MATING SYSTEMS IN PLANTS : MATING SYSTEMS IN PLANTS Copyright of original figures used in this presentation from other sources is duly acknowledged and the copyright remains with its original creator. These have not been used for commercial purpose but for educational use only. INTRODUCTION AND HISTORY : INTRODUCTION AND HISTORY May be defined as the method by which individuals are paired for crossing.
Or various schemes which are used for crossing or mating of individuals.
Five systems of mating was given by Sewall Wright in 1921 SEWALL WRIGHT : SEWALL WRIGHT Who have given five systems of mating. VARIATION OF MATING SYSTEMS IN PLANTS : VARIATION OF MATING SYSTEMS IN PLANTS Plants vary in their mating system from completely selfing to completely outcrossing.
Anther - stigma distance is a useful measure of mating system .
Anther stigma distance determine if the mating system differed between the two species
For example.. Braya longii
(worked by Kim Parson)
Ref – www.digitalnaturalhistory.com MIXED MATING SYSTEM : MIXED MATING SYSTEM For example… Erogonum heracleoids
( Studied by Jennifer L. Ison)
Ref – www.2uic.edu PLANT MATING SYSTEM FLEXIBILITY : PLANT MATING SYSTEM FLEXIBILITY Tremendous variation in pollination both within and among genera & species.
Such developmental changes can result in mating systems among populations
For example… Collinsia spp.
(By Susan Kalisz primary research)
Ref – www.pitt.edu/kalisz/floral development1.com Example contd.. : Example contd.. For example…
.. Collinsia parviflora
Mating system evolution is due to flower size and type of pollination
Susan kalisz Example continued : Example continued For example
1. Collinsia heterophylla
2.Collinsia verna Example continued… : Example continued… For example collinsia barstifolia MIXED MATING SYSTEM : MIXED MATING SYSTEM For example…
* Studied by Jenifer L. Ison DETERMINATION OF MATING SYSTEMS… : DETERMINATION OF MATING SYSTEMS… In flowering plants mate recognition is developmental process
Involves physical interactions i.e., male & female gametophyte & sporophytes, zygotes & endosperm.
The outcome of this cryptic interactions determines the mating system.
[ Research by Joe Williams ]
Ref – www.bio.utk.edu/william/images/joe.jpg. TYPES OF MATING SYSTEMS : TYPES OF MATING SYSTEMS THERE ARE FIVE DIFFERENT TYPES OF MATING SYSTEMS
5.PHENOTYPIC DISASSORTATIVE RANDOM MATING SYSTEM : RANDOM MATING SYSTEM Each female gamete has equal chances to unite with every male gamete.
Form of outbreeding
In plant breeding some form of selection is practised such mating system called as random mating with selection
With selection –
1.Increases frequency of alleles for which selection is practised
2.Reduces frequency of other alleles
4.changes mean of character RANDOM MATING SYSTEM : RANDOM MATING SYSTEM Rate of reproduction of each genotype is equal
Without selection –
1.Gene frequency – constant *
2. Variance for character – constant *
3. Correlation between relatives or prepotency – constant
4.Degree of homozygosity - constant
* Has additive, dominance & epistatic components USES OF RANDOM MATING IN PLANT BREEDING : USES OF RANDOM MATING IN PLANT BREEDING Progeny testing
Production and maintenance of synthetic and composite varieties
Production of polycross progenies
Evolutionary advantages – maintained high level of diversity GENETIC ASSORTATIVE MATING SYSTEM : GENETIC ASSORTATIVE MATING SYSTEM Mating occurs between individuals that are more closely related by ancestry than in random mating.
More commonly known as INBREEDING.
A. Genetic variability
a. Without selection –
1.Total variability among lines increased
2.Total variability within lines decrease due to random fixation of genes in different families. GENETIC ASSORTATIVE MATING SYSTEM : GENETIC ASSORTATIVE MATING SYSTEM b. With selection –
1.Variability is reduced towards the direction of selection
* Homozygosity – Increased due to fixation of genes
Heterozygosity – Elimination of heterozygotes from a populations due to fixation of genes.
Population mean - Reduced due to decrease in number of hybrid genotypes which have more number of dominant genes.
Genetic correlation – Increased due to increase in prepotency. USES OF GENETIC ASSORTATIVE MATING SYSTEM : USES OF GENETIC ASSORTATIVE MATING SYSTEM Leads to purity of types.
Useful tool for development of inbred lines both partial and complete GENETIC DISASSORTATIVE MATING SYSTEM : GENETIC DISASSORTATIVE MATING SYSTEM Such individuals are mated which are less closely related by ancestry than random mating.
Commonly called as outbreeding.
Totally unrelated individuals are mated.
These individuals belongs to different populations.
For example – Intervarietal & interspecific crosses. GENETIC DISASSORTATIVE MATING SYSTEM : GENETIC DISASSORTATIVE MATING SYSTEM Effect similar to those of migration.
* A. Variability –
Increased due to combining of two or more genes from two or more different sources.
*B. heterozygosity – Increased due to combining of genes from different lines Continued… : Continued… C. Homozygosity – reduced rapidly because outbreeding favours heterozygotes.
D. Population mean – increased due to combining more dominant genes from different lines.
E. Genetic correlation – decrease due to decrease in homozygosity.
F.decrease in prepotency PHENOTYPIC ASSORTATIVE MATING SYSTEM : PHENOTYPIC ASSORTATIVE MATING SYSTEM Mating between individuals which are phenotypically more similar than would be expected under random mating.
Refers to mating of extreme types, i.e., cross between AA & AA and aa & aa, also Aa & aa
Only two extreme phenotypes i.e., lowest and highest remain in the population
Variability : Increase since it divides the population into two extreme phenotypes.
Homozygosity : Leads to complete homozygosity in single generation PHENOTYPIC ASSORTATIVE MATING SYSTEM CONTD… : PHENOTYPIC ASSORTATIVE MATING SYSTEM CONTD… Genetic correlation : Perfect genetic correlation between number of progenies is achieved in one generation
Population mean : Divided into two according to variability. USES OF PHENOTYPIC ASSORTATIVE MATING SYSTEM : USES OF PHENOTYPIC ASSORTATIVE MATING SYSTEM In some breeding schemes like recurrent selection
Useful in isolation of extreme phenotypes.
# IMP Note : The changes due to this mating system are disappear randomly when random mating is restored PHENOTYPIC DISASSORTATIVE MATING SYSTEM : PHENOTYPIC DISASSORTATIVE MATING SYSTEM Mating between phenotypic dissimilar individuals belonging to same populations.
I.e., mating between individuals having genotypes AA & aa and Aa & aa
Variability : Constant, since it reduces inbreeding.
Heterozygosity : Remains constant or slight increase PHENOTYPIC DISASSORTATIVE MATING SYSTEM CONTINUED… : PHENOTYPIC DISASSORTATIVE MATING SYSTEM CONTINUED… Genetic correlation : Decrease due to decrease in prepotency.
Prepotency : decreased due to decrease in homozygosity USES OF P. D. M. SYSTEM… : USES OF P. D. M. SYSTEM… In making population stable i.e., maintaining variability.
Progeny more desirable than parents.
Useful when desirable type is an intermediate one and the available parents have the extreme phenotypes.
Most notable – Maintaining variability in relatively smaller populations