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MATING DESIGNS ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts RANA ARSALAN JAVAID 13-ARID-435 PMAS ARID AGRICULTURE UNIVERSITY RWP

Mating designs

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Page 1: Mating designs

MATING DESIGNS

ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts

RANA ARSALAN JAVAID13-ARID-435

PMAS ARID AGRICULTURE UNIVERSITY RWP

Page 2: Mating designs

MATING DESIGNDEFINITION

Schematic cross between two groups or strains of plants made to produce progenies in plant breeding that is concerned in agriculture and bio sciences.

OBJECTIVES i. To obtain information and understand genetic control of a trait or

behavior that is observedii. To get base population for development of plant cultivars

NEED FOR MATING DESIGNAnalysis of variance in offspring plants resulted from a mating design was used to evaluate effects of additive genetic, dominance level, epistasis and heritability value equal to value of genetic expectations.

Page 3: Mating designs

Factors affecting choice of Mating Design

i. The type of pollination (self- or cross-pollinated)ii. The type of crossing to be used (artificial or natural)iii. The type of pollen dissemination (wind or insect)iv. The presence of a male-sterility systemv. The purpose of the project (for breeding or genetic studies)vi. The size of the population required

Keen interest to discoveri. How significant is genetic variation?

ii. How much of the variation is heritable?

A main interest of the breeder is identifying plants with superior geno-

types as judged by the performance of their progeny.

Page 4: Mating designs

Genetic Assumptions

i. Diploid behavior at meiosis

ii. Uncorrelated genes distribution.

iii. Absence of non-allelic interactions.

iv. No multiple alleles at those loci controlling the character.

v. Absence of reciprocal differences.

vi. Ideally the diallel cross should be restricted to crosses

among homozygous lines.

vii. Absence of genotype-environment interaction (epistasis).

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MAJOR MATING DESIGNS IN PBG

Several studies described and contrasted different mating designs and six mating designs are considered more beneficial and helpful.

1. Biparental Mating:

• Also called paired crossing design

• Large no of plants are selected at random and then crossed in pairs.

• They produce 1/2n full sib families

• Progenies are tested by simply analysis of variances into between and within the families

• Most limitation of this design is its inability to provide sufficient information about all parameters required by the model.

Page 6: Mating designs

PolycrossIt is for intermating a group of cultivars by natural crossing in isolated blocks.

• Polycross refers to progeny from seed of a line allowed to outcross freely with other selected lines in same nursery.

• It is most suitable design for obligate cross pollinators.• It provides equal opportunity to each & every clone to cross with each other in

block thus preventing selfing.

• Entries must be equally represented and randomly arranged.• Latin square experimental design is most suitable, also can use Completely Randomized Block Design

• Ideal requirements are hard to meet in this design

• The design is used in breeding to produce synthetic cultivars, recombining selected entries of families in recurrent selection breeding programs, or for evaluating the GCA of entries

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Polycross contd.

• GCA helps in estimation of heritability• If parents are from different origin then progeny will be sensitive to environmental changes

• Half sibs are generated in a polycross because progeny from each

entry has a common parent.

• Progenies from individual plants (half sibs) are tested .• Cavariance within progenies = Cov = • : F = inbreeding coefficient of genotypes tested • F indicates precision of parent-offspring covariance

• Selection is done on half sib family means.

• Random mating & Insufficient statitics to estimate all parameters.• No control on pollen source. Expected genetic gains are reduced.

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TOP CROSSTopcross refers to a mating between a selection, line, clone and a common pollen parent which may be a variety, inbred line or single cross.

• The selected plants are crossed with a common tester(s) of known performance, generally in open pollination.

• The purpose of using top is to increase the chance of obtaining a desirable gene or genes from exotic or difficult materials

• In making top crosses, only single cross F1's are utilized because they are uniform.

• Topcross has been fairly widely used for preliminary evaluation of combining ability of new inbred lines

• The design has two shortfalls. • First, a single tester variety may not offer wide genetic background for

testing the inbred stocks. • Secondly, the numbers of crosses become large if the test inbred lines

are many.

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NORTH CAROLINA North Carolina design was developed in order to obtain more information about combining ability without much labor comparing to full diallel.

North Carolina Design I :-• It is a very popular multipurpose design. • It is commonly used to estimate additive and dominance variances as well as for the evaluation of full- and half-sib recurrent selection. • It is applicable to both self- and cross-pollinated species.• Each member of a group of parents used as males is mated to a different group of parents. • The progenies include both full-sibs and half-sibs. • It is commonly used to estimate additive and dominance variances • The main advantage of design I is its ability to supply a test of

significance for the additive genetic variance. • It is also used for tree breeding.

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NORTH CAROLINA contd. North Carolina Design II :-

• In this design, each member of a group of parents used as males ismated to each member of another group of parents used as females.

• It is used to evaluate inbred lines for combining ability

• The design is most adapted to plants that have multiple flowers.

• The design is essentially a two-way ANOVA .

• Allows measure of both GCA and SCA . But don’t test for epistasis.• In North Carolina II, every progeny family has half sib relationships through both common male and common female.

• It is therefore a rectangular mating design, unless n1=n2.

• Reciprocal crosses may be carried out to analyze maternal effects

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NORTH CAROLINA contd. North Carolina Design III :-

• In this design, a random sample of F2 plants is backcrossed to the two inbred lines from which the F2 was descended.

• It is considered the most powerful of all the three NC designs. • A modification called the triple test cross has also been introduced i.e added a third tester not just the two inbreds.

• The parents being progenitors of the F2, are very special testers. • It is capable of testing non-allelic (epistatic) interactions, also capable of estimating additive and dominance variance. • Moreover, both in its original and extended form design 3 has a general utility for investigating any population, irrespective of gene frequency or mating system.

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NORTH CAROLINA contd. North Carolina III :-

• The NCIII is a special case of NCII, therefore the ANOVA is similar to that of the NCII although it differs in one special feature; • Two testers are not a random sample from any population but are two

very particular lines, the progenitor of the F2.

• Tester must be derived from the population under investigation as the model developed for this mating design is only valid within a population.

• Main use of triple test cross will be to investigate inheritance of quantitative traits in natural population and relating this to natural selection and ecology.

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Method 1 or full diallel design

• The method F1 or full diallel design consists of parents, one set of F1’s and reciprocal F1’s.

• This system gives n2 genotypes.

Method 2

• This method includes parents and one set of F1’s without reciprocal F1’s.

• This design gives p(p+1)/2 genotypes.

Page 14: Mating designs

Method 3

• In this method one set of F1’s and the reciprocals are included.

• This type of mating designs give rise to a=p(p-1) different number of genotypes.

Method 4• In this method only one set of F1’s are included.

• Most common of diallel crossing systems.

• There are a=p(p-1)/2 different genotypes evaluated.

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Line X tester design

• An Extension of top cross design

• More than one testers are used in L*T Mating design

• Involves hybridization between lines (F) and wide based testers in one to one fashion.

• Simplest mating design providing both full sibs and half sibs.

• Provides SCA of each cross but provides GCA of both lines and testers.

• Important in estimating various types of gene actions important in expression of quantitative traits.

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CONCLUSION• Selection of suitable parents and good mating designs are keys to

success of plant breeding schemes • Selection of mating design depends on various factors.• For instance in early stages of breeding programme appropriate designs

would be polycross and perhaps the topcross • Polycross is particularly suited to the identification of potential parents of

synthetic varieties. A comparative evaluation summarized mating designs in two ways In terms of coverage of the population

BIPs > NC I > polycross > NC III > NC II > diallel, In terms of amount of information,

diallel > NC II > NC III > NC I > BIPs • Diallel mating design is the most important for GCA and SCA • The proper choice and use of a mating design will provide the most

valuable information for breeding

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JUGNO GROUP