| Chromosomal introgression and genomic reorganization
by the interspecific hybridization in polyploid species of Triticum
and Aegilops YOSHIHIKO FURUTA Laboratory of Genetics and Plant Breeding Faculty of Agriculture, Gifu University, Gifu 501-11, JAPAN With respect to the origin of second modified genomes in tetraploid species of Triticum and Aegilops. Zohary & Feldman (1962) emphasized the introgressive hybridization or the introgression. In order to evaluate the introgression in tetraploid species, chromosomal and morphological analyses were carried out in the offsprings derived from some interspecific hybridizations (Furuta & Tanaka 1970, Furuta 1982, 1983). In cytogenetically stable F4 population derived from fertile F1 hybrid between Ae. triaristata (CuMt genome) and Ae.columnaris (CuMc), in addition to both types, the restitution (triaristata) and the substitution (columnaris) types, the intermediate type occurred. Frequency of the restitution type is higher than those of two other types, however. Morphological hybrid swarm was also observed in the F4 population. Two other F1 hybrids, between Ae. triuncialis (CuC) and Ae. columaris and between Ae. variabilis (CuSv) and Ae. columnaris differed from each other in the amount of chromosome pairing, but were sterile in common. The F1 hybrids were backcrossed with each recurrent parent. B1 plants with alien chromosome(s) from the non-recurrent parent were selected and B1F4 populations were obtained by selfing these B1 plants at the following three generations. Among B1F4 populations, stable plants which form 14 bivalents in all or almost all PMC's at meiosis were analyzed as to chromosomal and morphological introgression. The chromosome constitution of B1F4 plants were tested by the observation of chromosome pairing in RF1 plants derived from B1F4 plants crossed with the recurrent parent. The experimental results obtained are similar between these two hybrid combinations (Table 1). That is, about 70% Plants in both B1F4 populations restituted to genome constitution of the recurrent parental type. Ten or 22% plants were substituted one non-homologous chromosome from the non-recurrent or pollen parents. One percent had two non-homologous substituted chromosomes. In several plants, translocation occurred in the previous generation or the translocated chromosome was introduced from the donor parent. Two or 12% of the plants tested were combination type of those mentioned above. Chromosomal variations occurred in these two cross combinations are similar to intraspecific variation in natural populations of Ae. triuncialis (Furuta et al. 1984) and Ae. variabilis (Furuta 1981). Moreover, various morphological characters were introgressed from non-recurrent or pollen parents in both cross combinations. |
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