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Combined Effect of Zinc and Boron with Fruit Thinning on the Quality Seed Production of Tomato

An experiment was conducted at the Horticulture Farm of Sher-e-Bangla Agricultural University, Dhaka during the period from October 2017 to April 2018. The present research was aimed to study effect of combinations of zinc and boron with fruit thinning on the quality seed production of tomato. There were four combination of zinc and boron viz. T0 =Zn0 kgB0kg/ha, T1=Zn2 kg B1.5 kg/ha, T2=Zn4kg B2 kg/ha, T3=Zn6B2.5 kg/ha and four levels of fruit thinning viz. P0= control (without fruit thinning), P1= 10 fruits were retained per plant, P2=20 fruits were retained per plant and P3 =30 fruits were retained per plant. The experiment was laid out in a Randomized Complete Block Design with 3 replications and there were altogether 48 plots. Application of micronutrients with fruit thinning significantly influenced the growth and seed yield of tomato. The highest seed yield (297.82 kg/ha) was found from T3 and the lowest yield (260.69 kg/ha) was obtained from T0. Due to the fruit thinning, the highest seed yield (337.41 kg/ha) was obtained from P3 and lowest yield (190.69 kg/ha) was recorded from P1. In case of combined effect, the highest yield (360.39 kg/ha) was found from T3P3 and lowest yield (180.39 kg/ha) was found from T0P1. So, application of Zn6 kg B2.5 kg/ha along with 30 fruits were retained per plant was the best for yield of tomato seed.


INTRODUCTION
Tomato (Lycopersicun esculentum L.) belonging to the family Solanaceae. It is one of the most popular, important and nutritious vegetable grown in Bangladesh mainly during the Rabi season. The food value of tomato is very high because of higher contents of vitamins (A, B, C), minerals and carotene [1]. The demand of tomato in both domestic and foreign markets increased manifold in recent years. Adequate supply of nutrient can increase the quality fruit and seed yield. For harnessing the higher seed yield, supplementation of micronutrients is essential. Amongst the vegetables, tomato is very responsible to the application of micronutrients. It is realized that productivity of crop is being adversely affected in different areas due to deficiencies of micronutrients [2]. In Bangladesh, majority of the growers do not get high quality fruit and higher seed yield because of their ignorance about proper thinning practices. Tomato fruit thinning practice may give good result for getting uniform sized quality fruit, increased yield and less infestation of insects and diseases. An increase in total number of flowers and fruits has been shown to increase competition for photosynthesis and thus, decrease fruit size [3]. Yield and quality size of tomatoes are influenced by many factors, including fruit pruning [4]. Hanna, 2019 [5] found that pruning clusters to three fruits significantly increased total marketable fruit and seed yield. For successful production of quality tomato seed determination of actual number of fruit thinning is needed. Although, micronutrients and fruit thinning is important factor for growth, yield potentiality and quality seed production of tomato.
Seed is the basis of agricultural production. Quality of seed not to speak of hybrids, contributes to about 25% increases in crop yield remaining all other factors of production constant [6]. For sustainable crop production, good quality seed is very important. If the seed is not of standard quality, use of other inputs is less useful and economic loss is incurred. According to [7] seeds are the focal points which strategies to boost crop yield. So, there is a strong demand for higher quality seed. In developing countries like Bangladesh, the unavailability of good seed is a major problem due to the absence of good variety, inadequate technology for seed production, poor quality control, post handle seed handling etc. The seeds are mainly collected by the farmers/ traders from the leftover of tomato crop, which cannot fetch better price. So quality seed is obligatory in this situation to maximize tomato production. In this regard application of zinc, boron with fruit thinning can be effective in seed production. At present situation of Bangladesh, there is a great need to information about micronutrients application and optimum number of fruit per plant for quality seed production of tomato. These factors, if taken into consideration, may lead to production of quality tomato seed within the country. So the research was conducted to investigate the best treatment combination of zinc boron and fruit thinning of tomato for quality seed yield.

Climate and Soil of the Experimental Area
The experiment was conducted at Horticultural farm of Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka during the period of October 2017 to April, 2018. The location of the experimental site was at 23°46 ' N latitude and 90°22 ' E longitudes with an elevation of 8.24 meter from sea level. The experimental area is characterized by subtropical rainfall during the month of May to September and scattered rainfall during the rest of the year. Soil of the study site was silty clay loam in texture belonging to series. The area represents the Agro-Ecological Zone of Madhupur tract (AEZ No. 28) with pH 5.8-6.5, ECE-25.28 [8]. The analytical data of the soil sample collected from the experimental area were determined in the Soil Resources Development Institute (SRDI), Soil Testing Laboratory, Khamarbari, Dhaka.

Layout and Design of the Experiment
The tomato variety used in the experiment was "BARI Tomato-15". This is a high yielding semiindeterminate type variety. The seeds were collected from Olericulture division of Horticulture Research Centre, Bangladesh Agricultural Research Institute (BARI) Joydebpur, Gazipur. The two factorial (Factor A & Factor B) experiment was laid out in a Randomized Complete Block Design with three replications. The whole experimental area was divided into three blocks, representing three replications. Each block was further subdivided into 16 unit plots. The four levels of Zn and Boron nutrients combinations and four levels of fruit thinning formed sixteen (16) treatments. The plots were raised by 15 cm from the ground level. Unit plot size was 2 m × 1.5 m accommodating 12 plants in each plots having row to row and plant to plant spacing 50 cm × 50 cm respectively. The unit plots and blocks both were separated by 100 cm and 50 cm respectively.

Data Collection
Six plants were selected randomly from each plot for data collection in such a way that the border effect could be avoided for the highest precision. Data were recorded on plant height (cm), number of leaves per plant, number of branches per plant, days to first flowering, number of clusters per plant, number of flowers per cluster, number of fruits per cluster, fruit length (cm), fruit diameter (cm), individual fruit weight (g), fruit yield per plant (kg), fruit yield per plot (kg), number of seeds per fruit, seed yield per plant (g), seed yield per plot (g), seed yield per hectare (t), from sample plants during the course of experiment.

Percentage of Seed Germination
One hundred seeds were taken from each treatment and placed in the petri-dishes for germination. Sprouting of seeds were from 3 DAS and continued up to 10 DAS. The germination percentage was calculated as % seed germination= X 100

Seed Vigor Index (SVI)
The vigor of seeds of various treatments were calculated by determining the germination percentage and seedling length prescribed by [9]. Fifty seeds each in 4 replications were taken from each treatment sample and placed for germination. At the time of final counting of germinated seedlings, the length of five randomly selected seedlings from the normal seedlings were measured and seed vigor index was calculated as: SIV% = % germination x seedling length (root to shoot tip)

Statistical Analysis
Collected data were statistically analyzed using MSTAT-C computer package program. Mean for every treatments were calculated and analysis of variance for each one of characters was performed by F-test (Variance Ratio). Different between treatments was assessed by Least Significant Difference (LSD) test at 5% level of significance [10]. This might be due to the fact that the increase in plant height could be due to balanced absorption of nutrients, increased rate of photosynthesis and stimulation of root system. This finding of present study is in close conformity with the results of [9]. Zinc application also helps in increasing the uptake of nitrogen and potash [11]. Davis et al. [12] noticed that the total uptake of N, K, Mg and Ca by tomato plant increased with the application of boron. Makhan et al. [13] reported that Zinc may serve as source of energy for synthesis of auxin which helps in elongation of stem. Ali et al. [14] conducted an experiment to increase the yield of BARI hybrid tomato 4, cultivated in summer season of Bangladesh, foliar application of zinc and boron and supported the similar results.

Factor. A (4 levels of zinc and boron combinations)
The fruit thinning of tomato plant for seed production had significant effect on plant height ( Table 2). At 80 DAT the tallest plant obtained from P 2 (97.94 cm) treatments where 20 fruits retained for seed production, which was statistically similar to P 3 (97.83 cm) treatment and shortest plant was observed from P 0 (93.43 cm) treatment. These results differed with that of [15] who reported that green fruit thinning had no effect on plant height. This might be due to the variation in growing environment and management practices. The combined effect of zinc and boron application with fruit thinning on the plant height at different days after transplanting was found statistically significant on all dates of observation (Table 3). At 80 DAT the maximum plant height (108.27 cm) was measured from T 3 P 2 treatment, which is statistically similar (104.00 cm and 103.00 cm) to T 3 P 3 and T 3 P 1 treatment combinations respectively. The lowest plant height (88.23 cm) was observed from T 0 S 0 treatment. Hence, it may be inferred that the increase in plant height could be due to balanced absorption of nutrients, increased rate of photosynthesis and stimulation of root system. The findings of the present study are in close conformity with the results of [9].

Number of Branches per Plant
The significant difference was observed on number of branches plant -1 due to the application of different levels of zinc and boron combination ( Table 4). The maximum number of branches per plant (7.83) was obtained from T 3 (Zn 6kg B 2.5 kg/ha) treatment and followed by (7.26) T 2 (Zn 4.0 kg B 2.0 kg/ha) treatment. On the other hand, the minimum number of branches per plant (5.19) was recorded from T 0 (control) treatment. Ullah et al. [16] found among different levels of Zn 0.4% showed significant increased in number of branches plant -1 and yield (t ha -1 ). Boron also significantly affected growth and yield components. Shnain et al. [17] supported the results.
The number of branches per plant was varied significantly among the treatments due to the fruit thinning at different levels ( Table 5). The branch per plant was the lowest (6.26) in the plants where no fruits were thinning from P 0 (without fruit thinning) treatment and was statistically different from the plants where fruit thinning was made as per treatment. The number of branch per plant was the maximum (7.02) in the plants where 20 fruits retained for seed production which was statistically identical with P 3 (30 fruits retained) treatment. The result indicates that fruit thinning encouraged branching in plants.
The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the number of branches per plant ( Table 6). The maximum number of branches (8.50) per plant was observed from T 3 P 2 treatment, which is statistically similar (8.00 and 7.76) to T 3 P 3 and T 3 P 1 treatment combinations respectively. The minimum number of branches (4.56) was observed from T 0 P 0 treatment. Without zinc and boron might have reduced the efficiency of plants in uptaking the nutrients for normal growth.      In most cases the number of branches per plant increased with the increasing levels of zinc and boron. This might be due to the fact that zinc and boron influence the cell division, meristematic activity of tissue expansion of cell and formation of cell wall and helps in increasing the uptake of other nutrients especially nitrogen and potash. Yadiv et al. [11] obtained maximum secondary branches with the application of 7.5 ppm zinc and 100 ppm boron.

Days to First Flowering
The significant difference was observed on days to first flowering due to the application of zinc and boron on days to first flowering ( Table 4). The maximum days required to first flowering (37.44 days) was found from T 0 (control) treatment and followed by T 1 (35.42 days) treatment. The period was maximum when no zinc and no boron were applied. This result is in agreement with the findings of [18] and [19]. On the other hand, the minimum days required to first flowering (30.77 days) was recorded from T 2 treatment which is statistically identical to T 3 treatment. This might be due to a positive role of regulating the zinc and boron helps in balanced absorption of nutrients leading to favorable C: N ratio. Patil et al. [20] obtained the minimum number of days for initiation of flowering and 50% flowering with Boron 50ppm and 100ppm application, while the maximum number of days was recorded in control.
The fruit thinning treatments had no significant effect on the days to first flowering ( Table 5). The number of days took by the plants for first flowering ranged from 32.96 (in which 30 fruits were retained) to 35.80 days (in plants where without fruit thinning). The longest period for first flowering took by the P 0 treatment and was comparable to that of other treatments. The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the days required to first flowering per plant ( Table 6). The maximum days to first flowering 39.51 days was observed from T 0 P 0 treatment, which is statistically similar 38.13, 37.31 and 37.39 days to T 0 P 1 T 0 P 2 and T 1 P 0 treatment combinations respectively. The minimum (28.63) days was observed from T 3 P 2 treatment.

Number of Clusters per Plant at 60 DAT
The significant difference was observed on number of clusters per plant at 60 DAT due to the application of zinc and boron micro nutrients ( Data presented in Table 7 showed that number of clusters per plant at 60 DAT differed significantly due to fruit thinning. It was revealed that number of cluster was increased with the increasing zinc and boron levels. The highest number of cluster (21.80) was observed from P 2 (20 fruits were retained/plant) treatment which was statistically identical (21.56) with P 3 (30 fruits were retained/plant) treatment and lowest number of cluster (19.24) per plant was observed from P 0 (without fruit thinning/plant) treatment. The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the number clusters per plant at 60 DAT ( Table 7). The highest number of clusters per plant was observed from T 3 P 2 (26.20) treatment, which is statistically

Number of Flowers per Plant
The significant variation was observed in respect of number of flowers per plant due to the application of different levels of zinc and boron (  [21] stated that boron increases the stability of plant cells and is involved in the reproductive process of plants and its inadequacy is often associated with sterility and malformation of reproductive organs. Sivaiah et al. [22] found combined application of micronutrients produced the maximum fruit yield followed by application of boron and zinc. The fruit thinning treatments had no significant effect on the number of flowers per plant ( Table  8). The number of flowers per plant ranged from 53.59 to 59.87. The maximum number of flowers per plant (59.87) was found from P 2 (20 fruits were retained/plant) treatment and the minimum number of flowers (53.59) per cluster was recorded from P 0 (without fruit thinning).
The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the on the number of flowers per plant ( Table 9).The maximum number of flowers per cluster (70.70) was observed from T 3 P 2 treatment, which is statistically identical (69.03 and 68.20) to T 3 P 3 and T 2 P 3 treatment combinations and similar to T 2 P 1 , T 2 P 2 , T 3 P 1 and T 2 P 0 respectively. The minimum number of flowers per plant (34.36) was observed from T 0 P 0 treatment.

Number of Flowers per Cluster
The number of flowers per cluster increased significantly with an increase in zinc and boron levels ( Table 7). The maximum number of flowers per cluster (7.11) was found from T 3 (Zn 6 kg B 2.5 kg/ha.) treatment and followed (6.60) by T 2 (Zn 4.0 kg B 2.0 kg/ha). On the other hand, the minimum number of flowers (3.95) per cluster was recorded from T 0 (control). Similar observation was reported by [16]. The fruit thinning treatments had no significant effect on the number of flowers per cluster ( Table 8). The number of flowers per cluster ranged from 5.40 to 5.95. The maximum number of flowers per cluster (5.95) was found from P 2 (20 fruits were retained/plant) treatment and the minimum number of flowers (5.40) per cluster was recorded from P 0 (without fruit thinning). The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the on the number of flowers per cluster ( Table 9). The maximum number of flowers per cluster (7.56) was observed from T 3 P 2 treatment, which is statistically similar (7.23) to T 3 P 3 treatment combinations respectively. The minimum number of flowers per cluster (3.46) was observed from T 0 P 0 treatment.

Fruit Length (cm)
The length of fruit was found to vary significantly due to the effect of zinc and boron application    (Table 10) and increased with the increased dose of zinc and boron. The maximum length of fruit (6.72 cm) was found from T 3 (Zn 6 B 2.5 kg/ha) treatment and followed by (6.51 cm) T 2 (Zn 4 B 2 kg/ ha) treatment while, the minimum length of fruit (5.93cm) was recorded from T 0 (control) treatment. The increase in fruit length was associated with increase in size of fruit, and was probably due to increased photosynthesis and translocation of food materials. Similar observation was reported by [23]. Luis et al., 2012 [24] also supported the similar results.
The fruit thinning treatments was found significant effect in this respect ( Table 11). The maximum fruit length (6.59 cm) was found from P 1 (10 fruits were retained/plant) treatment and the minimum length (6.08 cm) was recorded from P 0 (without fruit thinning). The combined effect of zinc and boron application with fruit thinning was found significantly influenced on the on the length of fruit (Table 12). The maximum fruit length (7.06 cm) was observed from T 3 P 1 treatment, which is statistically similar to T3P2, T 3 P 3 and T 2 P 1 treatment combinations respectively. The minimum fruit length (5.83cm) was observed from T 0 P 0 treatment.

Fruit Diameter (cm)
There was no significant variation among the treatments in respect of fruit diameter, which range from 5.30 cm under control to 5.68 cm in 6 kg zinc and 2.5 kg boron/ha. (Table 10). The fruit thinning treatments had no significant effect in this respect (Table 11). The fruit diameter ranged from 5.18cm to 5.40cm. The maximum diameter (5.40cm) was found from P 2 (20 fruits were retained/plant) treatment and the minimum was recorded from P 0 (without fruit thinning). The combined effect of zinc and boron application with fruit thinning was found no significant variation on diameter of fruit (Table 12). The maximum diameter of fruit (6.06cm cm) was observed from T 3 P 1 treatment and the minimum diameter (5.10cm) was observed from T 0 P 0 treatment.

Individual Fruit Weight (g)
Distinct variation was observed among the treatments due to the application of different levels of zinc and boron. (Table 10). It was found that individual weight of fruit increased with an increase in zinc and boron levels. The highest fruit weight (112.74 g) was recorded from T 3  (Table 11). The treatment P 1 (10 fruits were retained/plant) produced the highest weight (111.05g) of individual fruit, which was statistically similar (107.21g) to P 2 (20 fruits were retained/plan) treatment. The minimum weight (97.87 g) was recorded from P 0 (without fruit thinning) treatment.
The combined effect of zinc and boron application with fruit thinning was found significant variation on weight of individual fruit ( Table 12). The maximum weight (121.63g) of individual fruit was observed from T 3 P 1 treatment, which was statistically similar to T 3 P 2 (115.00 g) treatment and the minimum weight (83.90 g) was observed from T 0 P 0 treatment. It was observed that the highest weight of individual fruit produced plants receiving more zinc and boron level with minimum number of fruits were retained. On the other hand minimum weight of individual fruit was obtained from the plants receiving no zinc and boron with without fruit thinning. This might be due to zinc and boron increased photosynthesis and translocation of food materials in fruits. Paithankar et al., 2004 [27] reported in tomato highest number of fruits and weight due to micro nutrient application.

Fruit Yield per Plot (kg)
A significant difference in yield of tomato fruits per plot among the treatments of zinc and boron was observed (Table 10). The highest fruit yield per plot (19.05 kg) was found from T 3 (Zn 6 B 2.5 kg /ha) treatment and followed by (14.63 kg) T 2 (Zn 4 B 2 kg/ ha) treatment. On the other hand, the lowest fruit yield per plot (10.80kg) was recorded from T 0 (control) treatment. Ali et al., 2015 [14] conducted an experiment to increase the yield of BARI hybrid tomato 4, cultivated in the summer season of Bangladesh, foliar application of zinc and boron and supported the similar results. Naz et al., 2012 [28] conducted a study to observe the effect of Boron on physiological growth on tomato. They reported that boron also plays an important role in production of any crop in terms of yield, quality and control of some diseases and increase the yield.
The treatments of fruit thinning per plant differed significantly in respect of fruit yield per plot ( Table 11). The treatment P 3 (30 fruits were retained/plant) produced the highest fruit yield (16.54kg) of tomato per plot, which was statistically similar (15.71 kg) to P 2 (20 fruits were retained/plan) treatment. The minimum yield (10.91 kg) per plot was recorded from P 0 (without fruit thinning) treatment. The combined effect of zinc and boron application with fruit thinning was found significant variation on fruit yield per plot ( Table 12). The maximum fruit yield (22.37 kg) of tomato per plot was observed from T 3 P 3 treatment, which was statistically similar to T 3 P 2 (20.68 kg) treatment and the minimum yield (7.97 kg) per plot was observed from T 0 P 0 treatment. Paithankar et al., 2004 [27] reported in tomato highest number of fruits and weight due to micro nutrient application.

Number of Seeds per Fruit
The significant difference was observed on number of seeds per tomato fruit due to the application of different micro nutrients (Table 13). The maximum number of seeds per fruit (138.42) was found from T 3 (Zn 6 B 2.5 kg /ha) treatment and followed by (133.25) T 2 (Zn 4 B 2 kg/ ha) treatment. On the other hand, the lowest (124.08) was recorded from T 0 (control) treatment. The results revealed that number of seeds per fruit increased with the increasing dose of micronutrients but without micro nutrients it decreased. Possibly zinc and boron increased the photosynthetic rate and translocation of food materials to seed resulting increased number of seeds per fruit. Kumari, 2005 [19] suggested that 100 ppm boron spray 30 days after transplanting and repeated at 10 days interval twice in tomato could result in maximum seed yield.
The treatments of fruit thinning per plant differed significantly in respect of number of seeds per fruit of tomato (Table 14).The treatment P 3 (30 fruits were retained/plant) produced the highest number of seeds (151.17) per fruit. The minimum number of seeds (98.83) per fruit was recorded from P 0 (without fruit thinning) treatment. The combined effect of zinc and boron application with fruit thinning was found significant variation on number of seeds per fruit (Table 15). The maximum seeds per fruit (163.67) was observed from T 3 P 3 treatment, which was statistically similar to T 1 P 1 (155.67), T 1 P 1 (155.33) and   Means in a column followed by the same letter do not differ significantly at 5% level; Here, T0 = Zn0 kgB0 kg/ha, T1 = Zn 2 kgB1.5 kg/ha , T2 = Zn 4.0 kgB2.0kg/ha and T3 = Zn 6kg B2.5kg/ha. and P0 = without fruit thinning per plant, P1 = 10 fruits were retained/plant, P2=20 fruits were retained/plant and P3 = 30 fruits were retained per plant T 3 P 2 (151.33) treatments respectively, while the minimum seeds (97.67) per fruit was observed from T 0 P 0 treatment.

Weight of Seeds per Fruit
The effects of micronutrients on the weight of seeds per fruit of tomato were found to be statistically significant (Table 13). The maximum weight of seeds per fruit (0.557g) was found from T 3 (Zn 6 B 2.5 kg /ha) treatment and followed by (0.533g) T 2 (Zn 4 B 2 kg/ ha) treatment. On the other hand, the lowest (0.496g) was recorded from T 0 (control) treatment. The treatments of fruit thinning per plant differed significantly in respect of weight of seeds per fruit ( Table  14).The treatment P 3 (30 fruits were retained/plant) produced the highest weight of seeds (0.604g) per fruit of tomato . The minimum weight of seeds (0.395g) per fruit was recorded from P 0 (without fruit thinning) treatment.
The combined effect of zinc and boron application with fruit thinning was found significant variation on weight of seeds per fruit of tomato (Table 15). The maximum weight of seeds per fruit (0.654g) was observed from T 3 P 3 treatment, which was statistically similar to T 3 P 2, T 2 P 2 and T 2 P 3 treatments respectively, while the minimum weight of seeds (0.397g) per fruit was observed from T 0 P 0 treatment.

Seed Yield per Plant
Significant influence was also found as to the tomato seed yield per plant due to the application of different levels of micronutrients (Table 13). It ranged from 6.41g to 5.54g. Distinct variation was observed as to the varied levels of zinc and boron regarding this trait. The maximum seeds yield per plot (6.41g) was found from T 3 (Zn 6 kg B 2.5 kg /ha) treatment which was statistically similar to (6.30g) T 2 (Zn 4kg B 2 kg /ha) treatment.
On the other hand, the lowest (5.54 g) was recorded from T 0 (control) treatment. Seed yield per plant differed significantly due to the fruit thinning per plant (Table 14). The highest tomato seed yield (8.17g) per plant was found with P 3 (30 fruits were retained per plant) treatment and followed by (7.31g) P 0 (without fruit thinning per plant) treatment. Besides the lowest seed yield (3.02 g) per plant was recorded from P 1 (10 fruits were retained per plant) treatment.
The combined effect of different levels of micronutrient application with fruit thinning was found statistically significant variation on seed yield per plant of tomato (Table 15). The maximum seed yield per plant (8.68g) was observed from T 3 P 3 treatment, which was statistically similar to T 3 P 2 (8.44 g) treatment, while the minimum yield (2.68 g) per plant was observed from T 0 P 1 treatment which was statistically identical with T 1 P 1 , T 2 P 1 and T 3 P 1 treatments respectively.

Seed Yield per Plot
Significant influence was found as to the seed yield per plot of tomato due to the application of different levels of micronutrients (Table 13). The maximum seed yield per plot (89. 35g) was found from T 3 (Zn 6 kg B 2.5 kg /ha) treatment and followed by (86. 23g) T 2 (Zn 4kg B 2 kg /ha) treatment. On the other hand, the lowest (78. 21 g) was recorded from T 0 (control) treatment. Seed yield of tomato per plot differed significantly due to the fruit thinning per plant (Table 14). The highest seed yield (101.22 g) per plot was found with P 3 (30 fruits were retained per plant) treatment and followed by (98.14g) P 0 (without fruit thinning per plant) treatment. Besides the lowest seed yield (57.21 g) per plot was recorded from P 1 (10 fruits were retained per plant) treatment. The combined effect of different levels of micronutrient application with fruit thinning was found statistically significant variation on seed yield of tomato per plot (Table 15). The maximum seed yield per plot (108.12 g) was observed from T 3 P 3 treatment, while the minimum yield (54.12g) per plot was observed from T 0 P 1 treatment which was statistically identical with T 1 P 1 , T 2 P 1 and T 3 P 1 treatments respectively.

Seed Yield per Hectare
Seed yield per hectare of tomato was found to be significantly influenced by the application of different levels of micronutrients (Fig. 1). The maximum seed yield per hectare (297.82 kg) was found from T 3 (Zn 6 kg B 2.5 kg /ha) treatment and followed by (287.44 kg) T 2 (Zn 4kg B 2 kg /ha) treatment. On the other hand, the lowest (260.69kg) was recorded from T 0 (control) treatment.
Seed yield of tomato per hectare significantly varied due to the fruit thinning per plant (Fig. 2). The highest seed yield (337.41 kg) per hectare was found from P 3 (30 fruits were retained per plant) treatment and followed by (327.15 kg) P 0 (without fruit thinning per plant) treatment.
Besides the lowest seed yield (190.69 kg) per hectare was recorded from P 1 (10 fruits were retained per plant) treatment.
The combined effect of different levels of micronutrient application with fruit thinning was found statistically significant variation on seed yield of tomato per hectare (Table 15). The maximum seed yield per hectare (360.39 kg) was observed from T 3 P 3 treatment, while the minimum yield (180.39 kg) per hectare was observed from T 0 P 1 treatment.

Seed Germination Percentage
Application of different levels of zinc boron combinations showed non-significant effect on the percent seed germination of tomato (Table  16). The germination percentage varied from 97.83% to 96.66%. The effect of different levels of fruit thinning was found to be non on the seed germination percentage (Table  17).The combined effect of both was also found to be statistically non-significant in this respect (Table 18). Singh and Kanwar, 1995 [15] reported that fruit thinning had no effect on  The combined effect of different levels of micronutrient application with fruit thinning was found statistically significant variation on seed yield of tomato per hectare (Table 15). The maximum seed yield per hectare (360.39 kg) was treatment, while the minimum yield (180.39 kg) per hectare was

Seed Germination Percentage
Application of different levels of zinc boron significant effect on the percent seed germination of tomato (Table  16). The germination percentage varied from 97.83% to 96.66%. The effect of different levels nd to be non-significant on the seed germination percentage ( Table  17).The combined effect of both was also found significant in this respect (Table 18). Singh and Kanwar, 1995 [15] reported that fruit thinning had no effect on germination percentage of seeds. Similar results were also reported by [29].

Seed Vigor Index
The variation in the vigor of produced seed was found significant in tomato due to the application of different levels of zinc and boron co (Table 16).It was observed that the highest seed vigor index (1234.2) was found in T kg/ha) treatment and T 0 (Zn 0.0 treatment gave the lowest seed vigor index (848.9 ). Seed vigor index significantly varied due to the fruit thinning per plant (Table 17). The highest seed vigor index (1163.3) was found from P 2 (20 fruits were retained per plant) treatment which was statistically identical to (1145.0) P 3 (30 fruits were retained per plant) treatment. Besides the lowest seed vigor index (897.9) was recorded from P 0 thinning per plant) treatment. The combined effect of zinc boron combinations with fruit ination percentage of seeds. Similar results The variation in the vigor of produced seed was found significant in tomato due to the application of different levels of zinc and boron combinations (Table 16).It was observed that the highest seed vigor index (1234.2) was found in T 2 (Zn 4.0 kgB 2.0 0.0 kgB 0 kg/ha ) treatment gave the lowest seed vigor index (848.9 ). Seed vigor index significantly varied due e fruit thinning per plant (   Means in a column followed by the same letter do not differ significantly at 5% level; and P0 = without fruit thinning/plant, P1 = 10 fruits were retained/plant, P Table 18. Combined effect of zinc and boron with fruit thinning on germination percentage and Treatments T 0 P 0 T 0 P 1 T 0 P 2 T 0 P 3 T 1 P 0 T 1 P 1 T 1 P 2 T 1 P 3 T 2 P 0 T 2 P 1 T 2 P 2 T 2 P 3 T 3 P 0 T 3 P 1 T 3 P 2 T 3 P 3 CV (%) LSD (0.05) Means in a column followed by the same letter do not differ significantly at 5% level; Here, T0 = Zn0 kgB0 kg/ha, T1 = Zn 2 kgB1. 5

CONCLUSION AND RECOMMENDA-TION
Growth features, fruit yield components and seed yield in tomato were significantly influenced after micronutrients application along with fruit thinning practice. On the basis of the findings of the present study, the following conclusions could be drawn:  A combination of 6 kg zinc and 2.5 kg boron per hectare demonstrated was better result in respect of plant growth and fruit and seed of tomato.  Considering the yield attributes and seed yield of tomato exhibited better performance in case of P 3 (30 fruits were retained per plant) treatment.  The results of the investigation suggested that, high seed yield and good quality seed of tomato can be obtained with the application of 6 kg zinc and 2.5 kg boron per hectare in combination with 30 fruits were retained per plant.  Based on the findings of the study, trial may be given at different tomato growing regions of Bangladesh with the selected dose of Zn and B before more conformation of the results.