Agriculture Reference
In-Depth Information
Chapter 17
Success in Wheat Improvement
Jackie C. Rudd
SUMMARY
(4) Reduced height, increased harvest index,
and greater kernel number per unit area are
primary contributing factors to improved
yield, even among semidwarf cultivars.
New studies have shown that simultaneous
improvement in harvest index and biomass
occurred in recent years.
(5) The mean yields of wheat and soybean
( Glycine max L.) in the US increased
from about 1,200 kg ha −1 in 1950 to near
3,000 kg ha −1 in recent years. During this
same period, maize ( Zea mays L.) yield
increased from 2,000 kg ha −1 to over
9,000 kg ha −1 . These statistics, and the
fi vefold (or greater) difference in program
support for maize versus wheat across
public and private domains, clearly show
the value of investing in plant breeding.
(1) Wheat grain yield throughout the world has
increased by two- or threefold since 1950.
The UK currently has the highest yield
in the world at 7,700 kg ha −1 . China has
experienced the greatest percentage gain,
increasing yield by 450% since the 1960s.
(2) Historically, the genetic component of
grain yield improvement in wheat has been
estimated at 50%. Evidence now indicates
this fraction may have increased in recent
years.
(3) Annual genetic gain for grain yield has aver-
aged about 40 kg ha −1 , or about 1%. Gains
have been reported even at very low produc-
tion levels, but they have been highest in the
most productive environments.
WORLD YIELD GAINS
The rate of gain also has varied widely among
countries. France, Germany, and the UK all had
gains over 100 kg ha −1 yr −1 . China's annual gain
was 88 kg ha −1 yr −1 and clearly showed the great-
est percentage change. Wheat yield in China
during the 1960s was 940 kg ha −1 ; it has increased
by a factor of 4.5 to 4,190 kg ha −1 so far this decade
(Table 17.1 and Fig. 17.1). India and Pakistan
increased wheat yields by 40-50 kg ha −1 yr −1 ,
while yields in the US, Russia, Canada, Turkey,
Argentina, and Iran have shown yield gains
between 20 and 35 kg ha −1 yr −1 (Table 17.1). The
annual yield increase in Australia has been
12.9 kg ha −1 yr −1 since 1961. Australia experienced
severe droughts in 2002, 2006, and 2007, and as
a result, the yield for the current decade is lower
than for the 1990s. Australia did have substantial
World wheat grain yield rose slowly or not
at all during the fi rst half of the 20th century
but has increased by two- or threefold during
the past 50 years (Calderini and Slafer 1998).
Table 17.1 shows the yield progression by
decade since 1961 for the 15 leading wheat
producing countries, ranked according to
2001-to-2007 production data. The yield across
all countries averaged 1,300 kg ha −1 in the
1960s but is close to 3,000 kg ha −1 currently, an
increase of 40 kg ha −1 yr −1 . As expected, these
numbers differ by country. Grain yield in the
UK has averaged 7,700 kg ha −1 this decade, while
the yield in Kazakhstan averaged just over
1,000 kg ha −1 .
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