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Wheat Information Service
Number 92: 9-11 (2001)
Research article
The possible candidate of Vrn-B1 in wheat,
as revealed by monosomic analysis of Vrn gene carried by
Triple Dirk (B), the former Vrn2
Kazunari Iwaki1, Kiyokazu Nakagawa2 and
Kenji Kato1*
1Faculty of Agriculture, Okayama University, 1-1-1
Tsushima-Naka, Okayama 700-8530, Japan
2Faculty of Agriculture, Kochi University, 200
Monobe-Otsu, Nankoku, Kochi 783-8502, Japan
Summary
Chromosomal location of the former Vrn2 was analyzed by
using monosomic lines of a winter wheat, Dwarf A. Segregation ratio
of spring and winter type plants fitted well to an expected ratio of
3:1 in most cross combinations. On the contrary, for the cross with
mono 5BL-7BL line, segregation of winter type
was significantly less than expected, 8/107, and thus was concluded
that Vrn2 should be located on 5BL-7BL
chromosome.
Key words: monosomic analysis, Vrn-B1, vernalization,
wheat
Introduction
Vernalization requirement is one of the most important traits for
the adaptation to cold winter, and wheat cultivars are classified
into two groups, spring and winter types, according to their
requirement. Genetic analysis of vernalization requirement revealed
the involvement of four (or five) major Vrn genes, formerly
termed as Vrn1, Vrn2, Vrn3, Vrn4 and Vrn5 (reviewed by
Flood and Halloran 1986). Cytological analysis located Vrn1
and Vrn3 on the long arm of 5A and 5D, respectively (Law
et al. 1975). Based on the result of RFLP mapping, synteny. between
homoeologous chromosomes and orthologous genes for vernalization
requirement (Vrn1, Vrn3, Sp1, Sh2) has been confirmed
in wheat, rye and barley (Nelson et al. 1995; Dubcovsky et al. 1998).
Then gene nomenclature has been changed as Vrn-A1, Vrn-D1,
Vrn-R1 and Vrn-H1(McIntosh et al. 1998). Another Vrn gene
is located on 5B chromosome (Hoogendoorn 1985a), and is termed as
Vrn-B1 (McIntosh et al. 1998).
However, there have been two conflicting reports about Vrn gene on 5B
chromosome. Vrn2 was located on 5B by Hoogendoorn (1985b),
while Vrn4 was located on 5B by Maystrenko (1980). Reflecting
such confusion, McIntosh et al. (1998)summarized that the genes
formerly designated 1 as Vrn4 Vrn2 are or, probably the same
allelic, and then two genes are designated as Vrn-B1 in the
new nomenclature system. However, independence of Vrn2 and
Vrn4 was clearly shown by test cross between four
near-isogenic lines (NILs) (Gotoh 1979; Kato unpublished), and by the
existence of cultivars< carrying either Vrn2 or Vrn 4
(Kato et al. 1988). Considering the importance of Vrn2 in
spring type cultivated in the Mediterranean countries, chromosomal
location of Vrn2 and Vrn4 should be clarified to solve
such a confusion.
Therefore, in the present study, chromosomal location of Vrn2
was analyzed by using monosomic series. of Dwarf A.
*Corresponding author: Kenji Kato, Fax. +81-86-251-8388,
E-mail:kenkato@cc.okayama-u.ac.jp
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