(go
to KOMUGI Home) (go
to WIS List) (go
to NO.76 Contents)
In summarizing the
representative dwarf-source varieties or dwarfing genes which led to
successful development of semidwarf cultivars in China in the past 20
years, five categories are recognized: (1) Suwon 86 which carries two
pairs of GA3 insensitive semidwarf genes, Rht1 and Rht2,
located on 4B* (new designation) and 4D, respectively. (2)
St2422/464 (a material of Italian origin) bearing one pair of
semidwarf genes similar to that Saitama 27 with weak GA3
insensitivity designated as Rht1s on 4B*. (3) Huixian Red and
Youbao, each carrying a pair of sernidwarf genes Rht2. (4)
Funo, Abbondanza, Mara, and other similar derivatives of Akagumughi,
each carrying one or two pairs of GA3 sensitive dwarfing gene(s)
designated as Rht8 or Rht9 and located on 2D or 7BS
(Jia et al 1992). These two pairs of dwarfing genes are common in the
Chinese varieties as the above-mentioned source-varieties were
extensively used in breeding programs. Although their height reducing
capacity is weak they may, if properly mated, manifest some auxiliary
effect on dwarfing plant stature. (5) Tom Thumb carrying Rht3
and Aibian bearing Rht10 were used in hybrid wheat
development and reccurent selection for dwarfness, respectively, by
some institutes. These will be mentioned hereinafter in the text.
Breeding for dwarfness, however, does not mean the shorter the
better. Dwarf stature can increase harvest index but it tends to
decrease biomass production. Moreover, in the areas where heat stress
is a problem in ripening, dwarf or semidwarf wheats are proned to
give a sympton of presenility or "precocious senescence." Therefore
the optimal plant height of a wheat variety must bejustified from
ajoint consideration of ecological environment, cultural condition
and prevalence of disease epidemic.
Breeding for bread baking
quality
Wheat in China is mainly consumed as foods such as steamed bread,
oriental noodle, pitta bread, pancake, etc. Selection for bread
baking properties has not been practised until early 1980's. Firstly,
screening among the released varieties,existing breeding lines and
germplasms available is emphasized. In 1987 and 1992 two contests for
"high quality" wheats were organised respectively. Table
2 provides a
comparison of major indices for bread baking quality between the top
ten varieties in the two contests.
As indicated in Table
2, there was not
mu ch improvement on the bread baking quality during the period
1987-1992. The bread baking quality of the so-called "high quality"
Chinese wheats is, in general, inferior to that of the hard red
winter wheats from the U. S. The former are characterized with a
short dough development time, short dough stability time, less
tolerance to mixing, and finally smaller loaf volume (about150 and
more nil less than the standard U. S. flour from 100 g bake).
Nonetheless, a few varieties with durum parentage such as Zhongzuo
8131-1 and its sister selections possess a bread quality score
approaching to that of the U. S. hard red winter wheats. This infers
that A and B genomes may play a considerable role in bread baking in
addition to D genome. In the present quality breeding programs good
baking quality wheats from the U. S., Canada, Mexico, the former
USSR, southern and eastern European countries are widely used as
parents in crossing and sedimentation value is adopted as a main
selection criterion for bread baking quality in early
generations.
<--Back |-->Next
(go
to KOMUGI Home) (go
to WIS List) (go
to NO.76 Contents)