1. BACKCROSS METHOD FOR TRANSFER OF RECESSIVE GENE
Dev Hingra
Mail Id- mail2devhingra@gmail.com
Department of Genetics and Plant Breeding
Faculty of Agriculture
Sam Higginbottom Institute Agriculture, Technology and Sciences
(Formerly Allahabad Agriculture Institute)
Deemed-to-be-University
Allahabad
2. A cross between a hybrid F1 and one of
its parents is known as backcross
method. The backcross method was first
proposed as an appropriate breeding
method for cereal crops in 1922 by
Harlan and pope .
The variety which receives gene is ‘recipient parent’
and variety which is the source of gene is called as
‘donor parent’
Recipient parent is used repeatedly hence also named
as ‘recurrent parent’. Donor parent is ‘non-recurrent
parent’. Repeated backcrossing leads to homozygosity
INTRODUCTION
3. 4) BC1 (F2) Generation:
Rust resistance plants are selected and backcrossed
with recurrent parent. i.e variety ‘A’. Selection is
made for the plant type and other characteristics of
the variety ‘A’.
5) BC2 Generation:
No rust resistance test, plants are selected, which is
identical to the recurrent parent ( A) and backcrossed
with the recurrent parent.
Procedure of backcross method
for the transfer of Recessive
Gene:
1) Hybridization:
The recurrent parent is crossed with rust resistant
donor parent. The recurrent parent is generally used
as female. i.e ( rr X RR).
2) F1 Generation:
F1 plants are backcrossed to the recurrent parent.
3) BC1 Generation:
If rust resistance is recessive all the plant will be
rust susceptible. Therefore, there is no test for rust
resistance. All the plants are self- pollinated.
4. 8) BC4 Generation:
No rust resistance test plants are backcrossed to variety
‘A’.
9) BC5 Generation:
No rust resistance test plants are self pollinated to raise F2
generation.
10) BC5 (F2) Generation:
Plants are subjected to rust epidemic, resistance plant for
rust and having similar characteristic of variety. ‘A’ is
selected and self seed are harvested separately.
11) BC5 (F3):
Individual plant progenies are grown and subjected to
rust epiphytotic selection is done for rust resistance and
for characteristics of variety ‘A’ seeds from several similar
rust resistant homozygous progenies are mixed to
constitute new variety.
12) Yield Test and seed multiplicaion :
The new variety is tested in R.Y.T i.e replicated yield trials
along with the variety ‘A’ as a check.The newly constitute
variety should be similar to the variety A for most of the
important characters. Seeds are multiplied for distribution.
7) BC3 F2 Generation:
Plants are inoculated with stem rust. Rust resistant plant,
similar to ‘A’ are selected and backcrossed to variety ‘A’.
6) BC3 Generation:
No disease resistance test. The plants are self – pollinated
to raise F2. selection is made for the plant type identical
to variety ‘A’.
5. Application of Backcross method
This method is commonly used for the transfer of
disease resistant from one variety to another. But is
also suitable for the transfer of quantitative characters
and is applied is both self and cross pollinated crops.
Intervarietal transfer of simply inherited characters
such as disease resistance , seed colour , plant
height etc.
Intervarietal transfer or quantitative characters. Such
as earliness, seed size, seed shape may be transferred
from one variety to another belongings to same
species.
6. MERITS OF BACKCROSS METHOD
It is not necessary to test the variety
developed by this method because the
performance of recurrent parent is already
known.
Much smaller populations are needed in
this method.
It does not require record keeping.
It is not affected by environmental
conditions.
7. 1)The new variety generally cannot be superior to the recurrent
parent, expect for the character that is transferred.
2)Hybridization has to be done for each backcross; this is often
difficult, time taking and closely.
3)Underisable genes closely linked with the gene being transferred
may also be tranferred to the new variety producing linkage drag.
DEMERITS OF BACKCROSS METHOD
8. Backcross method has been widely used for
the improvement of disease resistant
varieties.
COTTON: Gossypium herbaceum varieties-
Vijapla,Vijay,Digvijay and Kalyani.
WHEAT: Kalyan sona, Kharchia
65, NP-853, NI-5439 etc.
ACHIEVEMENTS
9. CONCLUSION
Today , the backcross method has been used to
transfer traits such as disease resistance controlled
by one or a few genetic loci. It is important that
backcross programs make efficient use of the
breeder’s resources.
The backcross method has been used extensively for
transferring qualitative characters (characters with
clear phenotypes that are easy to identify in cross
progeny) such as disease resistance. It is effective in
both self and cross pollinated crop species.
