Faculty of Agriculture, Kyushu University, Hakozaki, Fukuoka, 812 Japan
A series of 12 different types of trisomics had been isolated earlier
from a Japonica variety, Nipponbare (Watanabe and Koga 1975). However, the
investigation of karyotypes of extra chromosomes by Kurata et al. (1981)
revealed that four of the trisomics had the same extra chromosome (K1O).
Thus, these four were reclassified to be identical and the trisomics for the
three longest chromosomes (K1, K2 and K3) were not present in our series.
The extra chromosomes of the 9 types were identified by crossing them with
marker stocks (Iwata and Omura 1975, 1976; Iwata et al. 1984). The
relationships between Nagao and Takahashi's (1963) linkage groups and
chromosomes numbered for designation of interchanged segments by Nishimura
(1961) were established by using the trisomics and reciprocal translocation
lines (Iwata and Omura 1971a, b, 1975, 1976; Iwata et al. 1984; Kinoshita et
al. 1975; Sato 1976; Sato et al. 1973, 1975, 1982; Yoshimura et al. 1982).
The trisomics having chromosomes K1, K2 and K3 (chromosomes 3, 8 and 5, respectively, of Nishimura's designation), which were lacking in our series, were discovered recently, as types O, N and M, from the progeny of triploid plants of Nipponbare. The results from crossing experiments with these new trisomics are summarized in Table 1. In crosses with type M, marker genes dl, ch-2 and v-2 located on chromosome 5 (K3) showed trisomic ratios either in BF\1\ or in F\2\. Similarly, the N and O types were found to have chromosome 8 (K2) and 3 (K1) as extras, respectively. The respective correspondence of chromosomes 3, 8 and 5 to K1, K2 and K3 was thus established.
Table 1. Segregation for some marker genes located on chromosomes 3, 5 and 8
in BF\1\ or F\2\ of crosses with M, N and O types of trisomics
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Cross combination Segregation mode
Trisomic F\1\ marker Dominan Recessive Total 1 : 1 2 : 1 3 : 1
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(M type x d1) x d1 17 6 23 5.26* 0.54 -
(M type x ch-2) x ch-2 19 9 28 3.57 0.02 -
(M type x v-2) x v-2 34 10 44 13.09*** 2.23 -
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(N type x gh-2) x gh-2 132 41 173 47.86*** 7.22**
(N type x gh-2) selfed 136 9 145 - - 27.31***
(N type x d1 gh-2) x gh-2 209 60 269 82.53*** 14.72*** -
(N type x d1 gh-2) x d1 349 335 684 0.25 65.72*** -
(N type x ch-2) x ch-2 220 180 400 4.00* 24.50*** -
(N type x v-1) x v-1 70 61 131 0.68 10.32*** -
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(O type x lax v-6) x v-6 66 21 87 23.28*** 3.31 -
(O type x lax v-6) selfed 549 34 583a - - 114.24***
(O type x lax v-6) selfed 113 3 116b - - 31.08***
(O type x d-18) x d-18 96 30 126 34.57*** 5.14* -
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a) Segregation for v-6.
b) Segregation for lax.
In this cross, only v-6+ plants were used to observe the segregation for lax.
*,** and ***: Significant at 5%, 1% and 0.5% levels, respectively.
Table 2. Morphological features of 12 primary trisomics derived from a
japonica cultivar, Nipponbare
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Type Short name Morphological features
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A Pale Pale green leaves at heading stage, fertile
B Awned Somewhat rough and lax panicles, awned spikelets
C Small grain Fine stature, bushy, small grain
D Erectoides Dark green leaves, erect panicles, short grain
E Spreading Open tiller, more or less narrow grain
F Rolled leaf Semi-rolled leaves, imperfect panicle emergence
G Pseudo-normal Nearly the same morphological features as disomics
H Large grain Dark green leaves, large grain, excess of nucleolar
chromosomes
L Short panicle Short in height, short panicles, small grain
M Sterile Dark green leaves, short in height, perfectly sterile
N Smooth glume Dark green leaves, small and smooth glume, highly
sterile
O Grassy Pale green and droopy leaves, bushy, small and narrow
grain, highly sterile
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(References - See the next note, No. 34)