Agronomy Department, Zheiian Agricultural University, Hangzhou, 310029 China
The fertility restoration of cytoplaslmic male sterility (CMS) in rice (BT-type sterility) was reported to be controlled by a dominant restoring gene, Rf-1 located on chromosome 10 (Shinjyo 1975). For the WA-type, however, either one or multiple genes were found to be involved (Gao 1981; Raj et al. 1984). In the present study, three Japonica restorer lines, C57 (an elite restorer for hybrid rice in North China), ZH157 (a "wide-compatible" restorer) and T65R (established by Shinjyo 1975) were each crossed with two Japonica CMS lines, Shuang-Bai (SBA, a BT type) and 02428A (a WA-type derived from Zhen-Shan 97A/02428 7) for genetic analysis.
Taking seed setting rate as fertility criterion, the F`1` SB A/C57 showed 92% fertility (fertile, F) and SB A/ZH157 showed 43% fertility (partly fertile, PF). The F`2` segregation pattern fitted 1F:1S for SB A/C57 and 1PF:1S for SB A/ ZH157 (Table 1). This indicates that fertility restoration for the BT type is controlled by a dominant gene Rf-1 carried by C57 or by an incompletely dominant gene of ZH157, which is different from Rf-1.
Table 1. Spikelet fertility segregation in SB A/C57 and SB A/ZH 157
progenies
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Cross Fertility distribution (%)
______________________________________ Total Chi2
5 15 25 35 45 55 65 75 85 95 (df=1)
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SB A/C57 F`1` 7 11 18
SB A/C57 F`2` 72 48 120
SB A//SB B/C57 41 2 2 4 12 29 90 41:49 0.54
(1S:1F)
SB A/ZH157 F`1` 4 6 2 12
SB AZH157 F`2` 12 8 22 37 7 2 88
SB B/ZH157F`1` 4 8 12
SB A//SB B/ZH157 53 3 8 28 5 1 98 53:45 0.50
(1S:1F)
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SB=Shuangbai; SB B=maintainer line
Table 2. Spikelet fertility segregation In 02428 A/C57 and 02428 A/ZH157
progenies
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Fertility distribution
Crosses ____________________________________ Total Chi2
5 15 25 35 45 55 65 75 85 95
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02428A/C57 F`1` 5 4 3 12
02428B/C57 F`1` 4 8 12
02428A/C57 F`2` 37 3 4 13 18 6 9 8 9 7 114 37:53:24 3.53
(1F:2PF:1S)
02428A/ZH157 F`1` 2 6 8
02428A/ZH157 F`2` 27 1 3 4 5 18 60 118 27:91 0.18
(1S:3F)
02428A/ZH157 46 2 4 26 15 93 48:45 0.04
//02428B (1S:1F)
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PF: partly fertile, 02428B: maintainer line
On the other hand, the F`1` 02428A/C57 showed partial fertility, while
02428A/ZH157 was fertile (Table 2). In the F`2` of 02428A/C57, fertile,
partly fertile and sterile segregants occurred in a 1F:2PF:1S ratio - The
F`2` of 02428A ZH157 showed a 3F:1S segregation, although a few partly
fertile plants were included into the fertile group (Table 2). When the
02428A/ZH157 F`1` plants were backcrossed with 02428B (maintainer), a 1F:1S
segregation was observed. These results suggest that there are two restoring
genes for the WA-type CMS, a dominant gene in the cross of ZH157, and an
incompletely dominant gene in addition to the dominant one in the cross of
C57. These restoring genes would differ from Rf-1 and the above-inferred
second gene. In this relation, a dominant restoring gene for the WA-type CMS
was reported by Zhang et al. (1987) in IR29, and by Singh et al. (1994) in
Pusa 33.In order to test the allelism of these restoring loci, the C57/ZH157 hybrid which was fertile was used as the male parent and crossed with SB A and 02428A, respectively (Table 3). The F`2` of these crosses showed a 2F: 1PF: 1S segregation, suggesting that the four genes assumed would be independent of one another. So far, there is no evidence for interaction between restoring genes, and the restoring genes for BT- and WA-type CMS do not seem to have a pleiotropic effect. In addition, the restoring gene carried by C57 was found to be allelic to Rf-1 of T65R (Table 3).
Table 3. Allelism test for restoring genes
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Fertility distribution (%)
Crosses _____________________________________________ Total Chi2
5 15 25 35 45 55 65 75 85 95
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C57/ZH157 F`1` 3 7 2 12
C57/Zhl57 F`2` 3 17 29 20 3 72
SB A//C57/ZH157 5 2 4 4 15 6 7 11 29 16 89 15:28:46 3.90
(1S:1PF:2F)
02428 A//C57/ZH157
19 15 3 4 14 4 2 10 26 19 116 37:24:55 3.22
(1S:1PF:2F)
SB A/ZH157 F`1` 4 6 2 12
02428 A/C57 F`1` 5 4 3 12
02428 A/T65 R F`1`
18 18
SB A/T65 R F`1` 2 8 2 12
T65 R/C57 F`1` 2 10 12
SB A//T65 R/C57 17 36 23 76
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ReferencesGao, Mingwei, 1981. A Preliminary analysis of the genotype of hybrid shen rice with wild rice cytoplasm. Acta Genetica Sinica 8: 66-74.
Faj, K. G. and E. A. Siddiq, 1984. Genetics of fertility restoration and biochemical basis of male sterility-fertility restoration system in rice. RGN 1: 103-104.
Shinjyo, C., 1975. Genetical studies of cytoplasmic male sterility and fertility restoration in rice (Oryza sativa L.). Ryukyus Univ., College Agric. Sci. Report 22: 1-55.
Singh. P. K., R. Thakur and V. K. Chaudhary, 1994. Genetics of fertility restoration of wild abortive cytoplasmic male sterile lines in rice. IRRN 19(1): 5. Zhang, W. G. and Z. T. Shen, 1987. Genetic analysis for fertility restoring genes in some varieties of rice (Oryza sativa L.). Acta Agronomica Sinica 13: 97-101.