GENETIC IMPROVEMENT OF WHEAT YIELD POTENTIAL AND ADAPTATION IN CHINA - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 185

(53.0%), spring (36.1%) and early heading (10.9%) cultivars were grown in the Yellow
and Huai River Valleys Facultative Wheat Zone. Most of the spring genotypes from this
zone carried only the dominant Vrn-D1 allele, which was also predominant (64.1%) in
the Middle and Lower Yangtze Valleys Autumn-Sown Spring Wheat Zone and
Southwestern Autumn-Sown Spring Wheat Zone. The average frequency of the
photoperiod-insensitive Ppd-D1a allele was 66.0%, with the frequencies of 38.6% and
90.6% in landraces and improved cultivars, respectively. Therefore, in addition to
utilization of dwarfing genes and the 1B/1R translocation, dominant vernalization and
photoperiod genes for early maturity have also contributed to yield improvement of
Chinese wheat. The future challenge of wheat breeding is to continually raise grain yield,
or to both maintain the genetic gain in grain yield and improve grain quality, without
increasing inputs for the wheat based double cropping system.
I NTRODUCTION
China is the largest wheat producer and consumer in the world and wheat ranks as the
third leading crop in China after rice and maize.
Chinese wheat area has been divided into ten major agro-ecological zones (Figure 1),
based on wheat types, varietal reactions to temperature, photoperiod, moisture, biotic and
abiotic stress, and wheat growing seasons (Jin, 1986, 1997; He et al., 2001). At present,
autumn-sown wheats account for about 90% of production and acreage and include zones I
(4%), II (60%), III (13%), IV (minor area of production) and V (10%). Spring-sown wheats
represent 7% of the wheat acreage in China and are grown in zones VI, VII, and VIII. Zones
IX and X cover less than 3% of the total wheat area and include both spring- and fall-sown
wheats. Although wheat is grown in 30 of the 31 provinces, more than 90% is produced in 13
provinces; of these, more than 70% of Chinese wheat is produced in five provinces, i.e.,
Henan, Shandong, Hebei, Anhui, and Jiangsu.
Great progress has been achieved in wheat production during the last 57 years, average
yield has increased 1.9% annually from 660 kg/ha in 1950 to 4487 kg/ha, and the production
has increased more than six times, from less than 20 million tones in 1950 to 105 million
tones in 2007. Many factors have contributed to the significant increase of average yield,
including adoption of improved cultivars, extension of high-yielding cultivation technologies,
increased use of fertilizers and irrigation, expansion of farm mechanization, and improvement
of rural policy. More than 2000 wheat cultivars have been released, and 59 outstanding
cultivars, each covering annually an acreage of 670,000 hectares, had made significant
contribution to China wheat production. It has been recorded that farmers have replaced their
wheat cultivars six to eight times in the major wheat areas (He et al., 2001; Zhuang, 2003).
The objective of this chapter is to review the advances in genetic improvement of wheat grain
yield, and adaptation in China accomplished by breeders from 1950s to the present.