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Results and
discussion
Segregation for seedling reactions in F2 and
F3 generations and its intercross obtained from the
crosses of resistant cultivars with Malvi Local are given in
Table
2. The
F2 and F3 generations obtained from the cross
Malvika x Malvi Local segregated in a 15 resistant (R): 1 susceptible
(S) ratio and in a 7 homozygous resistant (HR): 8 segregating (Seg):
1 homozygous susceptible (HS) ratio against race 1, respectively.
This indicates the presence of two independently inherited dominant
genes in Malvika against the race 1. The F2 and
F3 generations obtained from the cross CPAN 6051 x Malvi
Local segregated in an 3R : 1S ratio and in a 1 HR : 2 Seg : 1 HS
ratio respectively indicating presence of one dominant gene against
race 1. Against race 77A, the F2 and F3
generations obtained from the crosses Malvika x Malvi Local and CPAN
6051 x Malvi Local segregated in a 15R : 1S ratio and in a 7
HR : 8 Seg : 1 HS ratio. These observations indicated presence of two
independently inherited dominant genes in Malvika against race 77A.
The F2 and F3 generations from the cross CPAN
6051 x Malvi Local segregated in a 3R : 1S ratio and 1HR : 2 Seg :
1HS ratio, respectively, indicating presence of a dominant gene in
CPAN 6051 against race 108.
Susceptible seedlings against races 1, 77A and 108 were not observed
in F2 generation obtained from the cross Malvika x CPAN
6051, indicating that at least one of the genes present in
Malvika and CPAN 6051 is allelic or tightly linked.
Inheritance studies and allelic tests revealed the presence of at
least two different leaf rust resistance genes from cultivars Malvika
and CPAN 6051.
Since the near isogenic testers are not available in durum.
background it is not possible to designate Lr genes in any of
these two wheats. Saini (1987) has identified Lr23
from CPAN 6051 using Australian rust cultures. Since CPAN
6051 did not
segregate for susceptible seedling against race 1 in its cross with
Malvika therefore this cultivar may also have Lr23.
This gene gives post seedling resistance against races 77A and
108 (Saini et al 1988, Dhindsa et al 1991), therefore, resistance of
both these cultivars in epiphytotic of race 77A may be due to
Lr23. The other gene conferring resistance to races 77A and
108 in seedlings of CPAN 6051 needs to be identified as yet. Although
virulence against Lr23
is now available in the Indian subcontinent (Nayer et al 1988),
the other gene(s) from these wheats are still effective and can be
used in breeding programmes.
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