EFFECT OF MATING SYSTEM,MUTATION,MIGRATION AND SELECTION IN HORTICULTURAL CROPS

P.KAVIYARASU ID-10-532-004

MATING SYSTEM

It 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.

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 intractions determines the mating system(by Joe Williams)

EFFECT OF MATING SYSTEM

Inbreeding depression in a perennial plant, Lychni viscaria, in three populations differing in their inbreeding

history and population size by measuring several traits at two nutrient levels over the plant's life cycle.

The observed levels of inbreeding depression (cumulative inbreeding depression, from –0.057 to 0.629) were high for a plant with a mixed mating system.

CONT As expected, the population with a low

level of isozyme variation expressed the least inbreeding depression for seed germination.

Highest inbreeding depression for germination was found in the largest and genetically most variable population.

( Mary Jo W Godt 1995) Departments of Botany and Genetics,

University of Georgia, Athens, USA 

EFFECT OF MATING SYSTEM

1.Mating system in plants increases homozygosity and reduces heterozygosity.

2.Alleles as a results, the characters for the

Variation produced by the environment.3.Under intense inbreeding, the number

of non-interbreeding groups increases rapidly.

4.Prepotency of individuals increases under inbreeding. Prepotency is effected by homozygosity,dominance epistasis and linkage.

EFFECT ON THREE BACKCROSS MATING SYSTEMS Effects of three backcross mating

systems upon the introgression of a quantitatively determined morphological character, hypogeal germination, from Phaseolus coccineus into

P. vulgaris. The mating systems evaluated measured

gene flow through (1) male gametes, (2) female gametes, and (3) female gametes when a random sib mating generation was inserted between backcross generations.

CONT The results demonstrate that mating

systems significantly affect gene flow between partially isolated species

effects of recombination which lead to hybrid breakdown and a disruption of interspecific gene flow.

Reciprocal backcrosses of the BC1 (P. vulgaris x F1 ) to P. vulgaris again resulted in greater donor parent germplasm transmission through female gametes.

CONT BC1 increased phenotypic variance for

the selected character (hypogeal-like germination)

BC3 populations in all instances greatly increased phenotypic variance for the selected character and led to some hybrid breakdown in the progeny.

MUTATION

Mutation is a sudden and heritable change in an organism and is generally due to a structural change in a gene.

Mutation may produce a new allele not present in the population or may change the frequencies of existing all.

EFFECTS OF MUTATION

Effects Of mutation Lethal : They kill each & every individual that carry them in appropriate genotype .

Dominant lethal : It can’t survive. Recessive lethal : kill in homozygous state. Sub Lethal & Sub Vital :- Both mutation reduce

viability but don’t kill all the individual carrying them in appropriate genotype.

Sub Lethal : Kill more than 50%. Sub Vital : Kill less than 50%. Vital :- a) Don’t reduce the viability. b) Crop improvement can utilize only such mutations.

 

EFFECT OF MUTATION BREEDING Desirable mutations are commonly

associated with undesirable side effects due to other mutations, chromosomal aberrations.

Often mutation produce pleiotropic effects.eg: delayed flowering.

Quantitative traits are usually in the direction away from the selection history of the parent variety. e.g: yield.

Most of mutation are recessive.eg: clonal crops, polyploidy species.

MIGRATION Migration is the movement of

individuals into a population from different population.

Migration may introduce new alleles into the population or may change the frequencies of existing alleles.

Migration is represented by intervarietal crosses ,polycrosses,etc.,

SELECTION

Differential reproduction rates of various genotypes is known as selection.

EFFECT ON SELF POLLINATED CROPS During selection in self pollinated crops

every generation self-pollination will reduce the frequency of heterozygote Aa to 50% in the previous generation.

Three genotypes AA, aA and aa have a equal survival. If there is un equal survival, it may increase or decrease the rate at homozygosivity.

Self pollinated plant population completely homozygous after selection mixture of several homozygous genotypes.

EFFECT ON SELF FERTILIZATION

No. Of generation

Frequency(%)AA

Frequency(%)Aa

Frequency(%)aa

Homozygosity (%)

heterozygosity(%)

1 25 100 25 50 100

2 (25+12.5 50 37.5 75 50

3 37.5+6.25

25 43.75 87.5 25

4 43.75+3.1

12.5 46.8 93.7 12.5

5 46.8 6.25 48.4 96.8 6.2

6 49.21 3.12 49.20 98.4 3.1

7 49.60 1.5 49.60 99.2 1.5

8 49.80 0.78 49.90 99.6 0.7

INDEL-ASSOCIATED MUTATION RATE VARIES WITH MATING SYSTEM IN FLOWERING PLANTS

A recently proposed mutational mechanism, index-associated mutation (IDAM), posits that heterozygous insertions/deletions (indels) increase the point mutation rate at nearby nucleotides due to errors during meiosis.

In this study, They investigated the consequences of IDAM for species differing in mating system using both forward population genetic simulations and genomewide DNA resequencing data from Arabidopsis thaliana, Oryza sativa, and Oryza rufipogon.

CONT

Simulations of different levels of selfing suggest that the effect of IDAM on surrounding nucleotide diversity should decrease with increasing selfing rate.

selfing also affects patterns of nucleotide diversity due to IDAM. Population genetic analyses of A. thaliana and Oryza DNA sequence data sets empirically confirmed our simulation results, revealing the strongest effect of IDAM in the outcrossing O. rufipogon, weaker effect in the recently evolved selfer O. sativa, and the weakest effect in the relatively ancient selfer A. thaliana.

These results support the novel idea that differences in life history, such as the level of selfing, can affect the per-individual mutation rate among species.

THE EFFECT OF MATING SYSTEM DIFFERENCES ON NUCLEOTIDE DIVERSITY AT THE PHOSPHOGLUCOSE ISOMERASE LOCUS IN THE PLANT GENUS LEAVENWORTHIA.

To test the theoretical prediction that highly inbreeding populations should have low neutral genetic diversity relative to closely related outcrossing populations,

On the basis of sequences of intron 12 of this gene, the expected low diversity was seen in both populations of the selfers Leavenworthia uniflora.

L. torulosa and in three highly inbreeding populations of L. crassa, while high diversity was found

In self-incompatible L. stylosa, and moderate diversity in L. crassa populations with partial or complete self-incompatibility.

(F Liu, D Charlesworth, and M Kreitma)

EFFECTS OF POPULATION SIZE, MATING SYSTEM, AND EVOLUTIONARY ORIGIN ON GENETIC DIVERSITY IN SPIRANTHES SINENSIS AND S. HONGKONGENSIS

Hong Kong once supported more than 109 species of wild orchids,

allotetraploid, Spiranthes hongkongensis, and its diploid progenitor, S. sinensis, to assess the effects of the population associated with the origin of the polyploid and to investigate the relationships between number of breeding individuals, mating system, and level of isozyme variation in their populations.

CONT

complete genetic uniformity was observed both within and among populations of S. hongkongensis.

S. sinensis had high levels of genetic variation for all of the genetic parameters examined various measures of within-population variation, the proportion of polymorphic loci (P) and average number of alleles per locus (A) or per polymorphic locus (Ap) were the most sensitive to population size.

THE EFFECT OF MATING SYSTEM ON GROWTH OF ARABIDOPSIS LYRATA (P. N. HOEBE†, M. STIFT, E. B. HOLUB, B.

K. MABLE)¶

Inoculated individuals from outcrossing and inbreeding populations of North American Arabidopsis lyrata with Albugo candida (white blister rust) to test the effect of mating system and heterozygosity on disease response

We observed three host infection phenotypes, classified as fully resistant, partially resistant and fully susceptible

CONT Mating system did not affect relative

growth rate of inoculated plants, but there were strong effects of population and infection phenotype.

Increased variability in responses among inbreeding populations may be due to reduced effective population size.

THE EFFECT OF ECOLOGICAL FACTORS ON THE MATING SYSTEM OF A SOUTH AMERICAN SHRUB SPECIES (HELICTERES BREVISPIRA)

Mating systems are influenced by several ecological factors, including plant density, number of flowers per plant, and pollinator movements.

In this study, we investigated the simultaneous effects of these three factors on the mating system of a self-compatible Brazilian shrub species:Helicteres brevispira

Outcrossing rate is directly correlated with plant density. Changes in the number of flowers per plant affect outcrossing rate through their effect on the density of flowers.

REFERENCES1.Genetics. 1999 January; 151(1): 343 –

357 F Liu, D Charlesworth, and M Kreitma

Genetic variation within and among populations of Arabidopsis thaliana.

2.Conservation Biology Volume 10pages 785–795, June 19963.Division of Ecology and Evolutionary

Biology, University of Glasgow, Glasgow, UK Article first published online: 22 NOV 2010.

4.PLANT BREEDING PRINCIPLES AND METHODS B.D.SINGH.

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