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Fujian Agricultural College, Fuzhou, 350002, China
Early-maturing mutant line 5460 was bred by radiating dry seeds of late maturing rice variety IR54 with C0603.5 KR. It has many good traits such as male-sterile restorer gene of IR54 and strong disease resistance besides it's much earlier heading than IR54. Therefore, it can be used as early Indica male-sterile restorer line. Their relationship in heading time between 5460 and IR54, however, was unknown (Yang and Chen 1989; Yang et al. 1986). 5460, IR54 and an early-maturing Indica male-sterile line V20A were used as parents to produce crosses of three combinations. The experiments were carried out in Fuzhou (26.05 deg N) by seeding on May 15, 1986 and May 30, 1989.
Their parents, F1, F2, B1F1, B2F1 and three-line crosses were observed for heading time. The F1 plants of V20A/5460 were close to 5460 in heading time (Table 1). Their F2 and B1F1 (V20A//V20A/5460) populations showed continuous and transgressive segregation in heading time (Figs. 1, 2). The F1 plants of V20A/ IR54, however, were 22(1989)-34(1986) days later than the late-maturing parent IR54 (Table 1), and the F2 plants segregated into early- and late-heading types in a ratio fitting 37: 27. The backcrosses, V20A//V20A/IR54 showed a 3 early: 1 late
Table 1 - Days to heading of three parents and their F1 plants
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May 15, 1986 May 30, 1989
Parent/F1 ====================== ==========================
X+/-S MP X+/-S MP
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V20A 63.0+/-2.48 62.2+/-2.27
5460 72.8+/-2.03 71.2+/-1.45
IR54 107.8+/-2.56 111.5+/-1.27
V20A/5460 73.1+/-1.92 67.9 71.5+/-1.24 67.7
V20A/IR54 141.3+/-2.18 85.3 132.6+/-1.57 86.4
5460/IR54 88.2+/-2.21 90.2 86.0+/-1.75 91.9
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No. of plants/plot: 20 on average.
Fig. 1. Distribution of heading time Fig. 2. Distribution of heading time in V20A/5460 F2 plants. in V20A//V20A/5460 plants.ratio, and V20A/IR54//IR54 showed a 1 early: 1 late ratio (Table 2). The heading time of 5460 was 35(1986)-40(1989) days earlier than that of IR54. The F1 plants of 5460/IR54 showed a heading time close to that of their middle-parent value (Table 1), and the segregating proportion of early-, intermediate- and late-heading plants showed a good agreement with the 1 : 2: 1 ratio in the F2 population. B1F1 (5460//5460/IR54) segregated into 1 early: 1 intermediate, and B2F1(5460/IR54// IR54) into 1 intermediate: 1 late (Table 2). The three-line crosses, V20A//5460/ IR54 and V20A/IR54//5460, showed the ratios of 1 early: 1 late and 3 early: 1 late respectively (Table 2).
From above segregation patterns observed, it may be assumed that three dominant genes, A, B and C, are involved and when they are combined, their complementary interaction expresses a late-heading phenotype which is sensitive to photoperiod (V20A/IR54 F1 plants showed a larger number of days to heading when seeded on May 15 than when seeded on May 30; Table 1). As V20A is assumed to have abC (Cai et al. 1987), it is expected that IR54 has ABc, and 5460 has Abc. This means that gene b in 5460 is a single locus recessive mutation
Table 2. Segregation into early-, intermediate- and late- heading types
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early-heading intermediate- late-heading X2
Cross and Year ============== ============== ================ (ratio)
generation plant no X+/-S plant no X+/-S plant no X+/-S
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V20A/IR54F2 1986 186 90.5+/-18.17 0 125 145.5+/-6.17 0.51(37:27)
P>0.25
V20A//V20A/IR54 78 76.9+/-13.09 0 20 147.5+/-9.45 1.10(3:1)
P>O.10
V20A/IR54//IR54 26 90.1+/-7.51 0 22 130.9+/-14.44 0.33(1:1)
P>O.50
5460/IR54F2 85 75.0+/-6.12 178 91.0+/-5.10 71 109.3+/-8.96 2.75(1:2:1)
P>0.25
5460/IR54//IR54 0 40 92.5+/-4.74 46 113.3+/-9.89 0.42(1:1)
P>O.50
V20A//5460/IR54 25 75.2+/-5.60 0 29 128.1+/-7.71 0.30(1:1)
P>O.50
V20A/IR54F2 1989 232 81.1+/-14.86 0 149 127.1+/-7.22 1.48(37:27)
P>O.10
V20A//V20A/IR54 102 71.9+/-11.45 0 38 120.1+/-7.88 0.34(3:1)
P>O.50
5460/IR54F2 100 73.0+/-5.16 173 91.9+/-5.70 79 113.3+/-7.10 2.61(1:2:1)
P>0.25
5460//5460/IR54 45 74.4+/-5.34 34 90.0+/-6.49 0 1.53(1:1)
P>O.10
5460/IR54//IR54 0 36 89.6+/-6.42 27 112.3+/-5.62 1.29(1:1)
P>0.25
V20A//5460/IR54 53 75.7+/-4.60 0 49 126.1+/-5.43 0.16(1:1)
P>0.50
V20A/IR541/5460 75 75.0+/-6.58 0 29 125.9+/-3.63 0.40(3:1)
P>0.25
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for early-maturity B in IR54.
References
Cai Choonmai, Weiming Li and Yuanchang Zhou, 1987. Complementary genes controlling photoperiod sensitivity in hybrid rice. RGN 4: 90-91.
Yang Hefeng, Xiulan Chen, 1989. The types and genetic analysis of radiation induced early maturity mutants of rice. Acta Agriculture Nucleatae Sinica, 3(4): 199-205.
Yang Rencui, Naiyuan Wang and Kangiing Liang, 1986. Inheritance of early-maturity and semi-dwarfing mutants of rice. Application of Atomic Energy in Agriculture, (4): 24-29.
