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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
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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.
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