8. Identification of interchanged chromosomes in twenty-five reciprocal translocation lines newly established in rice cultivar Nipponbare

2) Institute of Postgraduate Studies, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

We have newly developed 67 homozygous lines for reciprocal translocations in rice cultivar Nipponbare (called RT line, 101-167) in the progenies of gamma- ray irradiated seeds. To use them for genetic studies, we have initiated cytological identification of interchanged chromosomes involved in each of them based on the theory advocated by Burnahm (1956).

The chromosomes involved in the interchange of an RT line were analyzed by observing their association pattern at diakinesis in the F\1\ plants from crosses between the RT line and 12 reciprocal translocation testers (RT testers), and also from the intercrosses among the RT lines. The RT testers are selected homozygous lines with identified interchanges (Nishimura 1961; Yoshimura et al. 1980; Sato 1981). Chromosome numbering in this note follows Nishimura's designation. Twenty-five RT lines were examined so far.

The results obtained from crosses with the RT testers and intercrosses are given in Tables 1 and 2, respectively. Interchanged chromosomes were identified by crossing with the RT testers in 21 out of 25 RT lines examined (Table 1, right column). The chromosomes in other four lines, RT 112, 119, 120 and 121, were determined from the intercrosses (Table 2, right column, upper 4 rows). The results from intercrosses among 14 lines (Table 2, lower 14 rows) were not contradictory to the results from crosses with the RT testers (Table 1) at all. Most of the RT lines had the same interchanged chromosomes as those found in reciprocal translocation lines identified earlier (List of translocation, RGN 1, p. 49-52). Therefore, the new and old lines must be examined as to whether the point of interchange is different or identical. The identification work of the RT lines is still under way.

Table 1. Pattern of chromosome associations observed at diakinesis in F\1\ plants from crosses between 21 reciprocal translocation lines of Nipponbare (RT lines) and the RT testers carrying interchanges as shown in parentheses.

Table 2. Pattern of chromosome associations observed at diakinesis in F\1\ plants from intercrosses between reciprocal translocation lines of Nipponbare

Nishimura, Y., 1961. Studies on the reciprocal translocations in rice and barley. Bull. Natl. Inst. Agr. Sci., Japan, D9: 171-235. (Japanese/English)

Sato, S., 1981. Identification of interchanged chromosomes in isogenic translocation lines of a rice variety, Taichung 65. Bull. Coll. Agr., Univ. Ryukyus 28: 41-47. (Japanese/English)

Yoshimura, A., N. Iwata and T. Omura, 1980. Identification of interchanged chromosomes in isogenic reciprocal translocation lines originated from rice variety Taichung 65. Sci. Bull. Fac. Agr. Kyushu Univ. 34: 97-104. (Japanese/English)