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Sabikei 50 is also a leaf
rust resistant wheat parental line developed at the Tohoku National
Agricultural Experiment Station (Mukade et al. 1987). It was selected
from a triple cross, Sabikei 25/Sabikei 23//Hanagasakomugi. This
cross was made in 1976 with the view of accumulating three different
leaf rust resistance genes, the first from Sabikei 25 whose complete
resistance gene is inherited from RW-12 (see Sabikei 40), the second
from Sabikei 23, a line which shows adult plant resistance probably
derived from Elytrigia intermedia through WA-3, and the third
from Hanagasakomugi, a cultivar which shows slow-rusting resistance
probably derived from Triticum turgidum ssp. dicoccoides
or T. turgidum ssp. durum through Hope-Timstein
1139-44. However, Sabikei 50 did not inherit the complete resistance
gene from Sabikei 25. Sabikei 50 shows susceptible or mixed reaction
to the leaf rust races 6A, 37B and 21 B at the seedling stage, while
the degree of resistance gradually increases as the plant grows
(adult plant resistance). In the field, Sabikei 50 is resistant in
the early period of ripening but becomes slightly infected towards
maturity. However, the progress of leaf rust lesions is very slow
(slow-rusting resistance) and hardly affects the photosynthetic
ability of the plant. Sabikei 50 was registered by the MAFF as a
wheat parental line no. 3 in 1986 (Table
1).
AS-5 is also a leaf rust resistant wheat parental line developed at
the Tohoku National Agricultural Experiment Station (Yamaguchi et al.
1993). AS-5 carries the gene Lr19 conferring resistance to the
leaf rust races 6A, 37B and 21 B for all the growing periods of
wheat. The gene Lr19 of AS-5 derived from Elytrigia pontica
through a chromosome substitution line, Agrus. The endosperm of
AS-5 is rich in lutein which is a carotenoid pigment and hence
produces a flour with a yellowish color. This character is considered
to be controlled by a gene(s) closely linked to Lr19. AS-5 was
registered by the MAFF as a wheat parental line no. 6 in 1991
(Table
1).
3) Breeding for resistance to scab: In the south-western Japan,
especially in Kyushu, scab disease caused by Gibberella zeae
(Schw.) Petch, Fusarium graminearum Schw., etc. causes
considerable damage and has become one of the most important problems
in wheat production. No gene for complete resistance or immunity to
scab has been identified yet. Extensive efforts to breed more
resistant cultivars have been made by the accumulation of polygenes
for resistance or by the induction of mutations mainly at the Kyushu
National Agricultural Experiment Station and one parental line has
been developed (Table
1).
Akakabikei 2 (synonym: Akakabi-kei 2), a scab resistant wheat
parental line, was developed at the Kyushu National Agricultural
Experiment Station from a cross between Nobeokabozu-komugi (synonym:
Nobeokabozu- komugi) and Sobaku 3 (synonym: Sumai 3) (Gocho et al.
1992). Both parents showed a higher resistance to scab than the other
wheat varieties. However, Nobeokabozukomugi and Sobaku 3 cannot be
commercially used due to their poor agronomic characteristics such as
long culm and late maturity. The resistance of these varieties was
conferred by polygenes. The cross between Nobeokabozukomugi and
Sobaku 3 was made in 1977 with the view of accumulating these
polygenes for resistance. No selection was made from F1 to
F4 bulk populations and the F5 generation was
screened for lodging resistance. The derived lines were screened for
scab resistance and other agronomic characters in succeeding
generations. One promising line was obtained and named Akakabikei 2
in the F10 generation in 1984. "Akakabikei" means "scab
resistant line". It was registered by the MAFF as a wheat parental
line no. 4 in 1986 (Table
1).
The possibility of using Elytrigia and Elymus as
sources of resistance to scab is now being investigated at the Kyushu
National Agricultural Experiment Station.
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