Heterosis and Combining Ability in Pumpkin Inbreds (Cucurbita moschata Duch. Ex Poir.)

Research Article

Austin J Plant Biol. 2022; 8(1): 1030.

Heterosis and Combining Ability in Pumpkin Inbreds (Cucurbita moschata Duch. Ex Poir.)

Shafin MS1, Parvin MS2,4*, Haque MDE3 and Akhter F2

¹Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh

²Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

³University of North Dakota, Grand Forks, USA

4Leibniz University Hannover, Germany

*Corresponding author: Most Shanaj Parvin, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh; Leibniz University Hannover, Germany

Received: December 14, 2021; Accepted: January 24, 2022; Published: January 31, 2022


Twenty hybrids along with five parents evaluated in the study were mainly contemplated to find out the best cross combinations and the best general and specific combiners as well as to estimate the nature and magnitude of the gene action for different qualitative traits. Using Griffin’s and Hayman’s approach through a 5 X 5 full diallel cross fashion, an investigation on heterosis and combining ability in pumpkin was undertaken following RCBD design with three replications at the experimental field. Both positive and negative significant GCA and SCA variances were obtained from few parents and hybrids. Predominance of additive-additive gene action was noted for most of the characters except hollowness and dry matter content, where additive-dominance gene action was predominant; flesh thickness and brix (%), where dominance- dominance gene action were predominant. A single parent was not found as good combiner for more than two characters. The best specific combiners were IBD 40 X IBD 47 for beta-carotene, total sugar and fruit yield; IBD23 X IBD40 for brix (%), hollowness and flesh thickness; IBD40 X IBD57 for fruit breadth; IBD47 X IBD50 for non-reducing sugar; and IBD47 X IBD57 for reducing sugar. The Vr- Wr graphs exhibited complete, partial and over dominance effect of genes for different characters. Complete dominance was observed only for beta-carotene whereas over dominance was noticed for hollowness and flesh thickness. Partial dominance was ensured for fruit breadth, dry matter, brix (%), reducing sugar, non-reducing sugar, total sugar and fruit yield. Significant heterosis of some crosses against mid parent and better parents were observed for some characters.


Pumpkin (Cucurbita moschata Duch. ex Poir.) is locally known, as ‘Misti kumra’ or ‘Mistilau’ or ‘Misti kudu’, is an important common vegetable in Bangladesh. Pumpkin originated in equatorial and sub-equatorial America [1]. It starts from Southern part of USA and continues up to Peru of South America. It grows throughout the entire tropical and sub-tropical regions of the world and milder areas of the temperate zones of hemispheres. It is widely cultivated in India, China, Malaysia, Taiwan, and Bangladesh. It is distributed widely in Southeast Asia, tropical Africa, tropical South and Central America (Peru and Mexico), the Caribbean and most part of tropics.

Pumpkin belongs to the family Cucurbitaceae. There are 27 species under the genus Cucurbita, five of which are in cultivation. These are C. moschata, C. maxima, C. ficifolia, C. pepo and C. mixta, commonly known as pumpkin. Pumpkin is highly cross-pollinated crop having chromosome number 2n=40. C. moschata is probably the most widely grown species of Cucurbita and this species is cross compatible with C. maxima, C. pepo and C. mixta. It is insectpollinated and 1000 m isolation distance is necessary to maintain purity of cultivars plants and vine crop. It is an annual crop having a climbing or trailing habit [2].

Pumpkin is relatively high in energy and carbohydrates and a good source of vitamins, especially high carotenoid pigments and minerals [3]. The nutrient per 100 g edible portions of fruit is cited in appendix 1. Night-blindness is a serious problem in Bangladesh, which happens due to vitamin A deficiency. It may certainly contribute to improve nutritional status of the people, particularly the vulnerable groups in respect of vitamin A requirement. Encouraging the mass people to take more pumpkin can easily be solved the problem. As a matter of fact, there is a program from Health Department to encourage feeding mature pumpkin to the children.

The delicate shoots and leaves are used as delicious vegetables. The fleshy large fruits can be consumed at mature and immature stages. It is one of the main vegetable in a wedding party or on other occasional party in northern India [4]. The sweet pie and pumpkin haluwa are the delicious items prepared from matured fruit [5]. The seed are very nutritious (it contains 40-50% oil and 30% protein) and eaten as food in many countries of the world [6].

The pumpkin has good medicinal value. It is used against many diseases like gonorrhea, urinary problem. The paste of the dried fruitstalk, which is in immediate contact with the ripe gourd, is used as the remedy for the bites of venomous insects of all kinds, especially for the centipedes [4].

It is a very common vegetable in Bangladesh and particularly popular among the rural people. It is grown round the year in our country. It becomes available even in the lean period when other vegetables are scarce in Bangladesh. It has the longest storability among all the cucurbits. The well-matured fruits (ripe fruits) can be stored for 2 to 4 months [7]. Due to its good taste and keeping quality, nutritional status, easier cooking quality, reasonable market price and year-round availability, its demand is increasing day by day in the country.

Vegetable production rate in Bangladesh is very low; yearly only 8.542 million M tones [8]. Vegetables consumption rate is 104 g per day per adult, against the optimum amount of about 300 g per day per adult [9]. The total area under cultivation of pumpkin is 27,935 ha with a total production of 2, 63, 000 MT having national average of 9.42 ton/ha in a year of this country [10].

The productivity of local genotypes ranged from 6.93 t/ha to 19.07 t/ha [11]. On the other hand, there are many exotic genotypes, which have short life cycle but high yield potential. Some of these exotic genotypes bear deep green long fruits, which are attractive. Flower buds of these genotypes appear 20 to 25 days earlier than the local genotypes. The exotic genotypes do not need big trellis because of their medium climbing habit. However, the exotic types are more susceptible to different virus diseases than the local genotypes. These variabilities among the indigenous and exotic genotypes are genetic attributes, which can be combined through hybridization to develop short vine type varieties with high yield, with smaller fruit type with high carotene content virus resistance and high number of female flowers. Being a cross-pollinated crop, it seems easy to transfer suitable traits by crossing appropriate genotypes of sweet gourd.

Though it is a very common crop, it may be mentioned that until to date there is no released variety of pumpkin with high yield potential and better nutritional quality. Further, a very limited attempt had been made for the genetic improvement of this crop, particularly with quality traits. An understanding of the nature and magnitude of variability among the genetic stocks is of prime importance to the breeder. Good knowledge of genetic resources might also help in identifying desirable cultivars for commercial cultivation. Because of its high cross-pollination, genetically pure strain is available hardly to the growers. Lack of high yielding, disease and pest tolerant variety is the main constraint towards its production. Among the cultivated landraces, a wide range of genetic variability exists in this crop that can be exploited for its improvement. It is the touchstone to a breeder to develop high-yielding varieties through selection, either from the existing genotypes or from the segregates of a cross. Hence, information on gene action, its nature and magnitude in respect of quality characters aspects is required to be properly assessed for its improvement.

Heterosis breeding is a potential tool to achieve improvement in the quality, quantity, and productivity of pumpkins [12]. Heterosis and combining ability is a powerful tool in identifying the best combiner that may be used in crosses either to exploit heterosis or to accumulate fixable gens and obtain desirable segregates. It will help to understand the genetic architecture of various characters that enable the breeder to design effective breeding plan for future up gradation of the existing materials. The information may also be useful to breeders for genetic improvement of the existing genotypes on the basis of performance in various hybrid combinations.

There have been not many studies on heterosis and combining ability of pumpkin in Bangladesh particularly with quality traits except Rana et al., [13]. Though pumpkin as a vegetable is becoming an important ingredient in daily diet, relatively little attention has been paid towards the development of hybrids/varieties, which are rich in beta-carotene with high Brix content; high reducing sugar with high yielding capacity. Therefore, considering the above facts the present investigation was carried out to achieve the following objectives:

• To identify potential parents and productive hybrids of pumpkin.

• To estimate the combining ability effects and variances for quality traits in pumpkin.

• To identify of best cross combination for higher yield and other quality characters.

• To estimate the heterosis against mid and better parents of different characters.

Materials and Methods

Experimental site

The experimental site is located at the centre of Modhupur tract (24.09o N latitude and 90.26o E longitude), which is 8.4 m above the sea level. It is about 40 km North of Dhaka, The site was previously under shal forest and developed later for research purpose.


The Experimental site is situated in the sub-tropical climate zone, characterized by heavy rainfall during the month of May to September and scanty rainfall during rest of the year. During crossing of parents, the average temperature, relative humidity and rainfall was 27.26 oC (max) and 18.18 oC (min), 85.03 % and 3.48 mm per month, respectively (Appendix 3). During studying combining ability of the parents and hybrids, the average temperature, relative humidity and rainfall was 28.05 oC (max) and 16.28 oC (min), 78.86 % and 26.31 mm per month, respectively.


The soil is terrace soil, which is nearly equivalent to Ochrept sub order of USDA soil taxonomy and belongs to the locally termed Salna series of Shallow Red Brown Terrace soil [14]. The soil is silt loam in texture having acidic (pH=5.5) in nature, poor fertility status, and impeded internal drainage.


Five (5) advanced Inbreds of pumpkin viz IBD 23, IBD 40, IBD 47, IBD 50 and IBD 57 developed by the GPB, BSMRAU was used in the study for combining ability analysis in a 5x5-diallel population. The Inbreds were synthesized in the previous year.

Design and layout

The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications.

Raising of seedlings

The seeds were sown in 9 cm x 15 cm sized polyethylene bags. Two seeds were sown in each bag. The growth medium was prepared by mixing compost and soil in 50:50 proportions. Intensive care was taken for production of healthy seedlings.

Preparation of land and pits

The experimental land was prepared by deep and cross ploughing and harrowing followed by laddering. The plots were raised 10 cm above the ground level. Pits of 50 x 50 x 50 cm size were dug at a spacing of 2 x 2 m.

Manure and fertilizer applied in each pit

Around 10 kg Cow dung, 52 g TSP, 60 g Urea and 40 g MP were applied in each pit. Cow dung and pit soils were mixed together. The fertilizers were applied on the top and worked up to 10 cm soil of the pits.


Twenty-four days old, seedlings were transplanted in wellprepared experimental plot on 17th December, 2013. The seedlings were watered immediately after transplanting. Four plants of each genotype were accommodated in each replicated plot maintaining 2x2 m spacing.

Intercultural operations

Intercultural operations were done as necessary during the growing period for proper growth and development of the plants and to protect the fruits from rotting.


Immediately after planting, the field was covered with straw to ensure optimum moisture for easy emergence of buds.


Routine weeding were done to keep the field free from weeds and to pulverize the soil.

Irrigation and drainage

Irrigation was applied as and when required.


The fruits were harvested when the peduncle dried on maturity.

Data collection

Three plants were selected at random from each plot for recording data. Both quantitative and qualitative characters were recorded.

Quantitative characters

a) Days to first male and female flower: The number of days to first male and female flower was recorded.

b) Days to first male and female flower opening: The number of days to first male and female flower opening was also recorded.

c) Nodes for first male and female flowers: The nodes at the ground level to the nodes of first blooming of male and female flowers were recorded.

d) Number of male and female flower per plant: From the first blooming of male and female flowers were counted.

e) Number of nodes for first fruit setting: The numbers of nodes from the first fruit setting were counted.

f) Fruit yield per plant (Kg): Total numbers of fruits from three randomly selected plants were weighed and their average value was taken.

g) Fruit length: Fruit length was measured using scale.

h) Fruit breadth: Fruit breadth was measured using scale.

i) Hollowness: Fruit hollowness was measured using scale after cutting the whole fruit into two pieces.

j) Flesh Thickness: Flesh thickness was measured using scale.

Qualitative characters

a) Dry matter (%): Dry matter percentage was also calculated from matured fruit. For dry matter content, 200 gm of matured pumpkin was cut into small pieces and dried in the sun for 3 to 4 days. After that it was again kept in an oven at 60 oC for 72 hours. Then the weight was taken using electric balance.

b) Brix (%): It was measured with the help of a Brix meter (Model: ATAGONI Brix 0-32%, Made in Japan).

c) Carotene (mg/g): Three fruits of each genotype were used for carotene analysis and their average value was taken. At first 10 g flesh of pumpkin was taken and crushed by mortar and pastel. After then 10 ml mixture (Acetone: Hexane=2:3) was added in the paste. Then the solution of pumpkin paste and acetone hexane was filtered in a vial having airtight lid. Then the nascent spectrophotometer reading was recorded at four different nano meter length viz 663 nm, 645 nm, 505 nm and 453 nm. Finally, β-carotene was calculated by the following formula: B-carotene (mg) = (Reading of 663 nm) + (Reading of 453 nm) - (Reading of 645 nm) - (Reading of 505 nm).

d) Sugar (gm/100gm) Estimation: One fruits of each genotype from each replication were used for reducing sugar analysis and their average value was taken.

Reducing sugar

Ten ml of each of Bertrand A (40 g of CuSO4. 5H2O dissolved in water and diluted to 1 liter) and Bertrand B (200 g of sodiumpotassium tartarate and 150 g of NaOH dissolved in water and diluted to 1 liter) solutions were added to 5 ml of sample solution. The conical flask was placed on a hot plate (sand bath) and boiled for about 3 minutes and kept overnight for cooling. The supernatant was decanted and discarded very carefully by keeping the precipitation. The precipitation was washed repeatedly until blue color was present. Then 10 ml of Bertrand C [50 g of Fe2 (SO4)3 and 115 ml of concentrated H2SO4 was added and diluted to 1 litre] solution was added to dissolve the precipitation (Cu2O). Finally, it was titrated with 0.4 % KMnO4 solution. Reducing sugar was calculated comparing tabulated values. Before calculation of reducing sugar factor of 0.4 % KMnO4 was determined.

Total sugar

Ten ml of extract solution was taken in a volumetric flask and 2-3 drops of 4 N HCl was added. The flask was then boiled for about 3 minutes on a hot plate for hydrolysis. After cooling in tap water, the extract was neutralized with 0.1 N NaOH. The rest of the procedure was same as mentioned in reducing sugar.

Non-reducing sugar

Non- reducing sugar was calculated by deducting reducing sugar from total sugar.

Statistical analysis

Method 1 model II of Griffing [15] was followed for combining ability analysis. The recorded data were analyzed by using Diallel analysis and simulation program by Mark, D. Burow and James G [16]. Coors, copyright 1993 and version 1.1.Vr-Wr graph of different traits was drawn according to Hayman [17].

Results and Discussion

Analysis of variance (ANOVA) for heterosis and combining ability

The mean sum of squares from analysis of variance due to heterosis and combining ability for fruit length, fruit breadth, hollowness, flesh thickness, dry matter (%), brix (%), reducing sugar, non-reducing sugar, total sugar and fruit yield have been shown in Table 1.