International Rice Research Institute, P.O. Box 933, Manila, Philippines
Twelve linkage groups corresponding to the haploid chromosome number of
rice were suggested by Nagao and Takahashi (1963). However, these linkage
groups have not been associated with the cytologically identifiable
chromosomes and their independence has not been tested. We established all
the twelve possible primary trisomics in the background of a disease and
insect resistanct and widely grown indica variety, IR36. The extra
chromosome of each of the trisomics was identified at pachytene stage of
meiosis following the numbering system of Shastry, Ranga Rao and Misra
(1960). Accoridng to this system the longest pachytene chromosome was
numbered as 1 and shortest as 12. We studied the segregation of 22 marker
genes in the trisomic progenies. In all we tested 120 out of 264 possible
combinations involving 22 genes and 12 trisomics. On the basis of modified
trisomic ratio technique we were able to identify marker genes for all the 12
chromosomes. Three linkage groups (VI, IX, and XII) were associated with
chromosome 5 and linkage groups VII and V were associated with chromosome 9.
New linkage groups for chromosomes 6, 8 and 10 were established. The
relationships between the chromosome numbering systems of Shastry, Ranga Rao
and Misra (1960), Nishimura (1961), Kurata and Omura (1978) and the linkage
groups of Nagao and Takahashi (1963) are shown in Table 1. The table also
shows the relationships between our trisomics and those of lwata and Omura
(1975). Detailed paper on these investigations will appear in volume 106 of
Genetics.
Table 1. Relationships between various systems of numbering chromosomes,
trisomics, linkage groups, and marker genes of rice
============================================================================= Chromosomes Trisomics Linkage groups ============================ ============== Shastry, Kurata Iwata Nagao Maker Ranga Rao Nishimura, and This and and genes and Misra (1961) Omura study Omura Takahashi (1960) (1978) (1975) (1963) ============================================================================= 1 3 K1* 1 O* III eg. lax 2 8 K2* 2 N* X tri 3 6 K6 3 B I wx,ws 4 5 K3* 4 M* XI bc\1\,ch\1\,dl 5 2 K9 5 L VI,IX,XII gh\1\,nl\1\,gl\1\ 6 4 K5 6 A - spl\1\, rl\1\ 7 10 K11 7 F IV g 8 12 K7 8 D - v\8\,su 9 1 K1O 9 H VII,V dp\2\,drp\2\,I-Bf 10 7 K12 10 C - pgl,fl 9 K8 11 G VII la, z\2\ 12 11 K4 12 E II lg, Pl ============================================================================= *added by editor as per lwata, Satoh and Omura (No. 34)
Iwata, N., and T. Omura, 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.
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.
Nagao, S., and M. Takahashi, 1963. Genetical studies on rice plant. XXVII. Trial construction of twelve linkage groups of Japanese rice. J. Fac. Agric. Hokkaido Univ. 53: 72-130.
Nishimura, Y. 1961. Studies on the reciprocal translocations in rice and barley. Bull. Natl. Int. Agric. Sci. Jpn. Ser. D 9: 171-235.
Shastry, S. V. S., D. R. Ranga Rao and R. N. Misra, 1960. Pachytene analysis in Oryza. I. Chromosome morphology in Oryza sativa. Ind. J. Genet. Breed. 20: 15-21.