9. A new zebra-leaf mutant obtained from anther culture

Masahiko MAEKAWA

Agriculture Experiment Farm, Hokkaido University, Sapporo, 060 Japan

Mutations are induced in cell cultures of plants (Lorz and Scowcroft 1983; Oono 1984). The author found two zebra (cross-banded chlorophyll deficiency) plants among the selfed progeny of a regenerated plantlet, consisting of 15 plants; the plantlet was obtained from anther culture of F1 plants of H-50 X N-71. This mutant, designated as AC-100, expressed the zebra character in the leaf blade and sheath invariably throughout the growing period.

Table 1. Analysis of linkages between the zebra gene and four marker genes in the fourth linkage group

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Marker Phase of  Normal    Zebra leaf     R.V.C. Goodness of fit
gene    Link.  _________   _________             _______________
                                      Total  (%)    X2      P
              Dom.  Rec.  Dom.  Rec.                             
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Rc           302    5     9    103    419        374.4*   <0.001
       Coup. 307.5  6.8   6.8  98.0       3.3+0.9  1.5  .50-0.75
d-6          337   147    127   10    621         30.8*   <0.001
       Rep.  322.1 143.7 143.7 11.6      27.3+3.7  2.9  .25-0.50
g-1          330   154    129    8    621         39.0*   <0.001
       Rep.  319.4 146.4  146.4 8.9      23.9+3.7  2.9  .25-0.50
rfs          257   106    127    8    498         32.9*   <0.001
       Rep.  257.0 116.5  116.5 8.0      25.3+4.1  1.9  .50-0.75
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*Chi-square value for 9: 3: 3: 1.
To identify the gene for this zebra character, AC-100 was crossed with five linkage testers. The five F2 populations, when pooled , showed a 1445 normal: 477 zebra ratio which gave a good fit to the 3:1 ratio, and were homozygous in this respect. Linkage analysis showed that the recessive zebra gene was linked with Rc, d-6, g-1 and rfs belonging to the fourth linkage group (Table 1). So far, five zebra genes are known (RGN 1, p.32), but none of them belongs to the fourth linkage group. Therefore, the new zebra gene is symbolized z-6. Based on its recombination values with the above four genes, the location of z-6 is determined as follows:

Fig. 1.

It may be inferred that the plantlet regenerated from anther culture was heterozygous for z-6 which arose spontaneously in the regeneration process from the cultured cells. Since only a few gene markers are known in the fourth linkage group, z-6 will serve as a useful marker in this linkage group.

References

Lorz, H. and W. R. Scowcroft, 1983. Variability among plants and their progeny regenerated from protoplasts of Su/su heterozygotes Nicotiana tabacum. Theor. Appl. Genet. 66: 67-75.

Oono, K., 1984. Genetic variability in cultured cells and their use for breeding. Plant Tissue Culture Letters 1: 2-7. (Japanese)