1. CREDIT SEMINAR ON HETEROSIS BREEDING IN CUCURBITACEOUS
VEGETABLE CROPS.
By:
A.Gopala krishna reddy
RAD/06-33.

2. Introduction
Vegetables occupying an important place in crop diversification, play a key role in food, nutritional and economic security of our country.
The vegetable production is around 1 billion tonnes with an average productivity of 15.1tonnes/ha.( )
To meet the availability of 300g/caput/day, India will need to produce 128 and 160 million tonnes of vegetables by 2011and 2021.(Table 1)

3. Period Production (Million tonnes) Demand 2005-06 103.12 108.1 2011-12
Table 1. Projected demand of vegetables
Period
Production
(Million tonnes)
Demand
103.12
108.1
116.25
128.0
150.91
160.0
(Mathura rai, 2006)

4. Concept of heterosis Hybrid vigour is synonymous to heterosis.
Heterosis is referred as a biological phenomenon in which F1 population obtained by crossing of two genetically dissimilar individuals, which shows increased or decreased vigour over better parent or over mid-parental value.
Generally, heterosis is manifested as an increase in vigour, size, growth rate, yield, earliness or some other characteristics etc.
(Shull,1914)

5. .
Concept of heterosis
But in some cases, the hybrid may be inferior to the weaker parent. This is also represented as heterosis (average heterosis) .
Heterosis is estimated over superior parent, such an estimate is sometimes referred to as heterobeltiosis.
Power (1944) also suggested that the term heterosis should be used only when the hybrid is either superior or inferior to both the parents.
Other situations should be regarded as partial or complete dominance. (Table 2)

6. Heterosis and dominance in relation to parental value(Table 2)
Phenomenon
Value of F1 hybrids
Position and value of parents
Heterosis
> 10
Parent A (10)
Complete dominance 10
Partial dominance
< 10 but > 8
No dominance 8
Mid-parent
< 8 but > 6 6
Parent B (6)
< 6

7. The general features of heterosis :
Heterosis is a widely occurring biological phenomenon in both the plant and animal species.
In plants, it has been reported to occur more frequently in a number of naturally cross-pollinated crop species as compared with self-pollinated ones.
The specific heterotic crosses usually show increase in size, vigour, seed producing capability, usually better resistance to insect pests or diseases, increased metabolic activity, earliness, better stability and thus ultimately result in better performance of hybrids than parents.
contd….

8. Heterosis is a genetically governed phenomenon.
Usually, these hybrids show better fitness and breeding value as compared to parents from which they are made.
Heterosis is a genetically governed phenomenon.
Heterosis is confined only to specific F1 or first hybrid generation and considerably diminishes in F2 and the later segregating generations.
This reduction in performance in later generations is because of the breakdown of specific gene combination building up the expression of heterosis.
contd….

9. It has been observed that the expression of heterosis is usually more in hybrids obtained from genetically unrelated lines.
The expression of heterosis is highly associated with specific combining ability of a cross.
Heterosis is usually unfixable from generation to generation .
But some natural contrivances, mechanism in nature are balanced lethal factors, apomixis or the use of vegetative reproduction. (fixable)

10. Types of heterosis (Dobzhansky, 1952).
Heterosis can be classified into two :
(i) Euheterosis (true heterosis) and
(ii) Pseudoheterosis (luxuriance)
Euheterosis is further divided into:
(a) Mutational euheterosis and
(b) Balanced euheterosis.
(Dobzhansky, 1952).

11. Mutational Euheterosis
It is the result of natural consequences of the phenomenon of dominance.
This is the simplest type of euheterosis derived from the overshadowing the deleterious, unfavourable often lethal, recessive mutants by their adaptively superior dominant alleles in population of sexually reproducing cross-fertilizing organisms.
(Dobzhansky, 1952).

12. Balanced Euheterosis
It is based on the theory of over-dominance and a type of true heterosis which arises out of a balanced, specifically-adapted gene combination or from the occurrence of rather special type of adapted mutations.
This makes the cross-pollinated species virtually and potentially self-improving ones under natural conditions.

13. Positive and Negative Heterosis
The superiority of F1 over its superior parent is referred as positive heterosis, whereas, its inferiority over inferior parents is negative heterosis.
Useful Heterosis
It refers to superiority of F1 over the standard commercial check variety. It is also called economic heterosis. This type of heterosis is of direct use in plant breeding.

14. Standard heterosis
Sometimes heterosis is worked out over standard commercial hybrid.
It is estimated in those crops where hybrids are already available for comparison.
This is also of direct practical importance in plant breeding.

15. Luxuriance
Luxuriance is the increased vigour and size of interspecific hybrids.
The difference between heterosis and luxuriance lies in the reproducing ability.
Heterosis is accompanied with an increased fertility ,while Luxuriance is expressed by interspecific hybrids that are generally sterile or poorly fertile.

16. Measurement of Heterosis
In a particular cross, heterosis is usually measured in terms of two parameters,
(i) heterosis over mid-parental (MP) value
(ii) heterosis over better parent (BP).
In plant breeding programmes, however, it is also estimated in terms of heterosis over the check variety.

17. Heterosis over mid parental value (relative heterosis):
F1 – MP
= x 100 MP
Heterosis over better parent (heterobletiosis):
F1 – BP BP
Where BP is the average performance of the better parent

18. Heterosis over the check parent (standard heterosis)
F1 – Check variety
= x 100
Check variety
Where check variety denotes its average performance.

19. BASIS OF HETEROSIS Genetic Basis of Heterosis
Physiological Basis of Heterosis
Biochemical Basis of Heterosis
Molecular Basis of Heterosis
Genetic Basis of Heterosis
1) Dominance Hypothesis
2) Over-dominance Hypothesis
3) Epistasis Hypothesis

20. Explanations of heterosis 1) Dominant-gene theory
This hypothesis suggests that dominant allels have favourable effect,while the recessive allels have unfavarable effect.
Parent lines should complement each other:
Inbred A x Inbred B AABBccddEE aabbCCDDEE
F1 hybrid
AaBbCcDdEE
(Davenport 1908).

21. 2) Theory of overdominance
Heterozygous loci contribute more to productivity than loci that are homozygous.
Contrasting alleles at a locus produce different favourable effects in the plant
Inbred A x Inbred B
a1a a2a2
F1 hybrid
a1a2
(East and shull 1908)

22. 3) Epistasis Hypothesis:
Gowen (1952), suggested that influence of one locus on the expression of another may be involved in heterosis.
It is also known nonallelic interaction. It is of three types viz. additive x additive, dominance x dominance and additive x dominance.
Majority of heterotic crosses show epistasis,but all heterotic crosses do not show epistasis, and all crosses that show epistasis are not heterotic.

23. Heterosis breeding involves three important stages:
Production of inbred lines.
Testing of combining ability of inbred lines and
Production of seed in bulk of promising and desirable F1 hybrids.

24. Inbreeding and hybridisation to produce desirable hybrids
YIELD
Parent population
Inbreeding
F1 hybrid population
Inbred line
population
Each hybrid can
be produced large
scale from its two
parental inbreds
Genotypes
cannot be
reproduced
Rare desirable
genotypes

25. Inbreeding and Production of Inbredlines
Inbreeding increases homozygosity and reduces the proportion of heterozygosity in population, thus reducing the vigour of plants.
For inbreeding, usually selfing and sibmating.
In cucurbitaceous crops, homozygous varieties can be used directly in place of inbred lines.

26. 2. Testing Combining Ability of Inbred Line
The successful exploitation of hybrid vigour depends upon combining abilities (General combining ability and Specific combining ability) of parental lines.
Generally, SCA value of the cross gives better predictive information than GCA of parents.
Besides, sca is also more reliable for the selection of parents for hybrid production.
The combining ability of inbred lines can be tested in top cross, single cross or diallele cross and polycross.

27. 3. Method of Hybrid Seed Production
Hybrid seed production in cucurbits has been simplified by manipulation of sex mechanism and sex expression.
Sex expression in cucurbits is under genetic as well as environmental influences.
Three of the primary variables of the plant environment, i.e. mineral nutrition, light and temperature regimes.

28. Different sex forms in cucurbits:
1) Monoecious : staminate and pistillate flowers.
2) Androecious : only staminate flowers.
3) Gynoecious : only pistillate flowers.
4) Hermaphrodite : Bisexual flowers.
5) Andromonoecious : staminate and Hermaphrodite flowers

29. Pinching of Male Flowers and Artificial pollination.
Production of hybrid seeds by this method is the most economical and practical way, which can easily be adopted by growers.
Female mature buds are identified from female parent plants and covered using paper bag in the evening before pollination takes place.

30. Male flower
Female flower

31. Matured male flower buds from male parent plants, which will open the next morning are identified and covered with paper bags.
Hybridization is done early the next morning ( am).
The paper bags are removed from female and male flowers.
Pollen-grains are collected using a fine brush and transformed to the stigma of female flowers.

32. Removal of Male Buds and Use of Insect Pollinators
The rows of female and pollen parent's lines are planted alternatively in an isolated field.
In this method, insect and natural pollen vector proof greenhouses can also used for hybrid seed production.

33. Chemicals on Sex Expression
Increasing female tendency:
Auxins ) Ethylene ) Acetylene
Increasing male tendency:
GA ) Silver nitrate (Ag No3)
3) Silver Thiosulphate [Ag(S2o3)2].
4) Aminoethoxy-vinylglycine(AVG).

34. Chemicals on Sex Expression
F1 seeds can be produced by application of ethrel (2-chloroethyl-phosphonic acid) at the rate of ppm at two true-leaf and four true-leaf stages.
Ethrel helps in suppressing the staminate flowers and initiating pistillate flowers successfully in the first few flowering node on female parent.
(Swarup, 1991)

35. Use of Gynomonoecious Lines (Muskmelon, Cucumber, Ridge gourd)
The gynomonoecious and monoecious (pollen parent) lines are planted alternately.
The monoecious and other intermediate plants from ‘gynomonoecious’ line must be removed at an early stage, preferably before the pistillate buds on gynoecious plants open.
Hybrid seed is collected from gynoecious plants which are left for seed production.

36. Use of Male Sterility (Water melon, Musk melon & Cucumber)
First recessive ms gene was reported by Bohn and Whitakar (1949), since then at least four additional male sterile recessive alleles, viz. ms-2 (Bhon and Principe, 1962), ms-3 (McCreight and Ebmstrom, 1984), ms-4 (Pilral, 1990) and ms-5 (Lecouviour et al, 1990) have been identified.
The ms-1 line has been successfully utilized in muskmelon to develop first commercial hybrid Punjab Hybrid-1 (ms-1 x Hara Madhu)
(Kumar et al., 2000).

37. Inheritance pattern male sterility
Male sterile Male fertile
ms1 ms X Ms1 Ms1
F Ms1 ms Male fertile
F % [ 1Ms1 Ms1: 2 Ms1 ms1 : 1 ms1 ms1 ]
F % [ 2 Ms1 ms1 : 1 ms1 ms1 ]
F % [1 Ms1 ms1 : 1 ms1 ms1]
Male fertile Male sterile
(Napuri et al.,1982)

38. Heterosis in Cucurbits can be manifested in different ways
1)High yield due to larger size or weight of fruit (watermelon, pumpkin, and squashes)
2) Early maturity (watermelon, muskmelon)
3)Better resistant to pest & diseases ( watermelon, cucumber)
4) Better resistant to drought (watermelon)
5) Better fruit quality (watermelon- better flavour and more sugar)

39. Heterosis for fruit yield in Bitter gourd
Eight promising lines viz;PBIG1,PBIG2,PBIG4, PBIG11, PBIG56, PBIG68, Kalyanpur Sona and Kalyanpur Baramasi along with their twenty eight F1 hybrids were tested at Vegetable ResearcCentre,Panthnagar.
The highest standard heterosis for fruits yield was observed for Kalyanpur Sona × Kalyanpur Barahmasi
(41.9%),followed by PBIG 68 × Kalyanpur Sona (19.3%) and PBIG 2× PBIG 1 (10.0%). (Table)
(Arunkumar,. et al 2004)

40. Character Crosses Stndard heterosis ( % )
Kharif Summer Avrage
Number of fruits KS × KB
per plants PBIG 68 × KS
PBIG 2 × PBIG
PBIG2 × PBIG
Fruit yield KS × KB
PBIG 68 × KS
PBIG 2 × PBIG
PBIG2 × PBIG
(Arunkumar., et al 2004)

41. Heterobeltiosis for fruit yield Standard heterosis for fruit yield
Estimates of heterobeltiosis, standard heterosis for fruit yield per vine (kg) in Bitter gourd
Crosses
Heterobeltiosis for fruit yield
Standard heterosis for fruit yield
Summer
Rainy
Average
PBIG-1 X PBIG-2
27.56
0.78**
14.17
47.27
73.33**
60.30**
PBIG-1 X PBIG-4
42.73
77.33**
58.03**
PBIG-1 X KS
-12.41
25.33**
6.46**
15.46
25.33
20.40**
PBIG-1 X KB
46.36
91.71**
69.04**
82.67**
64.52**
PBIG-1 X PW
56.36
61.95**
60.16**
88.00**
72.18
PBIG-2 X PBIG-4
30.71
-24.03**
3.34**
50.91
30.67**
40.79*
PBIG-2 X KS
24.14
19.38**
21.76**
63.64
105.33**
84.49**
PBIG-2 X KB
-12.59
-19.38
-15.99
0.91
38.67
19.79**
PBIG-2 X PW
80.32
8.53**
44.43**
108.18
86.67**
97.43**
PBIG-4 X KS
18.62
69.23**
43.93**
80.85**
PBIG-4 X KB
66.28
30.14**
48.21*
30.00**
26.67
28.34*
PBIG-4 X PW
20.59
26.74**
23.67*
11.81
45.33
28.57**
KS X KB
42.76
97.8**
70.28**
88.18
104.00**
114.09**
KS X PW
24.83
46.15**
33.49**
64.55
70.94**
KB X PW
38.24
112.79**
75.52**
28.18
144.00**
86.09**
* & ** significant at 5% & 1% level of significance, respectively. (Tiwari et al., 2001)

42. Heterosis for yield and yield related attributes in muskmelon (Cucumis melo L.)
Eight genetically diverse inbred lines viz., MS1,RM-43, MHY-3,Panjab Sunheri, Jobner Local, Hara Madhu, Tonk Local and Durgapura Madhu were crossed in a diallel fashion excluding reciprocals.
(Chowdary .,et al )

43. Performnce of two superior F1’S (for each observation ) selected out of
28 crosses in Muskmelon ( *Significant at 5% level )
Crosses Heterosis per cent over Hybrid CD at 5%
Better Standard mean
parent check
Number of marketable fruits/plants
Hara Madhu ×Tonk Local * *
MS1 × hara Madhu
Fruit yield/plant(kg)
MS1 × Hara Madhu *
Jobner Local × Durgapura madhu *
Total soluble solids(%)
Panjab Sunheri × Tonk Local *
Panjab Sunheri × Jobner Local * *
Severity of downy mildew (%)
MS1 × Durgapura Madhu
RM-43 × Punjab Sunheri
Severity of powdery mildew (%)
MS1 × Durgapura Madhu *
RM-43 × MHY *
(Chowdary .,et al )

44. Heterosis in cucumber
Fifteen lines namely DC-1, B-159, B-157, B-184, VRC-11-2, VRC-7, VRC-19,Bihar-10, Patna-3, VRC-18-2,CHC-1, poinsette, FZCU-4, PCUC-1 and EC , were used to develop 77 F1 in different combinations.
High yielding F1 hybrids DC-1 x B-159 and VRC-11-2 xBihar-10 which recorded highest heterosis over better parent and mid parents with total fruit yield of kgand 60.19kg.(Table)
(pandey et al.,2005)

45. Heterosis in cucumber Hybrids Heterosis(%) Total fruit wt. kg
BP MP
DC-1 x B-159
VRC-11-2x Bihar-10
VRC-19 x B-157
FZCU-4 x Patna-3
EC x CHC-1
VRC-18-2 x B-184
VRC-7 x PCUC-1
Poinsette x VRC-18-2
PCUC-1 x PCUC-1
VRC-18-2 x CHC-1
LSD at 0.055
SE+-
** **
** *
(pandey et al.,2005)

46. Cross Attributes Promising crosses of cucumber showing high heterosis
VIR-50 x VIR-505
Intense photosynthetic activity and high-yielding
Conqueror x Vijazhiki-37
Early and high-yielding
Don-175 x Boston
High germination, growth rate and better pollen viability
MSU x Spartan-27
(Japanese gynoecious line) x Green long of Naples), Pusa Sanyog
Udipi x Kasargod
High yielding
Nileswar x Udipi
CH x CH
Number of fruits
( Prasad and Singh 1992 )

47. Crosses showing high heterosis in watermelon Cross Attributes
Special 1 (Round) x Charleston Gray (long)
Round-fruited, high-yielding and high TSS
Shipper (round) x Harleston Gray’ (long)
Sweet Princess (long) x Special 1 (round)
Round-fruited and high-yielding
Crimson Sweet x New Hampshire
High-yielding and high TSS
Midget IHR 6 x Charleston Gray
( Peter 1998 )

48. Heterosis for high yield in Ridge gourd
Rao (2000) showed appreciable heterosis over better parental lines consistently over the seasons for yield and its contributing characters.
The FI hybrids, LA-46 X LA-99 and LA-12 x LA-76, showed 51.8 and 125.9,81.8 and 121.1% higher yield over the better parent in kharif and summer seasons, respectively.
The best F1 hybrid LA-46 X LA-99, which gave 51.8 and 125.9% higher yield over better parent and top-parent.

49. Heterosis in Bottle gourd
Bottle gourd, two lines, Sel-2 in long type and Sel-ll in round type, have been found to combine well the IARI recommended varieties.
Two hybrids have released as Pusa Meghdoot (Pusa Summer Prolofic Long x Sel-2) and Pusa Manjari (Pusa Summer Prolific Round x Sel-11).
Pusa Meghdoot recorded 75% increase in total yield, while Pusa Manjari increased 106%.
( Verma 1997)

50. Number of fruits per vine
Heterosis over the better parent Bottle gourd.
Crosses
Number of fruits per vine
Vine length
Yield per vine
Yield per hectare
PSPL
x LC2-1
29.03*
-22.05*
31.27*
x Pusa Naveen
4.05*
-20.56*
-2.95
x KBG-16
3.00*
-24.04*
17.10*
x NDBG-56
12.92*
-9.95*
-16.53*
-16.52*
x PBOG-40
-21.21*
-4.89*
-25.18*
x PBOG-61
-21.05*
10.38*
10.19*
x ARBGH-7
7.05*
-36.45*
ARBGH-7
29.87*
-20.47*
72.50*
58.63*
-20.09
84.53*
27.79*
-13.73*
37.41*
29.71*
-4.12*
2.48
23.66*
-13.60*
-17.95*
-10.97*
-3.87
6.70
(Singh et al.,2000)

51. Number of fruits per vine
Crosses
Number of fruits per vine
Vine length
Yield per vine
Yield per hectare
PBOG-61
x LC2-1
16.01*
8.13*
29.90*
x Pusa Naveen
17.65*
-5.36*
10.36*
x KBG-16
-13.49*
5.04*
14.32*
x NDBG-56
-16.77*
14.23*
-1.10
x PBOG-40
24.39*
-1.73*
16.20*
PBOG-40
1.58
-24.76*
4.23
3.17*
-11.82*
-3.99
-17.93*
-1.58*
5.98
-1.46*
-0.32
-4.49
NDBG-56
12.20*
5.27*
25.59*
29.72*
0.99*
3.86
4.01*
-2.34*
1.65
(Singh et al.,2000)

52. Number of fruits per vine
Crosses
Number of fruits per vine
Vine length
Yield per vine
Yield per hectare
KBG-16
x LC2-1
11.22*
-6.48*
4.53
x Pusa Naveen
51.07*
-3.24*
43.28*
Pusa Naveen
28.058
3.37*
23.26*
CD at 5%
2.99
0.69
0.28
14.07
(Singh et al.,2000)

53. * & ** Significant at 5% & 1% level of significance, respectively
Estimates of heterosis (%) over better parent (BP), standard varieties PN (SV1), in Bottle gourd.
Name of the crosses
Total yield plant-1
Heterosis over BP
Heterosis over (SV1)
Sel. 16 x 9503
30.27**
3.58
Sel. 16 x KLG
38.23**
0.92
Sel. 16 x PN
4.87**
4.86
Sel. 16 x PSPL
6.34**
-6.94
Sel. 16 x BTG1
16.28**
-23.58**
9503 x KLG
18.92**
-5.43
9503 x PN
16.37**
16.30**
9503 x PSPL
59.73**
39.65**
9503 x BTG 1
-30.05**
-44.39**
KLG x PN
31.37**
31.33**
KLG x PSPL
26.33**
10.52**
KLG x BTG 1
-2.88**
-29.02**
PN x PSPL
43.82**
PN x BTG-1
2.13**
2.08
PSPL x BTG 1
-5.57**
-17.46**
(Pandey et al.,2004)
* & ** Significant at 5% & 1% level of significance, respectively

54. Heterosis studies in Ridge gourd
No. of fruits per plant Yield per plant Average fruit weight
crosses
HB (%) SH (%) HB (%) SH (%) HB (%) SH (%)
LA 81X LA
LA 81X LA ** 129.0** ** **
LA 81X LA ** ** **
LA 81X LA
LA 43X LA ** ** *
LA 43X LA ** * *
LA 43X LA *
LA 44X LA ** *
LA 44X LA
LA 87X LA * 54.71* ** SE
CD(0.05)
CD(0.01)
* & ** Significant at 5% & 1% level of significance (T.J Mole et al .,2001)

55. Conclusion:
Heterosis plays a major role in improving cucurbitaceous vegetables by development of hybrids. Large experimental evidence indicates that heterosis is exploited only to some extent, but still there is lot of scope to exploit heterosis as cucurbits have wide range of genetic variability.

56. Thank you