Backcross breeding is generally used for all of the following, except transferring
(a).
monogenic recessive trait
(b)
monogenic dominant trait
(c)
polygenic trait
(d)
male sterility
Answers
Answer:
. Back cross method and various modified methods
Backcross Method
In backcross method of breeding, the hybrid and the progenies in subsequent
generations are repeatedly backcrossed to one of the parents. As a result, the genotype of
the backcross progeny becomes increasingly similar to that of the recurrent parent. The
objective of backcross method is to improve one or two specific defects of a high
yielding variety.
Pre-requisite for back cross breeding
1. A suitable recurrent parent must be available which lacks in one or two characteristics.
2. A suitable donor parent must be available
3. The character to be transferred must have high heritability and preferably it should be
determined by one or two genes.
4. A sufficient number of back crosses should be made so that the genotype of recurrent
parent is recovered in full.
Application of back cross method
This method is commonly used to transfer disease resistance from one variety to
another. But it is also useful for transfer of other characteristics.
1. Intervarietal transfer of simply inherited characters
E.g. Disease resistance, seed coat colour
2. Intervarietal transfer of quantitative characters.
E.g. Plant height, Seed size, Seed shape.
3. Interspecific transfer of simply inherited characters
E.g. Transfer of disease resistance from related species to cultivated species.
E.g. Resistance to black arm disease in cotton from wild tetraploid species into
G.hirsutum
4. Transfer of cytoplasm
This is employed to transfer male sterility. The female parent will be having the
sterile cytoplasm and recurrent parent will be used as male parent.
E.g. Sesamum malabariucum x S.indicum
Female parent Recurrent parent.
Explanation:
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