This document discusses conventional and non-conventional breeding methods for improving cucurbits. It begins with an introduction to cucurbits and their importance. It then describes various conventional methods used in cucurbit breeding like plant introduction, mass selection, backcrossing, and heterosis breeding. Non-conventional methods discussed include mutation breeding, polyploidy breeding, molecular markers, QTL mapping, genetic transformation, and tissue culture techniques. Several case studies of varieties developed for different cucurbit crops using these breeding methods are also provided.

1. Submitted By :-
Vishal Thakur
Ph.D. (Vegetable Science)
Conventional and Non-Conventional breeding
methods for improvement of cucurbits
Topic:-

2. Introduction
Conventional methods
Non-Conventional methods
Case studies
Conclusion
References
Content

3. Introduction
• Cucurbits belong to family Cucurbitaceae, includes about 118 genera and 1000 species.
• Cucurbits term given by Liberty Hyde Bailey.
• In India, a numbers of major and minor cucurbits are cultivated, which shares about 5.6 % of the
total vegetable production.
• consumed in various forms i.e., salad (cucumber, gherkins, long melon), sweet (ash gourd, pointed
gourd), cooked as vegetable (bottle gourd, bitter gourd, ridge gourd, sponge gourd) and deserts
(melons).
• All cucurbits are botanically ‘pepo’.
• The bitter principle in cucurbits is cucurbitacin.
• Chemically cucurbitacins are tetracyclic triterpenes.
• Highest concentrations of cucurbitacins are found in the fruits and roots.
• Bitter gourd is rich in vitamin C, pumpkin contains high carotenoids pigments, kakrol is rich in
protein and chow-chow is high in calcium.

4. NAME SCIENTIFIC NAME ORIGIN 2n
Cucumber Cucumis sativus India 14
Bitter gourd Momordica charantia Indo-Burma 22
Bottle gourd Lagenaria siceraria Ethiopia 22
Watermelon Citrullus lanatus Tropical Africa 22
Melon Cucumis melo Tropical Africa 24
Long/serpent
melon
Cucumis melo var. flexuosus
India
24
Snapmelon Cucumis melo var. momordica India 24
Ridge gourd Luffa acutangula India 26
Sponge gourd Luffa cylindrica India 26
Commonly grown major cucurbits in India

5. Continued….
Pumpkin Cucurbita moschata Peru and Mexico 40
Summer Squash Cucurbita pepo Peru and Mexico 40
Winter Squash Cucurbita maxima Peru and Mexico 40
Ash gourd Benincasa hispida South East Asia 24
Pointed gourd Trichosanthes dioica India 22
Ivy or scarlet gourd Coccinia indica India 24
Round melon Praecitrullus fistulosuos Indo-Burma 24
Sweet gourd Momordica cochinchinensis South East Asia 28

6. Breeding Objectives of cucurbits:
• Early maturity
• Higher yield
• To improve stability of the crops against disease, heat,
drought, etc.
• To enrich health-promoting properties in cucurbits.
• To develop virus resistance in cucurbits, using a
combination of molecular genetics and conventional
breeding approaches.

7. Conventional and Non-Conventional Breeding
Conventional Non-conventional
Time-consuming comparatively less time consuming
High cost less costly
Selection on the basis of phenotypes Selection on the basis of genotypes
Chances of introduction of contamination
is high
Less chances or no chance of
contamination
Genus or species barriers No genus or species barriers

8. Conventional methods in Cucurbits
•Plant introduction
•Mass selection
•Back cross method
•Heterosis breeding

9. Non-conventional methods
•Mutation breeding
•Polyploidy breeding
•Molecular markers
•QTLs mapping
•Genetic transformation
•Tissue culture techniques

10. Breeding methods in cucurbits
Crops Breeding Methods
Muskmelon Selection, Heterosis breeding, Hybridization, polyploidy breeding
Cucumber Introduction, Selection, Hybridization, Heterosis breeding
Watermelon Introduction, Selection, Hybridization, Heterosis breeding,
Polyploidy breeding
Bitter gourd Heterosis breeding, Synthetic breeding
Summer squash Introduction, Selection, Heterosis breeding,
Pumpkin Mass selection, interspecific hybridization
Ridge gourd Mass selection, hybridization, back-cross breeding

11. Plant Introduction
Taking a genotype or a group of genotypes in to a new place or environment where they were not grown
previously. Thus introduction may involve new varieties of a crop already grown in that area, a wild relative of
the crop species or totally a new crop species for that area.
Merits of plant introduction
1. It provides new crop varieties, which are high yielding and can be used directly.
2. It provides new plant species.
3. Provides parent materials for genetic improvement of economic crops.
4. Enriching the existing germplasm and increasing the variability.
5. Introduction may protect certain plant species in to newer area will save them from diseases.
Demerits of plant introduction
1. Introduction of weeds, diseases and insects.

12. Introduction varieties in cucurbits
Crops Varieties
Cucumber Japanese Long Green, Straight Eight, Poinsette, Chinese long
Watermelon Sugar Baby, Improved Shipper, Asahi Yamato and New Hampshire Midget
Summer squash Patty Pan, Early Yellow Prolific, Australian Green

13. Mass selection
• In mass selection, a large number of
plants are selected on the basis of
their phenotype and the open pollinated
seeds from them are bulked together to
constitute a new variety.
• In cucurbits, effective in improving
qualitative characters such as sugar
content in melons and water melon.
• Musk-Melon varieties: Hara Madhu,
Arka Jeet, Arka Rajhans

14. Other cucurbits varieties
Crops Varieties
Cucumber Sheetal, Khira 90, khira 75
Bitter gourd Pusa do Mausami, Pusa Vishesh, Konkan Tara, Coimbatore Long, Priyanka, Harikini
Summer squash Early Yellow Prolific
Watermelon Durgapur Meetha, Durgapur Kesar, Special no. 1, Durgapur Kesar, Pusa Rasal
Muskmelon Durgapur Madhu, Hara Madhu, Pusa Madhuras, Arka Rajhans, Arka Jeet
Bottlegourd Pusa Summer Prolific Long, Punjab Long, Punjab Round, Arka Bahar
Pumpkin Arka Suryamukhi, Arka Chandan, Pusa Vikas

15. Back cross method
• A system of breeding whereby recurrent
backcrosses are made to one of the parents
of a hybrid accompanied by selection for a
specific characters is known backcross
breeding.
• Objective is to improve one or two specific
defects of a high yielding variety.
• A cross between a hybrid (F1 or a
segregating generation) and one of its
parents is known as backcross.
TT X tt
(Tall) (Dwarf)
F1 Tt X TT OR Tt X tt
• In BACKCROSS METHOD, the hybrid
and the progenies in the subsequent
generation are repeatedly backcrossed to
one of the parents of the F1.

16. Backcross method in cucurbits
Crop Varieties
Watermelon Arka Manik
Muskmelon Cantaloupe 45 (PMR-45)
Cucumber Chinese long, Tokyo long green

17. Heterosis breeding
• It has been exploited for earliness,
high yield and quality fruits.
• It refers to superiority of F1
hybrid in one or more characters
over its parents.
• The word hybrid vigour is a
synonym for heterosis. George
Harrison Shull coined the term
heterosis in 1914.

18. Heterosis breeding in cucurbits
Crops Varieties
Muskmelon Pusa Rasraj, Punjab Hybrid
Cucumber DCH-1,DCH -2 (Tropical gynoecious hybrids), Pusa Sanyog
Summer Squash Pusa Pasand
Pumpkin Arka Suryamukhi, Pusa Biswas
Bitter gourd Pusa Hybrid -1, Pusa Hybrid-2
Watermelon Arka Jyoti

19. Mutation breeding
Mutation is a sudden heritable change in an organism and is
generally due to a structural change in a gene.
Mutagens
A. Physical Mutagens
1. Ionising radiations: α-rays, β-rays, thermal neutrons, X-
rays, gamma rays
2. Non-Ionising radiations: ultraviolet radiations
B. Chemical Mutagens
1. Alkylating agents: Ethylmethane sulphonate (EMS),
Ethylene imine, Methylmethane sulphonate (MMS), etc.
2. Acridine dyes: Ethidium bromide, Acridine orange.
3. Base analogues: 5-bromouracil, 5-chlorouracil.
4. Others: Nitrous acid, Hydroxyl amine, Sodium azide.

20. Crop Variety
Bitter gourd MDU1 (Gamma ray mutant of MC-103)
Cucumber Swarna Ageti
Ridge gourd PKM1
Mutation breeding Varieties

21. Polyploidy breeding
• An organism or individual having more than two basic sets or
monoploid sets of chromosomes is called polyploid and such
condition is known as polyploidy.
Types of Polyploidy
Types Description
1. Autopolyploidy
(a) Autotriploidy
(b) Autotetraploidy
(c) Autopentaploidy
(d) Autohexaploidy
Multiplication of the same genome
Three copies of the same genome (3x)
Four copies of the same genome (4x)
Five copies of the same genome (5x)
Six copies of the same genome (6x)
2. Allopolyploidy
(a) Allotetraploidy
(b) Allohexaploidy
(c) allooctaploidy
A condition in which complete genomes of two or more species combine together.
Two copies each of two distinct genomes (2x1 + 2x2)
Two copies each of three distinct genomes (2x1+2x2+2x3)
Two copies each of four distinct species (2x1+2x2+2x3+2x4)

22. Crop Variety
Muskmelon Delta Gold
Watermelon Pusa Bedana, Seedless Sugar Baby, Crimson Sweet ( triploid variety)
Polyploidy breeding cucurbits

23. Tissue culture techniques
Tissue culture emerged as a significant advancement in breeding practices since traditional breeding methods
were unable to meet the demand for crops. It utilises a plant's component elements to quickly produce several
duplicates of the plant. The method takes advantage of the plant cell's totipotency, which allows any cell from
any region of the plant to be used to create an entirely-new plant.

24. Achievements of Tissue culture techniques
Sr.
No.
Crop Explant Best treatments
(mgl-1)
Result Author
1 Cucumis sativus L. Node MS + BAP (1.5) Full plantlet in
soil
Firoz Alam, et al.,
(2015)
2 Cucumis melo L. Shoot tip MS + BAP (2.0) Full plantlet in
soil
Faria, et al., (2013)
3 Citrallus lanatus L. Cotyledon MS + BAP (20.0
µM)
Full plantlet in
soil
Suratman, et al.,
(2009)
4 Luffa acutangular L. Cotyledon MS + BAP(1.5) Full plantlet in
soil
Karim (2013)
5 Momordica charantia L. Node ½ MS + BAP (0.5) Full plantlet in
soil
Verma, et al., (2014)

25. Molecular markers
• Molecular marker is identified as genetic marker.
• Molecular marker is a DNA or gene sequence within a recognized location on a chromosome
which is used as identification tool.
• In the pool of unknown DNA or in a whole chromosome, these molecular markers helps in
identification of particular sequence of DNA at particular location
• Molecular markers are widely used in the cucurbits family for various applications in plant
research, breeding, and crop improvement. These markers are DNA-based tools that allow
researchers to analyze genetic diversity, identify traits of interest, and make informed decisions in
breeding programs.
• Applications
- Genetic diversity assessment
- Marker-assisted selection (MAS)
- Quantitative trait loci (QTL) mapping
- Genetic linkage map construction
- Genomic selection
- Marker-assisted gene pyramiding

26. Achievements of Molecular Markers in cucurbits
Crop Botanical name Molecular markers References
Bottle gourd Lagenaria siceraria L. ISSR
SSR
Bhawna et al., 2014
Bhawna et al., 2015
Melon Cucumis melo L. SSR
SCAR
Bhawna et al., 2015
Watermelon Citrallus lanatus L. SCAR
RAPD and SCAR
Lin et al., 2009
Oumouloud et al., 2008
Cucumber Cucumis sativus L. AFLP
SSR
Sigva et al., 2015
Fukino et al., 2008
Pepo Cucubita moschata L. RAPD Gwanama et al., 2000

27. QTLs mapping
• A QTL {Quantitative Trait Locus (Loci)} term is coined by
Gelderman (1919) and is defined as “a region of the genome or locus
of gene that is associated with an effect on a quantitative trait”.
• QTL mapping is process of locating genes with effects on
quantitative traits using molecular markers.
• QTL mapping studies have reported in most of the crop plants for
diverse traits like yield, quality disease and insect pest resistance,
abiotic stress tolerance and environmental adaptation

28. Achievements of QTL Mapping in Cucurbits
QTL type Trait name Abbreviation QTL name Description of QTL
name
Single QTL Seed length SL Sl 1.1 First sl QTL on
Chromosome 1
Seed width SWD Swd 2.2 Second swd QTL on
Chromosome 2
Consensus QTL Watermelon
Seed size
CISS CISS 1.1 First consensus SS
QTL on watermelon
Chromosome 1
Cucumber
Seed size
CsSS CsSS 4.2 Second consensus SS
QTL on cucumber
chromosome 4
Melon
Seed size
CmSS CmSS 3.1 First consensus SS
QTL on melon
chromosome 3

29. Genetic Transformation
• Genetic engineering, also known as genetic modification or recombinant DNA technology, has
been extensively applied in the Cucurbitaceae family to introduce desirable traits, improve crop
performance, and enhance resistance to biotic and abiotic stresses
• R-DNA technique involves breaking of a DNA molecule at two desired places to isolate a specific
DNA segment and then inserting it into another DNA molecule at a desired position. The product
thus obtained is called Recombinant DNA and this technology is known as R-DNA technology
(Jakhar & Sastry 2002).
• Transgenics: A plant in which a foreign has been transferred through genetic engineering is called
a transgenic plant and the gene so transferred is called transgene (Singh 2001)..
• Applications
- Disease resistance
- Insect resistance
- Herbicide tolerance
- Improved nutritional quality
- Extended shelf life
- Abiotic stress tolerance

30. Transgenic developed in Cucurbits
Crop Gene Trait References
Watermelon WUSCHEL-related
homeobox (WOX)
Regeneration Zhang et al., (2015)
Cucumber CMV-cp Virus resistance Nishibayashi et al., 1996
Cucumber ZGMMV-cp Virus resistance Lee et al., 2002
Cucumber Thaumatin II Sweetening Szwacka et al., 2002
Cucumber DHN10 Abiotic stresses Yin et al., 2005

31. Case study (Mutation Breeding)
AL-Kubati et al., 2022 studied that Cucumber green mottle mosaic virus (CGMMV)
is a major threat to cucurbits-producing regions worldwide. Conventional breeding
process takes much time to cross plants and to select a good variety. In contrast to
conventional breeding, mutation breeding accelerates the process of cultivar
development and increases variety within a crop species. Hence, the aim of this
study was to develop bottle gourd lines that were resistant to CGMMV using
Ethyl Methane Sulfonate (EMS) mutagenesis. Total ≈10,000 seeds were treated
with two concentrations (v/v) of EMS (Aladdin, Shanghai), viz, 1.2% and 1.5%
at 25±2 °C for 8 h. By treating wild-type seeds (M0) with EMS, bottle gourd
lines (M1) were produced. "M1" lines were self-pollinated; as a result, 303
"M2" families were obtained. From M2 families, a total of 2444 "M3" lines
were obtained to screen resistance to CGMMV. These lines were then
transplanted in the field. Four of the 44 "M3" lines were asymptomatic in the field
and tested negative for CGMMV. The new findings show that using EMS-induced
mutations can create novel CGMMV highly resistant bottle gourd cultivars.

32. Case study (QTL Mapping)
Liu et al., 2021 studied QTL Mapping of Heat Tolerance in Cucumber (Cucumis sativus L.) at Adult
Stage. In this study, a set of 86 recombinant inbred lines (RILs) derived from “99281” (heat-
tolerant) and “931” (heat-sensitive) were used to identify the heat tolerance QTL in summer
2018, 2019, and 2020. Eight-week-old plants were exposed to a natural high temperature
environment in the field, and the heat injury index was used to indicate the heat tolerance
performance. Genetic analysis showed that the heat tolerance of adult cucumber is quantitatively
inherited. One QTL named qHT1.1 on chromosome 1 was identified. The efficiency of marker qHT-
1.1, which is closely linked to the locus, was tested using 62 cucumber germplasm accessions and
was found to have an accuracy of 97.8% in heat sensitive plants. The qHT1.1 was delimited to a
694.5-kb region, containing 98 genes, nine of which may be involved in heat tolerance. Further
sequence analysis showed that there are three single-base substitutions within the coding sequences
of Csa1G004990. Gene expression analyses suggested that the expression of Csa1G004990 was
significantly higher in “99281” than “931” at 14d, 35d, 42d, and 49d after transplanting. This
study provides practically useful markers for heat tolerance breeding in cucumber and
provides a basis for further identifying heat tolerant genes.

33. Conclusion
Although main breeding objective will continue to be increasing yield to meet
the food requirement of ever increasing population, but in order to ensure
health security, it is imperative that nutrition rich varieties are breed. We had
attained self sufficiency in food grains through conventional breeding
approach but now there is a need for second green revolution where not only
production/yield alone but quality food is the major breeding objective, this
cannot be realized alone with conventional as well as biotechnological
approach alone, so we have to find a mid-way where we will integrate these
two novel approaches for vegetable improvement. Conventional breeding in
conjunction with molecular biology has bright prospects of developing
vegetable varieties with high nutraceuticals and bio active compounds
suitable for fresh market.

34. References
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