A codominant DNA marker closely linked to the rice nuclear restorer gene, Rf-1, identified with inter-SSR fingerprinting

A new molecular marker (OSRRf) closely linked to the nuclear restorer gene (Rf-1) for fertility in rice has been found. The Rf-1 gene is essential for hybrid rice seed production. A PCR-fingerprinting technique using simple sequence repeats (SSRs) was applied to compare two near-isogenic lines with (MTC-10R) or without (MTC-10A) the Rf-1 gene. Of 76 inter-SSR primers tested, only one primer, (AG)8YC, generated polymorphisms. The tetranucleotide repeats generating polymorphisms were found within each amplicon. The genetic distance between OSRRf and Rf-1 was 3.7 ± 1.1 cM. As in the case of a codominant marker, this marker will be applied not only to breeding both restorer lines and maintainer lines, but also to the purity management of hybrid rice seeds. Key words : Oryza sativa L., restorer gene Rf-1, microsatellite, inter-repeat fingerprinting.

MATHEMATICAL STUDY OF THE EVOLUTION OF GYNODIOECY WITH CYTOPLASMIC INHERITANCE UNDER THE EFFECT OF A NUCLEAR RESTORER GENE

ABSTRACT A study is described of the influence of the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious plant population. This study includes the consideration of separate effects on the relative female fertility of nuclear, cytoplasmic and sex (phenotypic) factors. Under these assumptions, the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious population can lead to several different situations: persistence of cytoplasmic gynodioecy, appearance of a nuclear-cytoplasmic gynodioecy, appearance of a nuclear gynodioecy or complete restoration of male fertility. The development of stable nuclear-cytoplasmic gynodioecy in a mathematical model is new and is possible because of the consideration of the separate relative female fertilities. The possibility of a transformation of cytoplasmic gynodioecy into a nuclear one has never been obtained before. It could constitute a route for the appearance of this latter kind of gynodioecy in plant populations. Finally, the possibilities of evolution of gynodioecy from one kind to the other, and towards dioecy, are discussed, as are some theoretical schemes that seem to correspond to observed actual situations.