This document discusses distant hybridization in fruit crops. It begins by defining interspecific and intergeneric hybridization. It then reviews the history of important early hybrids created, such as triticale. The main features of distant hybridization are that it is used to transfer desirable genes between related species when the trait is lacking within a species. It can result in fully fertile, partially fertile, or fully sterile crosses depending on the species. Problems that can occur include cross incompatibility, hybrid inviability, hybrid sterility, and hybrid breakdown. Techniques to overcome these barriers include manipulation of ploidy levels, use of growth regulators, embryo rescue, somatic hybridization, and use of bridge species. Several case studies are presented

1. 5/16/2020 1
Distant Hybridization in Fruit Crops
Credit Seminar On
Sanjay K S

2. Introduction
Interspecific Hybridization
Species 1 of Genus A X Species 2 of Genus A
F1
Intergeneric Hybridization
Species of Genus A X Species of Genus B
F1

3. History
• Thomas Fairchild (1717): First interspecific hybrid
Carnation Sweet William
(Dianthus caryophyllus) (Dianthus barbatus)
x

4. • Rimpau (1890): Produced the first intergeneric hybrid Triticale
Wheat Rye
x

5. • Karpechenko (1928): Intergeneric hybrid- Raphanobrassica
Raphanus sativus B. oleracea var. capitata
X
x

6. Main features of Distant hybridizatiton
 It is used when the desirable character is not found within the species
of a crop
 It is an effective method of transferring desirable gene into cultivated
plants from their related cultivated or wild species.
 It gives rise to three types of crosses viz. a) fully fertile, b) Partially
fertile and c) Fully sterile in different crop species.
 It leads to Introgression which refers to transfer of some genes from
one species into genome of another species.
 F1 hybrid between two genus are always sterile. The fertility has to be
restored by doubling of chromosome through colchicine treatment.

7. Types of crosses obtained during distant hybridization
• Fully fertile crosses: Between species that have complete chromosomal
homology. Chromosome in such hybrids have normal pairing at meiosis.
E.g., Mango, citrus
• Partially fertile crosses: Between species which differ in chromosome
number but have some chromosome in common. In such situation , F1
plants are partially fertile and partially sterile.
• Fully sterile crosses: Between species which do not have chromosomal
homology. Such hybrids can be made self fertile by doubling the
chromosomes.

8. Problems associated with wide crosses
• Cross Incompatibility
• Hybrid Inviability
• Hybrid Sterility
• Hybrid Breakdown

9. Cross Incompatibility
Pre –fertilization barriers
• Lack of pollen germination
• Insufficient growth of pollen tube to reach ovule
• Inability of male gamete to unite with the egg cell.
Overcome by
• Reciprocal crosses
• Bridge crosses
• Using pollen mixtures
• Pistil manipulations
• Use of growth regulators etc.

10. Hybrid Inviability
development of the zygote is arrested
embryo gets aborted
• Unfavourable interactions between chromosomes
• Unfavourable interaction of the endosperm with the embryo
• Disharmony between cytoplasm and nuclear genes
overcome by
• Reciprocal crosses
• application of growth hormones
• embryo rescue

11. Hybrid Sterility
• Inability of a hybrid to produce viable
offspring
• Incomplete pairing of chromosomes.
• overcome by amphidiploidization using
colchicine

12. Hybrid Breakdown
• F1 hybrid plants of an interspecific crosses
are vigorous and fertile but there F2 progeny
is weak and sterile
• Due to the structural difference of chromosomes
or problems in gene combinations

13. Techniques To Overcome Barriers In Wide
Hybridization
Manipulation of ploidy level
Strawberry:
Fragaria x annanasa X Fragaria nilgerrensis
(Cultivated strawberry) (wild species having peach aroma)
Sterile Hybrid having peach aroma
chromosome doubling
Fertile hybrid having peach aroma

14. Use of nutrient solution or growth regulators
Resistance source for PRSV and cold- Vasconcellea genus
Incompatible with cultivated species-Carica papaya
Using nutrient solution (sucrose 5%) (Jayavalli et al.,2011)
enhanced pollen germination and pollen tube growth
generation of viable hybrid embryo

15. Embryo rescue

16. Somatic Hybridization Technique

17. Incompatible
X V. candamarcensis
Failure to form hybrid
Compatible
Carica papaya X
F1 X
Hybrid formation

18. Carica papaya and V. candamarcensis are incompatible
Vasconcellea parviflora is compatible with both the species
As a bridge species Vasconcellea parviflora can be utilized
Use of Bridge Species

19. Desirable gene sources
Mango
Mangifera caesia White pulp, sweet and fragrant
M. decandra, M. gedebe Rootstock for water-logged conditions
M. Indica var. mekongensis Fruits twice a year
M. pajang Fruits can be peeled like Banana
M. similis Freestone mangoes
Annona
A. purpurea Orange flesh, thick fruit skin resistant to
cracking
A. scleroderma, A. festudinea Thick and hard shell

20. Grapes
Disease/ pest/ stress Resistance source
Downy mildew V. riparia, V. rupestris, V. labrusca
anthracnose V. simpsoni, V. rotundifolia
powdery mildew V. aestivalis, V. cinerea, V. barlendieri
RKN V. champini, V. candicans
pierce’s disease V. rotundifolia, V. vulpina
cold damage V. riparia, V. labrusca, V. amurensis
Iron chlorosis V. Berlandieri
salinity V. champini, V. berlandieri

21. Disease/ pest/ stress Resistance source
Papaya
Papaya ringspot virus V. cauliflora, quercifolia
Cold hardiness V. candamarcensis
Distortion ringspot virus V. pubescence, V. stipulate, V. heibornii
Guava
wilt Psidium molle, P. guineese
Banana
black sigatoka M. a. ssp malaccensis, M. a. ssp
burmanica
Panama wilt M. balbisiana, M. a. ssp burmanica

22. Apple
Disease/ pest/ stress Resistance source
Rosy leaf curl aphid M. xrobusta
Powdery mildew
M. xrobusta, M. xzumi
Scab
M. baccata, M. floribunda, M.
micromalus
Apricot
cold Prunus sibirica, P. mandschurica

23. Applications
1. Improvement of fruit quality
2. Fruits with less seeds
3. Abiotic stress tolerance
4. Biotic stress tolerance
5. Alternatives for GM crops

24. Case Studies

25. Case Study 1

26. Fig. 2. Production of intergeneric hybrid plants by embryo rescue

27. Table 1. Evaluation of PLDMV resistance in the parent plants and intergeneric
hybrids by means of mechanical inoculation
Plant material
No. of
plants
tested
No
symptoms
Typical
symptoms
Necrotic
lesions
C. Papaya (control) 23 23 0 0
C. papaya (PLDMV) 27 0 27 0
V. cundinamarcensis
(control)
50 50 0 0
V. cundinamarcensis
(PLDMV)
66 66 0 0
Intergeneric hybrid
(control)
84 84 0 0
Intergeneric hybrid
(PLDMV)
134 41 0 93

28. Fig. 3. Confirmation of intergeneric hybridization by flow cytometry to
determine the relative nuclear DNA content.

29. Continued…

30. Fig. 4. Confirmation of intergeneric hybridization by PCR

31. Fig. 1. Symptoms on the inoculated leaves

32. Fig. 5.Detection of the partial coat protein gene of PLDMV by RT-PCR
C. papaya with severe mosaic
symptoms
V. cundinamarcensis with no
symptoms
Intergeneric hybrid with no
symptoms
Intergeneric hybrid with
necrotic lesions

33. Case study 2

34. Table 1 Reaction of parents and F2 progenies against artificial inoculation of
PRSV under glass house conditions.
parents
Hybrids
5 5 0.216

35. Case study 3

36. Materials and methods
F. x annanasa cv. Toyonoka X F. nilgerrensis cv. Yunnan
TN-13 (Pentaploid and sterile)
(colchicine treatment)
TN13-113 and TN13-125( Decaploid and fertile)
TN13-125 X F. x annanasa cv. Pajaro
(Back crossing)
TNP-05 and TNP-14

37. Lines
Relative value of peaks (%)
components
Ethyl
acetate
Methyl n-
butyrate
Ethyl n-
butyrate
Butyl
acetate
Formic
acid
Caproic
acid
furano
ne
TN13-125 23.0 1.5 1.3 6.6 4.8 1.5 2.4
TNP-05 5.8 6.9 2.8 12.3 - 0.9 1.2
TNP-14 5.9 1.1 8.7 6.0 - 1.2 1.8
Toyonoka 1.9 8.5 21.5 3.7 1.3 1.4 3.1
Yunnan 19.5 0.0 5.5 7.0 1.4 0.8 3.4
Table 2 : Comparison of the main aroma components of Interspecific
hybrids

38. Case Study 4

40. Table. 1. Average berry and seed weight

41. seeded berries from C41-7
Parthenocarpic berries from C41-7
mature berries from C41-5
overripe berries from C41-5

42. Aborted seed of
Thompson Seedless
Flame Seedless
C41-5
Seeded Black Corinth
C41-7
seed of

43. Case Study 5

44. Table 1. Reaction of resistance (R) or susceptibility (S) to Meloidogyne enterolobii
•

45. Table 2. Tolerance reaction (R) or susceptibility reaction (S) assessed 120 days after
inoculating with an initial population of 10,000 eggs

46. Fig 1. Absence of galls in the root
system of the hybrid
GUA161 PE X ARA138 RR
Fig 2. presence of galls in the root
system of the hybrid
GUA161 PE X ARA153 BA

47. Fig 3. Three-months-old plant of the
GUA 161 PE × ARA138RR hybrid
grafted with ‘Paluma’
Fig 4. Four-months-old plant of the
GUA 161 PE × ARA138RR hybrid in
the field infested with M. Enterolobii.

48. CONCLUSION
Varieties 1. Resistant to destructive pest and disease
2. Tolerant to abiotic stress
3. With improved quality fruits
Increase in germplasm resources which can be utilized to cross with
different varieties in different combinations
Alternatives for GM crops
Rootstock breeding is needed
Need to develop improved methods of crossing and overcoming
barriers
Need to work on wild species to identify genes of interest

49. THANK YOU ALL