agricultural Research Center, Egypt, A.R.E.
Assuit El-Galaa Street. A.R.E, 71111, PH 02-088-325807, Fax 02-088-363639,
[email protected], Oral, Entomology.
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