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Japonica rice and African rice
K. Dol, K. TAGUCHI and A. YOSHrMURA
Plant Breeding Laboratory, Faculty of Agriculture, Kyushu
University, Fukuoka, 812-8581 Japan
Some QTLs affecting pollen sterility were detected in advanced
backcross QTL analysis using BC2F1 population which was obtained from the
cross between Japonica rice (Oryza sativa L. cv. Taichung 65) as a recurrent
parent and African rice (0. glaberrima Steud., Acc. IRGC 104038) as a donor
parent (Doi eta!. 1997). We report here the identification of one of the
QTLs detected on chromosome 10 (referred to as S(t) hereafter).
Further backcrossing with Taichung 65 was continued after
QTL analysis. The BC5F1 plants heterozygous for putative S(t) region of
chromosome 10 were selected using RFLP markers and they were backcrossed
with Taichung 65. Resulting BC6F, population consisting of 57 plants was
used as the mapping population. Flowering spikelets were collected from
each plant and stored in 70% ethanol. Pollen fertility was estimated as
the percentage of pollen grains that could be stained with 12-KI solution.
The mapping population was classified into three groups
with discrete pollen fertility classes; high-sterile (pollen fertility
was 0-20%), semi-sterile (40-60%) and fertile (80- 100%) (Fig. 1). The
number of plants in each group were 28, 23 and 6, respectively. When divided
into two groups; high sterile group and semi-sterile plus fertile group,
the observed segregation of 28 : 29 fit the expected monogenic ratio of
1: 1. Linkage analysis using RFLP markers revealed that S(t) was located
between G1084 and R1629 on chromosome 10. The gene S(t) was linked to G1084
and R1629 with map distances of 3.5 cM and 1.8 cM, respectively (Fig. 2).
Since no locus affecting such high F1 pollen sterility has been reported
in this region, S(t) is a new locus for F1 pollen sterility. Therefore,
this gene contolling high F1 pollen sterility was designated as S18.
Sano (1990) reported that the F1 sterility locus Si found
in the progenies from the cross between 0. sativa and 0. glaberrima caused
semi-sterility and it was tightly linked to wx locus. All semi-sterile
plants observed in the present population were heterozygous for wx-linked
RFLP markers (C1496 and C1084). However, this Si-region did not affect
the high pollen sterility. Therefore, the high-sterility and the semi-sterility
are separately governed by Si8 and Si, respectively.
This study was supported in part by the Program for Promotion
of Basic Research Activities for Innovative Biosciences.
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References
substitution lines of rice. — QTL analysis for pollen fertility
and days to heading in the BC7F1 population —. Breed. Sci. 47 (Suppl. 1):
44. (in Japanese)
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