4. introduction
Tree improvement
◦ Concerned with how trees vary and how this variation can
be utilized to improve forest productivity
◦ Three method
◦ Species/ Provenance selection
◦ Population improvement
◦ Hybridization
Hybridization
◦ the process of interbreeding between individuals of different
species or genetically divergent individuals from the same
species.
◦ Create variation
5. Cont.
intro
Objective of hybridization
◦ To create genetic variation
◦ Transfer of one or few qualitative characters into a single
variety from another varieties (combination breeding).
◦ Improvement in one or more quantitative characters through
transgressive segregation (transgressive breeding).
◦ Use of F1 as a hybrid variety
Type of hybridization
◦ Intervarietal hybridization (Intraspecific hybridization):
◦ crosses between parents belong to the same species
◦ Simple cross: two parents are crossed to produce F1
◦ Complex cross: more than two parents are crossed to produce
hybrids
6. CONT..
INTRO
◦ Distant hybridization (interspecific hybridization):
◦ crosses between different species.
◦ between the species and within the same genus.
◦ commonly used for transferring the genes of disease, insect pests and drought
resistance varieties.
◦ All the interspecific hybrids of two homozygous plants are uniform as a
consequence of their identity in genetic constitution.
◦ Intergeneric hybridization:
◦ the crosses made between the plants belonging to two different genera.
◦ usually used for transferring the characters like disease, insect and drought
resistance from wild genera into the cultivated plants.
◦ Introgressive hybridization:
◦ one species is completely replaced by another in nature.
◦ if one species is more abundant than the other, the F1 and subsequent hybrids
will have more opportunities of backcrossing to that species than to the less
abundant species. After a few such backcrosses, most of the individuals of
hybrid population will appear as pure species rather than hybrids. This
absorbing of one species by another is known as introgressive hybridization.
7. methodology
Method of hybridization
Prerequisites of hybridization
Pedigree selection
◦ All the requirement of the tract
produces new cultivars
◦ All• the local condition faster than mass selection
• In self-pollinated crop, it is used to release new varieties.
◦ Facilities
• In cross-pollinated crops, it is used to develop inbred lines.
◦ Existing varieties of the crops
Bulk method
◦ Plant materials
• This method can handle segregating generations, in which F2 and subsequent generations
◦ Objectives to be attained grow the next generation.
are harvested in bulk to
• At the end of bulking period, individual plant selection and evaluation is carried out in
the similar way as in pedigree method.
Single seed descent
• modification of the bulk method.
• Instead of bulking a whole seed lot of selected plant, a single seed is selected randomly
from each selected plant to make bulk.
Backcross breeding
• A cross between a hybrid and one of its parents is known as backcross.
• applicable to both self and cross-pollinated species
• used for development of multiline and transfer of male sterility.
8. Cont.
methodology
Procedure of hybridization
Emasculation
Choice of
parents
Evaluation of
parents
• Forcep or scissor method
• Hot or cold water and
alcohol emasculation
• Male sterility method
Tagging
Artificial
pollination
Bagging
Harvesting and
storing of F1
seed
Raising of
hybrids
Trials,
multiplication
and distribution
10. CONT.
Discussion
METHODOLOGY
Application of hybridization in tree improvement
◦ Used in commercial plantation
◦ Insect resistant and good quality tree production
◦ Reduce inputs and increase yields to meet
increasing demand of wood, pulp and paper based
industry.
◦ Large gains in productivity more quickly than
population improvement
11. CONT.
DISCUSSION
Advantage
Disadvantage
◦ • Tedious, time consuming and expensive procedure
Creation of heritable variation
The crossing
•◦Hybrid sterility of unlike individuals gives rise to entirely
new plants showing variations in their characters as
• Technical procedure parents. This variation is not due to
compared to their
creation of any new genes but simply due to Mendelian
recombination of the genes already present in the
population.
◦ Production of superior varieties
◦ Hybridization brings all these useful factors together and
concentrates them into a single variety.
12. CONT..
DISCUSSION
Some examples of hybridization
◦ Acacia
◦ naturally crossed hybrids of A. Mangium and A. Auriculiformis have been
found in acacia plantation area of bangladesh. The hybrid has also been found
in sabah, malaysia, vietnam, and thailand. Most of the report shows that
hybrid acacia is more productive than either parent species on different site
types (lapongon 1998, pinos and nasi 1991, hardwood 1999, kijkar 1999,
cited by ghani, et al. 2001).
◦ Prosopis
◦ Artificial interspecific hybridization of P. cineraria and P. juliflora has been
carried out at Hariyana Agricultural University in India (Dhillon and Hooda,
2005)
◦ Leucaena
◦ Interspecific hybridization in Leucaena has also been done in Brazil. The
crosses performed in between L. leucocephala x L. diversifolia and L.
leucocephala with L. pulverulenta, L. esculenta, and L. shanonii.
13. CONT..
DISCUSSION
Some examples of hybridization
◦ Pinus
◦ Interspecific hybridization of P. Caribaea and P. Tecunumanii has been performed in
queensland which has early fast growth for successful establishment in grassland
(nikles, 1993).
◦ Intraspecific hybridization of P. caribaea var. Hondurensis (fast growth and adaptablity)
and P. caribaea var. caribaea (cyclone and tip moth resistance) is being tested in
queensland (nikles, 1993)
◦ Populus
◦ The hybrids which are widely planted and conspicuously effective in afforestation in
china are as follows: P. Popularishsu., P. Simonii, P. Simonii nigra var. Italica keohe
no. 12', p. Pekineca hsu, P. Simonii P. Italica (jusheng, H. 1984 ).
◦ Eucalyptus
◦ The successful operational use in brazil and congo of interspecific hybrids involving E.
Grandis, E. Pellita and E. Urophylla is widely known.
◦ Industrial plantation of eucalyptus are being conducted extensively already in
indonesia, india, nepal, pakistan, philippines and thailand (nikles, 1993).
14. CONT..
DISCUSSION
◦ Larix
◦ The interspecific hybridization of larix conducted in forest research institute in
china. The hybrids obtained are: larix gmelini L. Leptolepis, L. Leptolepis
L. Olgensis (jusheng, 1984).
◦ Improvement obtained over hybrids of larix deciduas with l. Leptolepis is 9-15%
in ht, 9-18% in diameter and 3-27% in volume than their parent trees (venkatesh,
1981).
◦ Others
◦ Some successes have been achieved in hybridization of other species, such as
liriodendron chinense L. Tulipifera, juglans mandshurica J. Regia,
paulownia fortunei P. Fargesii, paulownia kawakamii P. Fortunei, and
aleurites fordii, thea oleosa, etc in forest science research institute of heilongjian
province and northeastern forestry college of china (jusheng, 1984).
15. CONT.
conclusion
METHODOLOGY
◦ Hybridization is common method of tree improvement
which is used to create genetic variation performed by very
professional technicians.
◦ It can be applied in both self and cross pollinated species.
◦ Four type of hybridization can be performed i.e. Intervarietal
hybridization (Intraspecific hybridization), distant
hybridization (Interspecific hybridization), Intergeneric
hybridization, and Introgressive hybridization by applying
pedigree selection, bulk method, single seed descent and
backcross breeding menthod.
◦ Hybridization has been applied in Acacia, Prosopis,
Leucaena, Pinus, Populus, Eucalyptus, Larix and some other
species in the different parts of the world.
