CYTOGENETICAL GENE-MAPPING BY RECIPROCAL TRANSLOCATION AND TERTIARY TRISOMIC ANALYSES IN RICE (ORYZA-SATIVA L)

The orientation of RFLP linkage map and the assignment of RFLP markers to the restricted chromosomal segment were determined on seven pachyt ene chromosomes (1, 3, 4, 5, 8, 9 and 12) of rice. A total of 24 inter change breakpoints were detected by pachytene analysis of reciprocal t ranslocation (RT) heterozygotes derived from crosses between 12 RT lin es and normal diploid varieties. Further, 19 strains of japonica-indic a hybrid tertiary trisomics were developed and provided for RFLP gene dosage analysis, resulting in locating 32 breakpoints of the extra ter tiary chromosomes within genetic linkage segments defined by RFLP mark ers. From these results, the orientation of RFLP linkage groups on pac hytene chromosomes and the assignment of 113 RFLP markers and four clo ned rice genes to chromosome arms were conducted, together with the de limitation of centromeres on 6 RFLP linkage groups (1, 3, 4, 8, 9 and 12). Meanwhile, 15 groups of RFLP markers were incorporated with the r estricted segments of pachytene chromosome. Compared with RFLP map, th e physical distance of a part of the long arm of chromosome 1 was 5.4 to 8.8 cM/mu m at the pachytene stage.