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Hybridization

A Term Paper on SFB 705 Advanced Silviculture

Prepared and Presented by:Shankar TripathiM.Sc. In Forestry

Roll No.15

Table of Content

◦Introduction

◦Methodology

◦Discussion

◦conclusion

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

Cont. introObjective 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

◦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.

CONT.. INTRO

methodologyPrerequisites of hybridization

◦All the requirement of the tract

◦All the local condition

◦ Facilities

◦ Existing varieties of the crops

◦ Plant materials

◦Objectives to be attained

Method of hybridization

Pedigree selection

• produces new cultivars faster than mass selection

• In self-pollinated crop, it is used to release new varieties.

• In cross-pollinated crops, it is used to develop inbred lines.

Bulk method

• This method can handle segregating generations, in which F2 and subsequent generations are harvested in bulk to grow the next generation.

• 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.

Cont. methodology

Procedure of hybridization

Choice of parents

Evaluation of parents

Emasculation• Forcep or scissor method• Hot or cold water and

alcohol emasculation• Male sterility method

BaggingArtificial pollinationTagging

Harvesting and storing of F1

seed

Raising of hybrids

Trials, multiplication

and distribution

Difficulties in hybridization

◦Isolation of suitable parents and hybrids

◦Different times of maturity

◦Susceptibility to mutations

◦Incompatibility and sterility

CONT. METHODOLOGY

Discussion

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

CONT. METHODOLOGY

Advantage◦Creation of heritable variation◦The crossing of unlike individuals gives rise to entirely

new plants showing variations in their characters as compared to their parents. This variation is not due to 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.

CONT. DISCUSSION

Disadvantage

• Tedious, time consuming and expensive procedure

• Hybrid sterility

• Technical procedure

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.

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).

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).

conclusion

◦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.

CONT. METHODOLOGY

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