18. Location of chl-7 on linkage group 6

A. C. SANCHEZ and G. S. KHUSH

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

A chlorina gene was assigned by Librojo and Khush (1986) to linkage group 6 through genetic analysis using primary trisomics. This gene was designated as chl-7 (Khush and Cruz, 1988). To determine the map position of this gene on the linkage group, we crossed st-1 (RGS 002) with chl-7 (RGS 263). RGS 002 has the Pgi-21 allele while RGS 263 chl-7 has the Pgi-22 allele.

The data of Table 1 show that chl-7 is linked with both st-1 and Pgi-2. Recombination values were computed using the LINKAGE 1 program of Suiter et al. (1983). The map distance was calculated to be 22.02±7.23 and 12.73±2.70 between st-1 and chl-7 and Pgi-2 and chl-7, respectively. Likewise, the map distance of 5.24±1.75 was observed between st-1 and Pgi-2. Figure 1 shows the relative positions of the three genes.

          
Table 1.  Segregation of three genes, st-1, chl-7 and Pgi-2 in the F2
population of RGS 002 x RGS 263
===============================================================================
                                 Pgi-2                       Recombination
Marker                   =======================   Total     value
                         1/1      1/2      2/2
===============================================================================
st-1    normal            7       99        39      145
        mutant           24        1         0       25      5.24±1.74
        total            31      100        39      170
===============================================================================
chl-7   normal           29       87        10      126
        mutant            2        8        34       44     12.73±2.70
        total            31       95        44      170
===============================================================================
                       Normal            Striped
        normal          102                 24      126
        chlorina         43                  1       44     22.02±7.23
        total           145                 25      170
===============================================================================

Fig. 1. Relative positions of the three genes on linkage group 6 of rice.

References

Khush, G. S. and A. Cruz, 1988. New chlorina markers for chromosome 8 (sugary linkage group). RGN 5: 83-84.

Librojo, A. L. and G. S. Khush, 1986. Chromosomal location of some mutant genes through the use of primary trisomics in rice. In Rice Genetics. pp. 249-255. IRRI, Manila, Philippines.

Suiter, K. A., J. F. Wendel and J. Stephens Case, 1983. LIKAGE-1: a PASCAL computer program for the detection and analysis of genetic linkage. J. Hered. 74: 203-204.