| II. Record The following article should have been included in the record section of WIS No. 63 concerning to the abstract papers presented in The Small Symposium on Genome Reorganization and Developmental Abnormality in Wheat (held at Mishima, Japan). Editorial office would like to express sencere sorry for this mistake to the author and concerned people. Genome rearrangement caused by a gametocidal chromosome in common wheat T. RYU ENDO Nara University, 1230 Horaicho, Nara, Japan 631 Previously, I reported that chromosome aberrations frequently occurred in the offspring from a cross between monosomic 4A and an alien chromosome addition line having a gametocidal chromosome derived from Aegilops longissima (2n = 14, S1S1), homoeologous to wheat group 4 chromosomes (Endo 1985a). In this study the effect of another gametocidal chromosome derived from Ae. sharonensis (2n = 14, S1S1) on the genome rearrangement in common wheat was studies. This chromosome, belonging to wheat homoeologous group 4, has the same gemetocidal action as the Ae. longissima chromosome, but they do not pair well and have different morphologies and N-banding patterns (Endo 1985). As shown in Table 1, a Chinese Spring line with a disomic substitution of the Ae. sharonensis chromosome for chromosome 4A was selfed or crossed with euploid and monosomic 4A lines of Chinese Spring, and the chromosome constitutions of the progenies were studied by C-banding. It may be concluded from the data in the table that chromosome structural changes were induced only when the substitution line was used as the male parent, and that the aberrations occurred in zygotes, not in gametes because no chromosome structural changes were found in the selfed offspring of the substitution line. In a few cases, both of the homologues had deletions in the same cell, which is evidence that the genome rearrangement occurred in both genomes from the male and female parents. Moreover, the absence of chromosome 4A in zygotes seems to be critical for the induction of the chromosome abnormality; Among the offspring from the cross between the monosomic 4A and the substitution line, one or more chromosome structural changes were detected in 29 out of 55 (60%) plants without chromosome 4A, whereas only in four out of 14 (29%) plants with chromosome 4A. Deletion and translocation were the major chromosome structural changes observed as the result of chromosome breakage. The chromosome arm or arms involved in them were identified by C-banding, being summarized in Table 2 as the frequency of breakage in each chromosome arm. Undoubtedly, a part of the chromosome structural changes must have been overlooked because such chromosomes as 1A, 4D, and 6D and minor structural changes were difficult to be identified by C-banding. The breakage in chromosome 4A was not detected mostly due to the absence of chromosome 4A in most of the offspring. Apparently chromosome breakage leading to deletion or translocation can occur in any chromosome arm; it occurred in the Ae. sharonensis chromosome itself. It is not known whether there was specific breakpoints or not. A similar phenomenon is reported in a gametocidal chromosome of Ae. speltoides (TSUJI- MOTO & TSUNEWAKI 1985). If these gametocidal chromosomes exert the same effect of genome rearrangement in the diploid species as in common wheat, they must have caused genome rearrangement whenever species without the gametocidal chromosome was pollinated with species with it, resulting in karyotype differentiation. Literature cited ENDO, T.R. 1985a. An Aegilops longissima chromosome causing chromosome aberrations in common wheat. Wheat. Inf. Serv. No. 60: 29. ENDO, T.R. 1985b. Two types of gametocidal chromosome of Aegilops sharonensis and Ae. longissima. Jpn. J. Genet. 60: 125-135. TSUJIMOTO, H. and K. TSUNEWAKI. 1985. Hybrid dysgenesis in common wheat caused by gametocidal genes. Jpn. J. Genet. 60: 565-578. |