Agriculture Reference
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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
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