(go to
KOMUGI Home) (go
to WIS List) (go to NO.92
Contents)
Susceptibility of the amphiploids and their F1 hybrids
with CS (PhI) under the field conditions as well as
to individual pathotypes of leaf rusts at seedling stage, clearly
indicated suppression of resistance gene(s) of Aegilops
caudata also by gene(s) of A and/or B genomes of durum wheat.
Suppression of rust resistance genes by the A or B genome of wheat
has already been reported (Kerber 1983; Ma et al. 1997). Innes and
Kerber (1994) reported suppression of resistance to leaf rust in
amphiploid of susceptible durum wheat and resistant Ae.
squarrosa.
Recovery of resistant plants in the F2 and subsequent
backcross generations (BC1 and BC2) of crosses
of amphiploids involving Ae. caudata with CS, due to
segregation of the resistance gene(s) from the suppression gene(s) of
durum wheat suggests the absence of suppression gene(s) in CS.
Furthermore, it also indicates the absence of suppressor genes in the
D genome of CS for resistance gene(s) of Ae. caudata.
T. durum cv. WH 890 was also susceptible to both the rusts under
field conditions and to most of the pathotypes of leaf rust and
pathotype P of stripe rust (Table 2).
However, in contrast to the previous amphiploids involving Ae.
umbellulata and Ae. caudata , the resistance gene(s) of
Ae. umbellulata Acc. 3732 was expressed in the amphiploid
T. durum cv. WH 890-Ae. umbellulata Acc. 3732
under field conditions whereas at the seedling stage the
amphiploid was susceptible to all the individual pathotypes of leaf
rust, except race 77-3. Ae. umbellulata Acc. 3732 was
resistant to all the races of leaf rust (Table
2), however, the amphiploid was resistant only to race 77-3
suggesting that Ae. umbellulata accession carried at least two
different genes. One of the genes effective at seedling stage against
race 77-3 was probably also expressed in the adult plants, the other
gene(s) which were suppressed at the seedling stage may or may not
have expressed at the adult plant stage. Recovery of plants in
segregating generations of crosses of amphiploids with CS that were
resistant to races to which durum wheat, amphiploid, and hexaploid
wheat were susceptible (Table 2) further
confirms the suppression of some of the resistance gene(s) of
Ae. umbellulata by the A and/ or B genomes of T.
durum parents and that the Chinese Spring did not carry any
suppressor system for resistance gene(s) of Ae. umbellulata.
In conclusion, the study unequivocally demonstrated the
suppression of leaf and stripe rust resistance of the C and U genomes
of Aegilops species by the A and/or B genomes of the T.
durum parents in the synthetic amphiploids. The study further
showed that the suppression system of T. durum suppressing the
expression of resistance genes from Aegilops species had
selective specificity as it suppressed only some of the resistance
gene(s) and not the other. The impediment of suppression of
resistance to interspecific gene introgression can, however, be
overcome by selecting the recipient wheat stocks lacking the
suppression system.
Acknowledgments
The first author is grateful to the Agricultural Research,
Education and Extension Organization (AREE0), Ministry of
Agriculture, Government of Islamic Republic of Iran for grant of
scholarship to study in India. Financial support made by the United
States Department of Agriculture under U.S.- India Fund is
acknowledged.
<--Back | -->Next
(go to
KOMUGI Home) (go
to WIS List) (go to NO.92
Contents)