Genetic Divergence Studies in Bottle Gourd. The Plant Lagenaria Siceraria

Contents

Chapter

1. Introduction

2. Review of literature
2.1 Genetic Variability
2.2 Heritability and genetic gain
2.3 Correlation and path coefficient analysis
2.4 Genetic divergence

3. MATERIALS AND METHODS
3.1 Experimental material
3.2 Characters studied and observational procedures
3.3 Statistical and biometrical analysis

4. EXPERIMENTAL FINDINGS
4.1 Mean performance and Analysis of variance
4.2 Coefficient of variability, heritability and genetic gain
4.3 Correlation coefficient
4.4 Path coefficient analysis
4.5 Estimation of genetic divergence
4.6 Percent contributon of traits

5. DISCUSSION
5.1 Mean performance of genotypes
5.2 Genetic variability, heritability and genetic gain (genetic advance as per cent of mean)
5.3 Correlation coefficients
5.4 Path coefficient analysis
5.5 Genetic diversity

6. Summary and Conclusion

LITERATURE CITED

APPENDIX

Certificate-I

This is to certify that the thesis entitled, “Genetic Divergence Studies in Bottle gourd [ Lagenaria siceraria (Molina) Standl.]” submitted in partial fulfilment of the requirements for the award of the degree of Master of Science in Horticulture (Vegetable Science), to the Faculty of Horticulture, Sher-e-Kashmir University of Agricultural Sciences & Technology of Kashmir is a record of bonafide research work carried out by Mr. Majid Rashid (Regd. No. 2017-H-190-M) under my supervision and guidance. No part of the thesis has been submitted for any other degree or diploma.

It is further certified that any help or information received during the course of investigation has duly been acknowledged.

Certificate – II

We, the members of the Advisory Committee of Mr. Majid Rashid (Regd. No. 2017-H-190-M) a candidate for the degree of Master of Science in Horticulture (Vegetable Science) have gone through the manuscript of the thesis entitled, “ Genetic Divergence Studies in Bottle gourd [ Lagenaria siceraria (Molina) Standl.]” and recommend that it may be submitted by the student in partial fulfilment of the requirements for the award of the degree.

Advisory Committee

Abbildung in dieser Leseprobe nicht enthalten

Abstract

The present investigation entitled “Genetic Divergence Studies in Bottle gourd [ Lagenaria siceraria (Molina) Standl.]” was carried out at the Experimental Field, Division of Vegetable Science, SKUAST-K, Shalimar during Kharief 2018. The experiment was laid out in randomized complete block design (RCBD) with three replications. Thirty genotypes were evaluated for various quantitative and quality traits. Analysis of variance revealed significant differences among genotypes for all the traits. The maximum fruit yield plant-1 was recorded in Shalimar improved (7.57 kg) followed by SH-BG-72 (7.30 kg), SH-BG-17 (7.28 kg) and minimum in SH-BG-53 (4.32 kg). The estimates of phenotypic coefficient of variance were slightly higher than the corresponding genotypic coefficient of variance for all the characters studied indicating the little influence of environment in the expression of these traits. The highest phenotypic and genotypic coefficients of variation were observed for fruit diameter (35.65 and 34.62) followed by total chlorophyll (30.08 and 20.02) and fruit length (23.70 and 23.44). High heritability coupled with high genetic gain was recorded for fruit length (0.97 and 47.74), fruit diameter (0.94 and 71.73), total sugars (0.74 and 24.05) and dry matter content (0.84 and 25.42) indicating that the heritability is most likely due to additive gene effects and thus the chances of fixing by selection are more. Fruit yield plant-1 was positively associated with traits like node number at which first male flower appeared, node number at which first female flower appeared, number of days to anthesis of first female flower, fruit diameter, dry matter content and total sugars. Moreover the traits like days to last fruit harvest and number of fruits plant-1 showed significant positive genotypic correlation with fruit yield plant-1 indicating that direct selection of these traits will be effective. Path coefficient analysis revealed appreciable amount of direct positive effects of component traits like node number at which first male flower appeared, days to anthesis of first female flower, days to last fruit harvest, number of fruits plant-1, fruit weight plant-1 and total sugars on fruit yield plant-1. D2 statistics grouped thirty genotypes of bottle gourd into three clusters. Cluster I had maximum number of genotypes (25) followed by cluster II (4) and cluster III (1). Maximum intracluster distance was observed in cluster II (70.46). Maximum intercluster distance was observed between cluster I and III (311.28) followed by cluster I and II (189.07). The per cent contribution of traits towards total genetic divergence revealed that fruit length was the main factor contributing to divergence accounting for about 32.41% followed by fruit weight plant-1 (15.67%) and fruit diameter (14.71%). Selection of parents for hybridization should be done from clusters having maximum intercluster distance and those selected parents should have high per se performance for the traits contributing maximum towards divergence.

Key words: Correlation, Clusters, Divergence, Genetic gain, Heritability,

Acknowledgement

In the name of Allah the most beneficent and most merciful. All praises are due to Allah, the lord of the world and endless blessings of Allah be upon Prophet Mohammad SAW the great benefactor of mankind t gives me immense pleasure to express my sincere and profound gratitude to Dr. Kouser Parveen Wani, Professor and Head Division of Vegetable Science, SKUAST Kashmir Shalimar, Chairman of my Advisory Committee for her keen interest, benevolent guidance, valuable suggestions during the entire course of investigation.. I owe a special debt of gratitude to Dr. Khursheed Hussain, Assistant Professor, Division of Vegetable Science, SKUAST-K, Shalimar, for his constant and relentless guidance, earned suggestion, and his candid and constructive criticism during the preparation of this manuscript.

I extend my sincere thanks to my Advisory Committee Members, Dr. Zahoor Ahmad Dar, Professor cum Chief Scientist, DARS Budgam; Dr. Shakeel Ahmad Mir, Professor and Head, Division of Agricultural Statistics, Dr. Pradeep Kumar singh, Assistant Professor, Division of Vegetable science; Dr. Aroosa Khalil (Dean P.G Nominee) Assistant Professor, Division of Fruit Science for their valuable suggestion and advice during the study programme and for the finalization of manuscript.

I am highly grateful to all the faculty members of Division of Vegetable Science particularly, Dr. Nayeema Jabeen, Professor, Division of Vegetable Science; Dr M.A.Chatto, Professor, Division of Vegetable Science; Dr. Sumati Narayan, Professor, Division of Vegetable Science; Dr. Baseerat Afroza, Associate Professor, Division of Vegetable Science; Dr. Faheema Mushtaq, Associate Professor, Division of Vegetable Science; Dr. Shehnaz Mufti, Associate Professor, Division of Vegetable Science; Dr. Ajaz Malik, Assistant Professor, Division of Vegetable Science; Dr. Ambreen Nabi (SMS KVK Budgam); Dr. Rizwan Rashid, Assistant Professor Division of Vegetable Science; Dr. Ummiyah Masoodi, Assistant Professor, Division of Vegetable Science, Dr. Mudasir Magray, Assistant Professor Division of Vegetable Science; for their valuable suggestion and advice during the study programme.

Special thanks to Dr. Zahoor Ahmad Dar, Professor cum Chief Scientist, DARS Budgam and Dr. Gowhar Ali, Assisatnt professor, Division of Genetics and plant breeding for helping me in analyzing the data.

I find myself hard pressed for words to reciprocate the affection, moral support, good wishes and sustained help rendered to me by my beloved Father Mr. Abdul Rashid Dar and Mother Mrs. Amina Akhter, who nourished and educated me well inspite of their hardships and difficulties. Whenever anything fascinated my eyes, I never received a “No” from them. I am extreamely grateful for help, support and assistance during entire course of my study and research work, extended to me by my sisters Ms. Shazia Rashid and Mrs. Nahida Rashid, my uncle Mr. Nazir Ahmad Dar, other Family members and Cousins.

I am highly thankful to field and lab staff members especially Mr. Fayaz Ahmad Mir, Mr. Maqbool Ahmad, Mr. Shabir Ahmad, Mr. zubair Ahmad, Mr. Bharat Bhushan for their help and assistance during my research work in the field and lab.

I acknowledge with deep sense of appreciation the nice company and cooperation of my friends and colleagues particularly Mr. Ghulam Jeelani, Mr. Mazahir Hussain, Mr. Ishfaq Ayoub, Mr. Muzamil Ahmad, Mr. Shayan Showkat , Mr. Tajamul Hussain, Mr. Danish Mushtaq, Mr. Tajamul Farooq, Mr. Zubair Ahmad , Mr. Showkat Hamid, Mr. Javaid Ahmad, Mr. Lateef Ahmad, Mr. Anil Sharma, Mr. Mohd. Abass, Mr. Suhail Nazir, Mr. Asif Ahmad, Mr. Tariq Ahmad, Mr. Tariq Parray, Mr. Irfan Ahmad, Mr. B. Srinivasulu, Mr. Nawaz Ahmad, Mr. Haroon Rashid, Ms. Insha Javid, Ms. Syedah Farwah, Mrs. Rani shama, Ms. Danishta yousuf, Ms. Afroza Akhter, Ms. Azra Andrabi, Ms. Seerat Rizvi, Ms. Amreena Sultan, Ms. Sameena Maqbool, other batchmates and division mates.

My sincere thanks are also due to all the non-teaching staff members of the Division of Vegetable Science particularly, Mrs. Shehnaz, Mrs. Pushvinder Kaur, Mrs. Nausrat, Mr. Mehraj and Mr. Mohammad Yaseen for their sincere help in laboratory and academic matters which led to successfully completion of my research programme.

I express my sincere thanks to the Head Central Library SKUAST-K and supporting staff for extending full cooperation in collecting the pertinent literature. The cooperation of ARIS and CAB staff is duly acknowledged.

List of Tables

1. List of genotypes

2. Analysis of variance for various characters in bottle gourd

3. Estimates of Genetic Variability Parameters for various quantitative and quality characters in bottle gourd

4. Estimates of genotypic correlation coefficients among different characters in bottle gourd

5. Estimates of phenotypic correlation coefficients among different characters in bottle gourd

6. Path analysis showing direct (diagonal) and indirect (off-diagonal) effects of different parameters in bottle gourd

7. Distribution of bottle gourd genotypes in different clusters

8. Average intra cluster (Diagonal) and inter cluster (Above diagonal) distance values in bottle gourd

9. Cluster means for various characters in bottle gourd

10. Per cent contribution of fifteen characters towards total genetic divergence in bottle gourd

List of Figures

1. Clustering by Tocher method (Dendrogram)

2. Mahalnobis Euclidean Distance (Not to the Scale)

List of plates

1. View of experimental field Variability observed among different genotypes

Chapter – 1

INTRODUCTION

Bottle gourd [ Lagenaria siceraria (Molina) Standl.] (2n=2x=22) belongs to family Cucurbitaceae and is one of the most ancient crop cultivated during summer throughout the world. The genus Lagenaria is derived from the word lagena, meaning the bottle. It is also known as Calabash, Doodhi and Lauki in different parts of India (Deore et al., 2009). Its primary centre of origin is Africa (Singh, 1990). The fossil records indicate its culture in India even before 200 B.C. It has been found wild in India, the Moluccas and Ethiopia. It has spread to western countries from India and Africa.The genus Lagenaria includes six species that are distributed in Africa, Madagascar, Indo- Malaysia and the neotropics. There is only one cultivated species, Lagenaria siceraria, which is annual and monoecious. The five other species are wild, perennial and dioecious, occuring in East Africa and Madagascar.

In India the total area under its cultivation is 185 thousand hectares with an annual production of 3072 thousand MT (NHB, 2018). However in Jammu and Kashmir it is grown over an area of 1.60 thousand hectares with a production 36.17 thousand MT (Anonymous, 2018). It is a highly cross pollinated crop due to its monoecious and andromonoecious nature (Swiander et al., 1994) and shows large amount of variation for various economic traits of which the most interesting variation is found for size, shape and colour of fruits. On the basis of fruit shape, the cultivars of bottle gourd are broadly classified into two groups viz., long fruited and round fruited.

It has a good amount of vitamins and minerals. Its fruit contains 95.54%moisture, vitamin C (10.1 g), vitamin A (16 IU), thiamine (0.029 g), riboflavin (0.022 g), niacin (0.320 g), carbohydrates (3.39 g), fats (0.02 g) and potassium (150 mg)/100g (USDA, 2018).

It is ideal for human food or for incorporation into livestock feed (Ogunbusola et al., 2010). It is easily digestible and is therefore recommended during convalescence. The dietary fiber present in the bottle gourd makes it a very useful vegetable in preventing digestive disorders such as constipation. A positive correlation has been found between fiber consumption and the reduction of coronary heart diseases and diabetes incidence (Hemeda et al., 2008). Bottle gourd juice is used traditionally as a medicine for treating acidity, indigestion and ulcers besides being a good thirst quencher. The fruit is found to be antidote to certain poisons and scorpion stings, and also has purgative and cooling effects. The fruit is believed to have ability to relieve pain and is effective against fever, and hence found useful in treatment of asthma and other bronchial disorders. It is also a good source of natural antioxidants (Deore et al., 2009). It helps in losing weight quickly, because of its high dietary fiber and low fat and cholesterol content (Parle and Kaur, 2011). A decoction made from leaves acts as medicine for curing jaundice. It has a cooling property. During hot season, the cut surface of small sized fruit is rubbed on the flat of the feet and hand to diminish the effect of heat. The seeds are rich in essential amino acids, minerals, lipids and fatty acids (Essien et al., 2013) and are also used for oil extraction. The fatty acid profile shows linoleic acid as the most abundant (62%) as compared to oleic (16.2%), palmitic (14.4%) and stearic (5.8%) acids. High linoleic and low linolenic acid levels of these oils suggest that they could be sources of good edible oils for cooking. The abundance of linoleic acid followed by oleic acid in bottle gourd seed makes them good oils for reducing serum cholesterol and low density lipoprotein (LDL) and increasing high density lipoprotein (HDL) levels, hence, they could be good oils to fight against cardiovascular illnesses (Fokou et al., 2009). Dry hard shells of the fruits have been used for making a wide range of articles of common use, including bowls, bottles, containers, floats for fishing nets and musical instruments (Wikipedia, 2018).

Bottle gourd flowers are produced at leaf nodes and are solitary. Flowering starts from about 40 days after planting during summer, however this may be influenced by cultivar differences (Morimoto et al., 2004). Generally male flowers appear before female flowers (Morimoto et al., 2004). Thereafter, a flush of male and female flowers occurs continuously. Male flowers remain open only for a few hours and eventually wither and die off, thus the flowering period is normally shorter in male flowers than in female flowers (Morimoto et al., 2004). Flower opening occurs late in the afternoon and sometimes during the night (Sugiyama et al., 2014). Pollen of male flowers is only viable for two days (Sugiyama et al., 2014). The ratio of male: female flowers may vary from 5:1 to 15:1 in the common types. Higher male: female sex ratio of 20: 1 and 26:1 have also been reported (Morimoto et al., 2004). Even though sex determination genes controls sex expression, several authors have indicated that environmental conditions (e.g. precipitation, temperature and light intensity) and plant growth regulators (e.g. auxins, ethylene, gibberellic acid) can alter sex ratio ( Mishra et al., 2013). Higher temperature, long day length, and high light intensity and high nitrogen levels are reported to result in more male flowers (Tan et al., 2009) while the opposite results in more female flowers. Fruit formation can occur only after 24 hours following pollination (Singh, 2008).

The fruit yield of bottle gourd is an economic character which is dependent on many other attributes. Other yield attributing traits like vine length, node at which first female flower appeared, number of fruits plant-1, fruit length, fruit weight etc. are inherited quantitatively and their expression is governed by polygenes which are highly influenced by environment and are less heritable. So selection based on yield components rather than yield itself is reliable and may be accomplished through the component approach of breeding.

The success of breeding programme depends on the availability of the genetic variability present in the available germplasm. The study of biological parameters of the crop is often considered to be a useful step in the study of genetic variability. Since most of the plant characters of economic importance are polygenic in nature and are highly influenced by environment, it is necessary to work out whether the observed variability is heritable or due to environment. This suggests the imperative need to work out the phenotypic variation into heritable and non-heritable components. Genotypic and phenotypic coefficients of variability helps to assess the divergence of the characters. Selection would be more meaningful for the characters which exhibit high genetic variability, heritability along with high genetic gain. Realizing the economic potential of the crop, there is an urgent need to isolate such breeding lines which have desirable horticultural traits, better quality coupled with high yield potential.

Keeping in view the above mentioned facts, the present study “ Genetic Divergence Studies in Bottle gourd [ Lagenaria siceraria (Molina Standl).]” was proposed with the following objectives:

- To determine the variability in yield and quality attributes among diverse genotypes of bottle gourd.
- To study correlation between various characters and their direct and indirect effects on fruit yield.

Chapter – 2

REVIEW OF LITERATURE

The understanding of magnitude and nature of variability, the extent to which a character is heritable and the direct and indirect effects of components on yield including their interrelationships, has been found very important for the improvement of yield and its components in vegetables. In the same context, the literature relevant to the present study is summarized under the following headings:

2.1 Genetic Variability
2.2 Heritability and Genetic Gain
2.3 Correlation and Path Coefficient Analysis
2.4 Genetic Divergence

2.1 Genetic variability

The presence of diversity is a pre requisite for undertaking any crop improvement programme. In order to make selection and improvement programmes effective, it is essential to study and partition the total variability existing in a germplasm into genotypic, phenotypic and environmental variability. This enables the breeder to adopt a suitable breeding programme. Therefore variability is a key factor, which determines the amount of progress expected from selection. The potential for improvement in crops is proportional to the magnitude of genetic variability present in the germplasm. The study of genetic variability was made for the first time by great biologist Fisher (1918) and subsequently, the estimation of genotypic and phenotypic variations were used to predict the expected genetic response.

Rahman et al. (1986) studied variability, correlation and path coefficients on four lines of bottle gourd. Genotypic and phenotypic variability were high for fruit length and number of branches plant-1, but very low for number of fruits plant-1 and length of main vine. Heritability (broad sense) and genetic gain in percentage of mean were high for fruit length, fruit diameter and fruit weight plant-1. Fruit weight plant-1 had strong positive genotypic correlation with days to first picking, length of main vine and fruit diameter and a negative correlation with fruit length.

Sharma and Dhankar (1990) evaluated thirty five genotypes of bottle gourd for variability during summer season and found that Hissar Local-3, a round genotype was earliest and highest yielder. Pusa Summer Prolific Long, Hissar Sel-1 and Hissar Sel-2 were most promising for earliness and high yielding among long types. Prasad et al. (1993) observed thirty genotypes of bottle gourd for their variability and the studies revealed highest genotypic and phenotypic coefficient of variability for fruit yield plant-1 followed by number of male flowers on primary laterals and fruits vine-1. The genotypic differences for all the characters were highly significant. The magnitude of PCV was higher than GCV for all characters suggesting the effect of environment.

Narayan et al. (1996) studied twenty five diverse populations of bottle gourd and reported high value of GCV for number of primary branches plant-1 and yield vine-1 indicating that these two characters had additive gene effect and are more reliable for effective selection. Hawlader et al. (1999) studied genetic variability in thirteen cultivars of bottle gourd for eight quantitative characters. A wide range of variability was recorded for most of the characters. Heritability was very high for all the eight characters. Number of male flowers, number of female flowers and fruit yield plant-1 exhibited high heritability coupled with high genetic advance.

Mathew et al. (2001) evaluated twenty eight bottle gourd accessions and reported that fruit shape and fruit colour exhibited high variation among the various qualitative characters. Significant difference was observed in accessions for vine length, number of primary branches, days to first female flower opening, nodes to first female flower opening, sex ratio, number of fruits plant-1, length of fruit, girth of fruit, 100 seed weight, number of seeds fruit-1 and crude fiber content. The highest GCV and PCV were recorded for number of fruits plant-1 (38.05 and 50.71) and the lowest for inter nodal length (0.22 and 6.95).

Singh and Kumar (2002) studied ten lines, two testers and twenty F1s of bottle gourd and reported that the phenotypic coefficient of variation was significantly higher than genotypic coefficient of variation for fruit yield plant-1, fruit diameter, fruit length, number of nodes to first male flower and vine length which were also characterized by high genetic variation.

Pandit et al. (2003) studied genetic variability, heritability and genetic gain in fifteen genotypes of bottle gourd. There was considerable variability in all traits except fruits plant-1. The moderate GCV and GA in fruit length and fruit weight indicate the probable likelihood of additive gene action. The correlation between both genotypes and phenotypes indicate the overriding importance of fruit length and fruit width in determining the average fruit weight, which in turn adequately describes the increase in fruit yield plant-1.

Munshi and Sirohi (2005) evaluated the performance of twelve bottle gourd cultivars and observed high genotypic and phenotypic coefficient of variation for vine length, number of primary branches vine-1, number of nodes on the main axis, number of fruits plant-1, fruit length, girth, weight and crop yield.

Munshi and Acharyya (2005) evaluated twelve genotypes of bottle gourd and observed high genotypic and phenotypic coefficient of variation for vine length, number of primary branches vine-1, number of nodes on the main axis, peduncle length, sex ratio, number of fruits plant-1, fruit length, girth and weight, crop yield and starch and calcium content. Fruit girth and length, number of days to first fruit harvest and number of days to first female flower anthesis exhibited moderate to high heritability with moderate genetic gain.

Gayen and Hossain (2006) studied genetic variability and heritability of bottle gourd and observed that magnitude of PCV was significantly higher than GCV for all characters suggesting the effect of environment on expression of these traits. GCV and PCV were high for fruit yield plant-1 and fruit length. The estimation of heritability ranged from 60.60 to 95.45%. A very high broad sense of heritability (80% and above) was recorded for length of main vine, number of primary branches plant-1, number of nodes of first male flower, number of nodes of first female flower, number of days to first male flower anthesis, number of days to first female flower anthesis, sex ratio, fruit length, fruit weight, number of fruits plant-1, fruit yield plant-1, TSS, ascorbic acid, total sugar, seed width, 100-seed weight and number of seeds fruit-1. High genetic gain as percentage of mean was recorded for sex ratio, fruit length, fruit yield plant-1 and TSS. The sex ratio, fruit length, fruit yield plant-1 and TSS showed high heritability (above 80%) coupled with high genetic gain.

Singh et al. (2008) studied genetic variability in bottle gourd during both summer and rainy seasons and recorded the highest genotypic and phenotypic coefficients of variation for yield vine-1. Yadav et al. (2008) evaluated nine characters, namely days to first male flowering, days to first female flowering, number of nodes of first male flowering, number of nodes of first female flowering, days to edible fruit, fruit length, fruit width, number of fruits plant-1 and yield plant-1 in eighteen genotypes of bottle gourd. All the characters showed considerable amount of variability. The fruit width had the highest coefficient of genotypic and phenotypic variability. An extent of genetic variability was present in the population because most of the plant characters were qualitatively inherited and were highly influenced by the environmental fluctuations.

Kumar and Syamal (2009) evaluated twelve diverse genotypes of bottle gourd and the extent of variability was measured in terms of range, mean, variations (PCV and GCV), heritability and genetic gain. The GCV which gives a picture of extent of genetic variability in the population ranged from 5.21 (days to first fruit harvest) to 23.68 (length of edible green fruit). The GCV values were considerably high for characters such as number of fruits plant-1, weight of edible green fruits yield plant-1. The heritability estimates of 100 seed weight (98.90%) were highest and were moderate for vine length (71.50%) and number of primary branches plant-1 (71.00%) which suggest the environmental effect constitute a major portion of total phenotypic variation and hence and direct selection for these characters will be less effective. High heritability along with high expected genetic gain was recorded for length of edible green fruit and 100 seed weight. High heritability along with low genetic gain was observed in characters namely number of seeds fruit-1, days to first pistillate flowers anthesis and days to first fruit harvest.

Sharma et al. (2010) conducted an experiment on nine diverse genotype of bottle gourd and reported variability for days to first female flower, first female flowering node, fruit diameter, internode length and fruits vine-1. Medium heritability was observed for days to first female flower, first female flowering node, fruit diameter, internode length, fruits vine-1 and ascorbic acid content whereas low heritability was observed for days to first picking, fruit length, vine length, branches vine-1, average fruit weight, total yield vine-1, chlorophyll content and dry matter content of fruit.

Kumar et al. (2011) reported that high heritability was recorded for all traits except number of branches plant-1 in bottle gourd. The estimate of heritability varied from 26.60% for number of branches plant-1 to 95.10% for fruit yield plant-1. The expression of genetic gain was estimated for all ten attributes viz., days to germination, days to first fruit setting, fruit length (cm), fruit diameter (cm), number of branches plant-1, vine length, number of seeds fruit-1, number of fruits plant-1, days to maturity, fruit yield plant-1 (kg) and observed that the number of seeds fruit-1 has the maximum value (224.75) and minimum value was observed for number of branches plant-1(0.35).

Mladenović et al. (2012) conducted an experiment to study the genetic variability to lay a foundation for future breeding work of bottle gourd. The broad intraspecific variation of the plant, fruit and seed morphology is a direct result of the research carried out. Principal component analysis (PCA) of thirteen quantitative traits showed continuous variation among accessions, primarily due to fruit and seed size and shape. The evident reduction in trait variation is a direct result of the preference for ornamental use that favored certain shapes and sizes of the fruit, which has not significantly changed over the centuries.

Narayan (2013) conducted an experiment on ten diverse genotype of bottle gourd and reported variability for fruit and seed characters viz., days to 50% germination, days to first male flower anthesis, days to first female flower anthesis, node number of first male flower, node number of first female flower, days to first fruit harvest, number of branches vine-1, vine length, fruit length, number of fruits vine-1, fruit yield vine-1, number of seeds fruit-1 and 100 seed mass.

Sharma and Sengupta (2013) studied variability in bottle gourd genotypes and revealed high heritability (97 to 99% ) for the characters viz., vine length (99.98%), fruit length and fruit width (99.97%), days to first appearance of male and female flower (99.95%), primary branches vine-1 (99.75%), fruit weight (99.16%), nodes fruit-1 set (99,13%) nodes vine-1 up to first female flower (98.83%), number of fruit vine-1 (99.72%) and nodes vine-1 up to first male flower (97.61%). High genetic gain as percent of mean was observed in fruit length (96.68%) followed by fruit weight (95.82%) which demonstrate the presence of additive genes effect and selection for genetic improvement for this trait would be effective.

Singh et al. (2014) carried out studies on genetic variability, heritability and genetic advance in eight genotypes of bottle gourd. The highest value of broad sense heritability was recorded for fruit length followed by days to opening of first male flower, fruit weight, fruit diameter days to opening of first female flower, fruit yield plant-1, days to first fruit harvest, vine length estimated yield and fruits plant-1. High value of heritability coupled with high genetic gain were noticed for fruit length, fruit yield plant-1, fruit diameter, estimated yield, fruit weight, vine length and fruits plant-1.

Muralidharan et al. (2014) studied heritability and genetic gain in various parameters like vine length (cm), number of primary branches, node number of first male flower appears, node number of first female flower appears, days to first male flower anthesis, days to first female flower anthesis, sex ratio, days to first harvest, fruit length (cm), fruit width (cm), fruit cavity (cm), fruit flesh thickness (cm), fruit weight (cm), number of fruit vine-1, number of picking, number of seeds fruit-1, weight of 100 seed (gm), TSS & yield vine-1 in bottle gourd. All the characters exhibited higher values of genetic gain as percent of mean except the node number at first female flower appearance, days to first male flower anthesis, days to first female flower anthesis and days to first fruit harvest along with higher estimates of heritability except the days to first female flower anthesis. He inferred that most of the characters exhibited high heritability and high genetic gain which indicated the pre dominance of additive gene action and hence selection was more effective.

Mandal et al. (2015) carried out variability studies in twenty seven genotypes of bottle gourd. High genotypic coefficient of variation, high heritability and high genetic gain was observed in traits like sex ratio, fruit length and number of fruits plant-1. Fruit yield plant-1 was also positively and significantly correlated at genotypic and phenotypic level with fruit length and fruit number plant-1.

Deepthi et al. (2016) carried out an experiment in twenty three genotypes and one check variety of bottle gourd to study the genetic variability, heritability and potential for screening suitable genotypes for future improvement programmes. The genotypes exhibited significant differences for all the traits under study. A wide range of variability along with high estimates of PCV and GCV were observed for number of primary branches vine-1, node at which first male flower appeared, number of fruits vine-1, fruit weight (g), fruit length (cm), fruit diameter (cm), yield vine-1 (kg), total yield (t/ha), number of seeds fruit-1 and 100 seed weight (g) indicating high variability available in the germplasm for these characters for further improvement. High heritability coupled with high genetic gain as per cent of mean was observed for tendril length (cm), number of primary branches, days to first male flower appearance, node at first male appeared, number of fruits vine-1, fruit weight (g), fruit length (cm), fruit diameter (cm), yield vine-1 (kg), total yield (t/ha), number of seeds and 100 seed weight (g) indicated these characters had additive gene effect and therefore, these are more reliable for effective selection.

Damor et al. (2016) studied the genetic parameters to elucidate the genetic variability, heritability and genetic advance in forty genotypes of bottle gourd. Analysis of variance revealed presence of considerable variability among the genotypes for all sixteen characters. PCV was somewhat higher than GCV for all the characters studied. High heritability combined with high genetic gain was observed for the characters first male flowering node number, first female flowering node number, length of pedicel, fruit length, fruit girth, fruit weight, number of fruits plant-1, fruit yield plant-1, total soluble solids, total sugar content, antioxidant activity and total chlorophyll content indicating the preponderance of additive gene action and better scope for improvement of these characters for effective selection of genotypes.

Jain et al. (2016) carried out an experiment with forty genotypes for thirteen characters. The characters studied were days to first harvest, number of fruits plant-1, marketable fruit yield plant-1 (kg). The marketable fruit yield plant-1(kg) was 4.37 kg with the lowest fruit yield plant-1 of 1.46 kg recorded in NDBG-613-2 and the highest fruit yield of 7.95 kg, fruit yield plant-1 recorded in NDBG-619-11-2. Other genotypes were found to be non-significant for this character. The general mean for all genotypes was 4.36 for this character.

Rambabu et al. (2017) conducted an experiment to carry out the morphological characterization as per minimal descriptors of NBPGR developed for bottle gourd. The results revealed that the greatest diversity was observed for fruit characters especially fruit shape and fruit colour among the genotypes studied. Analysis of variance revealed significant differences among genotypes for all the characters. In general PCV was marginally higher than the corresponding GCV indicating the less influence of environment in the expression of the characters under study. High heritability coupled with high genetic gain as percentage of mean was observed for vine length, number of primary branches, days to first male flower appearance, days to first female flower appearance, days to first harvest, number of fruits plant-1, average fruit weight, fruit length, fruit width, fruit yield plant-1, sex ratio, seed number per fruit, 100 seed weight, TSS of the pulp, total sugar content and ascorbic acid content of the pulp indicated that these characters were mainly controlled by additive gene effects and thus selection may be effective.

Singh et al. (2017) carried out field study on seasonal variability in bottle gourd to assess the genetic variability, heritability and genetic gain for eleven yield and its contributing traits in nine bottle gourd genotypes. Highly significant treatment differences for all traits in the three environments viz., E1, E2 and E3 except for fruit circumference in E2 and vine length in E3, represent inherent PCV was higher than the GCV in all environments and pooled for most of traits. The promising genotypes were Pusa Naveen and HZP-RC-1 for early maturity and high yielding in all environments.

Sultana et al. (2018) conducted an experiment to elucidate the genetic variability, correlation and path co-efficient analysis in thirty-nine genotypes of bottle gourd [ Lagenaria siceraria (Molina) Standl]. Observations were recorded for eleven quantitative characters viz., days to first male flower open, days to first female flower open, node number of first female flower, branches plant-1, days to harvest, number of fruits plant-1, fruit weight, fruit length, fruit girth, 100 seed weight and yield ton ha-1. The analysis of variance showed highly significant differences for all the characters studied indicating considerable variability among the genotypes. The highest GCV (35.57%) and PCV (35.62%) were observed for fruit length. The differences between GCV and PCV were high for fruit number plant-1 and days to first male flower open indicating environmental influences. High heritability associates with high estimates of genetic gain in percent of mean were noted for length of fruit, yield, girth of fruit and number of fruits plant-1. It indicated presence of additive gene effect and selection for these traits would be effective. Yield was positively and significantly correlated with fruit weight, 100 seed weight, branches plant-1 and number of fruits plant-1. Negative associations of yield were noted with days to first male and female flower open, days to harvest and length of fruit. Path analysis revealed that fruits plant-1 (0.93) and weight of fruit (0.467) had very high positive effect on fruit yield ton ha-1.

2.2 Heritability and genetic gain

Heritability has been widely used in determining the degree to which a character may be transmitted from parents to off springs. Heritability is a measure of the genetic relationship between parents and progeny. The concept of heritability was presented by Lush (1940), who described heritability in broad sense as the proportion of genetic variation to the total or phenotypic variation. Robinson et al. (1949) defined heritability as the additive genetic variance in per cent of the total variance. High heritability along with high genetic gain are important for making effective selections. Johnson et al. (1955) pointed out that without genetic advance the estimates of heritability would not be of practical importance in selection based on phenotypic appearance and therefore genetic advance should be considered along with heritability in streamlining the coherent selection breeding programme.

High heritability and low genetic advance was observed for number of days to first female flower appearance, number of flowers per vine and fruit length in bottle gourd, indicating non-additive gene effects (Johnson et al., 1955 and Choudhary et al., 1985). Prasad and Prasad (1979) studied the heritability in genotypically forty diverse lines of bottle gourd and reported high estimates of heritability for vine length, fruit length and fruit diameter.

Sharma and Dhankar (1990) evaluated thirty five genotypes of bottle gourd and observed that, Hisar Local-3, a round-fruited genotype, was the earliest and highest yielding (4.71 kg/plant). Amongst the long-fruited types, Pusa Summer Prolific Long selections were most promising for earliness and yield. High heritability along with high genetic gain was recorded for male to female flower ratio, vine length, total number of branches and fruits plant-1.

Prasad et al. (1993) reported high heritability estimates for all the characters studied and maximum genetic gain for fruit yield plant-1. A very high broad sense heritability (>90 %) was recorded for length of main vine, number of primary branches plant-1, node number of first male flower, node number of first female flower, fruit length, fruit weight, number of fruits plant-1, fruit yield plant-1. High genetic advance was recorded for sex ratio, fruit length and fruit yield plant-1. The sex ratio, fruit length and fruit yield plant-1 showed high heritability (> 80%) coupled with high genetic gain in bottle gourd.

Narayan et al. (1996) conducted an experiment in twenty five genotypes of bottle gourd and reported that heritability in the broad sense was very high for number of male flowers, number of female flowers and fruit yield plant-1 coupled with high genetic gain. Singh et al. (1996) studied genetic variability and correlation studies in bottle gourd and reported high magnitudes of heritability for most of the characters studied. However, from selection point of view only that part of heritability is desirable which is due to additive gene effects. High heritability with high genetic gain is considered more useful than heritability estimated alone in predicting resultant effect in the selection programme. Traits like node at which first female flower appeared, fruits plant-1, yield plant-1 were more responsive to selection in bottle gourd.

Singh and Kumar (2002) conducted a study in ten lines, two testers and twenty F1s of bottle gourd. High heritability and high genetic gain were recorded for fruit yield plant-1, vine length, fruit diameter, fruit length, fruit weight, number of nodes to first male and female flowers, and number of primary branches vine-1.

Munshi and Sirohi (2005) conducted a study in twelve genotypes of bottle gourd and it was recorded that fruit length, number of days to first fruit harvest and number of days to first female flower anthesis exhibited moderate to high heritability with moderate genetic gain. Kumar et al. (2007) evaluated twenty diverse genotypes of bottle gourd for heritability and reported high genetic gain coupled with high heritability for fruit yield vine-1, number of fruits vine-1, vine length, number of branches vine-1, node number of first male flower, 100 seed weight and fruit length.

Singh et al. (2008) reported high heritability coupled with high genetic gain for number of female flowers vine-1, number of primary branches vine-1 and yield vine-1 in bottle gourd genotypes which indicate that these characters are more reliable for effective selection. Yadav et al. (2008) evaluated eighteen strains of bottle gourd. High heritability coupled with high genetic advance was observed for fruit length, fruit width, days to first female flowering, days to first male flowering and yield plant-1 indicating that most likely that heritability is due to additive gene effects and selection may be effective.

Kumar et al. (2011) evaluated twenty four hybrids obtained by crossing eleven parents of bottle gourd and it was recorded that heritability was high for fruit yield plant-1, number of seeds fruit-1 and fruit diameter. Genetic gain was high for fruit yield plant-1. Husna et al. (2011) recorded high heritability with high genetic gain in bottle gourd genotypes for yield plant-1and days to first male flowering indicating that yield plant-1 was under additive gene control and selection for genetic improvement for this trait would be effective.

Emina et al. (2012) evaluated forty diverse genotypes of bottle gourd and recorded high heritability estimates (>90%) for plant height, fruit weight, fruit length, fruit circumference and number of seeds per plant where as lower heritability was observed for 100 - seed weight (78.29%).

2.3 Correlation and path coefficient Analysis

Correlation co-efficient analysis measures the mutual relationship between various plant characters and determines the component character on which selection could be based for the genetic improvement in yield. The basic concept of correlation was first developed by Galton (1889) and later it was elaborated by Fisher (1918) and Wright (1921) in the improvement of plant breeding programmes. The preliminary information on the nature and magnitude of genetic variation in the available material and association of characters with yield and among themselves is most important for a plant breeder for the development of good quality and high yielding varieties. However, yield being the resultant of interaction between a number of factors i.e. inherent and environmental. It is therefore, difficult to estimate or select for this complex character directly. Hence the association is usually determined by studying the correlations existing between different characters under study. The phenotypic correlation coefficient gives the extent of relationship between the two characters which include the genetic and environmental influences whereas genotypic correlation coefficient indicates the real association between two traits and may be useful in selection (Johnson et al., 1955).

The study of simple correlation does not provide an exact picture of relative importance of direct and indirect influence of each of the component characters towards the desired characters. So, this can be overcome by path coefficient analysis technique by further partitioning the correlation coefficient into direct and indirect effects.

Tyagi, (1972) studied genotypic and phenotypic variability with respect to different morphological characters which directly or indirectly bear upon yielding ability in varietal collection of bottle gourd. Characters like number of fruits plant-1, girth of fruit and length of fruit showed high heritability values accompanied by high genetic gain, which may be attributed to considerable additive gene effects. The high estimates of these characters are indicative of the usefulness of these characters in a breeding programme for bottle gourd. Yield was also found to have significant association with the characters having high heritability estimates, indicating thereby the possibility of success for selection in these characters.

Rahman et al. (1986) evaluated four lines of bottle gourd for path coefficient analysis and revealed that fruit diameter and fruit length had high positive direct effect on fruit weight plant-1. Number of fruits plant-1 also had considerable positive direct effect on fruit weight plant-1. Prasad et al. (1993) undertook correlation studies in thirty genotypes of bottle gourd which revealed highly significant and positive association of fruit yield with number of fruits vine-1, average weight of fruit and number of female flowers vine-1.

Narayan et al. (1996) reported that yield was positively and significantly correlated with number of fruits plant-1 and average weight of fruit. Negative and significant correlation between yield and days to anthesis of first male flower was observed in bottle gourd. Badade et al. (2001) conducted an experiment to study the correlation of twenty genotypes of bottle gourd (Lagenaria vulgaris). Yield was found significantly and positively correlated with number of branches vine-1, number of fruits vine-1 and significantly and negatively correlated with days to first male and female flower appearance and weight of deformed fruits per vine at both phenotypic and genotypic levels. Fruit length showed positive but insignificant correlation with fruit yield.

Umamaheswarappa et al. (2004) conducted an experiment on bottle gourd (Lagenaria siceraria). Path coefficient analysis revealed that number of fruits vine-1 had maximum direct effect on fruit yield followed by fruit weight. Ahmed et al. (2005) studied correlation and path coefficient in twenty three genotypes of bottle gourd and reported that fruit yield exhibited strong positive and significant correlation both at genotypic and phenotypic levels with number of fruits plant-1, average fruit weight and fruit length. The negative significant association with days to first fruit picking and fruit diameter indicate that selection for earliness and increased fruit diameter would not have positive bearing on fruit yield. The path coefficient analysis revealed appreciable amount of direct positive effect of average fruit weight, number of fruits plant-1, fruit length, number of female flowers plant-1 and vine length on fruit yield.

Parvathi and Reddy (2006) studied correlation in bottle gourd and reported that fruit yield vine-1 showed significant positive correlation with fruit weight, fruit girth, fruit flesh thickness, fruits vine-1 and 100-seed weight, indicating that selection for these characters may improve fruit yield in bottle gourd. Kumar et al. (2007) reported the value of correlation at genotypic level was higher than the phenotypic correlation, indicating that there is strong inherent association between the various characters in bottle gourd. The fruit yield vine-1 showed positive and significant correlation with number of branches vine-1, vine length, nodes number of first male flower, nodes number of first female flower, length of edible fruits, number of fruits vine-1, number of seeds fruit-1 and 100 seed weight at genotypic and phenotypic levels. Hence fruit yield can be improved by selecting genotypes on basis of number of branches vine-1, vine length, nodes number of first female flower, length of edible fruit and number of fruit vine-1.

Ram et al. (2007) evaluated some winter fruited bottle gourd and reported that genotypic correlations were higher than those of the corresponding phenotypic correlation coefficients indicating the inherent association among the various traits. At the genotypic level, days to first flowering had significant and positive association with days to edible maturity, number of branches plant-1, number of nodes on main vine and plant height. The highest positive direct effect (genotypic level) was exerted by vine length followed by fruit weight, yield plant-1, days to first flowering and fruit size.

Yadav et al. (2007) studied path coefficient analysis in eighteen bottle gourd strains which showed that days to first male flowering, number of nodes of first female flowering, days to edible fruit, fruit width, number of fruits plant-1 and yield plant-1 had maximum positive direct effect on yield. All the characters except days to first female flowering, number of nodes of first male flowering and fruit length had direct effect on yield. For indirect effects, the number of fruits plant-1 showed highly significant and positive association with yield plant-1 due to days to first male flowering, number of nodes of first female flowering, days to edible fruit, fruit width and number of fruits plant-1.

Wani et al. (2008) reported that in bottle gourd number of fruits plant-1, fruit yield plant-1, fruit length and average weight of edible fruit showed significant positive association with fruit yield hectare-1 and thus are important in selection for yield improvement. Pandit et al. (2009) while evaluating fifteen genotypes of bottle gourd revealed that the correlation between both genotypes and phenotypes indicated the over-riding importance of fruit length and fruit width in determining the average fruit weight, which in turn adequately described the increase in fruit yield plant-1.

Yadav et al. (2010) reported that the genotypic correlation coefficients are higher than the phenotypic correlation coefficient for all the twelve characters of bottle gourd and indicating strong inherent association between various traits under study and masking effect of environment in the total expression of genotypes. The fruit yield plant-1 had positive and significant genotypic and phenotypic correlation coefficient with number of fruits plant-1, weight fruit-1, length of fruit, number of primary branches plant-1, number of nodes vine-1, vine length and days to first female flower anthesis. The number of fruits plant-1 had positive and significant correlation with number of primary branches plant-1 and node number to first female flower anthesis both at genotypic and phenotypic level. The weight per fruit had positive and significant genotypic and phenotypic correlation with number of nodes vine-1 and vine length both at genotypic and phenotypic level. The node number to first female flower had positive and significant correlation with node number to first male flower both at genotypic and phenotypic level and significant correlation with days to first male flower anthesis. However, negative and significant correlations were observed for length of fruit and weight fruit-1 had negative and non significant correlation with days to 50% percent germination both at genotypic and phenotypic level. Path coefficient analysis revealed that weight fruit-1 exhibited maximum direct effect on fruit yield followed by number of fruits plant-1, number of nodes vine-1, length of fruit, days to first female flower anthesis and node number to first female flower, however, vine length, node number to first male flower, days to first male flower anthesis and number of primary branches plant-1 had negative direct effects on fruit yield. Indirect effect towards fruit yield through various characters suggested for selecting best genotypes with higher fruit yield.

Husna et al. (2011) studied correlation coefficients and path analysis in thirty one genotypes of bottle gourd. Correlation studies showed that genotypic correlation appeared to be higher than the corresponding phenotypic correlation. Number of fruits plant-1 and fruit weight has positive and highly significant influence on yield plant-1. Number of male flowers were highly significant and positively correlated with the number of female flowers. But number of male flowers produced significant and negative correlation with ratio of male and female flower and fruit length at both genotypic and phenotypic level indicating that if the number of male flower are increased, then ratio of male and female flower and fruit length are decreased. Fruit breadth was having positively significant correlations with fruit weight and negatively significant correlations with fruit length both at phenotypic and genotypic level. The estimated residual effect was 0.117 indicating that 90% of the variability in bottle gourd yield was contributed by characters.

Kumar et al. (2011) undertook Path coefficient analysis which revealed that the total number of fruits vine-1 (0.674) had maximum positive direct effect on total fruit yield followed by average fruit weight (0.390), number of branches vine-1 (0.219), number of nodes vine-1 (0.170), vine length (0.219) and days to first male flower (0.125). However, negative and direct effect was observed for yield through days to first female flower (-0.245), fruit diameter (-0.201), days to first fruit harvest (-0.109) and fruit length (-0.003) in bottle gourd.

Deepthi et al. (2012) carried out an experiment on twenty four genotypes of bottle gourd including one check variety i.e. Pusa Naveen, to assess the nature and magnitude of association among yield and its contributing traits in bottle gourd. Correlation studies revealed that yield vine-1 had significant positive association with tendril length (cm), number of nodes vine-1, number of primary branches vine-1, total vine length (m), internodal length (cm), number of fruits vine-1, fruit weight (g), fruit diameter (cm), number of seeds fruit-1 and 100 seed weight (g) both at phenotypic and genotypic levels indicating the importance of these traits in selection for yield and are identified as yield attributing characters. The character association revealed the overriding importance of fruit length and diameter in determining the average fruit weight. Path coefficient analysis revealed maximum direct contribution towards yield vine-1 with total vine length (m), number of fruits vine-1 and fruit weight (g). Hence, direct selection for total vine length (cm), number of fruits vine-1 and fruit weight (g) may be reliable for yield improvement in bottle gourd.

Emina et al. (2012) studied forty diverse genotypes of bottle gourd for correlation and reported positive correlation of plant height with fruit length, seeds plant-1 and 100 seed mass but negative correlation with fruit weight. Kamal et al. (2012) carried out an experiment in ten diverse bottle gourd genotypes. The fruit yield vine-1 showed positive and significant correlation with number of branches vine-1, vine length, node number of first male flower, node number of first female flower, length of edible fruits, number of fruits vine-1, number of seeds fruit-1 and 100-seed mass at genotypic and phenotypic levels.

Kumar et al. (2012) conducted an experiment comprising twenty four hybrids of bottle gourd obtained by crossing eleven parents with three testers and found that fruit yield of F1 plants had a high and significantly positive association with days to maturity and number of fruits plant-1 at genotypic and phenotypic levels. Raut et al. (2013) studied correlation between yield and its component characters in bottle gourd genotypes. Correlation coefficient of fruit yield plant-1 expressed significant and positive correlation with days to appearance of first male flower (0.117), number of male flower per plant (0.192), number of female flower per plant (0.405), fruits setting percentage (0.475), length of fruit (0.369), weight of fruit (0.157) and number of fruits plant-1 (0.766) has direct effect on fruit yield plant-1.

Janaranjani and Kanthaswamy (2015) carried out an experiment with eighteen different characters in bottle gourd comprising thirty six hybrids obtained by crossing nine lines and four testers by line x tester method to study the correlation and direct and indirect effects of different characters on fruit yield. The overall analysis revealed that fruit yield was positively and significantly correlated with fruit flesh thickness, number of fruits vine-1 and number of fruit pickings. The path analysis indicated that number of fruits vine-1, days to first female flower opening, fruit cavity and fruit weight had positive direct effect on fruit yield. Therefore, emphasis should be given on fruit flesh thickness, number of fruits vine-1, number of fruit pickings, days to first female flower opening, fruit cavity and fruit weight, while selecting a good hybrids for enhancing the yield of bottle gourd.

Rao et al. (2016) assessed the genetic diversity and relatedness among fifteen most common commercial bottle gourd [ Lagenaria siceraria (Molina) Standl.] genotypes of public sector institutes in India. Data was collected on morphological features of bottle gourd which include vine, leaf, flower, fruit and seed characteristics. A descriptor list with selected thirty two morphological (qualitative and quantitative) characters was adopted from NBPGR guidelines and used for characterization. The data was used to calculate genetic similarity and to construct a dendrogram using the unweighted pair-group method with arithmetic average (UPGMA). Data on quantitative characters was subjected to ANOVA using SAS and effects declared significant at 5% level. The procedure PRINCOMP was then used to perform a principle component (PC) analysis using fourteen quantitative variables and genotypes plotted on two dimensions using the first two principle components (PC1 and PC2). The results of quantitative characters of Pusa Santusti, Pusa Sandesh and Arka Bahar demonstrated highly significant variation between genotypes. Results of the principle component analyses for the traits indicated that the first five PCs explained a total of 80% of the total variation. The high morphological diversity observed among public sector genotypes emphasizes the need to expand the genetic base of the cultivated bottle gourd in India.

Malviya et al. (2017) conducted a study in bottle gourd [ Lagenaria siceraria (Molina) Standl.] to assess the extent of heterosis for thirteen quantitative traits including fruit yield plant-1. Eight parents were crossed in half diallel design to develop twenty eight F1 hybrids. The analysis of variance for experimental design revealed highly significant differences among the genotypes, parents and hybrids for all the characters, indicating the presence of sufficient amount of genetic diversity for the thirteen traits studied. Heterosis was worked-out over standard check MGH-4. The standard heterosis for fruit yield plant-1 ranged from 24.66 to 54.24. The crosses viz., Coimbatore-3 × JBOGL-01-6, JBOGL-01-6 × JBOGL-01-2 and Pusa Naveen × JBOGL- 01-6 showed significant and desirable standard heterosis for fruit yield plant-1 and its contributing characters.

Muralidharan et al. (2017) carried out an experiment for the analysis of quantitative and qualitative traits in twenty four genotypes of bottle gourd to partition the genotypic correlation into components of direct and indirect effects. The improvement in fruit yield plant-1 was found significant and positively correlated with fruit flesh thickness and fruit weight, and the result of path analysis study revealed that the characters like vine length, number of primary branches, number of seeds fruit-1 and number of pickings were the most important yield determinants, because of their high direct effects and high indirect effects. This suggested that emphasis must be given on such traits while exercising selection to improve the yield.

Ray et al. (2017) conducted an experiment for twelve different traits in bottle gourd [ Lagenaria siceraria (Molina) standl] comprising forty five hybrids obtained by crossing ten parental lines in diallel mating design to study the correlation and direct and indirect effects of different characters on fruit yield. The overall analysis reveals that fruit yield was positively and significantly correlated with fruit plant-1. The path analysis indicated that number of fruits plant-1, fruit weight, fruit length, primary branches plant-1 had positive direct effect on fruit yield while rest of the traits had indirect effect on fruit yield plant-1. Association of this yield-contributing character with yield and among its components is important for making selection in the breeding program and facilitates the partitioning of correlation coefficients on the direct and indirect effects of component characters on yield and any other attributes.

Thakur et al. (2017) carried out an experiment to study the correlation and path analysis among different characters of seventy three genotypes of bottle gourd. Observations were recorded for the characters viz., days to first male and female flower appearance, node number at which first male and female flower appears, days to 50% flowering, days to fruit set, number of branches plant-1, days to first fruit harvest, fruit length (cm), average fruit weight (g), fruit girth (cm), number of fruits plant-1, fruit yield (q/ha) and crop duration. Correlation and path studies revealed that number of fruits plant-1 and average fruit weight had highest significant positive association with yield per hectare at both phenotypic and genotypic levels and also had significant positive direct effect on fruit yield hectare-1.

Panigrahi et al. (2018) conducted an experiment to assess the relationship between different morphological traits of thirty seven genotypes of bottle gourd. Considerable amount of variability was noticed for the sixteen quantitative traits as indicated by the analysis of variance. The fruit yield vine-1 and hectare-1 had positive and highly significant correlation with most of the characters viz., number of primary branches, vine length, number of fruits vine-1 and length of fruit. Fruit yield vine-1 and yield hectare-1 were also positively correlated with each other at both genotypic and phenotypic level.

2.4 Genetic Divergence

The success of a breeding programme depends on the degree of genetic divergence. Genetic diversity is a key factor for crop improvement. More the diversity, better are the chances of improving economic characters under consideration in the resulting progenies. It is of paramount importance for heterosis. Hybridization between genetically divergent parents is expected to produce superior hybrids and desirable recombinants. The concept of D2 statistics was originally developed by Mahalnobis (1928). Then Rao (1952) suggested the application of this technique for the assessment of genetic diversity in plant breeding. Now this technique is extensively used in the vegetable breeding for the study of genetic divergence. This analysis also helps in the selection of diverse parents for the development of hybrids. Cluster Analysis helps to form the groups of closely related individuals which help in determining genetic distances between them.

Badade et al. (2001) studied genetic divergence using Mahalanobis D2 statistics for seven quantitative characters including yield vine-1 in a collection of twenty diverse cultivars of bottle gourd [ Lagenaria siceraria (Molina) Standl]. The cultivars differed significantly for almost all the characters and were grouped into 10 clusters based on the similarities of D2 value. Considerable diversity within and between clusters was noted and it was observed for the characters viz., vine length, number of branches, percentage of female flowers, fruits vine-1, length and diameter of fruit and yield vine-1. These were the important factors contributing towards genetic divergence in bottle gourd and may be useful for heterosis breeding in bottle gourd.

Mathew et al. (2001) studied twenty eight accessions of bottle gourd (Lagenaria siceraria) collected from different parts of the country to assess their genetic divergence using Mahalanobis D2 statistics. Based on D2 values of seventeen yield related characters, accessions were grouped into eight clusters, clustering pattern indicated that there was no association between geographical distribution of accessions and genetic divergence. The characters like number of fruits plant-1, number of seeds per fruit, length of fruit, average fruit weight, vine length and fruit set percentage contributed maximum to genetic divergence.

Islam (2004) estimated genetic divergence among forty two genotypes of bottle gourd accessions from Bangladesh using D2 analysis. The accessions were grouped into five clusters. No clear relationship was observed between geographic origin and genetic diversity. The maximum inter cluster distance was between cluster III and cluster IV. Primary branches plant-1, fruit length and weight, number of fruits and yield plant-1contributed the most to the total genetic divergence. The accessions included in the most divergent clusters I and II, are promising parents for a hybridization programme for obtaining high heterosis and thus, better segregants in bottle gourd.

Sharma and Sengupta (2008) carried out an experiment on sixteen genotypes of bottle gourd for evaluating their performance for various horticultural characters. There was a significant variation for all the characters among the genotypes. The significantly higher yield in Narendra Shivani (311.53 qha-1) would have been due to higher values of yield attributes (fruit set percentage, fruit length, number of fruit vine-1, fruit weight and fruit width) followed by Narendra Sanker Lauki. Whereas, the lower yield was found in case of Narendra Jyoti (101.86 qha-1), respectively due to lower yield attributes. High GCV was observed for fruit weight (39.48%). In all cases, phenotypic coefficient variances were higher than the genotypic coefficient variance. Among all the genotypes, Narendra Shivani, Narendra Sanker Lauki, and NS 421 gave promising results.

Choudhary et al. (2011) carried out genetic diversity studies on thirty five genotypes of bottle gourd. The genotypes were grouped into four clusters. Cluster IV was very large containing sixteen genotypes, while cluster III was represented by three genotypes. The maximum inter-cluster distance was recorded between cluster II and IV, while minimum distance was between cluster I and II.

Sarao et al. (2013) fingerprinted twenty accessions of bottle gourd using twenty simple sequence repeat (SSR) primers. Of these, ten primers exhibited polymorphic profiles, while nine exhibited monomorphic patterns and one revealed a null allele. The number of alleles ranged from 2 to 4 with an average of 2.6 alleles per locus. Unique DNA profiles of all the accessions could be created using a set of five polymorphic primers. Therefore, SSR markers used in the present study could precisely distinguish all the twenty accessions from each other, and these SSR markers can be further used to differentiate the future genotypes from the existing ones. The dendrogram depicting the genetic relationships as revealed by NTSYS-pc 2.02 and the tree diagram generated using the DARwin 5.0 program classified the accessions into two main clusters. There is no strong association between the clustering pattern and geographical origin of these accessions. This SSR marker-based diversity would facilitate the implementation of marker-assisted breeding schemes for efficient introduction of the desired traits into bottle gourd.

Ara et al. (2014) studied genetic divergence among twenty eight bottle gourd genotypes using D2 and canonical analysis. The genotypes were grouped into five clusters. The maximum intercluster distance was between cluster III and cluster I, and the minimum was between cluster IV and II. The crosses between the genotypes LS001, LS002, LS007, LS010, LS013, LS016, LS017, LS028 of cluster II and LS018, LS023 in cluster V would exhibit maximum heterosis and produce new recombinants with desired traits in bottle gourd.

Bhawna et al. (2014) carried out Genetic diversity analysis in forty two geographically distant genotype accessions of bottle gourd (Lagenaria siceraria) obtained from India northeastern (14) and northern region (28) using inter-simple sequence repeat (ISSR) markers. A total of 209 amplified bands were obtained from 20 ISSR primers used in this study, out of which 186 were polymorphic with 89.00 % band polymorphism. Various parameters namely, observed number of alleles, effective number of alleles, Nei’s gene diversity/heterozygosity, resolving power, Shannon’s information index and gene flow were estimated under experiment. Jaccard’s similarity coefficient matrix was generated for pairwise comparisons between individual ISSR profiles and UPGMA cluster analysis based on this matrix showed clustering into six groups. Jaccard’s coefficient of similarity values ranged from 0.409 to 0.847, with a mean of 0.628 revealing a moderate level of genetic diversity. The Bayesian model-based approach to infer hidden genetic population structures using the multi locus ISSR markers revealed two populations among the forty two genotypes. This is the first report on the assessment of genetic variation using ISSR markers in this vegetable plant, and this study of diversity analysis will be helpful in analyzing future hybrid breeding strategy and devising effective germplasm exploration and conservation strategy.

Sunil et al. (2014) carried out an experiment with a set of twenty diverse accessions of bottle gourd [ Lagenaria siceraria (Molina) Standl]. Which exhibited wide range of variability for qualitative and quantitative traits. The seed oil content ranged from 18.6% (IC446598) to 28.0 % (IC446592). The fatty acid composition of bottle gourd seed oil also varied. Days to 50% flowering and peduncle length had significant positive correlation with seed oil content, whereas inter nodal length had significant negative correlation. The intermodal length and number of primary branches plant-1 had high positive direct effect on fruit yield plant-1. Based on the traits, the accessions clustered into three distinct clusters. The diversity may be exploited for crop improvement and the potential of bottle gourd as edible oil source further explored.

Gurcan et al. (2015) carried out molecular analysis of sixty Turkish bottle gourds along with thirty one diverse exotic accessions. Eight Simple Sequence Repeats and two chloroplast loci of 91 accessions were analyzed. Capillary electrophoresis was used for DNA size fragment separation. The number of alleles per locus ranged from 2 to 13, with a mean of 7. Mean values for expected heterozygosity, observed heterozygosity, and polymorphism information averaged 0.5, 0.13 and 0.50, respectively, thereby suggesting very low (0.13) genetic diversity in a very diverse population. An unweighted pair group method with arithmetic mean dendrogram was constructed, Indian accessions clearly separated from the rest. Among the remaining samples, neither Turkish landraces grouped together based on their geographic origin, nor clear separation occurred according to origin continent. Interestingly, this co-dominant marker analysis shows close molecular allelic profile among bottle gourds originated from far different countries.

Mashilo et al. (2015) carried out an experiment to assess the genetic diversity present amongst bottle gourd landraces grown by smallholder farmers in South Africa using morphological traits and eleven selected polymorphic simple sequence repeat (SSR) markers. Marked phenotypic differences were observed amongst bottle gourd landraces. Principal component analysis on quantitative traits identified seven principal components, which accounted for 87% of the total variation. Number of alleles varied from 3 to 9 with a mean of 6 per SSR locus. Number of effective alleles ranged from 1.99 to 6.72 with a mean of 3.75. Shannon’s information index varied from 0.95 to 2.01 with a mean of 1.41. Expected heterozygosity values ranged from 0.5 to 0.87 with a mean of 0.71 with polymorphic information content values of 0.5 to 0.85 and a mean of 0.7. Morphological traits and SSR marker analyses showed a significant correlation in clustering the landraces. The present study demonstrated the presence of genetic diversity amongst bottle gourd landrace collections from South Africa useful for strategic improvement, direct production or conservation.

Visen et al. (2015) carried out an experiment to analyse genetic diversity for yield and its contributing traits in thirty one genotypes of bottle gourd. The cluster analysis grouped all the thirty one genotypes into five major clusters based on D2 value. Extreme genetic divergence was estimated among clusters. Maximum number of genotypes were grouped into cluster V including ten genotypes, whereas, cluster II included eight genotypes. The cluster I had six genotypes, which was followed by cluster IV and cluster III having only three genotypes in each cluster. Fruit length, fruit girth and average fruit weight contributed maximum towards genetic divergence.

Chetariya and Vaddoria (2017) conducted an experiment to assess the genetic diversity among fifty genotypes of bottle gourd (Lagenaria siceraria). The genetic diversity analysis revealed the formation of 13 clusters suggesting the presence of wide genetic diversity. The clustering pattern indicated that geographic diversity was not associated with genetic diversity. The analysis of per cent contribution of various characters towards the expression of total genetic divergence indicated that number of fruits vine-1 (22.45%) followed by number of primary branches vine-1 (13.80%), average fruit weight (11.51%), vine length (11.18%), fruit yield vine-1 (10.61%), number of male flowers (7.84%), fruit length (6.45%), ratio of male to female flowers (4.82%), days to first picking (4.49%) and days to opening of first male flower (3.84%) contributed maximum towards total genetic divergence. Based on the maximum genetic distance, it is advisable to attempt crossing of the genotypes from cluster XII (GP-14) with the genotypes of cluster IV (GP-25) and XI (GP-53), which may lead to the generation of broad spectrum of favourable genetic variability for yield improvement in bottle gourd.

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