Major advantages and limitations of backcross breeding

There are major advantages and limitations of backcross breeding.

Advantages

The method reduces the amount of field testing needed, as the new cultivar will be adapted to the same area as the original cultivar.

Backcross breeding is repeatable. If the same parents are used, the same backcrossed cultivar can be recovered.

It is a conservative method, not permitting new recombination to occur.

It is useful for introgressing specific genes from wide crosses.

It is applicable to breeding both self-pollinated and cross-pollinated species.

Disadvantages

Backcrossing is not effective for transferring quantitative traits. The trait should be highly heritable and readily identifiable in each generation. However, the

application of molecular markers is helping to change the application of backcrossing to improving quantitative traits.

The presence of undesirable linkages may prevent the cultivar being improved from attaining the performance of the original recurrent parent.

Recessive traits are more time consuming to transfer.

Modifications

When transferring a recessive gene the BC will segregate for both homozygous dominant and heterozygous genotypes.To identify the appropriate genotype to advance, it will be necessary to self the BC to distinguish the two segregants for the Rr. Alternatively, both segregants may be used in the next cross, followed by selfing. The BC progenies from the plants that produce homozygous segregates are heterozygous and are kept while the others are discarded. This is actually not a modification per se, since it is the way to transfer a recessive allele.

            If a breeding program is designed to transfer genes for multiple traits, it will be more efficient to conduct separate backcross programs for each trait. The backcross-

derived lines are then used as parents in a cross to develop one line that contains the multiple traits.

Advantages and disadvantages

There are major advantages and limitations of backcross breeding.

Advantages

The method reduces the amount of field testing needed, as the new cultivar will be adapted to the same area as the original cultivar.

Backcross breeding is repeatable. If the same parents are used, the same backcrossed cultivar can be recovered.

It is a conservative method, not permitting new recombination to occur.

It is useful for introgressing specific genes from wide crosses.

It is applicable to breeding both self-pollinated and cross-pollinated species.

Disadvantages

Backcrossing is not effective for transferring quantitativetraits. The trait should be highly heritable and readily identifiable in each generation. However, the

application of molecular markers is helping to change the application of backcrossing to improving quantitative traits.

The presence of undesirable linkages may prevent the cultivar being improved from attaining the performance of the original recurrent parent.

Recessive traits are more time consuming to transfer.

When transferring a recessive gene the BC will segregate for both homozygous dominant and heterozygous genotypes. To identify the appropriate genotype to advance, it will be necessary to self the BC to distinguish the two segregants for the Rr. Alternatively, both segregants may be used in the next cross, followed by selfing. The BC progenies from the plants that produce homozygous segregates are heterozygous and are kept while the others are discarded. This is actually not a modification per se, since it is the way to transfer a recessive allele. If a breeding program is designed to transfer genes for multiple traits, it will be more efficient to conduct separate backcross programs for each trait. The backcross- derived lines are then used as parents in a cross to develop one line that contains the multiple traits.