| Genetic variations in the AABB genome extracted from
Triticum durum-Elytrigia elongata (Agropyron elongatum, 2n=14)
chromosome addition lines Hajime ONO Laboratory of Genetics, Faculty of Agriculture, Kobe University, Kobe, Japan 657 A zygotic lethal mutation was found in the chromosome complements of A or B genome within a durum-Elytrigia chromosome addition line (Ono, Nakamura and Kido, 1981). The alien chromosome addition plants carrying the zygotic lethal gene(s) set seeds normally, but majority of them (ca. 80%) were shrivelled and ungerminated. The remaining plump seeds germinated well and grew to maturity. The matured plants had an alien chromosome with no exception and set shrivelled seeds with frequencies similar to their parent plants. This indicates that when the alien chromosome is incorporated in the durum wheat carrying the lethal gene(s), the lethal effect is compensated by the added chromosome. This type of change, if occurred, makes the alien chromosome indispensable for the addition line and seems likly to demonstrate an instance of chromosomal differentiation which must have occurred in the course of evolution of polyploid species. Mochizuki (1962) who produced the durum-Elytrigia addition lines reported that the added Elytrigia chromosomes more or less associated or paired with their corresponding wheat chromosomes at metaphase I, except for e4 chromosome. Under such condition, gene transfer to wheat from Elytrigia may have occurred by means of recombination between added chromosome and chromosome of the recipient. To examine if any differences in phenotypical expressions have occurred between the durum wheat and the extracted AABB genome plants from each addition line for the last 20 years since they were produced, the extracted AABB plants were compaired with normal durum wheat in several morphological characters, mainly quantitative ones, such as plant height, tiller number, ear length, ear density, seed fertility and so on. The extracted AABB plants were obtained from self-pollinated progenies of monosomic addition plants which were produced by crosses between monosomic durum and Elytrigia chromosome disomic addition, except for e5, in which the monosomic addition plants were obtained directly from disomic addition, because of their chromosomal instability. Table 1 records the frequencies of AABB plants derived from eight sources of monosomic additions and Table 2 shows the chromosome configurations at metaphase I of those monosomic additions. In an experimental field, every 80 plants of the normal durum and the seven extracted AABB plant, except for ones obtained from e5, were divided into four blocks, comprising eight randamized plots assigned to each of the eight kinds of AABB plants to be compared. The extracted AABB from e5 addition and durum wheat were grown in a greenhouse. Statistical analysis of the observation in ear length was presented in Table 3 as an example, revealing a significant difference at 1% level among AABB plants under test. |