34. RFLP mapping of complementary genes for hybrid
breakdown in cultivated rice
S. fukuoka and K. okuno
Laboratory of Plant Genetic Diversity, National Institute
of Agrobiological Resources, Kannondai 2-1-2, Tsukuba, Ibaraki. 305 Japan
Hybrid breakdown, which is one of the reproductive barriers
found in cultivated rice, was found in the progeny of the crosses between
the Thai and Japanese rice varieties. A pair of complementary recessive
genes control the hybrid breakdown in rice (Okuno 1985). This report deals
with the chromosomal location of complementary genes controlling hybrid
breakdown in Asian cultivated rice using restriction fragment length polymorphism
(RFLP) markers.
100 Rice Genetics Newsletter Vol. 14
Fig. 1. A linkage map of hwdl conferring hybrid breakdown
in rice.
Loci are shown on the right of the map and the distance
(cM) among RFLP markers is shown
on the left of the map.
Rice varieties with dominant alleles at either of complementary
loci, Siborunauli 1 from Indonesia and Col.No. 15 from Thailand, were crossed
to a tester line, W26, with four recessive alleles. A tester line was selected
in F3 generation from the cross between Col.No. 15 and the Japanese
variety, Sasanishiki which was homozygous for weakness. Two hundred and
twentyfive F2 plants of the cross between W26 and Siborunauli
1 segregated into 52 normal and 173 weak plant types. Ninetytwo F2
plants of the cross between Col.No. 15 and W26 segregated into 34 normal
and 58 weak plant types. DNA was extracted from leaves of each F2
plant and was used for RFLP analysis. Linkage analysis and
Fig. 2. A linkage map of hwd2 conferring hybrid breakdown
in rice.
Loci are shown on the right of the map and the distance
(cM) among RFLP markers is shown on the left ofthe map.
interval mapping were performed using MAPMAKER (Lander et
al. 1987).
Linkage between hybrid weakness genes and RFLP markers
located on chromosome 10 was detected in F2 plants from the
cross between W26 and Siborunauli 1. Interval mapping using 9 RFLP markers
located near the terminal end of chromosome 10 indicated that one of the
complementary genes, hwdl, was located between C701 at a distance
of 0.9cM and R2309 at a distance of 0.6cM (Fig. 1). Linkage between weakness
gene and
Rice Genetics Newsletter Vol. 14
RFLP markers located on chromosome 7 was found in F2
plants from the cross between Col.No. 15 and W26. Mapping of the other
complementary gene, hwd2, was undertaken using 18 RFLP markers in
the middle region of chromosome 7 (Fig. 2). Eight RFLP markers in this
region cosegregated with hybrid weakness and were mapped in two sites at
a distance of 1.1cM. The results showed that the chromosomal location of
hwd2 should be more precisely determined.
References
Lander, E.S., P. Green, J. Abrahamson, A. Barlow, M.J. Daly,
S.E. Lincoln and L. Newburg, 1987. MAPMAKER: an interactive computer package
of constructing primary genetic linkage maps of experimental and natural
populations. Genomics l: 174-181.
Okuno, K., 1985. Complementary recessive genes controlling hybrid breakdown
found in a varietal cross of
rice. RGN 2:52-54.