A variegated albino (96-1998 al-v) was found in the progeny of a variegated virescent that appeared in the F₂ of the cross between a variegated virescent (Shiokari BC₅F₂) x H-126 (a linkage tester of Hokkaido University). It was reported to be inherited as a recessive gene and linked to lg on chromosome 4 (Maekawa et al. 1998). The appearance frequencies of albinos including the variegated albinos varied considerably among 12 panicle-row lines of a single F₁ plant of the cross T-65 lg x 96-1998 al-v when it was grown at 25^oC (Maekawa et al. 1998; Table 1), and of these 12 lines, three segregated no albinos. The appearance frequencies of albinos including al-v varied among panicle-row lines of the

same F₁ plant (0-35%), when the F₁ plant was grown in a green house in winter, 1998-1999 or in a paddy field in 1998 (Table 1). Frequencies of panicle-row lines segregating no albinos were 25 (3/12), 45 (5/11) and 20 (1/5) %, when the F₁ plant was grown at 25^oC, in a green house in winter, and in a paddy field, respectively. It is likely that the F₁ plant grown in the green house in winter was influenced by low temperature in winter. Therefore, the high frequency of panicle-row lines segregating no albinos must be caused by low temperature during the growth of the F₁ plant. On the other hand, lg plants appeared in all the panicle-row lines of the same F₁ plant with almost the same frequency. Accordingly, non-segregation of albinos in panicle-row lines of the F₁ plant heterozygous for the variegated albino is considered to be caused by the nature of the variegated albino gene. In order to study the cause for non-segregation of albinos in panicle-row lines of the F₁ plant, the F₃ lines of lg and its wild-type plants selected from panicle-row lines segregating no albinos and those selected from panicle-row lines segregating albinos were examined for the segregation of albinos. As shown in Table 2, almost all the F₃ lines derived from Panicle no. 5,7,17 and 26 bred true for wild-type plants. However, one and two lines segregated albinos in Panicle no. 17 and 26, respectively. On the other hand, all the F₃ lines derived from lg and its wild-type plants of Panicle no. 1, 16 and 25 segregated albinos and showed the 1:3 ratio for the lg locus. These results indicated that non-segregation of albinos in panicle-row lines of the F₁ plant heterozygous for variegated albino is caused by the occurrence of reversion from the variegated albino gene to wild type before the differentiation of gametes. Variegated albino plants in BC₁F₂ of (T-65 lg x 96-1998 al-v) x T-65 lg were found to generate a few revertants as well as albinos and variegated albinos in their progeny, and some plants of revertants obtained were homozygous for wild

types (Table 3). These results demonstrated that the variegated albino gene is mutable even in both gametes. Therefore, it is concluded that non-segregation of albinos in paniclerow lines of the F₁ plant heterozygous for variegated albino is brought about by the mutability of the variegated albino gene. Moreover, other chlorophyl mutants, such as fine stripes or variegated yellow leaves were observed in panicle-row lines segregating no albinos (Table 2). These mutations are likely to be related to mutability of the variegated albino gene.

Reference

Maekawa, M., T. Rikiishi, T. Matsuura and K. Noda, 1998. A gene for variegated albino linked to lg on chromosome 4. RGN 15: 107-108.