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A successful culture
technique for haploid immature embryos of wheat and barley is
essential for the development of haploid plants. There are two
strategies for the development of haploid plants (Fig.
4). In the first
strategy, haploid plants can be grown directly from haploid immature
embryos on an agar medium without 2,4-D (Inagaki 1985a). This method
is advantageous because the breeding period can be shortened. The
other strategy involves culturing haploid immature embryos on an agar
medium supplemented with 2,4-D for the formation of calli.
Thereafter, haploid plants can be regenerated from the calli on an
agar medium without 2,4-D (Inagaki 1986a). In this system, natural
and artificial mutations can be expected during callus formation
(Fig.
4).
A successful chromosome doubling technique for haploid plants of
wheat and barley is essential for producing the doubled haploid
plants which are homozygous and set fertile seeds (Fig.
4). Factors
influencing chromosome doubling of wheat and barley haploid plants
have been investigated and some treatment methods using colchicine
solution have proved highly successful for chromosome doubling
(Jensen 1974, 1976; Thiebaut et al. 1979; Inagaki 1985b).
5. Conservation of wheat and barley genetic resources in MAFF
The current number of germplasm of wheat, barley, oats, rye,
triticale and their relatives preserved in the Center Ban k of the
National Institute of Agrobiological Resources, Tsukuba, is shown in
Table
4. A part of them
is also preserved in the Sub-Banks of the National Agricultural
Experiment Stations including the National Agriculture Research
Center. Some dozens of Elytrigia and Elymus clones are
preserved in the Sub-Bank of the Kyushu National Agricultural
Experiment Station. Almost two hundred clones of Hordeum bulbosum
L. are preserved in the Sub-Banks of National Agriculture
Research Center, Shikoku National Agricultural Experiment Station,
National Center for Seeds and Seedlings, etc. They have been
collected mainly by collecting missions and international
exchange.
References
Araki H (1990) Studies on practical use of hybrid wheat using
cytoplasmic male sterility. Bull Kyushu Natl Agric Exp Stn 26(2):
115-165 (in Japanese with English summary).
Barclay IR (1975) High frequencies of haploid production in wheat
(Triticum aestivum) by chromosome elimination. Nature 256:
410-411.
Falk DE and Kasha M (1981) Comparison of the crossability of rye
(Secale cereale) and Hordeum bulbosum onto wheat
(Triticum aestivum). Can J Genet Cytol 23: 81-88.
Falk DE and Kasha M (1983) Genetic studies of the crossability of
hexaploid wheat with rye and Hordeum bulbosum. Theor Appl
Genet 64: 303-307.
Falk DE, Kasha M and Reinbergs E (1981) Presowing selection of
genetic male sterile plants to facilitate hybridization in barley.
In Barley Genetics IV Proc Fourth Intl Barley Genet Symp,
Edinburgh Univ Press, Edinburgh: 778-785.
Fukuoka T, Furusho M and Makino T (1991) A new BaYMV resistant gene
of waxy barley variety 'Tokushimamochihadaka'. Japan J Breed 41
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Furusho M, Hamachi Y and Yoshida T (1990) Varietal difference in
crossability between Japanese two-rowed barley and Hordeum
bulbosum L. Japan J Breed 40: 411-417.
Furusho M, Suenaga K and Nakajima K (199 1) Production of haploid
barley plants from barley x maize and barley x Italian
ryegrass crosses. Japan J Breed 41: 175-179.
Gocho H, Hirai T and Kashio T (1992) Breeding of "Wheat Norin PL-4" a
new germplasm with resistance to scab (Gibberella zeae (Schw.)
Petch). Bull Kyushu Natl Agric Exp Stn 27(3): 317-331 (in Japanese
with English summary).
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