GENETIC IMPROVEMENT OF WHEAT YIELD POTENTIAL AND ADAPTATION IN CHINA - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 192

U TILIZATION OF 1B/1R T RANSLOCATION
In total, 162 predominant cultivars in recent 30 years from Chinese four main autumn-
sown wheat Zones (I, II, III and V) were examined by SDS-PAGE and SCAR for the
presence of 1B/1R translocation (Zhou et al., 2004). Overall, frequency of cultivars with
1B/1R translocation in four autumn-sown regions was 31.5%, but those in diverse zones were
different. The 1B/1R translocation was highest frequency in Zone I (52.0%), followed by
Zone II (33.7%), and the lowest was found in Zones III (10.5%) and V (15.0%). However,
cultivars with the 1B/1R translocation released before 1980 were absent in China. On
average, 40.2% of Chinese wheats released since 1980 contained 1B/1R, but its frequency
also differed in different zones, which was 59.1% for Zone I, 41.3% for Zone II and 20.0%
for Zone III and V (Table 8). From the late 1970s to the early 1990s, wheat breeding in
autumn-sown wheat regions focused on the utilization of the 1B/1R translocation from
introductions such as Lovrin 10, Lovrin 13, and Neuzucht, which showed resistance to rusts,
powdery mildew, and to heat stress after anthesis (He et al., 2001). Fengkang 8 in Beijing,
Jimai 24 in Hebei, Lumai 7 in Shandong, Yumai 13 in Henan, Een 1 in Hubei and Miannong
4 in Sichuan, all have 1B/1R, and were developed in 1980, 1982, 1981, 1987, 1982 and 1986,
respectively. The current leading cultivars in Beijing and Hebei continue to have 1B/1R. The
low frequencies of 1B/1R in Shandong and Henan are largely due to the intensive selection
for processing quality; thus good quality cultivars such as Jinan 17, Jimai 19, and Yumai 34,
which lack 1B/1R, are the primary cultivars being grown.
D ISTRIBUTION OF G ROWTH H ABIT AND V ERNALIZATION G ENES
The adaptation of wheat cultivars to diverse environmental conditions is greatly
influenced by flowering time (Whitechurch and Slafer, 2002), which is mainly determined by
three groups of genes: vernalization response genes ( Vrn genes), photoperiod response genes
( Ppd genes) and developmental rate genes (earliness per se, Eps genes) (Snape et al., 2001).
The first two groups of genes are environment-dependent, whereas the third is largely
environment-independent. Vernalization genes determine growth habits which divide wheat
into winter and spring types. Winter types require vernalization to promote flowering and
spring types do not. Photoperiod genes determine characters of photoperiod response in
wheat. Photoperiod response is described as sensitive when timely flowering occurs only in
long days, and insensitive when flowering occurs in either long- or short-day environments.
The different frequencies of Vrn alleles observed in different parts of the world suggest that
these allele combinations have an adapatative value (Gotoh, 1979; Stelmakh, 1990;
Goncharov, 1998; Iwski et al., 2000, 2001). Photoperiod response is closely associated with
adaptability and grain yield in European and Canadian wheat cultivars (Martiníc 1975; Hunt
1979; Worland et al. 1994; 1998). In Asia, Mediterranean and North African regions, most
landraces are sensitive to photoperiod, whereas all improved cultivars with high yield
potential are insensitive (Ortiz Ferrara et al. 1998). Therefore, understanding of the
vernalization and photoperiod genes present in wheat breeding programs is useful when
developing high yielding cultivars broadly adapted to different regions.