Course Content
Introduction to plant breeding
0/5
Introduction
Scope of plant breeding (Future Prospects)
Undesirable effects
History of plant breeding
Scientific contributions of eminent scientists
Domestication, plant introduction, and acclimatization
0/6
Acclimatization
Plant Introduction
Procedure of Plant Introduction
Purpose of plant introduction
Merits of Plant Introduction
Germplasm Collection
Modes of reproduction and pollination control
0/6
Mode of reproduction
Categories of mode of reproduction
Pollination
Mechanisms promoting self-pollination
Genetic Consequences of Self-Pollination
Genetic Consequences of Cross-Pollination
Qualitative and quantitative characters (qualitative and quantitative characters in crops and their inheritance)
0/2
Introduction
Role of the environment in Quantitative Inheritance
Biometrical techniques in plant breeding (assessment of variability, aids to selection, choice of parents, crossing techniques, genotype-by- environment interactions)
0/3
Introduction
Components of Genetic variance
Things to remember
Selection in self-pollinated crops (progeny test, pureline theory, origin of variation, genetic advance, genetic gain)
0/5
Progeny test
Pureline selection
General procedure for evolving a variety by pureline selection
Advantage of pureline selection
Origin of variation in pure lines
Hybridization techniques and its consequences (objectives, types, program, procedures, consequences)
0/4
Introduction
Some terminologies
Types of hybridization
Pre-requisites for hybridization
Genetic composition of cross-pollinated populations (Hardy-Weinberg law, equilibrium, mating systems)
0/4
Hardy-Weinberg law
Proof of Hardy-Weinberg law
Example of Hardy-Weinberg law
Factors affecting equilibrium frequencies
Selection in cross-pollinated crops (response and gain from selection, variability)
0/5
Introduction
MASS SELECTION
Recurrent selection
Procedure for Reciprocal recurrent selection
Half-sib and full-sib selection with progeny testing
Heterosis and inbreeding depression
0/5
Heterosis
Manifestations of Heterosis
Inbreeding depression
Degrees of inbreeding depression
Use of heterosis
Mutation breeding (types, use of mutagens, application)
0/8
Introduction
Classification of mutations
Characteristic feature of mutations
Procedure for irradiation
Selection of the variety and dose of mutagen
Mutation breeding for polygenic traits
Applications of Mutation Breeding
Advantages of mutation breeding
Polyploidy in plant breeding (aneuploidy, euploidy, allo- and autoploidy, applications)
0/6
Introduction
Origin and production of doubled chromosome numbers
Morphological and cytological features of auto polyploids
Application of Autopolyploidy in Crop improvement
Allopolyploidy
Limitations of Allopolyploidy
Breeding methods in self-pollinated crops (Mass, Pure line, Pedigree, Bulk, Backcross, etc)
0/5
Mass Selection
Bulk Method
Pedigree Method
Single Seed Descent
Backcross
Clonal selection
0/5
Clonal Selection
Advantages and disadvantages of clonal selection
Problems in Breeding asexually propagated crops
Genetic variation within a clone
Clonal degeneration
Release of new varieties
0/5
Introduction to Variety
Norms for Release of New Variety
Development of New Variety
Institutions Related with Release of Variety
Variety Release Procedure
Quality seed
0/4
Introduction
Importance of quality seed
Major seed quality characters
Characteristics of good quality seed
Breeding for pest resistance
0/3
Pest includes
Defense mechanisms of host against pathogen/parasite
Breeding for resistance
Intellectual property right
0/4
Introduction
Objectives
Types of Intellectual Property
Policy objectives favoring IPRs in new plant varieties
Learn Introductory Plant Breeding with Rahul
About Lesson

Application of Autopolyploidy in Crop improvement

A) Triploids

  • Triploids are produced by hybridization between tetraploid and diploid strains.
  • They are generally highly sterile, except in a few cases.
  • This feature is useful in the production of seedless watermelons.
  • In certain species, they may be more vigorous than the normal diploids, e.g., in sugarbeets. These two examples are described in some detail.
  • Seedless watermelons are produced by crossing tetraploid (4x, used as female) and diploid (2x, used as male) lines, since the reciprocal cross (2x x 4x) is not successful.
  • The triploid plants do not produce true seeds; almost all the seeds are small, white rudimentary structures like cucumber (cucumis stivus) seeds. But few normal size seeds may occur which are generally empty. For good seed setting pollination is essential.
  • For this purpose, diploid lines are planted in the ratio 1 diploid : 5 triploid plants.
  • There are several problem viz. genetic instability of 4x lines, irregular fruit shape, a tendency towards hollowness of fruits, production of empty seeds and the labour involved in triploid seed production.

 

Limitations of auto polyploidy:

  1. Larger size autopolyploid generally contain more water and produce less dry matter content than diploids
  2. High sterility with poor seed setting is observed
  3. Due to complex segregation, progress through selection is slow
  4. Monoploids and triploids cannot be maintained except through clonal propagation
  5. The varieties cannot be produced at will
  6. Effects of auto polyploidy cannot be predicted.

 

Segregation in Auto tetraploids

  • Depending upon the number of dominant alleles present, they are referred as simplex (Aaaa), duplex (AAaa), triplex (AAAa), Quadruplex (AAAA) and nulliplex (aaaa).
  • On selfing a simplex will produce two types of gametes Aa and aa in 1:1 ratio due to random chromosome segregation.
  • Self-pollination of such a simplex would produce. There genotypes AAaa, Aaaa and aaa in the ratio 1:2:1 giving the phenotypic ratio of 3 : 1. while produces 3 types of gametes viz., AA, Aa and aa in the ratio of 1:12:15 due to random chromatid segregation selfing of a simplex in such a case is expected produce the following progeny.

 

Note:

Quadraplix           AAAA        1

Triplex                 AAA a        24

Duplex                 AAaa          174

Simplex                Aaaa           360

Nulliplex              aaaa            225

Total:                                        784

 

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