Submitted to: Genome
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/19/2005
Publication Date: 6/8/2006
Citation: Wang, R., Li, X.M., Chatterton, N.J. 2006. Cytological evidence for assortment mitosis leading to loss of heterozygosity in rice. Genome 49:556-557 Interpretive Summary: Breeding of self-fertilizing crops such as rice, wheat, or inbred lines of corn takes many years after crossing parental plants to make hybrids. An unusual mitosis in rice plant named AMR results in early phenotype fixation in the progenies, thus saving years of time to achieve plant uniformity. The underlying mechanism for hastening the uniformity in rice hybrid progenies of AMR was attributed to assortment mitosis. In this communication, we present cytological evidence for assortment mitosis to substantiate our molecular evidence published in an earlier paper.
Technical Abstract: In the root-tip cells of the Chinese rice plant AMR, which causes "loss of heterozygosity" in its hybrids, both normal and "assortment" mitoses were observed. In the former, chromosomes do not form homologue pairs at the metaphase; all chromosomes lined up at equatorial plate; two chromatids of each chromosome split apart at the centromere and move toward opposite directions. In the "assortment mitosis," varying numbers of paired homologues were observed at the metaphase. Two groups of 12 chromosomes moved apart toward the opposite poles of daughter cells with few chromosomes having their chromatids separated at the anaphase. These observartions support the proposed mechanism that is responsible for early genotype fixation in rice hybrids involving AMR.