19. New chlorina markers for chromosome 8 (sugary linkage group)

Gurdev S. Khush and Alma Cruz

International Rice Research Institute, PO Box 933, Manila Philippines


Six chlorina mutants have been described in rice (RGN 1, p. 31). We received seeds of 6 additional chlorina mutants from Dr. R.N. Misra of Central Rice Research Institute, Cuttack, India (Table 1). Allele tests were made between the six known chl mutants and the new mutants. They were also crossed with IR36. As shown in Table 2, all the F\1s\ with IR36 were normal thus showing that the new mutants are recessive. Data of Table 2 also shows that RGS 347, RGS 348, RGS 349 and RGS 249 are allelic. Thus RGS 263, RGS 250 and RGS 347 have new chlorina genes. We have designated these mutants as chl-7 (RGS 263), chl-8 (RGS 250) and chl-9 (RGS 347). As already reported chl-7 was located on chromosomes 3 (Librojo and Khush 1986). We studied the genetic segregation of chl-8 and chl-9 in the F\2\ or backcross progenies of all the primary trisomics. Trisomic ratios were obtained in the F\2\ progenies of Triplo 8 and chl-8 as well as chl-9 (Table 3). All the other populations segregated in a digenic manner. Thus chl-8 and chl-9 are located on chromosome 8. Only two genes, sug and v-8 were known to be on chromosome 8 (Khush et al. 1984). Thus the location of chl-8 and chl-9 on chromosome 8 is a welcome addition. We have also located two isozyme loci (Amp-2 and Amp-4) to chromosome 8 (Wu et al. 1988). Thus six genes are now known to be on chromosone 8 and the gene order and map distances are being determined.


Table 1. Chlorina mutants from Dr. R.N. Misra and parental variety

===============================================================================

Stock No.          Parental variety        Gene symbol
===============================================================================
RGS 263            CR 113-32               chl-7
RGS 250            CH 45                   chl-8
RGS 347            CH 45                   chl-9
RGS 348            CH 45                   chl-9
RGS 349            CH 45                   chl-9
RGS 249            CH 45                   chl-9
===============================================================================



Table 2. Allelic tests for the chlorina mutants





Table 3. Segregation ratios for two chlorina genes in the F\2\ generation of primary trisomics of rice




References

Khush, G.S., R.J. Singh, S.C. Sur and A.L. Librojo, 1984. Primary trisomics of rice: origin, morphology, cytology and use in linkage mapping. Genetics 107: 141-163.

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. International Rice Research Institute, PO Box 933, Manila, Philippines.

Wu, K.S., J.C. Glaszmann and G.S. Khush, 1988. Chromosomal location of ten isozyme loci in rice (Oryza sativa L.) through trisomic analysis. Biochemical Genetics 26: 303-320.