23. A T65-like line obtained from Kameji x Shinriki cross

Kuo-Hai TSAI

Department of Agronomy, National Chung Hsing University, Taichung, Taiwan 40227, ROC

Taichung 65 (T65) was selected from a cross between two Japanese varieties, Kameji and Shinriki in 1923 (Iso 1957). It has a recessive allele ef-1 (chromosome 10), whereas both Kameji and Shinriki have dominant alleles Ef-1 for their early heading. To look into the origin of allele ef-1, Kameji and Shinriki were each crossed with T65, and semi-isogenic lines (3)Kameji-E and (3)Shinriki-E were established after three backcrosses, respectively. These lines showed almost the same heading date as of T65(20)Ea carrying Ef-1 derived from Tatung-tsailai, and were about 15 days earlier heading than T65 (Table 1). Their F1 plants with T65(20)Ea were slightly earlier than the parents, and the F2 plants were within the parental range in heading-date variation. This indicates that all these lines have dominant alleles at the Ef-1 locus. 

Table 1. Allelism test of earliness genes carried by Kameji and Shinriki
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Population          Sep.  (1990)               Oct.  No. of     Heading date
                   10  13  16  19  22  25  28   1     plants    Mean  Variance
===============================================================================
T65(-T)                                 1   6   1      8        Sep.28.0  2.57
T65(20)Ea           6   2                              8            10.8  2.25
(3) Kameji-E        2   6                              8            12.3  2.25
(3) Shinriki-E      8   3   1                         12            11.3  4.03
F2, T65(20)Ea  
  x(3) Kameji-E     6  54   9   4                     73            13.5  3.67
  x(3) Shinriki-E   9  63   4   5  1                  82            13.3  4.58
===============================================================================
The original varieties, Kameji and Shinriki both had heading dates about 10 days earlier than that of T65(20)Ea, and their cross showed a similar pattern of heading-date variations as mentioned above for their semi-isogenic lines (Table 2). The F2 variance of heading date was 5.96, being only slightly larger than the mean variance of parents, 5.11. However, the F2 plants had a large variance (31.8) for plant height, ranging from 68 cm to 110 cm among 351 plants; the mean variance of parents was 20.2. There were three tall offtypes with a T65- like height (Table 2).

Table 2. Distributions of heading date and plant height in F2 Kameji x Shinriki and parental varieties (1987) ============================================================================== 


                Heading Date
Kameji  (24   plants):  Sep. 11.7+/-2.20,  92.5+/-5.21 cm.
Shinriki (23  plants):       12.8+/-2.32,  84.6+/-3.60 cm.
T65(20)Ea (20 plants):     32.3+/-3.53,  98.0+/-3.51 cm.
T65 (T)  (27  plants):  Oct.  2.0+/-1.98, 108.0+/-3.90 cm.
The F3 lines raised from the tall offtypes showed a range of heading date from T65(20)Ea-like to T65-like ones. From a T65-like F3 plant (23-4 derived from the tallest F1 plant), an F4 line 23-4-24 was raised which was homzygous for both heading date and plant heiaht. It was similar to T65 in heading time and about 10 cm taller than T65. Its cross with T65 showed no significant segregation for heading time atid plant height, suggesting that it has an ef-1 allele like T65.

The dominance of gene Ef-1 is complete in the crosses between T65 and T65(20)Ea for heading date and plant height, but in its crosses with 23-4-24 the effect of Ef-1 derived ftom 23-4 on plant height showed an incomplete dominance. The F2 tall offtypes might have been heterozygous for this gene, and the F3 lines raised from them would be Ef-1/ef-1. Probably, the ef-1 allele has occurred from intra-locus recombination in the F1 plant, and an F4 line homozygous for ef-1 might be produced.

The T65 line we maintain in Taichung (T65-T) and that in Ryukyu University (T65-R) differ slightly but significantly, the latter heading a few days earlier than the former (Tsai 1986; Table 3). Recently, we have found that this difference was due to different ef-1 alleles carried by the two lines. It may be suggested that the ef-1 alleles were produced by recombination within the Ef-1 locus. 

Table 3. Days to heading and plant height of T65 lines
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                       Days to heading               Plant height (cm)
Line          ============================== =================================
               1st crop   2nd crop           1st crop   2nd  crop
==============================================================================
T65-T          0=128.3    0=79.4             0=106.0       0=102.5
T65-R             -4.4      -0.4                -0.2          +4.4
T65(20)Ea        -18.4     -11.9               -14.8         -14.0
F4 23-4-24        -0.5      +5.0               +17.6         +15.7
LSD  5%            0.61      0.57                2.52          1.13
     1%            0.80      0.75                3.31          1.50
==============================================================================
References

Iso, E., 1957. Lecture on rice culture. Department of Economics, Ryukyu District Government. 491pp. (in Japanese)

Tsai, K. H., 1982. Effects of an earliness gene, Eb, on character expression in different rice varieties. J. Agr. Assoc. China, N. S. 120: 42-64. (in Chinese)

Tsai, K. H., 1986. Possible genic differences between two T65 strains, one preserved at Taichung and the other from Ryukyus. RGN 3: 75-76.