Introduction
Tomato (Lycopersicon esculentum Mill), is one of the most popular and nutritious vegetable crops in Bangladesh which belongs to the family Solanaceae. It ranks next to potato and sweet potato in the world vegetable production (Anonymous, 1997) and tops the list of conned vegetables (Choudhury, 1979).
In Bangladesh, recent statistics shows that tomato was grown in 35000 acre of land and the total production was approximately 98000 metric tons in 1998-1999. Thus the average yield of tomato was 2.8 ton acre–1 (Anonymous, 1999). The yield is quite low as compared to that of other tomato producing countries such as India (15.14 t ha–1), Japan (57.14 t ha–1) and USA (65.06 t ha–1) respectively (Anonymous, 1998). The causes of low yield of tomato in Bangladesh are unavailability of quality seeds of improved varieties, fertilizer management, disease and insect infestation and improper irrigation. Tomato is very much susceptible to insect attack from seedling to fruiting stage. This crop is attacked by different species of insects in Bangladesh. Among them, tomato fruit borer, Helicoverpa armigera (Hub.) is the serious one. This has been reported to cause damage to the extent of about 50-60% fruits (Singh and Singh, 1977). The pest is active throughout the year at places having moderate climate but its activity is adversely affected by severe cold. A study revealed that it is very active during the Rabi season. The damage by H. armigera starts soon after fruiting periods of the crop and the newly hatched larvae bore into the fruit and feed inside. As a result, the fruits become unfit for human consumption.
Though the pest is serious in status, the management of this pest through non-chemical
tactics (cultural, mechanical, biological and host plant resistance etc.) undertaken
by the researcher throughout the world is limited. The research works on non-chemical
control measures of this pest are scanty. So, the use of chemical insecticides
is regarded to be the most useful measure to combat this pest. Now, our slogan
is “save the environment in order to save us”. For that reasons, the
Ecologists, Entomologists and Zoologists gave great importance to IPM programme.
There are six steps in IPM. Among them, use of resistant cultivars ranks the
first. So, developing the resistant variety tomato is urgent. Research works
in this discipline are few in Bangladesh. To minimize the use of synthetic insecticides
and problems arising out of their frequent use, it is very essential to cultivar
a resistant and tolerant variety against insect-pests specially tomato fruit
borer. Therefore, the present research programme was undertaken to use resistant
varieties of tomato in vegetable pest management programme, which is considered
to be economical and safer as compared to the chemical control. In view of this
requirement, an experiment was undertaken to find the resistant and tolerant
tomato varieties to fruit borer with the following objectives:
| 1) |
To test damage level caused by tomato fruit borer of resistant
and susceptible tomato varieties/lines by field screening, |
| 2) |
To identify the plant morphological characters influencing the infestation
rate of tomato fruit borer. |
| 3) |
To study the relation of leaf colour/pigment (i.e. chlorophyll ‘a’
and ‘b’) with infestation rate of tomato fruit borer. |
Materials and Methods
The research was work carried out at Genetics and Plant Breeding Farm (GPB Farm) and at different Laboratories of Bangladesh Agricultural University (BAU) and Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh during the period from November 1999 to March 2000. The experimental field belongs to the old Brahmaputra Alluvium Soil Tract characterized by sandy loam soil with fine texture having a pH value of 6.5 (Uddin, 1975; Anonymous, 1979).
For the experiment, thirty tomato varieties/lines were used. Most of them were obtained from Genetics and plant Breeding Department, BAU, Mymensingh and the rest were collected from Bangladesh Agricultural Research Institute (BARI), Gazipur and Asian Vegetable Research and Development Centre (AVRDC), Taiwan.
Field screening of tomato varieties/lines against tomato fruit borer: Thirty
tomato varieties/lines viz. V-40, V-80, V-187, V-231, V-250, V-258, V-259V-280,
V-282, V-321,V-332,V-374,V-378, Ratan,V-29,V-382,V-387,V-422,V-423,V-433,V-453,
Manik,V-14,V-8,V-52,V-56,V-94,V-3, BRRI-10 and V-167 were screened for tomato
fruit borer resistance. Seeds of different varieties/lines were sown separately
in a well- prepared seed- bed to raise seedling and proper care was taken during
raising of the seedlings, which were spaced at 1 m in a unit plot of 5.4 m2.
Twenty- days old seedlings were transplanted at the main field. The total plot
area was 1056 m2 which was divided into 3 replications, where each
replication contained 30 varieties/lines. Twenty-eight plants were planted in
each variety/line with 50 cm distance from plant to plant. Line to line distance
was 60 cm. Intercultural operations were performed as and when necessary throughout
the growth period of the crop. Chemical control measures were not taken against
insect pests.
Data were recorded at 30, 50 and 70 days after transplanting (DAT). Total number of infested and healthy shoots and fruits were counted and percentage of infestations of tomato fruit borer was calculated and graded from the mean percentages according to the method of Mukhopardhay and Mandal (1994). Statistical analysis was done by using MSTAT package computer programme. Mean differences were adjusted with DMRT (Duncan, 1955, Gomez and Gomez, 1984).
Calculation of percentage of tomato fruit borer infestation: For collecting data on the percentage of tomato fruit borer infested plant, total number of plants and the number of tomato fruit borer infested plants in each plot were recorded. Then the percentage of tomato fruit borer infested plants was recorded. The damaged plants were then graded by Mishra et al. (1996).
Identification of plant morphological characters influencing the infestation rate of tomato fruit borer: Data were collected from 10 plants of each variety/line of each replication. Data or morphological characters viz. Plant height (cm), stem diameters (cm), number of branches per plant, number of leaves per plant, second leaf area (cm), leaf hair per unit area, leaf chlorophyll, fruit no per plant were recorded at 30, 50 and 70 days after transplanting (DAT). Mean values of each entry from different DAT were analyzed statistically.
To determine the extent of interrelationship among tomato fruit borer infestations and tomato plant characters, correlation matrix for all possible data combinations was worked out by the method of Hayes et al. (1955). Correlation co-efficient were further partitioned into characters of direct and indirect effects by path co-efficient analysis originally developed by Wright (1923) and later described by Dewey and Lu (1959), taking all the characters into consideration. Tomato fruit borer infestations were considered as a resultant variable. The relative importance of each independent variable for tomato fruit borer infestations were carried out by logistic regression model since the independent variable was in percentage form.
Study on the relation of leaf colour/pigment (i.e. chlorophyll ‘a’ and ‘b’) with infestation rate of tomato fruit borer: Leaf chlorophyll was estimated from the second leaf counted from the top of shoot. For this purpose, second leaf was randomly selected from 10 different plants in each entry in a replicate and leaf pigment was estimated. Leaf pigments were estimated as outlined by Yoshida et al. (1976).
Results and Discussion
Percentage of tomato fruit borer infestation of selected tomato varieties/lines
at different ages: The percentage of tomato fruit borer infestation of different
varieties/lines at different plant ages has been presented in Table
1. The percentage of tomato fruit borer infestation ranged from 0.01057
(V-29) to 29.11 (29.11) at early stage of fruit and 17.33 (V-29) to 43.57 (V-422)
at ripening stage of fruit. The percentage of tomato fruit borer infestation
varied significantly among the tomato varieties/lines at different plant ages.
On an average, the highest percentage of infestation was found in V-422, which
was significantly different from other varieties/lines except V-321 and V-374.
| Table 1: |
Percentage of tomato fruit borer infestation of 30 selected
tomato varieties/lines at different ages, Rabi, 1999-2000 |
 |
 |
The lowest percentage of infestation was observed in the line V-29, which was
observed in the line V-29 and was also significantly different from other varieties/lines.
Percentage of tomato fruit borer infestation varied significantly with the age
of the tomato plants.
Among the thirty tomato varieties/lines none was found resistant to tomato fruit borer in Rabi season. Similar findings were observed by Mishra et al. (1996) and Husain et al. (1998). On an average, V-29 was found to be moderately resistant.
The lines of V-282 and V-332 were susceptible. The varieties/lines of V-40, V-80, V-187, V-250, V-258, V- 259, V-280, V-321, V-374, V-378, Ratan, V-382, V-387, V-422, V-423, V-433, V-453, Manik, V-14, V-8, V-52, V-56, V-94, V-3, BARI-10, V-167 were found to be highly susceptible. In all varieties/lines, the infestation was lower at early fruiting stage and increased gradually at the ripening stage of fruit.
| Table 2: |
Plant height (cm) of 30 selected Tomato varieties/lines at
different ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
Identification of the plant morphological characters
Plant height (cm): Plant height of different tomato varieties/lines
at different ages ranged from 54.54 (BARI-10) to 87.30 (V-187) at 30 DAT, 65.30
(V-433) to 100.2 (V-187) at 50 DAT and 80.15 (V-40) to 113.5 (V-187) at 70 DAT
(Table 2). Plant height varied significantly with ages of
the tomato plant. Average highest plant height (100.3) was recorded in the variety
V-187, which was significantly different from other varieties/lines. The average
lowest plant height was recorded in the line V-453, which was significantly
identical with that of the variety/line V-40, V-321, V-94 and BARI-10. Plant
height also varied significantly among the days after transplanting. The highest
plant height (93.84) was observed at 70 DAT, which was significantly different
from that at 30 and 50 DAT.
Stem diameter (cm): The stem diameter varied significantly among the
varieties/lines at different ages (Table 3). The stem diameter
of different tomato varieties/lines ranged from0.4910 (V-94) to 1.276 (V-187)
at 30 DAT, 0.9513 (V-94) to 1.675 (V-187) at 50 DAT 1.398 (V-8) to 2.333 (V-187)
at 70 DAT.
| Table 3: |
Stem diameter (cm) of 30 selected Tomato varieties/lines at
different ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
On the basis of average stem diameter V-187 was the thickest variety, which
was significantly different from other varieties/lines but identical to that
of V-258. Lowest stem diameter was recorded in the line V-94, which was significantly
identical from Ratan, V-8, V-52, V-56, BARI-10. Stem diameter varied significantly
with ages of the tomato plants. Significantly highest stem diameter (1.67) was
recorded at 70 DAT, which was significantly different from 30 and 50 DAT.
Number of branches per plant: The number of branches per plant varied
significantly among the varieties at different ages (Table 4).
Average highest number of branches was recorded in the line V-433, which was
significantly different from other varieties/lines. Average lowest umber of
branches was recorded in the line V-167, which was significantly identical from
that of V-259, V-280, V-282, V-321, V-321, V-374, V-14, V-8, V-52, V-56, V-94,
V-3, BARI-10.
| Table 4: |
Total number of branches per plant of 30 selected Tomato varieties/lines
at different ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
Significantly highest number of branches was observed at 70 DAT (19.50), which
was significantly different from 30 and 50 DAT.
Number of leaves per plant: Number of leaves per plant of different tomato varieties/lines at different plant ages ranged from 287.7 (V-374) to 778.4 (V-422) at 30 DAT, 276.0 (V-374) to 890.7 (V-422) at 50 DAT and 308.01 (V-374) to 1116.0 (V-433) at 70 DAT (Table 5). The average highest number (980.08) of leaves was recorded in the line V-433, which was significantly higher than the ages of tomato plant. The average highest number of leaves was recorded at 70 DAT (561.4), which was significantly different from 30 and 50 DAT.
Second leaf area (cm2): Second leaf area ranged from 9.90
(V-3) to 28.34 (Manik) at 50 DAT, 12.47 (V-3) to 28.65 (Manik) at 50 DAT and
13.03 (V-250) to 23.70 (V-29) at 70 DAT (Table 6). Area of
second leaf also varied significantly with the age of the tomato plant.
| Table 5: |
Total number of leaves per plant of 30 selected Tomato varieties/lines
at different ages, Rabi, 1999-2000. |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
Average largest second leaf area (26.71) was observed in the variety Manik,
which was significantly different from other varieties/lines but identical to
that of line V-374. The average shortest second leaf area 13.29 was recorded
in the line V-3, which was significantly different from other varieties/lines
but identical with V-250, V-433 and V-52. Significantly highest mean of second
leaf area (20.18) was recorded at 30 DAT, which was significantly different
from 50 and 70 DAT.
Total chlorophyll (mg g–1): Total chlorophyll content of different tomato varieties/lines ranged from 0.1247 (V-280) to 1.444 (V-52) at 50 DAT (Table 7). The average highest amount of total chlorophyll content was estimated in the variety V-52, which was significantly different from other varieties/lines but identical with V-8, V-374, V-56, V-94, V-3, BARI-10, V-167. In respect of total chlorophyll, the lowest amount was from other varieties/lines but identical with V-40, V-259, V-382 and V-453.
| Table 6: |
Second leaf area (cm2) of 30 selected Tomato varieties/lines
at different ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
Total leaf hair per unit area (10 mm2): Total number of leaf hair per unit area (10 mm2) of different tomato varieties/lines ranged from 7.787 (V-94) to 29.10 (V-433) (Table 7). The highest number of leaf hair per unit area was observed in the line V-433, which was significantly similar with V-453 and V-52 but different from other varieties/lines. The lowest number of leaf hair per unit area was observed in V-94, which was significantly identical with V-40, V-258, V-280, V-374, V-29, V-382, V-387, V-56 and V-3.
Number of fruits per plant: Number of fruit per plant of different tomato
varieties/lines at different plant ages ranged from 19.33 (V-422) to100.3 (Manik)
at 70 DAT and 27.00 (V-422) to 164.0 (BARI-10) at 90 (Table 8).
The average highest number of fruit (127.3) was recorded in the variety Manik,
which was also significantly different from that of other varieties/lines, but
identical with V-80, Ratan, V-423, V-453, V-14, V-94 and BARI-10.
| Table 7: |
Total leaf chlorophyll (mg/g) and total leaf hair per unit
area (10 mm2) of 30 selected Tomato varieties/lines at different
ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT
DAT = Days after transplanting. |
The average lowest number of fruit (22.97) was observed in the line V-422,
which was significantly different from other varieties/lines but identical with
V-187, V-259, V-280, V-282, V-321, V-374, V-378, V-29 and V-56. Fruit number
per plant varied significantly with the ages of tomato plant.
The highest plant height, stem diameter, number of branches per plant, number
of leaves per plant, second leaf area, number leaf hair, total leaf chlorophyll,
number of fruits per plant, percentage of tomato fruit borer infestation were
observed in the varieties/lines V-187, V-187, V-433, V-433, Manik, V-433, V-52,
Manik and V-422 resrectively although the lowest attack was found in the variety
Manik by Husain et al. (1998) and Ratan was found as a moderately susceptable
variety. On the other hand, the lowest plant height, stem diameter, number of
branches per plant, number of leaves per plant, second leaf area, number leaf
hair, total leaf chlorophyll, number of fruits per plant, percentage of tomato
fruit borer infestation were observed in the varieties V-433, V-94, V-167, V-374,
V-3, V-94, V-422, V-280 and V-29 respectively (Table 9).
| Table 8: |
Number of fruits per plant of 30 selected Tomato varieties/lines
at different ages, Rabi, 1999-2000 |
 |
Within column, means followed by same letter (s) did not differ
significantly at p < 0.01 by DMRT.
DAT = Days after transplanting. |
Quantitative relationships: Experimental information on correlation co-efficient is particularly useful for measuring the relationship among the variables. Tomato fruit borer infestation was found the be positively correlated with the plant height (0.243), stem diameter (0.101), number of branches per plant (0.256), number of leaf per plant (0.412) and leaf hair per unit area (0.068) but negatively correlated with second leaf area (-0.085) and leaf chlorophyll (-0.125) (Table 10). The results from correlation co-efficient indicate that plant height, stem diameter, number of branches per plant, number leaf leaves per plant can influence (induce) higher fruit borer infestation. On the other hand, second leaf area, leaf chlorophyll decrease the infestation of tomato fruit borer. Tomato fruit borer infestation had significant correlation with number of leaves per plant at 5% level.
The estimation correlation co-efficient among tomato fruit borer infestation
and tested plant characters were partitioned into direct and indirect effects
and have been presented by path co-efficient analysis (Table
11). The direct effect of plant height on tomato fruit borer infestation
was positive (0.0006).
| Table 9: |
Average plant character values and tomato fruit borer infestation
of 30 selected tomato varieties/lines at different ages resistant and susceptible
to tomato fruit borer Rabi, 1999-2000 |
 |
|
| Table 10: |
Co-relation matrix between Tomato plant characters and Tomato
fruit borer infestation rate Rabi, 1999-2000 |
 |
| * P < 0.05** P< 0.01 |
| Table 11: |
Path co-efficient analysis of plant characters influencing
tomato fruit borer infestation rate Rabi, 1999-2000 |
 |
| Residual effect is the square root of: 0.7029791N.B. : Bold
figure are the direct effects |
Its indirect effects via number of branches per plant, number of leaves per
plant, leaf chlorophyll, leaf hair per unit area, number of fruit per plant
were positive, but via stem diameter was negative, which made the correlation
co-efficient between plant height and tomato fruit borer infestation to be negative.
Stem diameters had a negative direct effect (-0.1979) and its indirect effect
via plant height, number of branches per plant, number of leaves per plant,
leaf chlorophyll, leaf hair per unit area, number of fruit per plant were positive,
which made the total correlation co-efficient between stem diameter and tomato
fruit borer infestation positive. The direct effect of number of branches per
plant on tomato fruit borer infestation were positive (0.0361). Its indirect
effects via plant height, number of leaves per plant were positive but via stem
diameter, leaf chlorophyll, leaf hair per unit area number of fruit per plant
were negative, which made the total correlation co-efficient between number
of branches per plant and tomato fruit borer infestation negative. Number of
leaf had a positive direct effect (0.4566). Its indirect effect via plant height,
number of branches per plant, leaf chlorophyll had a positive effect but via
stem diameter, leaf hair per unit area and number of fruit per plant had positive
effect which made the total correlation co-efficient between number of leaves
per plant and tomato fruit borer infestation was positive. The direct effect
of leaf chlorophyll on tomato fruit borer infestation were negative (-0.1431).
Its indirect effects via plant height, number of branches per plant, number
of leaves per plant and number of fruit per plant were negative but stem diameter
and leaf hair per unit area were positive, which made the total correlation
co-efficient leaf chlorophyll and tomato fruit borer infestation positive. Leaf
hair had a negative direct effect (-0.1145). Its indirect effects via plant
height and number of fruit per plant were negative but stem diameter, number
of brunches per plant, number of leaves per plant and leaf chlorophyll were
positive, which made the total correlation co-efficient between leaf hair per
unit area and tomato fruit borer infestation positive. The direct effect of
fruit no. per plant on tomato fruit borer infestation were negative (-0.3507).
Its indirect effects via plant height, leaf chlorophyll and leaf hair per unit
area were negative but stem diameter, number of branches per plant, number of
leaves per plant were positive, which made the total correlation co-efficient
between number of fruits per plant and tomato fruit borer infestation positive.
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