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4) Breeding for improved
grain quality: The nutritional quality of naked barley has been
improved using an Ethiopian local variety Hiproly with a gene lys
conferring a high lysine content as a gene source. The gene lys is
linked to the gene s conferring short rachilla hairs with a
recombination value of 8.4% on chromosome 7 (Munck et al. 1970;
KarIsson 1972). In grains with a high protein content, hardness
generally increases. Nanpuhadaka was used as the recurrent parent to
incorporate the high protein quality from Hiproly into Japanese
cultivars. In the early hybrid generations, the s gene and grain
hardness were used as markers for selection. Naked barley parental
line no. 1 (former name: Yonkei 8422) was developed at the Shikoku
National Agricultural Experiment Station in 1984 (Kato et al. 1987).
This line is comparable to Nanpuhadaka in agronomic characters such
as earliness, plant height and yielding performance, and contains 16
percent more crude protein and 27 percent more essential amino acids
than Nanpuhadaka. A new naked barley cultivar Sansyuu into which the
high protein quality of Hiproly has been incorporated was also
released from the Shikoku National Agricultural Experiment Station in
1989 (Ito et al. 1992).
5) Breeding high-yielding barley varieties using F1
hybrids: In order to breed F1 hybrids, attempts to use the
male sterile gene msg6 are being made at the National Agriculture
Research Center. The male sterile plants with a genotype o-
msg6-sex1a-Uc2/o-msg6-sex1a-Uc2 can be efficiently selected from
the sledded progenies of a maintainer with a genotype o-Msg6-Sex1
a-uc2/o-msg6-sex1-Uc2 because the o, msg6, sex1a and
uc2 loci are closely linked with each other on chromosome 6,
and the genes sex1a conferring shrunken endosperm and
uc2 conferring
uniculm are useful marker genes for the selection of male sterile
plants (Falk et al. 1981). On the other hand, a character to induce
chasmogamy is indispensable for the production of F1
seeds. Almost all the Japanese barley cultivars except for Satsuki
Nijo showed cleistogamy. The chasmogamy of Satsuki Nijo is controlled
by a single recessive gene (Kurauchi et al. 1993). Incorporation of
the recessive gene conferring chasmogamy into other Japanese barley
genotypes is also being carried out at the National Agriculture
Research Center.
4. Production of wheat and barley haploid plants through
intergeneric and interspecific crossing
The "bulbosum method" of haploid breeding using Hordeum
bulbosum L. has recently been used by breeders of both wheat and
barley. Tetraploid and diploid clones of H. bulbosum are used
as pollen parents for obtaining the haploid immature embryos of wheat
and barley (Kasha and Kao 1970; Barclay 1975). The "maize method"
using the pollen of maize (Zea mays L.) or teosinte (Zea
mays ssp. mexicana L.) has also been used to obtain haploid
immature embryos of wheat (Laurie and Bennett 1986, 1987, 1988;
Ushiyama et al. 199 1). The application of the bulbosum method for
wheat haploid production is restricted due to the presence of the
cross- incompatibility genes, Kr1 and/or Kr2, located
on chromosomes 5B and 5A, respectively (Snape et al. 1979; Falk and
Kasha 1981, 1983; Sitch et al. 1985). These cross-incompatibility
genes are frequently found in wheat genotypes other than Japanese and
Chinese ones (Snape et al. 1979; Falk and Kasha 198 1; Inagaki and
Snape 1982; Li and Hu 1986). Alternatively, the production of wheat
haploid plants using maize pollen is successful even for the wheat
genotypes which are cross-incompatible with H. bulbosum
(Laurie and Bennett 1986, 1987, 1988). Haploid production of
wheat from crosses between wheat x sorghum (Sorghum bicolor)
and barley haploid production from crosses between barley x maize and
barley x Italian
ryegrass (Lolium multiflorum Lam.) has been also reported
(Furusho et al. 1991; Ohkawa et al. 1992). An average of 20~30% of
wheat and barley florets formed immature embryos when pollinated with
H. bulbosum
or maize (Inagaki 1986b; Suenaga and Nakajima 1989; Furusho et
al. 1990; Inagaki and Tahir 1990). The injection of
2,4-dichlorophenoxyacetic acid (2,4-D) after pollination is necessary
for the formation of haploid immature embryos of wheat and barley in
the maize method (Suenaga and Nakajima 1989; Inagaki and Tahir 1990;
Furusho et al. 1991).
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