Fujian Acricultural College, Jinshan, Fuzhou, Fujian, China
On heading time of rice, previous authors have reported various F2 ratios for early: late or photoperiod insensitive: sensitive type, i.e., 3: 1 (Sampath and Seshu 1961; Ganashan and Whittington 1975), 1:3 (Nomura and Yamazaki 1925; Chandraratna 1955; Fuke 1955; Chang et al. 1969) 15: 1 (Fuke 1955; Sampath and Seshu 1961), 1: 15 (Sampath and Seshu 1961; Chang et al. 1969), 7: 9 (Chang et al. 1969), and 1 : 2 : 1 (Fuke 1955). However, only a part of the relevant genes were identified firmly (Sato 1986).
Two early-maturing Indica male-sterile lines (EV-A and EZ-A), their respective maintainer lines (EV-B and EZ-B), an early-maturing Indica restorer line (ER), and an American long-grain variety (BB) were used to produce crosses of various combinations. All these lines appeared to be insensitive to photoperiod as their days to heading did not differ significantly between May 15 (1986) and May 28 (1985) seedings when tested at Fuzhou (26.5 deg.N; Table 1).
Their F1, F2, B1F1 and three-line crosses were observed for heading date. The F1 plants of four crosses showed a heading time close to that of the early or late parant, but those of two crosses involving EV and ER or BB had a significantly delayed heading time (Table 2). The F2 and B1F1 populations between EV and EZ lines showed no wide seeregation, but the three-line crosses EV/EZ//ER and EV/EZ//BB segregated into early- and late-heading types in a 1 : 1 ratio (Table 2). The F1 of EVXER segregated into early- and late-heading types in a ratio fitting 37: 27. The backcrosses EV-A//EV-A/ER showed a 3 early: 1 late ratio and
Table 1. Days to heading of six parental lines and their
F1 plants
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Days to heading when seeded on:
Parent/F1 ____________________________________________________
May 15 (1986) May 29 (1985)
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EV-A 63.0+-2.48 64.4+-1.91 EV-A=V20A
EV-B 58.3+-3.22 62.3+-1.98 EV-B=V20B
EZ-A 63.7+-1.79 65.4+-3.18 EZ-A=Zhen Ding 28A
EZ-B 63.3+-2.77 63.5+-2.55 EZ-B=Zhen Ding 28B
ER 77.2+-3.06 77.3+-1.41 ER=IR30
BB 82.5+-2.90 84.0+-3.13 BB=Blue belle
EV-A/EZ-B 63.2+-1.76 62.5+-1.81
AV-A/ER 125.4+-2.71 117.6+-1.77
EV-A/BB 136.1+-5.49 119.7+-1.49
EZ-A/ER 73.9+-2.06 75.5+-2.77
EZ-A/BB 68.9+-2.07 66.6+-2.42
ER/BB 75.4+-2.43 76.7+-1.49
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No. of plants/plot: 11~59, 35 on average.
Table 2. Segregation into early- and late-heading types
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Early-heading Late heading Chi-square
Cross & gener- ______________ ______________ (ratio)
ation Plant# Mean+-* Plant# Mean+-*
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EV-B/EZ-B F2 319 63.8+-6.17 0
EV-A//EV-A/EZ-B 135 65.7+-5.15 0
EV-A/EZ-B//EZ-B 205 67.5+-4.40 0
EV-A/EZ-B//ER 85 77.2+-4.73 7 115.3+-7.63 1.08(1:1)
P>0.25
EV-A/EZ-B//BB 24 68.5+-4.82 23 130.1+-11.9 0.02(1:1)
P>O.75
EV-A/ER F2 199 76.5+-9.81 119 129.6+-15.9 2.96(37:27)
P>0.05
EV-B/ER F2 154 75.4+-9.17 106 130.5+-15.0 0.22(37:27)
P>O.5
EV-B/BB F2 184 74.1+-12.8 112 132.5+-13.3 2.30(37:27)
P>O.10
BB/EV-B F2 119 72.4+-12.0 97 134.4+-17.2 0.66(37:27)
P>0.25
EV-A//EV-A/ER 118 73.6+-12.4 38 131.7+-10.5 0.03(3:1)
P>O.75
EV-A/ER//ER 80 75.6+-5.79 73 121.9+-10.7 0.32(1:1)
P>O.50
EV-A/BB//EV-B 71 69.1+-11.5 25 130.2+-11.2 0.06(3:1)
P>0.75
EV-A/BB//BB 70 77.9+-7.52 69 131.6+-9.54 0.01(1:1)
P>0.90
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* = alpha
EV-A/ER//ER a 1 early: 1 late ratio. The same pattern of segregation was
also observed when BB was used in place of ER (Table 2).To elucidate the 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 (EV-A X ER or BB F1 plants showed a larger number of days to heading when seeded on May 15 than when seeded on May 28, Table 1). Tentatively, it is expected that EV-A and EV-B have a b C, EZ-A and EZ-B have A b c, and ER and BB have A B c. The control of photoperiod sensitivity by complementary genes has not been reported before.
The authors express their indebtedness to Professors Hao-Ran Lu, Wen-Kui Bao, Zong-Tan Shen, Ren-Cui Yang, and Xiu-Ying Zhu.
References
Chandraratna, M. F., 1955. Genetics of photoperiod sensitivity in rice. J. Genetics 53: 215-223.
Chang, T. T., C. C. Li and B. S. Vergara, 1969.Component analysis of duration from seeding to heading in rice by the basic vegetative phase and the photoperiod sensitive phase. Euphytica 18:79-91.
Fuke, Y., 1955. Genetical study of the photoperiodic reaction in the rice plant. Bull. Nat. Inst. Agric. Sci. Japan D5: 1-71.
Ganashan, P. and W. J. Whittington, 1976. Genetic analysis of the response to day length in rice. Euphytica 25: 107-115.
Nomura, M. and R. Yamazaki,1925. A study of the inheritance of the shooting time in rice. Jpn. J. Genet. 3(3): 114-130.
Sampath, S. and D. V. Seshu,1961. Genetics of photoperiod response in rice. Ind. J. Genet. Plant Breed. 21: 38-42.
Sato, S., 1986. Gene symbols for heading behavior. RGN 3: 10-12.