Taichung 65 (abbreviated as T65) is a well-known Ponlai (Japonica) rice variety
of Taiwan, selected from a cross of two Japanese varieties, Kameji and
Shinriki, in 1923 (Iso 1957). It is adapted to both the winter (January-June)
and summer (July-October) cropping seasons in Taiwan, and is known to have a
wide regional adaptability. By 1947, this variety covered most of the rice
fields in the Ryukyu Islands (Iso 1947). The author has obtained a T65 strain
from Dr. S. Sato of the University of Ryukus, which has long been used for
their experiments (designated as T65-R), and has compared it with the strain
preserved and used at Taichung (T65-T). The 1986 winter experiment showed that
T65-R was six days earlier heading than T65-T, and was significantly taller
(Table 1). To examine their photoperiodic responses, the T.D.M. degrees, as
proposed by Oka (1954, 1958), were computed by comparing their heading dates in
May and June plantings. T65-T showed a slight response while T65-R was non-
sensitive to photoperiod. In the summer cropping season, however, these
differences between the two strains disappeared. There would be some genic
differences between the two T65 strains, which need investigation in the
future.
Table 1. Dayes to heading and other traits compared between two Taichung 65
strains (winter season, 1986)
=============================================================================
Strain Days to Plant Panicle Spikelet no. T.D.M
heading height length per panicle degree
(cm) (cm)
=============================================================================
T65-T 127.3 108.1 21.2 103.1 4deg 36'
T65-R 121.5 111.3 20.4 109.2 0
S.E. 0.33 0.83 0.37 3.89
t 17.6** 3.9** 2.2* 1.6
=============================================================================
*,** Significant at 5% and 1% levels, respectively.
References
Iso, E., 1947. Some considerations on the regional adaptability of rice varieties with special reference to the recent development in the yield per unit area in Taiwan. Bull. Taiwan Agr. Res. Inst. 4: 1-108.
Iso, E., 1957. Lecture on Rice Culture. Department of Economics, Ryukyu District Government. 491pp (in Japanese).
Oka, H.I., 1954. Phylogenetic differentiation of cultivated rice, 3. Varietal variation in the responses to day-length and temperature and the number of days of growth period. Jpn. J. Breed. 4(2): 92-100. (in Japanese with English summary).
Oka, H.I., 1958. Photoperiodic adaptation to latitude in rice varieties. Phyton 11: 153-160.