plant breeding methods Flashcards
a. Domestication
b. Plant Breeding
c. selective breeding
a. It is process of bringing wild species under human management . the present day crops has been the result of domestication from wild species therefore the first step in development of cultivated plants was their domestication which is likely to continue .
b. plant breeding is the science of changing the traits of plants in order to produce desired characteristics.
c. The simplest methods breeding consists of selecting the best plants and growing them to full life cycle until it produces seeds which is used for future. in such selective breeding it changes the genetic composition of the plants over time. genetic variation in the desired character is the most important factor for plant breeding.
The most important factor for basic selective breeding is to start with plenty genetic variation and to select and multiply the plants of interest.
a. genetic diversity
b. gene pool
genetic diversity in the population means the number of different alleles( alternate versions of genes) in all the genes and frequency at which they appear. Variation is high when they is many different alleles of all genes and many different combinations of the those alleles.
b. gene pool is the collective set of all the alleles found in the population.
- what is the main aim or the purpose of plant breeding. what are the three operation steps involved in development of varieties of plants?
The main aim of plant breeding is to produce plants of superior quality that can adapt to specific environmental conditions and are suitable for economic production in commercial farming system.
The development of varieties involves three distinct operations.
a. production or selection of genetically variable germplasm (seeds, seedlings, plant parts that are capable of reproduction)
b. selection of the superior genes from the germplasm that are of desired characteristics .
c. multiplication of the superior genes and producing them at commercial scale.
1, Genetic Resources
It is the materials that are available for the improvement of genetic attributes of cultivated plant species. it involves populations, gene pools or species that are are found uniformly , breeding lines,
- differentiate between plant breeding methods and special breeding methods? list down the techniques for each methods.
- what are the factors that determines the methods of the breeding ?
- plant breeding is the different approaches and techniques uses improving the genetics of the cultivated crops for desired characteristics. examples - introduction, selecting from existing population, hybrid breeding , and cross pollination(hybridization)
special breeding methods are the techniques that are rarely used to improve the characteristics of genes for improvement of plant species. examples- mutation breeding , polyploidy breeding and wide hybridization.
- the factors which determines the use of methods includes mode of pollination, mode of reproduction and breeding objective of the crop species.
- Plant breeding methods
a, Introduction
a. it is the introduction of new species of crop or varieties into a new environment having suitable climatic conditions of the native habitat.
there are two ways of introducing the variety or species-
a, primary introduction- it the situation when the introduced crop variety or species adapts well in the new environment without the need to change the genotype. example IR 64 rice introduced in Bhutan, wheat varitey sonalika.
b. secondary introduction- when the introduced variety or the species needs some alternation in the genotype by hybridization with local varities to transfer characters. example- Bajo kaap and bajo maap developed from ir64 hybridized with local ones.
introduction consists of - procurement, quarantine, evaluation, multiplication and distribution.
what is the advantage of this introduction method and disadvantage of this method
introduction new superior species or varieties to a region or country.
it is a fast and economical method of crop improvement particularly when introductions are released as varieties directly or through selection.
disadvantage is that there is high risk of introduction of weeds, pests and diseases.
selection from preexisting populations
superior plants are selected from the field and improved over time using different methods such as;
Mass selections
pure line selections
Mass selections
it involves selection of seeds from individual plants of desirable characteristics in a population and the next generations is sown from the stock of mixed seeds.
this procedure is sometimes known as Phenotypic selection which is based on the looks of individual plants.
traditional methods
an alternate approach has been practiced for thousand years which is to eliminate undesirable types by destroying them.
modern methods- to harvest the best plants separately and to grow and compare their progenies.
the seeds of poorer progenies are destroyed and remainder are harvested. the selection is not solely on the appearance of the parent plants but also their performance.
pure line selection
numerous superior appearing plants are selected from a genetically variable population
progenies from the individual selected plants are grown and evaluated by simple observation, frequently over a period of several years.
when the selections can be no longer made by mere observations alone, trials such a careful measurements to determine whether the remaining selections are superior in yielding ability and other aspects of performance.
what is the key difference between mass and pure line selection?
in pure line the development of the variety is highly uniform involving a single plant.
in mass selection several purelines are mixed to develop a heterozygous variety with genetic variations.
a. Hybridization
b. what is the main drawback of this method
c. procedures in hybridization.
It is the controlled crossing of plants between carefully selected parents.
The main aim to combine desirable genes found in the two or more varieties and to produce a pure breeding progeny superior in many respect to the parents type.
b. The plant breeder problem is largely one of efficiently managing the enormous number of genotypes that occur in the generations after hybridization.
c. selection of parents plant emasculation bagging tagging hand pollination harvesting and storing the f1 seeds raising the f1 generation growing of succesive generations and selection of progenies
