Selection methods for cross pollinated crops
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This article throws light upon the top three breeding methods used for cross-pollinated crops. The methods are: 1. Mass Pedigree Method 2. Inbreeding 3. Recurrent Selection.
1. Mass Pedigree Method:
In this method of breeding, the best individuals with desired characters are selected on the basis of phenotypic performance in a source population. Open-pollinated seeds of the selected individual plants are divided into two halves. Second year replicated progeny row trial is conducted using one set of half seeds from each plant.
On the basis of the progeny performance, the best parental individuals are identified. The remnant half seeds from the superior parental plants are mixed and grown in isolation for random mating during the third year.
This method of breeding is equivalent to ear-to-row selection in context of maize originally proposed by C.G. Hopkins at the Illinois Agricultural Experiment Station in 1896 to improve protein and oil content of maize. This method has been named as mass-pedigree method by S.S. Rajan in India. This very method is called line breeding when selection is based on progeny tests and a group of progeny lines is composited.
The mating of individuals more closely related than individuals mating at random is known as inbreeding. The lines produced by continued inbreeding are known as inbred lines. Self-fertilization is the most intense form of inbreeding.
In plant breeding nearly homozygous lines are produced by continued self-fertilization accompanied by selection for five to six generations.
(i) To attain uniformity in plant characters.
(ii) To improve yield etc. by individual plant selection as in cucurbits in which there is no inbreeding depression.
(iii) To develop suitable inbred lines in production of hybrids and synthetics.
Synthetic Variety:
The term ‘synthetic variety’ has come to be used to designate a variety that is maintained from open pollinated seed following its synthesis by hybridization in all combinations among a number of selected genotypes, which have been tested for combining ability.
The components of a synthetic variety could be inbred (usually), clones, mass selected populations or various other materials. The component units are maintained so that the synthetic may be reconstituted at regular intervals.
The inbreeds to be used as component lines are chosen on the basis of combining ability tests. The component inbred are crossed in all possible combinations. This inter-crossed seed is called as Syn 0.
Equal quantity of seed from all crosses is composited and the mixture is allowed open-pollination in isolation and seed is harvested. This becomes Syn 1 generation. In absence of reconstitution of a synthetic at regular intervals, the population becomes an open-pollinated variety.
The testing for combing ability is the decisive criterion for a synthetic variety by which it can be distinguished from a conventional variety of a cross-pollinating species, which originates in a continuous selection of individuals and subsequent progeny tests. The greater variability caused by crossing several components with high general combining ability makes the synthetic varieties more adaptable compared to , but also on the number of components used in the Syn 0.
1. Mass Pedigree Method:
In this method of breeding, the best individuals with desired characters are selected on the basis of phenotypic performance in a source population. Open-pollinated seeds of the selected individual plants are divided into two halves. Second year replicated progeny row trial is conducted using one set of half seeds from each plant.
On the basis of the progeny performance, the best parental individuals are identified. The remnant half seeds from the superior parental plants are mixed and grown in isolation for random mating during the third year.
This method of breeding is equivalent to ear-to-row selection in context of maize originally proposed by C.G. Hopkins at the Illinois Agricultural Experiment Station in 1896 to improve protein and oil content of maize. This method has been named as mass-pedigree method by S.S. Rajan in India. This very method is called line breeding when selection is based on progeny tests and a group of progeny lines is composited.
The mating of individuals more closely related than individuals mating at random is known as inbreeding. The lines produced by continued inbreeding are known as inbred lines. Self-fertilization is the most intense form of inbreeding.
In plant breeding nearly homozygous lines are produced by continued self-fertilization accompanied by selection for five to six generations.
(i) To attain uniformity in plant characters.
(ii) To improve yield etc. by individual plant selection as in cucurbits in which there is no inbreeding depression.
(iii) To develop suitable inbred lines in production of hybrids and synthetics.
Synthetic Variety:
The term ‘synthetic variety’ has come to be used to designate a variety that is maintained from open pollinated seed following its synthesis by hybridization in all combinations among a number of selected genotypes, which have been tested for combining ability.
The components of a synthetic variety could be inbred (usually), clones, mass selected populations or various other materials. The component units are maintained so that the synthetic may be reconstituted at regular intervals.
The inbreeds to be used as component lines are chosen on the basis of combining ability tests. The component inbred are crossed in all possible combinations. This inter-crossed seed is called as Syn 0.
Equal quantity of seed from all crosses is composited and the mixture is allowed open-pollination in isolation and seed is harvested. This becomes Syn 1 generation. In absence of reconstitution of a synthetic at regular intervals, the population becomes an open-pollinated variety.
The testing for combing ability is the decisive criterion for a synthetic variety by which it can be distinguished from a conventional variety of a cross-pollinating species, which originates in a continuous selection of individuals and subsequent progeny tests. The greater variability caused by crossing several components with high general combining ability makes the synthetic varieties more adaptable compared to , but also on the number of components used in the Syn 0.
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