(go to
KOMUGI Home) (go
to WIS List) (go to NO.89
Contents)
Aiganfanmai showed short seedlings, as well as short straw. The
seedlings of Aiganfanmai are regularly vigor. A distinct phenotype,
thin stems with elongated leaf was observed in Aiganfanmai seedlings
treated with gibberellic acid (GA) after germination. Compared with
the check (CK), the GA treated seedlings of Aiganfanmai were 6.5 cm
longer in the first leaf, and 1.8 cm, longer in coleoptile (Table
3). Whereas seedlings of the hexaploid wheat variety, Tom Thumb
did not show notable variation in the length of the first leaf and
coleoptile after GA treatment (Table 3 ).
Obviously, Aiganfanmai is GA sensitive, in contrast to Tom Thumb
which is carrying Rht3 gene and considered as GA insensitive
(Gale et al. 1975; Morris et al. 1972 ).
Discussion
Many environmental and genetic factors that regulate development,
morphology or vigor, will have effects on plant height of wheat,
which give the plant height quantitative nature of variation. Among
them were the genes for spike length and the deepness of seeds in
soil in this experiment, so the effects of these two factors were
lessen by defining the term plant height as excluding the length of
spike and the first internode. Nevertheless, quantitative nature of
plant height was observed in Aiganfanmai, Fenzhilanmai and their
descendant generations. This revealed the environmental effect and
the complexity of the genetic basis of plant height.
The segregation ratio of 1 (dwarf) : 3 (tall) in F2
population means that a single Rht gene caused the difference
of plant height between Aiganfanmai and Fenzhilanmai. If the dwarf
trait of Aiganfanmai was resulted only from a single Rht gene,
the dwarf subpopulation in F2 population should show
similar mean value of plant height to Aiganfanmai. However, the mean
plant height of dwarf subpopulation was 94.2cm, which is
significantly higher than that of Aiganfanmai (t=5.904, p=0.001 ).
Furthermore, F-test indicated that variation value of dwarf
subpopulation in F2 population was significantly higher
than that of Aiganfanmai (F=2.361, p < 0.01). This difference
could not be attributed to the effect of environmental factors,
because of the random distribution of seeds that belonged to
different populations. The best explanation should be that there
existed more than one gene for dwarf trait. Considering that the
dwarf subpopulation in F2 population is just only slightly
higher than Aiganfanmai, the gene(s) for plant height other than
Rht was minor genes. In another word, the dwarf trait in
tetraploid wheat landrace Aiganfanmai was controlled by a major
Rht gene and some modifiers, which is similar to the situation
of hexaploid wheat.
The fact that the mainly genetic base for the dwarf trait of
Aiganfanmai was a single Rht gene indicated that it is very
useful in lodging resistance breeding program. Although the
recessiveness determined that the major Rht gene of
Aiganfanmai could not express in F1 progeny of crossing
with high-straw recipient variety, tetraploid wheat breeders can
successfully pick out dwarfing materials in segregating generations,
which is far more effective than interspecies crossing with hexaploid
wheat.
Besides the dwarf trait, Aiganfanmai showed high crossability with
cultivated rye (Peng et al. 1998). Breeders have used Aiganfanmai to
develop hexaploid Triticale. However, synthetic amphiploid
(Aiganfanmai x rye) expressed only a little shorter than that of
crossing ordinary tetraploid wheat with rye in our laboratory (data
unpublished). This may be because of the existence of inhibitor of
Rht in the R genome of rye, and indicating that the usage of
Rht gene in Aiganfanmai was limited in Triticale
lodging-resistance breeding program.
The coleoptile and first leaf length were associated with mature
plant height (Allan and Vogel 1964). In addition, Gale et al. (1975)
successfully used seedlings to test the reaction of wheat to GA.
Following their method, we revealed that short seedlings of
Aiganfanmai was attributable to GA-sensitivity. Thus the dwarf trait
of Aiganfanmai should be considered to be GA-sensitivity. However,
the relationship between the Rht gene of Aiganfanmai and its
response to GA may not be decisive only on the result of this study,
because contradictory conclusions were reported in hexaploid wheat;
the dwarf trait and the reaction to GA were under separate control by
linked genes Gai and Rht (Hu 1974), and on the other hand,
reaction to GA was pleiotropic effect of Rht gene (Gale and
Law 1973; Gale et al. 1975). To determine whether the Rht of
Aiganfanmai has this pleiotropic effect or not, a further study has
initiated in our laboratory.
<--Back | -->Next
(go to
KOMUGI Home) (go
to WIS List) (go to NO.89
Contents)