Announcement-Changes in the designation of trisomics of IR36

The primary trisomics of Indica rice variety IR36 were designated according to their extra chromosome (Khush, G. S., R. J. Singh, S. C. Sur, and A. L. Librojo 1984. Primary trisomics of rice: origin, morphology, cytology and use in linkage mapping. Genetics 107: 141-163). Thus, trisomic having extra chromosome 1 was designated as triplo 1 and the trisomic with extra chromosome 2 was designated as triplo 2 and so on. However, there was some disagreement about identification of extra chromosomes of some trisomics among rice geneticists. On the basis of observations and mutual discussions, it was decided to change the identification of extra chromosomes of four trisomics. (See the report of the committee on chromosome numbering system in rice in this volume). it was agreed that the extra chromosome of triplo 4 is number 3, that of triplo 3 is number 6, that of triplo 6 is number 12 and that of triplo 12 is number 4. We have consequently changed the designation of the four trisomics. The old and new designations are as follows:

Old designation  New designation
    Triplo  1    Triplo  1
    Triplo 2     Triplo 2
    Triplo 3     Triplo 6
    Triplo 4     Triplo 3
    Triplo 5     Triplo 5
    Triplo 6     Triplo 12
    Triplo 7     Triplo 7
    Triplo 8     Triplo 8
    Triplo 9     Triplo 9
    Triplo 10    Triplo 10
    Triplo 11    Triplo 11
    Triplo 12    Triplo 4

We have sent seeds of IR36 trisomics to numerous rice scientists in the past under old designations. They are kindly requested to use the new designations. Future seed supplies of trisomics will be sent under new designations.

(by G. S. Khush)