Studies on shoot and leaf characters of brinjal plants and their quantitative relationships with brinjal shoot and fruit borer

The field experiment was conducted with twenty brinjal varieties/lines during October 2007 to May 2008 to identify shoot and leaf characteristics of brinjal plants for their susceptibility/resistance against brinjal shoot and fruit borer infestation. Borer infestation was influenced by different characters of plant shoot and leaf. Various parameters like plant height, stem diameter, number of branches and leaves plant, third leaf length and width were recorded from different varieties used. The shoot infestation rate was found positively correlated with plant height (0.407), stem diameter (0.520), number of branches plant (0.255), number of leaves plant (0.478), third leaf length (0.373) and third leaf width (0.536). Considering all the recorded parameters, the infestation was found minimum on the variety katabegun WS (1.65%) followed by Marich begun S (1.74%).


Introduction
Brinjal is one of the most popular and principal vegetable crops grown in Bangladesh.It is the second most important vegetable crop after potato in relation to its total production (Anonymous, 1996).Various insects cause enormous losses to this vegetable throughout the season in Bangladesh as well as in Indian sub-continent (Alam, 1969 andDhankar, 1988), among them brinjal shoot and fruit borer (BSFB), Leucinodes orbonalis Guenee, is the most serious and destructive one.Due to the attack of this pest considerable damage is occurred each year affecting the quality and yield of the crop.Only the larvae of this pest cause 12-16 % damage to shoots and 20-60% to fruits (Alam, 1970;Maureal et al., 1982).The pest is very active during the rainy and summer season and often causes more than 90% damage (Ali et al., 1980;Kalloo, 1988).The yield loss has been estimated up to 86% (Ali et al., 1980) in Bangladesh and up to 95% (Naresh et al., 1986) in India.Indiscriminate use of synthetic chemicals for the controlling insect pest resulted hazardous effects causing serious problems including pest resistance, secondary pest outbreak, pest resurgence and environmental pollution.Considering the above fact, the present study was undertaken to find out whether the shoot and leaf characters influencing the infestation rate of BSFB and also their quantitative relationships with infestation which will help to develop resistant/tolerant varieties against this pest.

Materials and Methods
For the experiment twenty brinjal varieties/lines, collected from IPM laboratory of Plant Pathology Department, BAU, Mymensingh were used.The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications and the experimental field was divided into three blocks, each block consisted of twenty lines.The size of the whole field was 40m x 20m.Uniform and healthy seedlings of 45 days old were taken separately from the seedbed, transplanted in the experimental plots maintaining a spacing of 75cm x 60cm between the row to row and plant to plant.Different intercultural operations (weeding, gap filling and irrigation) were accomplished for better growth and development but no insecticide was used.The data on plant height (cm), stem diameter (cm), number of branches and leaves plant -1 , third leaf length (cm) and width (cm) and infestation were recorded at 60, 80, 100 and 120 days after transplantation.The data were analyzed by using MSTATC Package Computer Program and mean difference were adjusted with DMRT (Duncan, 1955).

Results and Discussion
The average values of shoot characters and brinjal shoot infestation of twenty selected brinjal varieties/lines at different days after transplantation (DAT) has been presented in Table 1.The average highest plant height was recorded in the variety Eye red (54.18) which was significantly different from that of other varieties/lines, whereas, lowest plant height was recorded in the variety Thamba (19.23) which was significantly different from that of other varieties/lines.On an average, the highest stem diameter was recorded in the variety Irribegun (1.54) which was significantly different from that of other varieties except Islampuri BADC and Kaikka N but the average lowest stem diameter was recorded in the variety Amjuri (0.93) which was significantly different from that of other varieties/lines.The average highest number of branches was recorded in the variety Amjuri (12.79) which was significantly identical with that of the varieties/lines BL-118, Bijoy, Irribegun and Kaikka N, whereas, the average lowest number of branches (6.52) was observed in the variety Thamba which was significantly identical with that of the varieties/lines Dharola, ISD 006 and Khatkhatia BAU.So it was found that the higher plant height and stem diameter increased infestation, on the other hand, more branches plant -1 reduced infestation because it may be reduced stem diameter which is uncomfortable for infestation.) which was significantly identical with that of the varieties/lines Borka, Amjuri, Deembegun, Thamba, Nayantara, Katabegun WS and Islampuri BADC.The average highest third leaf width was recorded in the variety Bijoy (12.21) which was significantly identical with that of varieties/lines Kaikka N, Khatkhatia BAU and Uttara, whereas, the lowest third leaf width was recorded in the variety Dharola (8.37) which was significantly identical with that of the varieties/lines Borka, ISD 006, Nayantara, Katabegun WS, Laffa S, Kajla, BL-118, Amjuri and Uttara.So it can be suggested that more leaf numbers and higher third leaf width might increase infestation because the more leaves and higher third leaf width may be favorable for egg lying of BSFB.Experimental information on correlation coefficient is particularly useful for measuring the relationship among the variables.The shoot infestation rate was found to be positively correlated with plant height (0.407), stem diameter (0.520), number of branches plant -1 (0.255), number of leaves plant -1 (0.478), third leaf length (0.373) and width (0.536) which was presented in Table 3.The estimated correlation coefficients among shoot infestation caused by BSFB and tested leaf and shoot characters were partitioned into direct and indirect effects and have been presented by path coefficient analysis in Table 4.The direct effect of plant height and stem diameter, number of leaves plant -1 and third leaf width against shoot infestation caused by BSFB were positive (0.396,0.248, 0.059 and 0.393 respectively) and higher in magnitude at 1% level of significance.The direct effect of number of branches plant -1 and third leaf length against shoot infestation were negative (-0.082 and -0.067 respectively) and lower in magnitude at 5% level of significance.It was observed that the higher plant height, stem diameter, third leaf width and more number of leaves increased infestation of BSFB, because more leaves and higher third leaf width may be suitable for oviposition and thick stem associated with succulent, thin cuticle and soft parenchymatous cells may be suitable to bore easily by young larvae.On the other hand, higher number of branches plant -1 reduced infestation because it may be reduced stem diameter.Malik et. al. (1986) reported that thin shoots of brinjal found tolerant to leucinodes orbonalis.

Table 1 . Average values of shoot characters and percent infestation of twenty selected brinjal varieties/lines at different days after transplantation (DAT)
Singnath (22.71)which was significantly identical with that of varieties/lines Kaikka N, BL-118, Eye red, Khatkhatia BAU, Laffa S, Bijoy, Irribegun, Marich begun S and Uttara, but The average lowest third leaf length was recorded in the variety ISD006 (16.23 The average values of leaf characters and brinjal shoot infestation of twenty selected brinjal varieties/lines at different days after transplantation (DAT) has been presented in Table2.The average highest number of leaves was recorded in the variety Kaikka N (53.13) which was significantly different from that of other varieties/lines except Irribegun.But the lowest number of leaves was recorded in the variety Thamba (35.11) which was significantly identical with that of varieties/lines ISD 006 and Dharola.The average highest third leaf length was recorded in the variety

Table 4 . Path coefficient analysis of brinjal plant characters influencing shoot infestation caused by brinjal shoot and fruit borer (BSFB)
Bold and underline figures are the direct effects, Residual effect is the square root of = 0.517