THE EFFECT OF SEEDLING PRODUCTION METHOD ON PLANT CHARACTERISTICS, YIELD AND QUALITY OF FRUITS OF THREE CULTIVARS OF EGGPLANT GROWN IN PLASTIC TUNNEL

Grażyna Kowalska
Department of Hydrobiology and Ichthyobiology, Agricultural University in Lublin, Poland

ABSTRACT

In a unheated plastic tunnel the experiments were carried out in 1998-2000. The aim of this study was to estimate the effects of seedling production method on the quality and quantity of the yield of eggplant fruits of three cultivars – ‘Black Beauty’ ‘Solara F₁’ and ‘Epic F₁’. Potted seedlings and non-potted seedlings were maintained in glasshouse culture, according to standard recommendation for that species. They were transplanted into a tunnel at the beginning of June. Spacing between plants was 50×50 cm. Eggplant plants were grown in plastic cylinders, each of 8 litres volume, in a peat substrate. Observations of eggplant’s growth and development were conducted during its vegetation period. Eggplant fruits were collected at a harvesting maturity stage, when they were 40 days old, in two weeks intervals, from the first decade of August to the first decade of October. Then marketable yields and number of marketable fruits per plant were evaluated and the weight, diameter and length of each fruit on plant were measured. Eggplant’s cultivation from a seedling prepared in pots positively affects the plant’s growth and development. In each study year, plants cultivated from potted seedling were significantly higher and produced significantly higher number of leaves as compared to those from non-potted seedling. It was found that preparation of seedlings in pots influenced on the increase of commercial yield of eggplant fruits. The yield elevation resulted from the fruit quality improvement. Plants grown from potted seedling produced fruits of higher weight and length as compared to those achieved from non-potted plants. The studied cultivars differed in the weight, size and shape of marketable fruits. ‘Black Beauty’ was distinguished by fruits of much greater weight in comparison with ‘Epic F₁’ an ‘Solara F₁’. Fruits of ‘Solara F₁’ and ‘Epic F₁’ were longer while ‘Black Beauty’ had a greater diameter. Tested cultivars significantly differed with plant’s morphology. ‘Solara F₁’ cv. and ‘Epic F₁’ cv. were higher and were characterized with another conformation than ‘Black Beauty’ cv. plants.

Key words: eggplant, Solanum melongena L., potted seedling, non-potted seedling, plant characteristics, weight, diameter and length of fruit.

INTRODUCTION

Eggplant is a vegetable that is relatively little known in cultivation and consumption in Poland. The reason is the lack of cultivation tradition and its great thermal requirements [7, 8, 9]. However, due to its high dietetic value, the eggplant is more and more appreciated among producers and consumers [10, 11]. The best results can be achieved from cover cultivation: greenhouses and tunnels. The eggplant’s seedling production time is about 8-10 weeks, and that period depends on the season the cultivation is performed. Maintenance of well developed eggplant seedling root system is a condition for achieving high yields of good-quality fruits. The seedling production is recommended to perform in pots due to great sensibility of eggplant’s root system during setting [6, 12].

The aim of the present experiment was to estimate of the effect of seedling production method on plant characteristics, yield and quality of eggplant fruits grown in plastic tunnel.

MATERIALS AND METHODS

In the years 1998-2000 an experiment was conducted in a two cold plastic tunnels of the Experimental Farm of Agricultural University in Lublin. The potted eggplant seedlings were produced in pots of 8 cm diameter; non-potted ones – directly in plastic boxes (50×40×16 cm), in which substrate thickness layer corresponded to pot height (8 cm) and number of plants with pots placed in the same box (35 plants). The plants were transplanted into a tunnel at the beginning of June.

The eggplant plants were grown in plastic cylinders, each of 8 dm³ volume, in a peat substrate. Fertiliser application (pretransplant and side – dressing) was based on a prior soil test. 240 plants of three eggplant cultivars – ‘Black Beauty’, ‘Solara F₁’ and ‘Epic F₁’ cultivated in two foil tunnels (120 plants each) were used for the study.

Observations of eggplant’s growth and development were conducted during its vegetation period. Measurements of plant’s height and counting of number of leaves per plant were made every 10 days. These measurements and counting were performed using 10 randomly selected plants in every combination of tested factors. Eggplant fruits were collected at a harvesting maturity stage, when they were 40 days old, in two – week intervals, from the first ten days of August to the first ten days of October. The marketable yields and number of marketable fruits per plant were then evaluated and the weight, diameter and length of each fruit on plant were measured.

The experiment was established as a two – factor one in a completely randomised design. Each combination of the factor at stake was represented by 40 experimental units. The yield data were analysed using the analysis of variance. Significant differences were detected using t-Tukey‘s multiply confidence intervals at α = 0.05.

RESULTS

The experiment was aimed to prove the influence of seedling preparation way on some morphological traits of three tested eggplant cultivars. In each year, potted plants were significantly higher (66.6-76.1 cm in 1998, 76.8-81.3 cm in 1999 and 58.9-72.8 cm in 2000) than non-potted ones (52.8-64.0 cm in 1998, 66.9-76.7 cm in 1999 and 52.7-60.1 cm in 2000) (fig. 1). For all study years, significantly higher mean number of leaves was recorded on plants cultivated from potted seedling (11.1-13.8, 12.0-12.7, and 13.2-14.0 leaves per plant) than on plants cultivated from non-potted seedling (7.2-10.0, 10.5-11.0 and 11.7-12.2 leaves per plant) (fig. 2). Different weather conditions had the influence on eggplant plants growth. Eggplant was the highest in 1999 (66.9-81.3 cm) as compared to another years: 52.8-76.1 cm in 1998 and 52.7-72.8 cm in 2000 (fig. 1). The highest number of leaves was produced by three eggplant cultivars in 2000 (11.7-14.0 leaves per plant) then in 1999 and 1998 (10.5-12.7 and 7.2-13.8 leaves per plant) (fig. 2). Regardless the way of seedling production method, plants of ‘Epic F₁’ cv. and ‘Solara F₁’ cv. were higher as compared to ‘Black Beauty’ cv. (60.1-81.3 cm, 55.1-79.8 cm and 52.7-76.8 cm, respectively) (fig. 1). The highest number of leaves at full of fruiting stage (10.5-14.1 leaves per plant) was observed in all study years on ‘Epic F₁’ cv. and ‘Solara F₁’ cv., less on ‘Black Beauty’ cv. (7.2-13.8 leaves per plant) (fig. 2).

A positive influence of seedling’s pot management on eggplant’s yielding was proved in present study. Significantly higher mean commercial yield of fruits was achieved from plants whose seedlings were produced in pots (3.05 kg^.m^-2) than from non-potted ones (2.80 kg^.m^-2) (tab. 1).

Regardless the seedling production manner, significant differences in relation to mean commercial yield and number of fruits in commercial yield were found between tested cultivars. Significantly higher mean commercial yield of fruits was achieved from ‘Epic F₁’ cv. (3.66 kg·m^-2) and significantly higher number of commercial fruits (15.1 fruits · m^-2) as compared to ‘Solara F₁’ cv. and ‘Black Beauty’ cv. (commercial yield: 2.92 and 2.19 kg·m^-2, number of commercial fruits: 12.3 and 8.4 fruits · m^-2, respectively) (tab. 1).

Significant differences of eggplant’s yielding between study years were found as well. The weather conditions in the period of eggplant vegetation differed in each year (tab. 2). The more favorable thermal conditions were recorded in 1999, when the sum of active temperatures was higher (373.3°C) than in 1998 (254.8°C) and 2000 (274.4°C). Higher mean commercial yield was harvested in 1999, when more favorable conditions for thermophilic plants cultivation under cover took place (4.06 kg·m^-2), than in 1998 and 2000 (2.38 and 2.33 kg·m^-2, respectively). Also significantly highest number of commercial fruits (14.2 kg·m^-2) was achieved in the second study year. Much less fruits per plant were achieved in 1998 (11.8 fruits · m^-2) and 2000 (9.8 fruits · m^-2) (tab. 1).

The present study revealed a significant influence of seedling pot cultivation on weight and size of eggplant’s commercial fruits. Fruits harvested from plants whose seedlings grown in pots were characterized by significantly higher mean weight (249.6 g) and mean length (13.9 cm) as compared to those cultivated from non-potted seedling (237.6 g and 12.9 cm, respectively) (fig. 3 and 4). No obvious influence of seedling cultivation way on mean commercial fruit diameter was found (fig. 5). The heaviest fruits were achieved in 1999 (288.8 g), significantly lightest in 1998 (202.0 g). The largest eggplant fruits were harvested in 1999 (length 14.7 cm, diameter 7.6 cm), significantly smaller in 1998 and 2000 (length 12.0 and 13.5 cm, diameter 6.5 and 7.4 cm, respectively) (fig. 3-5).

Among three tested eggplant cultivars, ‘Black Beauty’ cv. gave fruits of significantly highest mean weight (256.1 g). Fruits distinguished by significantly higher mean length were achieved from ‘Solara F₁’ cv. (14.9 cm) and ‘Epic F₁’ cv. (14.6 cm). Fruits harvested from ‘Black Beauty’ cv. were characterized by significantly highest mean diameter (10.6 cm) (fig. 3-5).

DISCUSSION

Studies conducted in 1998-2000 revealed differences in relation to eggplant height and leaf number depending on seedling preparation manner. In each study year, plants cultivated from potted seedling were significantly higher and produced significantly higher number of leaves as compared to those from non-potted seedling. Some differences between cultivars referring to eggplant growth dynamics were observed on a base of systematic plant measurements. Plants of ‘Solara F₁’ cv. grew the fastest in all study years. Cebula and Ambroszczyk [3] found similar differences of some eggplant cultivars’ growth dynamics. Among eight tested Dutch cultivars with heterosis, ‘Solara F₁’ cultivar was distinguished by the obviously intensive growth and the highest number of leaves. According to Cebula and Ambroszczyk [3], too fast growth of the cultivar makes it is less useful for cover cultivation. Present study proved that ‘Solara F₁’ produces good yields when cultivated under non-heated foil tunnel.

The way of seedling preparation did not affect the number of fruits harvested in commercial yield at three tested eggplant cultivars. Such results are confirmed by Buczkowska [1, 2] who found in studies upon sweet paprika and eggplant that the manner of seedling preparation had no effect on mean number of commercial fruits per 1 square meter.

Significant influence of seedling preparation in pots on fruit size in eggplant commercial yield was found in present study. Fruits harvested from plants previously grown in pots were characterized by higher mean weight and length as compared to fruits achieved from non-potted seedlings. These results find their confirmation in studies of Weston and Zandstra [14], Weston [13] and Kemble et al. [5] who found that fruits achieved from potted seedlings were of the highest unitary weight.

Experiments performed in 1998-2000 confirmed that preparation of seedlings by growing them in pots positively affected the yielding of three tested eggplant cultivars. Doruchowski [4] achieved similar results finding that application of pots at seedling production increased the commercial yield of eggplant growing on field by 0.25 kg·m^-2, on average, as compared to that achieved from non-potted plants. Different results were achieved by Buczkowska [2] who concluded in similar study that seedling growing in pot had no significant influence on mean commercial yield of eggplant fruits.

CONCLUSIONS

1. Eggplant’s cultivation from a seedling prepared in pots positively affects the plant’s growth and development. In each study year, plants cultivated from pot seedling were significantly higher and produced significantly higher number of leaves as compared to those from non-potted seedling.

2. It was found that preparation of seedlings in pots influenced on the increase of commercial yield of eggplant fruits. The yield elevation resulted from the fruit quality improvement. Plants grown from potted seedling produced fruits of higher weight and length as compared to those achieved from non-potted plants.

3. Tested eggplant cultivars differed with their prolificacy. Regardless the studied factors, ‘Epic F₁’ cv. and ‘Solara F₁’ cv. appeared to be more prolific than ‘Black Beauty’ cv. in each experiment.

4. The studied cultivars differed in the weight, size and shape of marketable fruits. ‘Black Beauty’ was distinguished by fruits of much greater weight in comparison with ‘Epic F₁’ and ‘Solara F₁’. Fruits of ‘Solara F₁’ and ‘Epic F₁’ were longer while ‘Black Beauty’ had a greater diameter.

5. Tested cultivars significantly differed with plant’s morphology. ‘Solara F₁’ cv. and ‘Epic F₁’ cv. were higher and were characterized with another conformation than ‘Black Beauty’ cv. plants.

6. Regardless of the factor, thermal conditions were found to have a great effect on yielding of eggplant. The highest marketable yield of fruits and the number of fruits in marketable yield was obtained in 1999, when the weather conditions were the most favourable for thermophilic plants as compared with those collected in 1998 and 2000.

ACKNOWLEDGEMENT

The experiment was carried out in Department of Vegetable and Medicinal Plants, University of Agriculture in Lublin. I woud like to thank Prof. Halina Buczkowska for her substantial assistance during preparation of my work.

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