6. Trisomic analysis of genes for isozymes: Location of Cat- 1, Acp- 1 and Pox-2 on chromosomes

R. ISHIKAWA1, T. KINOSHITA1 and H. MORISHIMA2

1) Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan

2) National Institute of Genetics, Misima, 411 Japan

Eight primary trisomics with Nipponbare background were crossed with an Indica tester (Ac 0 1 from Vietnam) which carries variant alleles at several isozyme loci as compared with the trisomic series. The plumules of F2 seedlings were used for isozyme assay. F2 ratios observed for three loci, Cat-1, Acp-1 and Pox-2, are given in Table 1. Deviation from expected ratios ( 1 : 2: 1 or 3: 1) was tested by chi-square values.

As to the Cat-1 locus, the cross of trisomic B (trisomy for chromosome 6) showed a trisomic ratio, homozygotes for the allele from the trisomic parent being significantly larger in number than those for the allele from the Indica tester, Ac 01. The cross of trisomic D also showed a deviation ftom 1: 2: 1, but the deviation seemed to be due to segregation distortion often occurring in Indica- Japonica crosses as the allele from the Indica tester increased.

As to the Acp-1 and Pox-2 loci which are linked with each other (Pai et al. 1975), all the F2 Populations showed segregation distortion, the alleles from Ac 01 increasing against those from the trisomic parents in most cases. Only the cross of trisomic A (trisomy for chromosome 4) showed significant excess of the alleles

Table 1. F2 ratios for alleles at Cat-1, Acp-1 and Pox-2 in crosses of 8 trisomic lines (with allele A) with an Indica tester (Ac 01 with allele B), trisomic ratios being given in italic letters

_______________________________________________________________
Primary          Cat-1            Acp-1            Pox-2
trisomics _________________ _________________  ________________
           AA    AB    BB    AA    AB   BB       AA     B-

     A     33    50    26    48   119   4**      58     117*
     B     46    67   17**   11    77  35**      16     123**
     C     13    48    17    10    22  24**       8      64**
     D     21    72   56**   38    82  60*       28     153**
     E     13    47    15     6    33  32**      10      71**
     F     15    37    23    12    29  37**      11      69**
     G     34    82    34    20    76  54**      24     128**
     H      6    26    11     7    22  13**       3      40**
_______________________________________________________________
*,**Significantly differing from theoretical ratio at 1% and 5%
 levels,respectively.
from the trisomic parent, at both the Acp-1 and Pox-2 loci.

It may be concluded that Cat-1 is located on chromosome 6 (linkage group 1) and Acp-1 and Pox-2 on chromosome 4 (linkage group of d-33).

Reference

Pai, C., T. Endo and H. 1. Oka, 1975. Genic analysis for acid phosphatase isozymes in Orvza perennis and 0. sativa. Can. J. Genet. Cytol. 17: 637-650.