33. A new locus affecting high F1 pollen sterility found in backcross progenies of Japonica rice and African rice
K. DOI, K. TAGUCHI and A. YOSHIMURA
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
(O. glaberrima Steud., Acc. IRGC104038) as a donor parent (Doi
et al. 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 BC6F1 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 I2-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 S1 found in the progenies
from the cross between O. sativa and O. 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 S1-region
did not affect the high pollen sterility. Therefore, the high-sterility
and the semi-sterility are separately governed by S18 and
S1, respectively.
This study was supported in
part by the Program for Promotion of Basic Research Activities for
Innovative Biosciences.
References
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