17. Linkage between z-9 and Pgi-1 markers of chromosome 3 in rice

International Rice Research Institute, P.O. Box 933, Manila, Philippines

A large number of mutant genes have been located on the linkage map of rice (Khush and Kinoshita, 1991). In addition, 33 isozyme loci have been assigned to specific rice chromosomes. However, only in few cases mutant genes and isozyme loci have been integrated in the linkage map.

We studied the linkage relationship between zebra mutant z-9 isozyme marker Pgi-1 (Phosphoglucose). Sanchez and Khush (1992) located z-9 on chromosome 3. Similarly Pgi-1 was assigned to chromosome 3 by Ranjhan et al. (1988). RGS 247, homozygous for z-9 and Pgi-1² was crossed with RGS 021 (++Pgi-1¹¹). The F\2\ Population was characterized for the mutant phenotype and for Pgi-1 alleles using starch gel electrophoresis. The mutant phenotype segregated in 3:1 ratio (X²=1.75) and Pgi-1 alleles segregated in a 1:2:1 ratio (X²=O.26). Cosegregation analysis indicates that z-9 and Pgi-1 are linked with a distance of 12.5+/-2.3 cM (Table 1). Crosses involving these two genes and other markers of chromosome 3 are under investigation.

Table 1.  Cosegregation of z-9 and Pgi-1 in F\2\ of a cross between 
RGS 021(++Pgi-111) and RGS 247 (z-9 z-9 Pgi_122)
==========================================================================
Phenotype  Genotype     Expected phenotypic    No. of plants       X2  
for z-9    for Pgi-1    (z-9) vs genotypic    ==================   
                        (Pgi-1) ratio         Observed  Expected
==========================================================================
  Normal       11              3                 49      41.4
               12              6                 99      82.8
               22              3                 10      41.4

  Mutant       11              1                  2      13.8
               12              2                 14      27.6
               22              1                 47      13.8     125.07**
==========================================================================
  Recombination value=12.5+2.3%

Khush, G.S. and T. Kinoshita, 1991. Rice karyotype, marker genes and linkage groups. In: Rice Biotechnology (G.S. Khush and G.H. Toenniessen eds.). p.83-108. CAB International, Wallingford, U.K.

Ranjhan, S., J.C. Glaszmann, D.A. Ramirez and G.S. Khush, 1988. Chromosomal localization of four isozyme loci by trisomic analysis. Theor. Appl. Genet. 75: 541-545.

Sanchez, A.C. and G.S. Khush, 1992. Seven new genes for zebra character in rice. RGN 9: 68-71.