24. Linkage analysis of a gene responsible for F2 weakness
in Japonica/Indica cross
of rice
T. Kubo and A. Yoshimura
Plant Breeding Laboratory,
Faculty of Agriculture, Kyushu University.
Fukuoka, 812-8581 Japan
Fukuoka, 812-8581 Japan
F2 weakness, which is controlled
by complementary recessive genes, has been found in distantly related crosses
of rice (Oka 1957, Fukuoka et a!. 1998). We found a novel gene responsible
for F2 weakness in the backcross progeny derived from the cross of Japonica/Indica
rice.
Kubo et at. (1999) established the
Indica chromosome segment substitution lines (CSSLs) in Japonica genetic
background. In the process of development of CSSLs, weak plants were observed
which had a small number of tillers, short cuim, pale green leaf and no
seed set in some of the BC3F2 populations. The frequencies of the weak
plants in each population were very low (2.7-17.4%), except in one population.
RFLP analysis was carried out to
determine the chromosomal location of the gene(s) responsible for F2 weakness.
Since all BC3F1 plants that resulted in the segregation of weakness in
their progeny possessed the IR24 substituted region on chromosome 12, it
was speculated that the gene for this F2 weakness was on chromosome 12.
In a BC3F2 population that segregated into 53 normal plants and 7 weak
plants, a RFLP marker C443 cosegregated with the weakness trait (Fig. 1).
These results revealed that the weakness was a monogenic-inherited character
and the causal gene was located near C443 on chromosome 12. Hereafter,
the gene for hybrid weakness is tentatively designated as hwel(t). The
Indica donor IR24 has a recessive allele hwel(t). The recessive homozygote
hwel(t)hwel(t) causes weakness, and hwer(t)hwei(t) and hweF(t)hweF~(t)
show normal plant type. The genetic basis of this F2 weakness assumed to
be controlled by a set of duplicate genes, one of which is hwel(t) and
the other one is now under identification. The reduction in the frequency
of hwel(t) allele was observed, even though the heterozygous plants at
hwel(t) locus gave full seed-sets and 12-KI stainable pollens. These results
indicated that the hwel(t) locus might control certation or may be tightly
linked to a gametophyte gene. This study was supported in part
by Bio-oriented Technology Research Advancement Institution (BRAIN), Japan.
References
Fukuoka, S., H. Namai and K. Okuno, 1998. RFLP mapping of
the genes controlling hybrid breakdown in rice (Oryza sativa L.). Theor.
AppI. Genet. 97: 446-449.
Harushima,Y., M. Yano,A. Shomura, M. Sato, T. Shinano, Y.
Kuboki, T. Yainamoto, S. Y. Lin, B.A. Antonio, A.
Parco, H. Kajiya, N. Huang, K. Yaniamoto, Y. Nagamura, N.
Kurata, 0. S. Khush andT. Sasaki, 1998. A
high-density rice genetic linkage map with 2215 markers using
a single F2 population. Genetics 148:
479-494.
|
Kubo,
|
T., K. Nakamura and A. Yoshimura, 1999. Development of a
series of Indica chromosome segment
|
substitution lines in Japonica background of rice. RGN 16
(in press).
Oka, H.I., 1957. Phylogenetic differentiation of cukivated rice. XV. Complementary lethal geses in rice. ipn.
Oka, H.I., 1957. Phylogenetic differentiation of cukivated rice. XV. Complementary lethal geses in rice. ipn.
J. Gcnet. 32: 83-87.