GENETIC IMPROVEMENT OF WHEAT YIELD POTENTIAL AND ADAPTATION IN CHINA - Soybean and Wheat Crops: Growth, Fertilization, and Yield - page 193

Table 9. Frequencies (%) of dominant alleles at Vrn-A1 , Vrn-B1 , Vrn-D1 and Vrn-B3
loci in spring cultivars of various wheat zones
Zone Genotype Total

I II III V VI VII VIII X

Vrn-A1

- - - 15.2 95.8 94.1 74.1 85.7 44.2

Vrn-B1

- 6.7 11.1 42.4 75.0 58.8 70.4 50.0 42.4

Vrn-D1

- 93.3 96.3 78.8 50.0 29.4 14.8 28.6 61.0

Vrn-B3

- - - - 8.3 - - - 1.2

Totally, 278 leading Chinese wheat cultivars released since the 1960s, and collected from
eight wheat growing zones (I, II, III, V, VI, VII, VIII and X) were characterized with
molecular markers for the vernalization genes Vrn-A1 , -B1 , -D , and -B3 , Heading time of the
266 cultivars tested was evaluated in a greenhouse under long days without vernalizaiton
(Zhang et al., 2008).
The frequencies of the different Vrn allele combinations were very different across
different wheat agro-ecological zones. Cultivars with recessive alleles at all the analyzed Vrn
loci represent 38.1% of the cultivars and are mainly concentrated in Zones I, II and X. The
other 61.9% includes cultivars with at least one dominant Vrn allele, which can be classified
as spring. These cultivars are found mainly in Zones III, V, VI, VII, VIII and X. The
dominant Vrn-D1 allele showed the highest frequency in Chinese wheats (37.8%), followed
by the dominant Vrn-A1 (27.3%), -B1 (26.3%), and -B3 (0.7%) alleles.
Among the cultivars with at least one dominant Vrn allele, the frequencies of the different
alleles varied in across regions (Table 9). The dominant Vrn-B3 allele is present only in two
cultivars from zone VI with the frequency of 1.2%. Among the Vrn-1 , alleles Vrn-D1 (61.0%)
showed highest frequency, followed closely by dominant Vrn-A1 (44.2%) and Vrn-B1
(42.4%) alleles. The dominant Vrn-A1 allele is not presented in Zones I, II, and III, and its
frequency is low in Zone V (15.2%). However, high frequencies are observed in Zones VI
(95.8%), VII (94.1%), VIII (74.1%) and X (85.7%). The dominant allele Vrn-B1 is not
presented in Zone I, and low frequencies are observed in Zones II (6.7%) and III (11.1%).
However, high frequencies are observed in Zones V (42.4%), VI (75.0%), VII (58.8%), VIII
(70.4%) and X (50.0%). The dominant allele Vrn-D1 is not presented in Zone I, but is present
at relatively high frequencies in Zones II (93.3%), III (96.3%), V (78.8%), VI (50.0%), VII
(29.4%), VIII (14.8%) and X (28.6%).
Among the four autumn-sown wheat zones (I, II, III and V), the frequency of dominant
Vrn-D1 allele is the highest, followed by Vrn-B1 and Vrn-A1 ( Vrn-B3 is absent). In contrast,
in three spring-sown wheat zones (VI, VII and VIII) the frequency of the dominant Vrn-A1
allele is the highest, followed by Vrn-B1 and Vrn-D1 , respectively. Vrn-B3 frequency (2.9%)
is the lowest.
Frequencies of the different combinations of vernalization genes were also very different
among the various wheat zones. In brief, nine combinations of dominant Vrn alleles were
identified (Table 10). Among them, the Vrn-D1 allele alone was the most frequent (72
cultivars), followed by the Vrn-A1 / Vrn-B1 (36 cultivars) combination. In summary, most
cultivars released in the autumn-sown wheat regions of south China (Zones III and V) and
north China (Zone II) possessed Vrn-D1 as a single dominant allele. In contrast, in spring-
sown wheat regions, cultivars carried the strongest dominant Vrn-A1 alleles and the majority