Evaluation of cucumber genotypes under plastic house and open field conditions in Lalitpur, Nepal

Abstract

The low production of cucumber (Cucumis sativus L.) in Nepal is associated with the lack of high-yielding gynoecious hybrids, the long gestation period and low yields of open-pollinated varieties and cold stress in open field conditions during the off-season. An experiment was conducted at the National Horticulture Research Centre, Nepal Agricultural Research Council, Khumaltar, Lalitpur, Nepal, from February to July 2019 to evaluate the performance of cucumber genotypes under open field and plastic house conditions. The experiment was laid out in a two-factor randomized complete block design (RCBD) with seven genotypes (Bhaktapur Local, HRDCUC-004 × HRDCUC-001, HRDCUC-004 × HRDCUC-003, HRDCUC-006 × HRDCUC-001, HRDCUC-006 × HRDCUC-003, HRDCUC-009 × HRDCUC-001, and HRDCUC-009 × HRDCUC-003) and two growing conditions (open field and plastic house). Genotypes and growing conditions affected yield and yield attributing characters. Genotype HRDCUC-004 × HRDCUC-001 grown under the plastic house was superior in terms of the number of fruits plant⁻¹ (28.33), yield plant⁻¹ (12.43 kg), and adjusted yield hectare⁻¹ (117 t ha⁻¹). The highest benefit-cost ratio (2.99:1) was also observed for the genotype HRDCUC-004 × HRDCUC-001 grown under plastic house conditions. Overall acceptability of consumers was higher in genotype Bhaktapur Local (7.6) followed by HRDCUC-004 × HRDCUC-001 (7.2). Cucumber genotype HRDCUC-004 × HRDCUC-001 was promising for yield and yield attributing characters under both growing conditions.

PUBLIC INTEREST STATEMENT

Cucumber, a globally popular vegetable crop, holds significant economic importance and is widely used in kitchens as a salad. Despite the availability of many exotic hybrid varieties, Nepal struggles with low cucumber production. Therefore, it is crucial to evaluate the performance of gynoecious hybrid cucumber varieties in terms of yield, quality, and maturity to meet the national demand. Additionally, ensuring year-round cucumber production is essential to guarantee its availability in the market. The production of high yielding gynoecious cucumber hybrids within protected structures such as plastic houses could be a feasible option to fulfill the domestic demand and ensure year-round availability in the market..

Keywords:

• Cucumis sativus
• genotypes
• growing conditions
• yield

REVIEWING EDITOR:

• Manuel Tejada, Universidad de Sevilla, Spain

SUBJECTS:

• Agriculture & Environmental Sciences; Agriculture; Horticulture

1. Introduction

Cucumber (Cucumis sativus L.) is an economically important vegetable crop of Nepal with the potentiality of income generation through year-round production. Cucumber is widely cultivated during the summer season in low to mid hills as the main season crop (Bhattarai & Subedi, 1995; Gautam et al., 2021) and during the winter under a plastic house as an offseason crop (Upadhyay, 2009). Although there is a market for the cucumber throughout the year, production is challenging during the periods of July to August due to high temperatures, extended daylight hours, and rainfall, and between November and February due to low temperatures and shorter daylight hours (Sharma et al., 2005). As a result, domestic demand is not being met (HRD, 2018). Off-season production of cucumber in a naturally ventilated polyhouse has been undertaken by some commercial farms due to increasing demand and high market value (Gautam et al., 2021). However, there is a lack of appropriate technology, resources, and climate resilience short duration high yielding varieties (Gautam et al., 2021). Average productivity of cucumber is low in Nepal as compared to the world average (FAOSTAT, 2021). Traditional methods of cultivation and the use of low yielding monoecious, local, and open pollinated varieties are the major reasons for the low productivity of cucumber in Nepal (Subedi et al., 1996; Gautam et al., 2021). Likewise, cucumber cultivation in Nepal is mainly restricted to open fields during the summer season which coincides with the rainy season which results in low yield and poor quality fruits (Gautam et al., 2021).

Kusle and Bhaktpur Local are the only two varieties released by the National Seed Board to date. Bhaktapur Local is popular among farmers, but it has some drawbacks like high male to female ratio, longer vegetative phase, misshapen fruits, presence of cavity in the fruit center, short harvesting period, and is susceptible to various fungal and viral diseases (Subedi et al., 1996; Gautam et al., 2008; Gautam et al., 2021). On the other hand, the Kusle variety is highly susceptible to viruses and powdery mildew and is not preferred by the farmers (Gautam et al., 2021). Likewise, the productivity of these varieties is low as compared to registered hybrids. Because of the low productivity of local and open pollinated varieties, 27 exotic hybrids have been registered under the National Seed Board (MOALD, 2020). To fulfil the national demand of seed, a large quantity of hybrid cucumber seeds has been imported into Nepal annually (Kafle & Joshi, 2018). The exotic hybrid varieties possess important traits of early fruiting, gynoecy, higher yield, and better fruit quality (Kumar et al., 2013; Khan et al., 2015; Ranjan et al., 2015; Chinatu et al., 2017; Pal et al., 2017; Sadiq et al., 2019). Recently developed gynoecious cucumber hybrids are promising for quality and yield in open fields and greenhouses (Kumar et al., 2016; More, 2002).

Commercialization of cucumber production through protected cultivation and the use of high yielding gynoecious hybrid varieties, tolerant to diseases, and have a short maturity time are necessary to fulfil demand of fresh cucumber. To reduce the import of hybrid seeds, it is necessary to develop hybrid varieties having a local taste and suitable for the climatic conditions of Nepal. The Horticulture Research Division has collected gynoecious lines from India and started hybridization in cucumber and developed some hybrids (HRD, 2018). Before being acceptable for commercial cultivation of such gynoecious hybrids, it is crucial to evaluate the production potential based on growth, earliness, yield and quality for a particular location. A promising cultivar would be a compromise between fresh yield and commercial quality traits (color, size, texture and shelf life) to satisfy the demands of the local market (Kumar et al., 2019). Therefore, this experiment was conducted to evaluate the growth and yield performance of different cucumber genotypes under open field and plastic house conditions.

2. Materials and methods

2.1. Location and site of experiment

This experiment was conducted at the National Horticulture Research Centre (NHRC), Nepal Agricultural Research Council (NARC), Khumaltar, Lalitpur, Nepal. Geographically, Khumaltar (27° 67’ N latitude and 85° 31’ E longitude) is located in the hilly region of Nepal with a subtropical climate at an altitude of 1365 m above sea level (Figure 1). The average temperature of plastic house and open field conditions during the research period was 23.2 °C (maximum 31.1 °C and minimum 16.2 °C) and 19.7 °C (maximum 25.7 °C and minimum 13.7 °C), respectively. Similarly, an average relative humidity of 80.32% and 76.6% was observed during the research period under plastic house and open field conditions, respectively (Appendices 1 and 2). The total rainfall reported during the research period (Feb, 2019–July, 2019) was 825.70 mm.

Figure 1. Map of the study area.

2.2. Design of experiment

The experiment was arranged in a two-factor randomized complete block design with fourteen treatment combinations which were replicated three times (Appendix 3). The first factor consisted of the seven genotypes (Bhaktapur Local, HRDCUC-004 × HRDCUC-001, HRDCUC-004 × HRDCUC-003, HRDCUC-006 × HRDCUC-001, HRDCUC-006 × HRDCUC-003, HRDCUC-009 × HRDCUC-001, HRDCUC-009 × HRDCUC-003) and the second factor consisted of growing conditions (open field and plastic house) (Table 1).

Table 1. Details of genotypes and growing conditions.

S.N		Treatments	Treatment details
Genotypes
1	G1	Bhaktapur Local (check)	OP (best commercial variety)
2	G2	HRDCUC-004 × HRDCUC-001	Gynoecious hybrid developed by HRD
3	G3	HRDCUC-004 × HRDCUC-003	Gynoecious hybrid developed by HRD
4	G4	HRDCUC-006 × HRDCUC-001	Gynoecious hybrid developed by HRD
5	G5	HRDCUC-006 × HRDCUC-003	Gynoecious hybrid developed by HRD
6	G6	HRDCUC-009 × HRDCUC-001	Gynoecious hybrid developed by HRD
7	G7	HRDCUC-009 × HRDCUC-003	Gynoecious hybrid developed by HRD
Growing conditions
1		C1	Open field (OF)
2		C2	Plastic house (PH)

OP: Open Pollinated; HRD: Horticulture Research Division.

2.3. Seedling raising and transplanting

Seeds of all genotypes were collected from the NHRC, Khumaltar, Lalitpur, Nepal. Seeds were sown in a polybag on 13th February, 2019 for both growing conditions. Twenty-five days old seedlings with one true and two cotyledon leaves were manually transplanted in a plot of 10.2 m² accommodating 12 plants per plot (4 plants in 3 rows) at a spacing of 1 m × 0.85 m. Gap filling was carried out within a week after transplanting.

2.4. Field preparation and fertilizer application

The experimental field was prepared by deep plowing with 3 cross harrowing followed by leveling 1 week before transplanting. The recommended doses of farmyard manure (FYM), a locally available animal manure, @30 t ha⁻¹, inorganic fertilizer @140 N: 40 P: 100K kg ha⁻¹, mustard oilcake @100 kg ha⁻¹, bonemeal @100 kg ha⁻¹, zinc @5 kg ha⁻¹, borax @5 kg ha⁻¹, and biozyme @5 kg ha⁻¹ were applied (HRD, 2018). All the FYM, phosphorus, potash, oilcake, bonemeal, micronutrients and half of the nitrogen was applied in a pit before transplanting while the remaining half dose of nitrogen were top dressed in 3 splits at a 20 day interval after transplanting.

2.5. Plastic house details

A top vent naturally ventilated plastic house with a length of 25 m and a breadth of 12 m was constructed. The centre height of the plastic house was 5 meters and side height was 4 meters. The permanent plastic house was made up of galvanized iron pipes, the roof was fully covered with UV stabilized low density polyethylene film of 200 microns having a thickness of 90 GSM and four sides of the plastic house were covered with a insect-proof net of mesh size 1.3 mm × 1.3 mm.

2.6. Cultural management practices

Irrigation, weeding, hoeing and staking were carried out uniformly. Irrigation was done at 3 days interval in plastic house conditions and 5 days interval in open field conditions up to 120 days after transplanting. Irrigation was done by the ring basin method. Shallow hoeing was done at the time of split application of nitrogen. First weeding was done at 30 DAT in plastic house and 20 DAT in open field conditions. Second and third weeding were done at a 20 day interval after the first weeding under both growing conditions. A vertical frame made up of bamboo poles connecting an overhead system consisting of plastic ropes spaced 15 cm apart was used to train the vine at 15 days after transplanting. Three branches per plant were maintained and each branch was trained upward to the frame by using the plastic rope. The incidence of insect pests and diseases was not severe in all genotypes under both growing conditions. One melon fruit fly pheromone trap was installed for 50 m² land.

2.7. Observation taken

2.7.1. Growth and yield

Data were obtained from randomly selected 4 plants from the middle rows for the vegetative, flowering and yield parameters. Five fruits were randomly selected from each treatment for recording observations on fruit characters. Observations were recorded on vine length, number of nodes vine⁻¹, internodal length, node number bearing first female flower, days to first harvest, fruit length, fruit diameter, fruit weight, number of fruits per plant, yield per plant, and adjusted yield per hectare. Vine length was measured from the collar region to the growing point of the middle vine at the final harvest. The total number of nodes per vine was counted from the primary vine which was also used for measuring vine length. Ten internodes were selected randomly from the base, middle and tip of sample plants and measured by scale. Node number at which the first female flower appeared on selected plants of each experimental unit was counted and days to first harvest from transplanting was also counted. Fruit weight, fruit length and fruit diameter were recorded by using a digital weighing balance, scale, and vernier caliper, respectively. Number of fruits per plant and yield per plant were determined from each sample plant on each harvest. Actual yield was converted to yield per hectare.

2.7.2. Consumer’s acceptability

Consumer’s acceptability of cucumber genotypes was tested by 10 panellist scientists from different divisions of NARC. The sensory parameters like; color, appearance and taste were evaluated using a hedonic rating method 1–9 (1 = dislike extremely, 2 = dislike very much, 3 = dislike moderately, 4= dislike slightly, 5 = neither like nor dislike, 6 = like slightly, 7 = like moderately, 8 = like very much, 9 = like extremely) in which 1 indicates poor and 9 the excellent performance (Lim, 2011). Overall acceptability was formed based on total perception but not as a mean from the evaluation of individual sensory parameters.

2.7.3. Economic analysis

The cost of cultivation of cucumber genotypes under the plastic house and the open field was estimated. The variable cost of inputs and labor costs were estimated and the fixed cost for the plastic house along with its depreciated cost was also estimated. Gross return, net return and benefit-cost ratio (BCR) were calculated based on yield of different genotypes under different growing conditions and the mean market price of cucumber during the entire research period. $$\begin{array}{c}\begin{array}{c}\text{Net Return\hspace{0.05em}\hspace{0.33em}}\left(\text{million}/\text{ha}\right)=\hspace{0.17em}\text{\hspace{0.33em}Yield \hspace{0.33em}}\left(\text{t}\hspace{0.17em}{\text{ha}}^{-1}\right)\times \hspace{0.17em}\text{\hspace{0.33em}Unit\hspace{0.33em} price\hspace{0.33em}}\hspace{0.17em}\left(\text{Rs.}\right)\\ \text{Gosss Return \hspace{0.33em}}\left(\text{million}/\text{ha}\right)\hspace{0.17em}=\hspace{0.17em}\text{\hspace{0.33em}Net\hspace{0.33em} return}\hspace{0.17em}-\hspace{0.17em}\text{Cost \hspace{0.33em}of \hspace{0.33em}cultivation}\end{array}\\ \text{BCR\hspace{0.33em}}\hspace{0.17em}=\hspace{0.17em}\text{\hspace{0.33em}Gross return}/\mathrm{C}\text{ost \hspace{0.33em}of \hspace{0.33em}cultivation}\end{array}$$

2.8. Statistical analysis

The recorded data were analyzed using statistical software Genstat for Teaching and Learning (18th edition). Least Significant Difference (LSD) Test was used for mean separation.

3. Results

The performance of different genotypes of cucumber under plastic house and open field conditions was evaluated. The interaction effect and main effect were studied and found statistically significant results on various parameters (Appendix 4–7).

3.1. Effect of genotypes and growing conditions on vegetative parameters

The maximum vine length was observed in genotype Bhaktapur Local (4.36 m) followed by HRDCUC-009 × HRDCUC-001 (4.03 m) grown under plastic house. However, the lowest vine length was observed in genotype HRDCUC-006 × HRDCUC-003 (2.58 m) grown in open field conditions. The number of nodes per vine is also an important character, which indicates the growth of crop plants and their potential for bearing flowers and fruits. The highest number of nodes per vine was found in genotype Bhaktapur Local grown under plastic house (44.11) and open field (43.17) conditions. The lowest number of nodes per vine was observed in genotype HRDCUC-009 × HRDCUC-003 (29.74) grown in open field conditions. The highest internodal length was found in genotype HRDCUC-009 × HRDCUC-003 grown under plastic house (12.73 cm) followed by the same genotype grown in open field conditions (12.23 cm). Bhaktapur Local showed significantly lower internodal length in open field conditions (9.42 cm) (Table 2).

Table 2. Interaction effect of genotypes and growing conditions on vine length, number of node per vine and internodal length.

Genotypes	Vine length (m)		Number of nodes per vine		Internodal length (cm)
	Open field	Plastic house	Open field	Plastic house	Open field	Plastic house
Bhaktapur Local	3.92^f	4.36^g	43.17^h	44.11^h	9.42^a	11.17^g
HRDCUC-004 × HRDCUC-001	3.16^b	3.43^ce	32.45 ^cd	36.74^f	10.50 ^cd	10.73^de
HRDCUC-004 × HRDCUC-003	3.00^b	3.10^b	30.10^ab	32.37^bcd	11.00^fg	11.10^fg
HRDCUC-006 × HRDCUC-001	2.73^a	3.20^bcd	29.90^a	31.24^abc	9.80^b	11.17^g
HRDCUC-006 × HRDCUC-003	2.58^a	3.20^bc	30.25^abc	35.55^ef	9.67^ab	9.91^b
HRDCUC-009 × HRDCUC-001	3.51^e	4.03^f	39.00^g	41.06^g	10.27^c	10.97^ef
HRDCUC-009 × HRDCUC-003	3.14^b	3.9^f	29.74^a	34.23^de	12.23^h	12.73^i
F-Test	**		*		**
LSD	0.22		2.09		0.25
SEM	0.07		0.72		0.08
CV (%)	4.0		3.6		1.4

Means separation in column followed by the same letters are not significantly different at p = 0.05, *= significant, **highly significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

3.2. Effect of genotypes and growing conditions on reproductive parameters

The lowest node bearing first female flower was observed in genotype HRDCUC-006 × HRDCUC-001 (5.83) followed by genotype HRDCUC-006 × HRDCUC-003 (6.7). In all hybrids, the female flower appears in the earliest node as compared to the open-pollinated genotype Bhaktapur Local (10.83). First female flower was observed at the lowest node number (7.04) in the open field as compared to the plastic house (8.09) (Table 3).

3.3. Effect of genotypes and growing conditions on days to harvest

Among different genotypes, days to first harvest was observed for genotype HRDCUC-006 × HRDCUC-001 (49.17 DAT) while the later days to fruit harvest was found in genotype Bhaktapur Local (62.92 DAT). The result revealed that days to first harvest was earlier in all hybrid genotypes tested as compared to check variety. Among growing conditions, the earliest days to first harvest was obtained in plastic house (50.79 DAT) as compared to open field conditions (56.50 DAT) (Table 3).

Table 3. Effect of genotypes and growing conditions on node number bearing 1st female flower and days to first harvest.

Treatment	Node number bearing first female flower	Days to first harvest
Genotypes
Bhaktapur Local	10.83^d	62.92^e
HRDCUC-004 × HRDCUC-001	7.16^bc	52.00^bc
HRDCUC-004 × HRDCUC-003	7.66^c	53.83^d
HRDCUC-006 × HRDCUC-001	5.83^a	49.17^a
HRDCUC-006 × HRDCUC-003	6.66^b	52.75 ^cd
HRDCUC-009 × HRDCUC-001	7.66^c	51.00^b
HRDCUC-009 × HRDCUC-003	7.16^bc	53.83^d
F-test	**	**
LSD	0.75	1.16
SEM	0.25	0.39
Growing conditions
Open field (OF)	7.04^a	56.50^b
Plastic house (PH)	8.09^b	50.79^a
F-test	**	**
LSD	0.40	0.62
SEM	0.13	0.21
Genotypes × Growing conditions
F-test	NS	NS
CV (%)	8.4	1.8

Means separation in column followed by the same letters are not significantly different at p = 0.05, **= highly significant, NS = Non-significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

3.4. Effect of genotypes and growing conditions on yield and yield attributing traits

The longest fruit length was observed in genotype HRDCUC-009 × HRDCUC-003 (31.62 cm) followed by genotype HRDCUC-004 × HRDCUC-003 (29.76 cm). However, the shortest fruit length was obtained from genotype HRDCUC-006 × HRDCUC-001 (23.85 cm) which was at par with HRDCUC-004 × HRDCUC-001 (23.92 cm) and HRDCUC-009 × HRDCUC-001 (24.28 cm). Among tested genotypes, the highest fruit diameter was observed in genotype Bhaktapur Local (66.01 mm) while the lowest fruit diameter was observed in genotype HRDCUC-006 × HRDCUC-001 (58.28 mm). Fruit weight is another important characteristic governing the yield of cucumber. The highest fruit weight was observed in genotype Bhaktapur Local (611.7 g) which was at par with genotype HRDCUC-009 × HRDCUC-003 (605.1 g). The lowest fruit weight was obtained in genotype HRDCUC-006 × HRDCUC-001 (394.5 g). However, the result showed that fruit length, fruit diameter, and fruit weight do not differ significantly under two growing conditions (Table 4).

Table 4. Effect of genotypes and growing conditions on fruit length, fruit girth and fruit weight.

Treatment	Fruit length (cm)	Fruit girth (mm)	Fruit weight (g)
Genotypes
Bhaktapur Local	27.98^b	66.01^d	611.7^e
HRDCUC-004 × HRDCUC-001	23.92^a	61.47^c	463.8^b
HRDCUC-004 × HRDCUC-003	29.76^c	59.74^ab	550.1^d
HRDCUC-006 × HRDCUC-001	23.85^a	58.28^a	394.5^a
HRDCUC-006 × HRDCUC-003	28.05^b	60.23^bc	515.9^c
HRDCUC-009 × HRDCUC-001	24.28^a	59.35^ab	457.7^b
HRDCUC-009 × HRDCUC-003	31.62^d	61.33^c	605.1^e
F-test	**	**	**
LSD	1.05	1.44	14.78
SEM	0.36	0.39	5.08
Growing conditions
Open field (OF)	27.21	61.29	516.8
Plastic house (PH)	26.93	60.54	511.4
F-test	NS	NS	NS
LSD	0.56	0.77	7.90
SEM	0.19	0.26	5.08
Genotypes × Growing conditions
F-test	NS	NS	NS
CV (%)	3.3	2	2.4

Means separation in column followed by the same letters are not significantly different at p = 0.05, **= highly significant, NS = Non-significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

The number of fruits per plant is one of the most important yields attributing characteristics of cucurbits. Significantly more fruits per plant was found in genotype HRDCUC-004 × HRDCUC-001 (28.33) grown under plastic house, however, the lowest number of fruits was found in genotype Bhaktapur Local grown in open field conditions (7.67). Genotype HRDCUC-004 × HRDCUC-001 resulted in a higher number of fruits in both growing conditions. The highest yield per plant was observed in genotype HRDCUC-004 × HRDCUC-001 (12.43 Kg) followed by genotype HRDCUC-009 × HRDCUC-003 (11.85 Kg) grown under the plastic house conditions. Similarly, the lowest yield per plant was observed in genotype HRDCUC-006 × HRDCUC-001 (3.82 Kg) which was at par with Bhaktapur Local (3.98 Kg) grown in open field conditions. Similarly, the results revealed that the highest yield per hectare was obtained from genotype HRDCUC-004 × HRDCUC-001 (117.0 t ha⁻¹) grown under plastic house conditions. The lowest fruit yield per hectare was obtained from genotype HRDCUC-006 × HRDCUC-001 (35.9 t ha⁻¹) followed by Bhaktapur Local (37.5 t ha⁻¹) grown in open field conditions (Table 5).

Table 5. Interaction effect of genotypes and growing conditions on number of fruits per plant, yield per plant and adjusted yield per hectare.

Genotypes	Number of fruits per plant		Yield per plant (Kg)		Adjusted yield (t ha^-1)
	Open field	Plastic house	Open field	Plastic house	Open field	Plastic house
Bhaktapur Local	7.67^a	10.67^b	3.98^a	6.10^de	37.5^a	57.4^de
HRDCUC-004 × HRDCUC-001	13.67^c	28.33^f	6.16^e	12.43^k	58.0^e	117.0^k
HRDCUC-004 × HRDCUC-003	10.33^b	21.67^e	5.36^c	11.36^i	50.4^c	106.9^i
HRDCUC-006 × HRDCUC-001	10.33^b	17.67^d	3.82^a	6.80^f	35.9^a	64.0^f
HRDCUC-006 × HRDCUC-003	10.33^b	20.67^e	5.21^bc	10.35^h	49.1^bc	97.4^h
HRDCUC-009 × HRDCUC-001	11.33^b	20.33^e	4.94^b	9.15^g	46.5^b	86.1^g
HRDCUC-009 × HRDCUC-003	10.00^b	20.33^e	5.78^d	11.85^j	54.4^d	111.5^j
F-Test	**		**		**
LSD	1.39		0.34		3.288
SEM	0.47		0.12		1.13
CV (%)	5.4		2.8		2.8

Means separation in column followed by the same letters are not significantly different at p = 0.05, **= highly significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

3.5. Effect of genotypes and growing conditions on quality parameters

Based on the evaluation of perception of color, appearance and taste (Appendix 8), the overall acceptability of consumers on different genotypes was computed. The result revealed that overall acceptability was higher in genotype Bhaktapur Local (7.8) followed by HRDCUC-004 × HRDCUC-001 (7.2) which was at par with HRDCUC-004 × HRDCUC-003 (7) and HRDCUC-009 × HRDCUC-003 (7). Likewise, the lowest score on overall acceptability was recorded from genotype HRDCUC-009 × HRDCUC-001(6.4) followed by genotype HRDCUC-006 × HRDCUC-001 (6.6) (Figure 2).

Figure 2. Hedonic rating (1–9) for overall acceptability of cucumber genotypes.

3.6. Economic analysis of cucumber production

Based on the economic analysis (Appendix 9–11 and Table 6), the highest gross return ($ 39350) and net return ($ 26220) per hectare was obtained from genotype HRDCUC-004 × HRDCUC-001 grown under plastic house conditions and the lowest gross return ($ 12090) and net return ($ 3450) per hectare was obtained from genotype HRDCUC-006 × HRDCUC-001 grown in open field conditions. Cucumber genotypes HRDCUC-004 × HRDCUC-001 cultivated in a plastic house had the highest benefit-cost ratio (2.99:1) followed by HRDCUC-009 × HRDCUC-003 (2.85:1) under the same growing conditions. However, genotype HRDCUC-006 × HRDCUC-001 grown under open field conditions resulted in the lowest benefit-cost ratio (1.40:1) followed by the same genotype grown under plastic house conditions (1.63:1).

Table 6. Interaction effect of genotypes and growing conditions on gross return, net return and benefit-cost ratio (BCR).

Genotypes	Gross return per hectare ($ thousands)		Net return per hectare ($ thousands)		BCR
	Open field	Plastic house	Open field	Plastic house	Open field	Plastic house
Bhaktapur Local	20.60^ef	31.52^h	12.07^f	18.49^h	2.41^g	2.41^g
HRDCUC-004 × HRDCUC-001	19.51^e	39.35^l	10.87^e	26.22^k	2.25^f	2.99^j
HRDCUC-004 × HRDCUC-003	16.97^c	35.97^j	8.34^c	22.84^i	1.96^d	2.73^h
HRDCUC-006 × HRDCUC-001	12.09^a	21.52^f	3.45^a	8.38^c	1.40^a	1.63^b
HRDCUC-006 × HRDCUC-003	16.50^bc	32.76^i	7.86^bc	19.62^h	1.91 ^cd	2.49^g
HRDCUC-009 × HRDCUC-001	15.64^b	28.99^g	7.00^b	15.84^g	1.81^c	2.20^ef
HRDCUC-009 × HRDCUC-003	18.30^d	37.52^k	9.66^d	24.38^j	2.11^e	2.85^i
F-Test	**		**		**
LSD	0.12		0.12		0.10
SEM	0.04		0.04		0.03
CV (%)	2.8		5.0		2.8

Means separation in column followed by the same letters are not significantly different at p = 0.05, **= highly significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

4. Discussion

The performance of gynoecious cucumber hybrids under plastic house conditions was found promising as compared to open pollinated variety due to their higher yield, earlier harvesting, greater number of female flowers, shorter vine length, and resistance to diseases (Kumar et al., 2016; Kumar et al., 2019; Gautam et al., 2021). The variation in vine length of genotypes under two growing conditions might be due to differences in growth habits, climatic factors and nutrient status of the soil and available metabolites and their allocation to different parts of the plant. Plant height is a function of the number of nodes and length of each internode (Chaudhari et al., 2016) and both are strongly influenced by temperature. Under the plastic house, plants received comparatively lower light intensity than the open conditions thereby facilitating cell elongation and increasing internodal length leading to an increase in plant height (Hamid et al., 2002). Similar results on vine length of cucumber genotypes grown in open field and plastic house were also found by Pandey (2002). The internodal length determines the height and number of nodes per plant. The parthenocarpic gynoecious cucumber hybrids bear fruits at almost every node. Therefore, plants with shorter internodal length and a higher number of nodes are desired for getting higher yields (Rawat et al., 2014). In cucumber, the number of nodes per vine and internodal length are directly proportional to vine length. Kumar et al. (2019) also reported a positive correlation between node number per vine and final vine length. The number of nodes per vine is a genetic characteristic and is also governed by the surrounding microclimatic conditions. Similar findings on the number of nodes per plant were also reported by Bhagwat et al. (2018) and Kumar et al. (2019). The higher number of nodes per plant under the plastic house might be due to optimum light intensity, relative humidity and temperature.

The variation in node number bearing first female flower might be due to the different genetic constitutions of different genotypes. Node bearing first female flower is an important genetic parameter that governs the yield of cucumber. Similar variations in node number bearing first female flower were also reported by Yadav et al. (2012) and Gautam et al. (2021). Jat et al. (2015), reported that the appearance of the first female flower at an early node is a good character in cucumber. The prevailing high temperature inside the plastic house altered the sex expression resulting in the appearance of the first female flower on a higher node inside the plastic house as compared to the open field. Similar results on node number bearing first female flower in open field and plastic house conditions was also reported by Pandey (2002) and Gautam et al. (2008). The variation among genotypes for days to first harvest was due to genetic factors along with temperature and day length which are in accordance with the findings of Sharma and Bhattarai (2006), Patel et al. (2013) and Gautam et al. (2021). Badgujar and More (2004) and Kumar et al. (2017), also reported the early picking of some cucumber cultivars under testing. The earlier harvest in plastic house conditions might be attributed to enhanced plant metabolic activities like photosynthesis and respiration due to the favourable microclimatic conditions. The accumulation of maximum photosynthates promotes rapid plant growth, which results in the early initiation of flowering under the plastic house. A similar result was recorded on days to first harvest of cucumber genotypes under plastic house conditions by Gautam et al. (2008).

Fruit length is also a major contributing factor to yield and generally consumers prefer medium sized, straight, cylindrical shaped and tender fruits for fresh consumption. Similar genetic variations concerning fruit length were also reported by Kumar et al. (2008) and Gautam et al. (2021). Among different genotypes, significant variations in fruit length might be due to genetic nature, hormonal factors, the vigour of the crop and environmental conditions. Gautam et al. (2008), also reported that there was no variation in fruit length under different growing conditions. Fruit diameter is one of the major yield determining as well as quality traits of fruits. Fruits having a smaller diameter are preferred the most, whereas, fruits having a larger diameter generally lead to carpel separation, which deteriorates the fruits quality and is also not preferred by consumers. A significant variation in fruit diameter might be due to the genetic nature of the genotype, hormonal factors and vigour of the crop. Similar results regarding fruit diameter among different genotypes were also reported by Kumar et al. (2013) and Ranjan et al. (2015). The role of growing conditions on the fruit diameter of cucumber was not observed by Gautam et al. (2008) and only genetic factors might have contributed to fruit diameter. The variation in the fruit weight of different genotypes is mainly due to the genetic characteristics of the genotype. Fruit length also governs the individual fruit weight of the cucumber. The finding of this research is in line with Shah et al. (2016). However, the present research is in contrast with Gautam et al. (2021) who reported the highest fruit weight in hybrid genotype (HRD CUM 009 x 003) which might be due to differences in the genetic characteristics of the genotype and growing conditions. The results also contradict the findings of Pandey (2002), who recorded significant differences in fruit weight under two growing conditions. The variations in the result might be due to differences in the genotypic makeup of tested varieties and the environmental factors of the two research sites.

The synthesis of a higher level of auxin and a lower level of abscisic acid in gynoecious hybrids along with more accumulation of photosynthates in leaves and their mobility to developing fruits in protected structure ultimately favoured more fruit set and increased the number of fruits per vine. Plant height, male to female ratio, vine length and first female flowering node primarily determine the number of fruits per plant (Gautam et al., 2021). These results were in accordance with the findings of Kumar et al. (2017), Nagamani et al. (2019), and Gautam et al. (2021). Fruit yield is directly governed by certain yield attributing traits like number of fruits per vine and individual fruit weight which may vary depending upon the genetic potential of the variety and growing environment (Kumar & Chauhan 2017). The present finding is in conformity with the findings of Bisht et al. (2011) and Chaudhari et al. (2016) on polyhouse cucumber. Fruit yield per plant had a phenotypic and genotypic significant positive correlation with major yield attributing characters such as the length of vine, number of fruits per vine, fruit length, fruit diameter and average fruit weight (Karthick et al., 2019; Kumar et al., 2019). Similar results on yield per plant were recorded by Gautam et al. (2021), Gautam et al. (2008), and Pandey (2002), while comparing the performance of cucumber genotypes under open field conditions and plastic house conditions.

Higher yield per hectare in most of the hybrid genotypes as compared to open pollinated variety could be attributed to the higher number of fruits per vine, a longer fruit and a larger diameter. Gangadhara et al. (2019) reported that yield and yield attributing characters are governed by genetic factors with high heritability. The result shows that cucumber yield per hectare was almost double in the plastic house as compared to open field conditions. Similar results on a higher yield of different cucumber hybrids grown under protected structures were recorded by Dingal et al. (2018) and Gautam et al. (2021). The findings of this research are also in accordance with Pandey (2002) and Gautam et al. (2008). Besides yield, emphasis should be given to physical appearance and quality parameters for the adaptation of new hybrid varieties. In eastern Nepal, where the majority of Gurung and Tamang communities live, dark green cucumbers with a mealy and soft taste are most preferred while in other parts of the country, light green cucumbers with a mealy and soft taste are most preferred (Gautam et al., 2021). The present result indicated that the overall acceptability of some hybrid genotypes was similar to Bhaktapur Local. In addition to this, in the past years, farmers emphasized producing larger sized fruits, but now, consumers prefer medium sized fruits (350–500 g) with more than 15 cm long and 5–6 cm diameter (Gautam et al., 2021). In the present study, a suitable size of fruits was observed in genotype HRDCUC-004 × HRDCUC-001 along with some other hybrids. The higher benefit-cost ratio of different cucumber genotypes under plastic house conditions as compared to open field conditions was due to the higher net and gross returns. Similar results on the benefit-cost ratio were recorded by Gautam et al. (2008).

5. Conclusion

In conclusion, the performance of cucumber genotypes differs significantly for growth and yield parameters under plastic house and open field conditions. Considering yield and yield attributing traits, genotype HRDCUC-004 × HRDCUC-001 was found to be promising under both open field and plastic house. Due to the superior performance of cucumber genotypes under plastic house, the off-season production of cucumbers under plastic houses could be a highly profitable and remunerative enterprise for the farmers of the mid-hills of Nepal. In the future, emphasis should be given to further breeding works to improve the qualitative traits of genotype HRDCUC-004 × HRDCUC-001.

Acknowledgements

The authors would like to acknowledge NARC for financial and materialistic support.

Disclosure statement

Authors have no conflicts of interest to disclose.

Additional information

Notes on contributors

Sujan Subedi

Sujan Subedi is a technical officer at the National Horticulture Research Center under the Nepal Agricultural Research Council (NARC), Lalitpur, Nepal. Mr. Subedi has been actively involved in various research activities related to horticulture with a strong passion for vegetable breeding for six years. Throughout his career, Mr. Subedi has published more than ten research articles and three technical booklets in various areas of horticulture. His area of research interest includes breeding of horticultural crops, crop management, plant propagation, and postharvest management.

Nirajan Bhandari

Nirajan Bhandari is a distinguished Assistant Professor at the prestigious Agriculture and Forestry University in Nepal. With an unwavering passion for horticulture, he actively engages in teaching and cutting-edge research activities under the department of Horticulture. Mr. Bhandari proudly boasts a wealth of teaching and research experience spanning over five years. Throughout his career, Mr. Bhandari has published more than fifteen research articles and technical papers in various areas of Horticulture, garnering him immense recognition and acclaim as a leading authority in his field. His area of research interest includes precision and protected cultivation, plant propagation, and postharvest management, where he has demonstrated exceptional expertise and insight.

Manoj Basnet

Manoj Basnet is currently an assistant professor at the Department of Horticulture, Institute of Agriculture and Animal Science, Tribhuvan University, Nepal. Mr. Basnet has more than ten years of teaching and research experience in the field of horticulture. He has published more than twenty research articles in various areas of horticulture.

Navin Gopal Pradhan

Navin Gopal Pradhan is a senior horticulturist at the National Horticulture Research Center under NARC, Lalitpur, Nepal. Mr. Pradhan has been actively involved in various varietal development projects and has developed different popular varieties of vegetables. He has published more than twenty-five research articles and booklets in various areas of horticulture.

Ishwori Prasad Gautam

Dr. Ishwori Prasad Gautam is a principal scientist and chief of the National Horticulture Research Center under NARC, Lalitpur, Nepal. Dr. Gautam has more than thirty-five years of research experience in the field of horticulture. His major contributions are plastic house technology for offseason vegetable production, the development of various varieties of vegetables, and postharvest management of fruits and vegetables. Dr. Gautam has published more than fifty research articles, technical booklets, and conference papers and has participated in national and international seminars and workshops.

Appendix 1

Figure A1. Mean monthly temperature and RH of open field conditions during the research period at Khumaltar, Lalitpur.

Appendix 2

Figure A2. Mean monthly temperature and RH of plastic house conditions during the research period at Khumaltar, Lalitpur.

Appendix 3

Table A1. Combination of genotypes and growing conditions.

S.N	Treatment	Genotypes	Growing conditions	Combination
1	T1	Bhaktapur Local (G1)	OF (C1)	G1×C1
2	T2	HRD CUC 004 × HRD CUC 001 (G2)	OF (C1)	G2×C1
3	T3	HRD CUC 004 × HRD CUC 003 (G3)	OF (C1)	G3×C1
4	T4	HRD CUC 006 × HRD CUC 001 (G4)	OF (C1)	G4×C1
5	T5	HRD CUC 006 × HRD CUC 003 (G5)	OF (C1)	G5×C1
6	T6	HRD CUC 009 × HRD CUC 001 (G6)	OF (C1)	G6×C1
7	T7	HRD CUC 009 × HRD CUC 003 (G7)	OF (C1)	G7×C1
8	T8	Bhaktapur Local (G1)	PH (C2)	G1×C2
9	T9	HRD CUC 004 × HRD CUC 001 (G2)	PH (C2)	G2×C2
10	T10	HRD CUC 004 × HRD CUC 003 (G3)	PH (C2)	G3×C2
11	T11	HRD CUC 006 × HRD CUC 001 (G4)	PH (C2)	G4×C2
12	T12	HRD CUC 006 × HRD CUC 003 (G5)	PH (C2)	G5×C2
13	T13	HRD CUC 009 × HRD CUC 001 (G6)	PH (C2)	G6×C2
14	T14	HRD CUC 009 × HRD CUC 003 (G7)	PH (C2)	G7×C2

OF: Open field condition (C₁); PH: Plastic house condition (C₂); G₁….G₇: Genotypes.

Appendix 4

Table A2. Analysis of variance of genotypes and growing conditions on vine length, number of nodes per vine and internodal length.

Source of variation	df	Vine length		Number of nodes per vine		Internodal length
		MS	F value	MS	F value	MS	F value
Replication	2	0.01	1.02	0.94	0.60	0.17	7.92
Genotype	6	1.28**	69.0	147.40**	94.27	4.35**	193.07
Growing condition	1	2.16**	116.1	91.76**	58.68	4.92**	218.50
Genotype x Growing condition	6	0.07**	3.8	4.38*	2.80	0.59**	26.54
Residual	26	0.01		1.56		0.22
Total	41

**Significant at P ≤ 0.01; *Significant at P ≤ 0.05, df = degree of freedom, MS = Treatment mean square.

Appendix 5

Table A3. Analysis of variance of genotypes and growing conditions on node number bearing first female flower and days to first harvest.

Source of variation	df	Node number bearing first female flower		Days to first harvest
		MS	F value	MS	F value
Replication	2	0.07	0.18	2.64	2.76
Genotype	6	14.82**	36.63	116.59**	121.84
Growing condition	1	11.52**	28.47	342.85**	358.28
Genotype x Growing condition	6	0.52 ^ns	1.29	2.00 ^ns	2.10
Residual	26	0.10		0.95
Total	41

**Significant at P ≤ 0.01; ns, not significant, df = degree of freedom, MS = Treatment mean square.

Appendix 6

Table A4. Analysis of variance of genotypes and growing conditions on fruit length, fruit girth, and fruit weight.

Source of variation	df	Fruit length		Fruit girth		Fruit weight
		MS	F value	MS	F value	MS	F value
Replication	2	1.19	1.53	0.80	0.54	140.7	0.91
Genotype	6	57.79**	73.84	37.73**	25.55	39147.6**	252.49
Growing condition	1	0.84 ^ns	1.08	5.89 ^ns	3.99	316.6 ^ns	2.04
Genotype x Growing condition	6	0.93 ^ns	1.20	2.00 ^ns	1.36	247.5 ^ns	1.60
Residual	26	0.78		1.47		155.0
Total	41

**Significant at P ≤ 0.01; ns, not significant, df = degree of freedom, MS = Treatment mean square.

Appendix 7

Table A5. Analysis of variance of genotypes and growing conditions on number of fruits per plant, yield per plant and yield ton per hectare.

Source of variation	df	Number of fruits per plant		Yield per plant		Adjusted yield (t ha^-1)
		MS	F value	MS	F value	MS	F value
Replication	2	0.38	0.55	0.00	0.13	0.00	0.00
Genotype	6	72.60**	105.43	16.73**	386.32	1482.40**	386.32
Growing condition	1	933.42**	1355.46	230.34**	5317.81	20405.70**	5318.81
Genotype x Growing condition	6	19.65**	28.54	4.02**	93.01	356.89**	93.01
Residual	26	0.68		0.04		3.83
Total	41

**Significant at P ≤ 0.01, df = degree of freedom, MS = Treatment mean square.

Appendix 8

Table A6. Performance of different cucumber genotypes for color, appearance and taste.

Treatment	Color (1–9)	Appearance (1–9)	Taste (1–9)
Bhaktapur Local	7.6^c	7.4^c	7.6^c
HRDCUC-004 × HRDCUC-001	7.0^bc	6.6^b	6.8^ab
HRDCUC-004 × HRDCUC-003	5.8^a	5.6^a	7.4^bc
HRDCUC-006 × HRDCUC-001	6.4^ab	6.8^bc	6.4^a
HRDCUC-006 × HRDCUC-003	6.6^b	6.4^b	6.6^a
HRDCUC-009 × HRDCUC-001	5.8^a	5.6^a	6.4^a
HRDCUC-009 × HRDCUC-003	6.6^b	6.8^bc	7.0^abc
F-test	**	**	**
LSD	0.70	0.67	0.72
SEM	0.24	0.22	0.25
CV%	8.4	8.1	8.1

Means separation in column followed by the same letters are not significantly different at p = 0.05, **= highly significant, SEM = Standard Error of Mean, LSD = Least Significant Difference, CV = Coefficient of Variation.

Appendix 9

Table A7. Analysis of variance of genotypes and growing conditions on gross returns, net returns, and benefit-cost ratio (BCR).

Source of variation	d.f	Gross returns		Net returns		BCR
		MS	F value	MS	F value	MS	F value
Replication	2	0.00	0.21	0.00	0.21	0.00	0.16
Genotype	6	1.29**	221.57	1.30**	222.14	0.82**	214.83
Growing condition	1	30.75**	5243.85	15.42**	2630.26	2.57**	666.88
Genotype x Growing condition	6	0.33**	56.60	0.33**	56.60	0.12**	33.60
Residual	26	0.005		0.005		0.003
Total	41

**Significant at P ≤ 0.01, df = degree of freedom, MS = Treatment mean square.

Appendix 10

Table A8. Construction cost of plastic house.

Particular	Unit	Quantity(m^2)	Cost/ha ($)
Galvanized frame (Avg. life 15 years)	1000/m^2	10000	90171.33
Plastic covering (Avg. life 15 year)	120/m^2	36000	38954.01
Insect proof net (Avg. life 15 year)	100/m^2	6600	5951.31
Total cost (15 year)			135076.65
Depreciated cost/year			9005.11
Depreciated cost/season (2 season per year)			4502.55

Appendix 11

Table A9. Production cost of cucumber per hectare for open field and plastic house.

Particular	Unit	Quantity	$/Unit	Hybrid		Bhaktapur Local
				Open	Plastic	Open	Plastic
Input Cost
Cocopeat (Block)	No.	10	4.51	45.09	45.09	45.09	45.09
Sand (Mini Truck)	Tailor	1	45.09	45.09	45.09	45.09	45.09
Seed	G	500	0.27	135.26	135.26	31.56	31.56
Polybag	Kg	60	2.71	162.31	162.31	162.31	162.31
Vermicompost	Kg	100	0.45	45.09	45.09	45.09	45.09
Polythene sheet	Kg	40	2.16	86.56	86.56	86.56	86.56
Fym	Ton	30	18.03	541.03	541.03	541.03	541.03
Mustard oil cake	Ton	1.2	405.77	486.93	486.93	486.93	486.93
Bone meal	Ton	1.2	586.11	703.34	703.34	703.34	703.34
DAP	Kg	87	0.54	47.07	47.07	47.07	47.07
Urea	Kg	270	0.32	87.65	87.65	87.65	87.65
MoP	Kg	166	0.81	134.72	134.72	134.72	134.72
Zinc + Borax + Biozyme	Kg	15	2.71	40.58	40.58	40.58	40.58
Fungicide	Kg	10	5.41	54.1	54.1	54.1	54.1
Insecticide	Litre	5	7.21	36.07	36.07	36.07	36.07
Vircon H	Litre	2	9.02	18.03	18.03	18.03	18.03
Micronutrient	Litre	2	4.51	9.02	9.02	9.02	9.02
Ploughing with tractor	Hour	2	18.03	36.07	36.07	36.07	36.07
Electricity for irrigation	Unit	200	0.14	27.05	27.05	27.05	27.05
Bamboo	No.	650	2.71	1758.34	1758.34	1758.34	1758.34
Rope	Kg	300	0.9	270.51	270.51	270.51	270.51
GI wire	Kg	200	1.35	270.51	270.51	270.51	270.51
Sum Input Cost (A)				5040.4	5040.4	4936.7	4936.7
Labour cost (B)
Nursery Preparation	MD	40	6.31	252.48	252.48	252.48	252.48
Bed Preparation	MD	120	6.31	757.44	757.44	757.44	757.44
Watering	MD	90	6.31	568.08	631.2	631.2	631.2
Weeding + top dressing	MD	80	6.31	504.96	441.84	441.84	441.84
Staking	MD	150	6.31	946.8	1009.92	1009.92	1009.92
Spraying	MD	30	6.31	189.36	189.36	189.36	189.36
Harvesting	MD	60	6.31	378.72	315.6	315.6	315.6
Sum Labour Cost (B)				3597.84	3597.84	3597.84	3597.84
Total Cost (A + B) ($)				8638.23	8638.23	8534.54	8534.54
Cost of Plastic house per season ($)				0	4502.55	0	4502.55
Grand Total Cost ($)				8638.23	13140.78	8534.54	13037.09