(go to
KOMUGI Home) (go
to WIS List) (go to NO.92
Contents)
The amphiploid of BY with Ace. 13749 was susceptible to both the
rusts under field conditions. At seedling stage it was susceptible to
77-5 and 104-2 races of leaf rust, and race N of stripe rust
(Table 2). The resistance of the amphiploid
to race 77-4 may be from either of the parents, or combination of
resistance genes from both of them. However, resistance to race 104B,
due to gene(s) from Ae. umbellulata, was expressed in the
amphiploid. As the hexaploid wheat, CS was also susceptible to race
104B, this race can, therefore, be used as the discriminating race to
screen the segregating generations for rust resistance of Ae.
umbellulata. The amphiploid of ML with Ae.umbellulata Acc.
13749, was also susceptible to both the rusts under the field
conditions and at seedling stage to race 77-5 of leaf rust and race N
of stripe rust, but was resistant to races 77-4 and 104-2, to which
ML was susceptible. The two races, 77-4 and 104-2 can therefore be
used for screening derivatives at seedling stage.
Susceptibility of the amphiploids and their F1 hybrids
with CS (PhI) indicated the presence of suppressor
gene(s) on A and /or B genomes of the durum wheat cultivars for the
resistance genes of Ae. umbellulata Ace. 13749. Resistance of
the donor species, Ae. umbelllulata Ace. 13749, to all the
races, and differential reaction of the amphiploid to different
pathotypes of leaf rust at seedling stage (Table
2) indicate that at least two different genes for rust resistance
may be present in the U genome of Ae. umbellulata Acc. 13749.
For instance, in amphiploid Bijaga Yellow-Ae. umbellulata
Acc. 13749, one of the genes was effective against race 104B,
which was expressed in the amphiploid, and the other effective
against races 104-2 was suppressed in the amphiploid due to gene(s)
on A and/or B genome of durum wheat. This may be a attributed to
selective specificity of the suppression system. Differential
specificity of suppressor genes has already been reported. Nelson et
al. (1997) reported a locus designated as SuLr23, from T.
tauschii, which suppressed Lr23 of durum wheat in an
amphiploid of these two species. However, the gene SuLr23
could not suppress other Lr gene in the F1
hybrid of the amphiploid and hexaploid wheat. Susceptibility of the
amphiploid, Bijaga Yellow-Ae. umbellulata, to the race
N of stripe rust and 77-5 of leaf rust, to which both the parents
were resistant, may be attributed to gene interaction in the
amphiploids.
The Ae. caudata Acc. 3556 showed consistent resistance to
prevalent races of leaf rust and stripe rust under the field
conditions (Dhaliwal et al. 1993 ; Harjit-Singh et al. 1998) and to
pathotypes 77A-1, 77-1, 77-2, 77-4 and 77-5 of leaf rust at seedling
stage (Table 2). T. durum cv.
A 206 and WH 868 were susceptible to these rusts under the field
conditions but resistant to pathotypes 77-5 and 104B at seedling
stage. The amphiploids of these two cultivars with Ae. caudata,
and their F1 hybrids with CS (PhI)
were also susceptible under the field condition as well as to
individual pathotypes of leaf rust, 77-2 and 77-4, to which the durum
cultivars were susceptible.
<--Back | -->Next
(go to
KOMUGI Home) (go
to WIS List) (go to NO.92
Contents)