Chromosome Instability Induced by Fragments in Trisomic Rice (Oryza sativa, L)

抄録

The chromosomal instability described herein occurred spontaneously among the progenies of Triplo 1 and Triplo 4, which are two of the twelve rice trisomic lines established at IRRI. In Triplo 1, some trisomic plants have been identified to have an extra chromosome 8 instead of extra chromosome 1. Cytological evidence revealed that the instability found in Triplo 1 was originated from the breakage of chromosome 8. The resulting chromosomal fragment carrying mainly heterochromatin could provoke chromosome non-disjunction at meiosis. We suggest that the appearance of non-parental trisomics was resulted from the event of non-disjunction of chromosomes 8. Since the longer chromosomes would cause more imbalance than the shorter ones, chromosome 8 is much smaller than chromosome 8 and greatly favored its transmission over chromosome 1 as extra chromosome found among the trisomic progenies of Triplo 1. Triplo 4 had been previously designated as Triplo 12 for having a very short extra chromosome. In this study, we present the evidence indicating that the instability of Triplo 4 was induced by two subsequent breaks of chromosome 4.