34. The relationships between chromosomes identified cytologically and linkage groups


Nobuo IWATA, Hiraku SATOH and Takeshi OMURA

Faculty of Agriculture, Kyushu University, Hakozaki, Fukuoka, 812 Japan


Since the establishment of 12 linkage groups corresponding to the haploid chromosome number of rice by Nagao and Takahashi (1963), we have been investigating the relationships between the linkage groups and chromosomes mainly by using trisomics and reciprocal translocations (Iwata and Omura 1971a, b, 1975, 1976, 1984; Iwata et al. 1984; Kurata et al. 1981; Sato 1976; Sato et al. 1982; Yoshimura 1982). Recently we have established the relationships between all the chromosomes and linkage groups. The results from different series of studies are summarized in Table 1.


Table 1. Relationships among chromosomes, trisomics and linkage groups in rice

=============================================================================
Chromosome    Trisomics     
===========  ===========    Linkage
RT Karyotype Jap- Indica    group            Marker genes
             oni-
             ca
=============================================================================
1  K1O        H  Triplo 9    VII   _Bp*,_Dn,_dp-2*,drp-2*
                             V     _I-Bf
2  K9         L  Triplo 5    VI    _bgl*,_d-1,_nl-2*,_ops*,_v-10(t)*
                             IX    _nl-1,_ri,spl-7*,spl-8*
                             XII   _gl
3  K1         O  Triplo 1    III   A,ch-5*,ch-6*,d-10*,_d-18,eg*,fs-2,
                                   _lax,Pn,Rd,rl-2*,spl-6*,_v-6*,shr-1*
4  K5         A  Triplo 6    -     _d-B*,_nal-2*,_rl-1,_spl-1*
5  K3         M  Triplo 4    XI    bc-1,ch-l*,_ch-2*,ch-3*,ch-7*,d-K-2*,
                                   _dl*,drp-3*,drp-4*,fc*,op*,rl-3*,spl-3*,
                                   stl*,v-1,_v-2*,v-5*,v-7*,z-3*
6  K6         B  Triplo 3    I     C,_ch-4*,_Cl,_dp-1*,spl-4*,v-3*,_ws*,_wx
7  K12        C  Triplo 10   -     _du*,_fl*,_pgl*,_Rf-1,_rk-2
8  K2         N  Triplo 2    X     bl-1,bc-3*,d-K-l*,d-K-4*,d-W*,_gh-2*,
                                   gh-3*,spl-2*,tri
9  K8         G  Triplo 11   VIII  d-C*,_D-K-3*,d-t*,_la,_sp*,_v-4*,_z-1*,
                                   z-2*,_v-9(t)*
10 K11        F  Triplo 7    IV    _d-6,_g,_ge*,_Rc,_rfs*,spl-5*,_v-11(t)*
11 K4         E  Triplo 12   II    d-2,d-11*,_lg,nal-1*,Ph*,Pl,_rk-1*,ylm*
12 K7         D  Triplo 8    -     _d-51*,_su*,_ur-2(t)*,_v-8*,_z-4*
=============================================================================
RT - Arbitrarily numbered on the basis of studies of reciprocal
translocations by Nishimura (1961).  
Karyotype - Numbered according to the length of somatic prometaphase
chromosomes in descending order by Kurata and Omura (1978).  
Trisomics, Japonica - Derived from Nipponbare, classified morphologically
(Iwata et al.  1970, 1984).  
Trisoics, Indica - Estblished by Khush et al.  (1984).  
Marker genes - Shown by symbols used at Kyushu University, Dept. of Plant
Breed.  Underline (_)indicates genes whose location was determined by trisomic
analysis.  * indicates genes described by the staff of Kyushu University.

In the table (1st column), the chromosomes are numbered 1-12 tentatively according to Nishimura's (1961) system which is based on studies of reciprocal translocations. They are also numbered K1-K12 (2nd column) according to the length of somatic prometapohase chromosomes in descending order on the basis of karyotype analysis by Kurata and Omura (1978). The trisomics derived from triploid plants of Nipponbare Uaponica) are classified into types A-O by morphological features (Iwata et al. 1984). Those derived from an Indica strain, made available through the courtesy of Dr. G. S. Khush (Triplo lines; Khush et ai 1984), are numbered according to the length of extra chromosomes at pachytene in descending order. The linkage groups, I-XII, are those of Nagao and Takahashi (1963). The relationships among these different series were determined by segregation patterns for marker genes as listed in the table, particularly by trisomic analysis.

Linkage groups VII and V were associated with chromosome I which is the extra chromosome of the H-type trisomics. Genes Bp, Dn and dp-2 (linkage group VII) and I-Bf (V) showed trisomic ratios in crosses with the H-type trisomics (Iwata and Omura 1975). Similarly, linkage groups VI, IX and XII were found to be associated with chromosome 2 which is the extra chromosome of the L-type trisomics (Iwata and Omura 1976). The linkage relations between I-Bf and genes belonging to linkage group VII still remain unknown. Linkage relations among genes of linkage groups VI, IX and XII were confirmed by both conventional and reciprocal translocation methods (Yoshimura et al. 1982; Sato et al. 1982).

None of the Nagao and Takahashi's linkage groups could be assigned to chromosomes 4, 7 and 12. However, several genes were located on them through trisomic analysis (Iwata and Omura 1975; lwata et ai. 1984; Yoshimura et al. 1982; Sato and Shinjyo 1978). Their linkage relations still remain unknown. The linkage groups assigned to respective chromosomes are shown in Fig. 1.

Many of the mutant genes listed in Table 1 were induced by irradiation or application of chemical mutagenes, but additional marker genes are necessary for preparing detailed linkage maps. The numbering system of rice chromosomes is not standardized as yet. It may be based on the length of chromosomes, but there is no complete agreement between the order of length of chromosomes at pachytene stage and that at somatic prometaphase. The adoption of an acceptable system would depend upon discussions among rice geneticists in the future.


Fig. 1. Linkage maps for 9 chromosomes. Gene symbols follow those traditionally used at Kyushu University.

  • Part 1: Chromosome 1 and 2"

  • Part 2: Chromosome 3 and 5"

  • Part 3: Chromosome 6"

  • Part 4: Chromosome 8 and 9"

  • Part 5: Chromosome 10 and 11"


    References

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    ----- and ----- 1971b. Ditto, 11. Linkage groups corresponding to the chromosomes 5, 6, 8, 9, 10 and 11. Sci. Bull. Fac. Agr., Kyushu Univ. 25: 137-153 (Jap./Eng.).

    ----- and ----- 1975. Studies on the trisomics in rice plants (Oryza sativa L.), III. Relation between trisomics and genetic linkage groups. Jpn. J. Breed. 25: 363-368.

    ----- and --- 1976. Ditto, IV. On the possibility of association of three linkage groups with one chromosome. Jpn. J. Genet. 51: 135-137.

    ----- and ----- 1984. Ditto, VI. An accomplishemnt of a trisomic series in japonica rice plants. Jpn. J. Genet. 59: (in press).

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    Kurata, N. and T. Omura, 1978. Karyotype analysis in rice, I. A new method for identifying all chromosome pairs. Jpn. J. Genet. 53: 251-255.

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