| II. Records Abstructs presented in a symposium Followings are the abstruct papers presented in Small Symposium on Genome Reorganization and Developmental Abnormality in Wheat held in August 2-3, 1987 at Mishima, Japan. The symposium was organized by Dr. K. Tsunewaki (Kyoto Univ.) under sponsership of National Institute of Genetics (Japan). Gametocidal chromosomes in Aegilops species T. RYU ENDO Nara Unirversity, 1230 Horaicho, Nara, Japan 631 Endo & Tsunewaki (1975) and Maan (1975) independently found for the first time the peculiar phenomenon that an alien chromosome in common wheat could not be eliminated after many backcrosses with common wheat. Wheat plants with a monosome of this chromosome are partially fertile in male and female, while disomic plants for the same chromosome are fully fertile in both sexes. The alien chromosome addition or substitution plants produce two types of gametes, those with the alien chromosome and those without it. Cytological studies revealed that only the former gametes can function normally. Thus, the alien chromosome alone causes sterility in gametes lacking it, regardless of the plasmatype, and it is selectively retained in the offspring at the expense of the fertility of the plants bearing it. Endo (1978) called such alien chromosomes gametocidal chromosomes, and Miller (1983) named them Cuckoo' chromosomes, because of their selfish nature; once they are introduced into wheat, they can hardly be expelled even though they have harmful effects on the wheats that have them. As shown in Table 1, gametocidal chromosomes have been transferred into common wheat from six Aegilops species. Ae. caudata. Ae. triuncialis, and Ae. cylindrica have the C genome in common, and the gametocidal chromosomes of the latter two species probably derived from their C genomes. Actually, the gametocidal chromosomes of Ae. caudata and Ae. triuncialis pair well, and the addition plant having both of them show a normal fertility. The Ae. cylindrica chromosome, acrocentric like the Ae. triuncialis and Ae. caudata chromosomes is not found in Ae. squarrosa, the D genome donor to Ae. cylindrica. The Ae. triuncialis chromosome is successfully substituted for wheat homoeologous group 3 chromosomes (Endo 1978). Ae. speltoides, Ae. sharonensis, and Ae. longissima all have the S or modified S genome, and two or three gametocidal chromosomes have been extracted from each of them. Only a segment of the gametocidal Ae. speltoides chromosome was translocated to the distal end of the long arm of the 2B chromosome (unpubl. data). |
| --> Next |