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Area (million ha)
40
35
30
25
Area of rough rice
Area of hybrid rice
20
15
10
5
0
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
Year
Fig. 1. Area of hybrid rice (million ha).
Current situation of breeding to increase rice yield in China
A look back at crop breeding for super high yield
A series of high-yielding semidwarf varieties has made dramatic
progress in rice cultivation since the 1950s. Hybrid rice
at the end of the 1970s marked another breakthrough in China’s
rice production (Yang et al 1996, Zhou et al 1997, Huang et al
2003). For the first time in 1977, hybrid rice was produced in
farmers’ fields. Subsequently, the area of hybrid rice expanded
rapidly to 54% of the total rice area in 1997, and has remained
at more than 60% since then (Fig. 1).
Despite this progress, China’s grain output dipped from
a record high of 512 million tons in 1998 to 435 million tons
in 2003. In view of the rising population and falling number of
hectares of land across the world, the most effective and economical
way to increase production is considered to be growing
hybrid rice. Hybrid rice, which has been grown in China
for a long period, will continue to play a significant role in
guaranteeing China’s food security.
Advancement of the program
for super high-yielding rice
The current technology of hybrid rice can increase the yield
ceiling by 15–20% over that of the best commercial varieties.
Several breeding programs for super high-yielding rice have
been proposed since the 1980s. In 1996, the Chinese Ministry
of Agriculture set up a super high-yielding rice program with
the targets listed in Table 1.
In recent years, a cooperative research program in hybrid
rice breeding has been conducted by the Jiangsu Academy
of Agricultural Sciences and China National Hybrid Rice
Research Center. In this program, TGMS (thermosensitive
genetic male sterility) line Pei’ai64S was used as the female
parent and test-crossed with a number of breeding lines. Then,
several combinations with a super high yield potential were
screened, including Pei’ai64S/E32, which attained an average
yield as high as 13.26 t ha –1 , with growth duration of 130 days
on a total area of 0.24 ha at three locations in 1997. This hy-
Table 1. Yield standards (t ha –1 ) set for super rice in China. a
Phase
Hybrid rice
Yield
Early-season Late-season Single-season increase
indica indica rice
Before 1996 7.50 7.50 8.25 0
1996-2000 9.75 9.75 10.50 >20%
2001-2005 11.25 11.25 12.00 >40%
a It is required that grain yield be up to standards at two locations of an ecological
area with a planting scale of 6.7 ha at each location for two consecutive years.
brid has met the standard of super high-yielding rice, though
only in a yield trial in a small area. Pei’ai64S/E32 is characterized
by a set of yield components that lead to a theoretical
yield of 13.95 t ha –1 and actual yield of 12.87 t ha –1 . Several
hybrids, such as Chuanxiangyou2, P088S/0293, and
IIyouming86, increased their yield by more than 20%.
Theory of breeding for super high-yielding rice
Two-line and three-line systems
Currently, the three-line system of hybrid rice production is
being followed. But it is known that the two-line system, based
on the photosensitive or thermosensitive genetic male sterility
(P or T-GMS) system, is more efficient and cost-effective.
Combination of ideotype and heterosis
Since Johan and Jeroen (2003) proposed the ideotype concept,
several models have been proposed for super high-yielding
rice: the low-tillering and large panicle model by Khush
(1996), the bushy type and rapid-growing model by Huang
(2003), the ideal plant type and huge rice model by Yang et al
(1996), and the heavy panicle model by Zhou et al (1997).
The new plant type (NPT) being developed by IRRI might
raise current yield by 20–25%. These models, yet to be proven
in practice, provide the leading concepts for super high-yield-
Session 4: Improving rice yield potential 133