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.
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
Table 1. Analysis of linkages between the zebra gene and four marker genes in the fourth linkage group
________________________________________________________________ Marker Phase of Normal Zebra leaf R.V.C. Goodness of fit gene Link. _________ _________ _______________ Total (%) X2 P Dom. Rec. Dom. Rec. ________________________________________________________________ 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 ________________________________________________________________ *Chi-square value for 9: 3: 3: 1.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 Sulsu 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)