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International Rice Research Institute, P.O. Box 933, Manila, Philippines
Six zebra mutants have been described in rice (Kinoshita and Takahashi, 1991). We received 10 additional zebra mutants from Dr. R. N. Misra of Central Rice Research Institute, Cuttack, India. We were able to study seven of these 10 zebra mutants. Remaining three are extremely weak and show poor transmission in segregating progenies. In addition, a spontaneous zebra mutant was isolated from the IRRI variety IR62. The eight zebra mutants studied are listed in Table 1.
The mutants were crossed with IR36 and as shown in Table 2, all the F1's were normal and all the F2 populations segregated in ratio of 3 normal to 1 mutant. These results show that the zebra trait in all of these mutants is monogenic recessive. These mutants were crossed with each other as well as with the known zebra mutants (z-1 to z-6). The F1 of RGS 242 and RGS 245 had a mutant phenotype. Thus, these two mutants have allelic genes. All the other F1s were normal (Table 3) thereby showing that the seven new mutants are nonallelic to each other as well as different from the six known zebra mutants. These seven mutants are designated as z-7 to z-13 (Table 1).
Closer observation of the 13 zebras revealed two kinds of banding pattern. One type possess distinctly horizontal bands on the leaf blades. To this group belong z-1 to z-5, z-7, z-8 and z-9. In the second group, the zebra bands on the leaf blades are irregular. Kinoshita and Takamure (1984) described a very similar mutant but designated it as zn for zebra necrosis. The genes z-6 (Mackawa 1987) and z-10 to z-13 possess the same phenotype. For simplicity of nomenclature, we have designated all these mutants as zebras.
Table 1. New zebra mutants, their parental varieties and the gene symbols
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Stock No. Parental Variety Gene Symbol
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RGS 1166 IR62 z-7
RGS 244 CR113-32 z-8
RGS 247 Ratna z-9
RGS 248 Saturn z-10
RGS 1136 z-11
RGS 243 Saturn z-12
RGS 242 Ptb 10 z-13
RGS 245 Ptb 10 z-13
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Table 2. Phenotype of F1 and F2 progenies from the crosses of IR36 with the
zebra mutants
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Phenotype Phenotype of F2 plants (No.) X2 3: 1
Cross of F1 plants ================================
Total Normal Mutant
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IR36 X RGS 1166 + 326 235 91 1.32
IR36 X RGS 244 + 392 305 87 1.50
IR36 X RGS 247 + 554 433 121 2.78
IR36 X RGS 248 + 339 259 80 0.28
IR36 X GRS 1136 + 191 155 36 3.53
IR36 X RGS 243 + 424 330 94 1.66
IR36 X RGS 242 + 521 403 118 1.41
IR36 X RGS 245 + 286 216 70 0.02
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Table 3. Phenotype of F1 progenies from intercrosses between different zebra
mutants as well as with known zebra mutants
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z-1 z-2 z-3 z-4 z-5 z-6 RGS RGS RGS RGS RGS RGS RGS RGS
1166 244 247 248 1136 243 242 245
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z-1 M + + + + + + + + + + + + +
z-2 + M + + + + + + + + + + + +
z-3 + + M + + + + + + + + + + +
z-4 + + + M + + + + + + + + + +
z-5 + + + + M + + + + + + + + +
z-6 + + + + + M + + + + + + + +
RGS 1166 + + + + + + M + + + + + + +
RGS 244 + + + + + + + M + + + + + +
RGS 247 + + + + + + + + M + + + + +
RGS 248 + + + + + + + + + M + + + +
RGS 1136 + + + + + + + + + + M + + +
RGS 243 + + + + + + + + + + + M + +
RGS 242 + + + + + + + + + + + + M M
RGS 245 + + + + + + + + + + + + M M
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References
Kinoshita, T. and M. Takahashi, 1991. The one hundredth report of genetical studies on rice plant-linkage studies and future prospects. J. Fac. Agr. Hokkaido Univ. 65(1): 1-61.
Kinoshita, T. and I. Takamure, 1984. Inheritance and linkage relationship on zebra chlorosis and zebra necrosis in rice-Genetical studies on rice plant LXXXVIII. J. Fac. Agr. Hokkaido Univ. 61(4): 445-455.
Maekawa, M., 1987. A new zebra-leaf mutant obtained from anther culture. RGN 4: 79-80.
