23. Multiple alleles detected at the Ef-1 locus
        Kuo-Hai Tsai
        Department of Agronomy, National Chung-Hsing University, Taichung, Taiwan 40227, ROC

    Taichung 65 or T65 is a representative Japonica or Ponlai variety in Taiwan; Taichung Native 1 or TN1 is an Indica variety having the semi-dwarfing gene, sd-I (Suh and Heu 1978; Kikuchi and Ikehashi 1984). TN1 produces panicles several days earlier than T65 in the first or winter crop and almost the same time as T65 in the second or summer crop season when grown in Taichung. The F1 plants between these two varieties produce panicles several days earlier than T65 in both the first and second crop seasons. The F2 population showed a transgressive mode of segregation ranging from plants a few days earlier than T65Ef-lb (a near isogenic line of T65 having an earliness gene) to those later than the parental strains.We have early-heading lines of T65 established after recurrent backcrosses, e.g., T65Ef-l carrying a dominant gene Ef-Ib derived from a Hokkaido variety Bozu 5, whose heading is about 2 weeks earlier than T65. Ef-I is known to be located on chromosome 10 (Sato et al. 1988), and T65 carries its recessive allele, ef-l. sd-1 is located on chromosome 1.
    In order to Find out heading-time genes involved in this cross, the T65 x TNI F1 plants were backcrossed to T65 five times, and three early-heading lines, T65E n.-1, -2 and -3, were established. The B5F2 population showed a segregation pattern : I T65Ef-l like : 2 intermdiate : 1 T65-like types, suggesting that the T65En lines have a gene derived from TNI and it is allelic to to Ef-1b.
    The T65En lines all showed a heading date some 6 days earlier than T65 Ef-Ib in the first crop, and the same heading date as of T65Ef-lb in the second crop season (Table 1). The F2 populations from T65En x T65Ef-lb had heading dates within the parental range, and the data of En type: Ef-1b type agreed with 1: 3 ratio.

Table 1. Distribution of heading dates in crosses between early-heading lines
 

Line/population Days to heading (1st crop, 1995) 
 		 No. of plants Mean Variance
102 105 108 111 114 117 120 123 126 129 132
T65 1 21 50 25 1 97 126 4.94
T65(20)Ef-1b. 9 15 1 25 110 1.74
T65En-1 10 16 4 30 104 3.97
T65En-2 11 14 3 28 104 3.90
T65En-3 9 20 1 30 104 2.44
F2:

T65(20)Ef-lb

 (En) (Ef-1b)
X T65En-1 10 12 56 61 15 1 155 109 9.19
" X T65En-2 9 19 36 56 29 4 1 154 110 13.11
" X T65En-3 17 13 57 44 14 8 1 154 109 14.75

T65(20) indicates backcrosses repeated 20 times with T65.
The F2 segregation pattern was considered to fit 1:3.

Table 2. Comparison of plant-height means and variances between En type and Ef-1b type F2 plants
Line/population No. of plants En type Mean (cm) Variance No. of plants Ef-lb type Mean (cm) Variance
T65(20)Ef-1b 25 97 10.6
T65En-1 30 88 6.5
T65En-2 28 87 12.6
T65En-3 30 87 11.4
F2:
T65(20)Ef-lb
X T65En-1 30 89 33.9 125 98 15.6
" X T65En-2 34 88 33.0 120 95 35.6
" X T65En-3 32 86 43.9 122 95 34.3
Data for the same materials as given in Table 1 are presented.     The F2 plants similar to T65En had a shorter stature than those ofT65Ef-l (Table 2). It was suggested from this study that the En alleles are incompletely dominant over Ef-1 alleles and exert a reducing effect on plant height pleiotropically.
    Thus, a multiple allelic series at the Ef-I locus is established to include alleles Ef-1, ef-1 and En or Ef-In. The En allele in TN1 would be incompletely dominant. The alleles at this locus are known to be distributed in various cultivars and wild strains (Tsai 1985, 1986a, b, 1987, 1992a, b).

References

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