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of them included additional dominant
Vrn
alleles at the
Vrn-B1
,
Vrn-D1
and
Vrn-B3
loci. On
the basis of the vernalization alleles found in our study, the vernalization requirement can be
ranked from strongest to weaker from Zone I, Zone II, Zone III, Zone V, with the weakest
requirement in the spring-sown spring wheat regions (Zones VI, VII, and VIII).
Table 10. Frequencies (%) of different
Vrn
allele combinations and their heading times
in spring cultivars of various wheat zones
Genotype and heading time
I
II
III
V
VI
VII
VIII
X
Total
-
-
-
-
12.5
23.5
26.0 35.7 11.0
Vrn-A1
alone = 39d
﹢
(33-46d)
Vrn-D1
alone
2
= 54d (36-
109d)
-
93.3 88.9 51.5 -
-
3.7 14.3 41.9
Vrn-B1
alone = 47d (36-73d)
-
6.7
3.7
15.2
-
-
11.1 -
6.4
Vrn-B1
+
Vrn-D1
= 42d (36-
49d)
-
-
7.4
18.1
4.2
5.9
11.1
-
7.6
Vrn-A1
+
Vrn-B1
=
38d (32 -
49d)
-
-
-
33.2 47.1
48.1
35.7 20.9
6.1
Vrn-A1
+
Vrn-D1
=
38d (36-
44d)
-
-
-
12.5 17.6 -
-
4.6
6.1
Vrn-A1
+
Vrn-B1
+
Vrn-D1
=
38d (33-50d)
-
-
-
29.2 5.9 -
14.3 6.4
3.0
Vrn-A1
+
Vrn-B1
+
Vrn-B3
=
30d
-
-
-
-
4.2
-
-
-
0.6
Vrn-A1
+
Vrn-B1
+
Vrn-
D1
+
Vrn-B3
= 31d
-
-
-
-
4.2
-
-
-
0.6
﹢
Average flowering time of tested genotypes with this genotype.
Heading dates showed a continuous distribution from 30 days to more than six months
after planting in the greenhouse. Out of 266 cultivars tested in the greenhouse, the 92
cultivars, which failed to head within 109 days all possessed recessive vernalization alleles at
the four
Vrn
loci. Most of them were classified as winter cultivars in the literature (Jin, 1986
and 1997; Zhuang, 2003). Among the 174 cultivars that headed within 109 days (early
heading), 164 of them carried at least one of the tested dominant vernalization allele, and
were classified as spring. The other cultivars, nine from Zones II (Jimai 36, Taishan 1, Lumai
23, Laizhou 953, Weimai 8, Xinmai 9408, Yumai 66, Yumai 70, Xuzhou 14) and one from
Zone III (Emai 6) carried recessive alleles at the four vernalization loci. The most likely
explanation for this discrepancy is the presence of an unknown allele at the four loci
characterized in this study or the presence of a spring allele at the
Vrn4
locus not included in
this survey because the gene is still unknown.
All 32 cultivars released in Zone I headed after 109 days, had all three recessive
vrn-1
alleles and were classified as winter. In Zone II, of 75 cultivars tested in the greenhouse, 44
(58.7%) headed after 109 days. Although both winter and spring types are found in all
provinces of Zone II, the late heading cultivars were mainly cultivated in the provinces of
Shandong (79.2%), Shaanxi (63.6%), and Anhui (100.0%), whereas the early heading
cultivars were mostly present in the provinces of Henan and Jiangsu. Most of the cultivars
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