Bulk Method Pedigree Method

&Line Breeding

PRESENTED BY: Pawan NagarReg. no.: 04-2690-2015M.Sc.(Fruit Science)

BULK METHOD The bulk method of breeding was first

used by Nilson – Ehle in 1908. This method is also known as “Mass

Method” or the “The Population Method”.

Bulk population breeding is a strategy of crop improvement in which the natural selection effect is solicited more directly in the early generations of the procedure by delaying stringent artificial selection until later generations.

In the bulk method , F2 and subsequent generations are harvested in mass or as bulks to raise the next generation.

At the end of bulking period , individual plants are selected and evaluated in a similar manner as in pedigree method.

The duration of bulking may vary from 6-7 to 30 or more generations.

During bulking period, artificial selection may or may not be practiced , but natural selection plays an important role in shifting gene frequencies.

When desirable purposes are fulfilled , bulking is stopped and individual plants are selected and evaluated.

ADVANTAGESLess record keeping than pedigree

which saves time & labour.Very simple, convenient & less

expensive.Natural selection increases the

frequency of superior genotypes in the population.

More useful than pedigree method with lower h2 traits

There is greater chance for isolation of transgressive segregates than in pedigree method due to large population.

Most suitable for improvement of small grains.

DISADVANTAGES

1.Environmental changes from season to season so adaptive advantages shift

2. It takes much longer time to develop a new variety.

3. Not useful in selecting plant types at a competitive disadvantage (dwarf types)

4.Final genotypes may be able to withstand environmental stress, but may not be highest yielding

5. If used with a cross pollinated species, inbreeding depression may be a problem

6. It provides little opportunity for breeder to exercise his skill or judgement in selection.

APPLICATIONS The bulk method is suitable for

handling the segregating generations of cereals, small millets, grain legumes and oilseeds. It may be for different purposes like :-

1) Isolation of homozygous lines with a minimum efforts and expenses.

2) Waiting for the opportunity for selection , natural /suitable environmental condition.

3) To provide opportunity for natural selection to change the composition of the population.

PEDIGREE METHODThe method was first described by

H. H. Lowe in 1927. Pedigree : “A description of the

ancestors of an individual and it generally goes back to some back to some distant ancestors in the past”

Thus, a pedigree would describe the parents , grand parents , great grand parents and so on.

The pedigree is helpful in finding out if two individuals are related by descent their ancestry, and therefore, are likely to have some genes in common.

PEDIGREE RECORD

In pedigree method, a detailed record of the relationships between the selected plants and their progenies is maintained.

As a result, each progeny in every generation can be traced back to the F2 plants from which it is originated such a record is known as Pedigree- Record.

PROCEDURES In pedigree method, individual plants

are selected from F2 and the subsequent generations, and their progenies are tested.

During the entire operation a pedigree record is kept.

Individual plant selection is continued till the progenies show no segregation. At this stage , selection is done among the progenies because there would be no genetic variation within the progenies.

ADVANTAGES1. Record keeping provides a catalog of

genetic information of the cultivar.2. Selection is based not only on

phenotype but also on genotype (progeny row).

3. Using the records, the breeder is able to advance only the progeny lines in which plants that carry the genes for the target traits occur.

4. A high degree of genetic purity is produced in the cultivar.

5. The breeding value of value of selected plants is ascertained by progeny test.

DISADVANTAGES1. Record keeping is slow, tedious, time-

consuming, and expensive. 2. The method is not suitable for species

in which individual plants are difficult to isolate and characterize.

3. Pedigree selection is a long procedure, requiring about 10–12 years or more to complete, if only one growing season is possible.

4. Since large number of progenies are rejected in this method, there are chances of elimination of some valuable material.

APPLICATIONS For the improvement of self pollinated

species for the development of new pure line varieties.

This method is also used in cross pollinated species for the development of inbred lines.

Used for polygenic traits than oligogenic.

It is used to correct some specific weakness of an established variety with aims to improve the yield and quality parameters.

It is also useful in the selection of new superior recombinants from segregating population.

ACHIEVEMENTSCrop ExamplesRice Krishna,Sarbarmati,Ratna,Padma,Jaya,Bala,Kave

riWheat HD 2281, HD2285,HD2380, ND 2402 , Janak ,

Pratp, Raj 2535Cotton LH 900, LH 1556, F 846, F 1054, F 1378, HS 6,

Vikas, Sharda , MCU 9, MCU 11, LRA 5166Pigeon pea T 21, PrabhatGreen gram T2, T 44 , T51, SheelaChickpea T1, T2, T3, T5 , RadheyPea Pant Matar 2, Jawahar Matar 1, Jawakar Matar 4

Pedigree Method Bulk Method

1 Most widely used Breeding method

Used only to a limited extent

2 Individual plants are selected in F2 & subsequent generations and individual plant progenies are grown

F2 and subsequent generations aregrown in bulk

3 Artificial selection ; artificial disease epidemics etc. are an integral part of the method

Mainly natural selection. In certaincases artificial selection may beessential

4 Pedigree Records have to bemaintained which is often time consuming &laborious

No pedigree records are maintained

5 Generally its taken 12-13 years to release new variety

Takes more than 15 years.

6 Requires close attention of breeder from F2 onwards

It is quite simple and does notrequire much attention

LINE BREEDING Three types of line Breeding

Approaches in Line Breeding

1. One Line Approach

2. Two Line Approach

3. Three Line Approach

ONE LINE BREEDING - APOMIXIS

Apomictic lines are those lines which are developed without means of sexual reproduction and they have different component ways in producing like parthenogenesis, apogamy, apospory,and adventive embryony .

Since these lines are capable of maintaining genetic purity over generations there is high regard for these to produce hybrid.

Apomixis is effective means for rapid production of pure lines

APOMIXIS Haploid parthenogenesis give rise to haploid

plants which upon colichine treatment will produce diploid pure lines that can be used in plant breeding programmes.

A superior plant type which produce seed by apomictic means will usually bread true for the characteristics of mother plant

Thus apomixis is useful in maintaining the characteristics of mother plant from generation to generation.

TWO LINE BREEDING

Two line Approach

Cytoplasmic Male Sterility

Genetic Male Sterility

GENETIC MALE STERILITY The male sterile line (ms ms ) is

allowed to be cross pollinated with a male fertile (Ms Ms ) that combines well with the male sterile line, the seed produced on the male sterile line is the hybrid seed, the hybrid is male fertile (Ms ms )

It commercially exploited in castor and pigeon pea.

GMS presents a serious problem , in the female parent , 50 % is male fertile which is identified and eliminated before they shed pollen.

THIS PROBLEM IS OVERCOME BY PHOTOPERIOD SENSITIVE OR TEMPERATURE SENSITIVE GENETIC MALE STERILITY . HOW IT IS WORKS IS SHOWN UNDER.

Location A(<28·c temp)

TGMS Line (5460S)

TGMS LINE

Male fertile selfing

Location B (>30·c temp)

TGMS Line × Male Fertile Line

Hybrid Seed

CYTOPLASMIC MALE STERILITY This type of male sterility is determined by the

cytoplasm. Since the cytoplasm of a zygote comes primarily from

egg cell, the progeny of such male sterile plants would always be male sterile.

Nuclear genotype of male sterile line would be almost identical to that of the recurrent pollinator strain.

The male sterile line is maintained by crossing it with the pollinator strain used as the recurrent parent in the backcross programme since its nuclear genotype is identical with that of this new male sterile line.

such a male fertile line is known as the maintainer line or B line as it is used to maintain the male sterile line is also known as the A line

Cytoplasmic male sterility may be utilized for producing hybrid seed in certain ornamental species, or in species where a vegetative part is of economic value.

But in those crop plants where seed is the economic part, it is of no use because the hybrid progeny would be male sterile.

Cytoplasmic male sterility is not influenced by environmental factors such as low or high temp.,in other words the sterility is stable.

THREE LINE BREEDING -- CGMS This is a case of cytoplasmic male sterility where a

nuclear gene for restoring fertility in MS line is known.

This system involves

1. Cytoplasmically determined MS plants known as A line in the genetic constitution.

2. Fertile counter parts of A line known as maintainer line or B line with the genetic constitution.

3. Restorer plants used to restorer the fertility in commercial seed plots known as R lines in the genetic constitution.

Maintenance of Male Sterile Line or A line:

Since A line does not produce pollen, seed is not formed for maintaining A line. It has to be crossed with its fertile counter part having similar nuclear genes with fertile cytoplasm which is known as B-line.

Production of Hybrid seed:• For production of hybrid seed, A-line has to be

kept as female parent and the pollen parent should posses the restorer genes in order to induce fertility and seed development in the next generation.

• Such line is known as restorer line and denoted as ‘R’ line.

• The A line & R line should be of different genetic constitution and should be able to give maximum heterosis.

LIMITATIONS IN USING MALE STERILE SYSTEMS:

1. Existence and maintenance of A, B & R Lines is laborious and difficult

2. If exotic lines are not suitable to our conditions, the native/adaptive lines have to be converted into MS lines

3. Adequate cross pollination should be there between A and R lines for good seed set.

4. Synchronization of flowering should be there between A & R lines.

5.Fertility restoration should be complete otherwise the F1 seed will be sterile Isolation is needed for maintenance of parental lines and for producing hybrid seed.

Thank You…..