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A nuclear gene modifying instability of fertility restoration in cytoplasmic male sterile rice
Published online by Cambridge University Press: 14 April 2009
Summary
The present study was carried out to examine the genetic mechanism responsible for reversions to fertile phenotype detected in cytoplasmic male-sterile plants of rice. The cms-bo cytoplasm of Chinsurah boro II gave rise to male-sterility in plants without a gametophytic restorer gene (Rf1). Taichung 65 (T65A) was known to be the maintainer which carries no restorer; however, Taichun 65 preserved in our laboratory (T65B) showed partial fertility (about 8% seed set) when crossed with the male-sterile plants. Unexpectedly, the seed fertility gradually increased with repeated selfings and almost fully fertile plants were obtained in the F6 generation. The cytoplasmic substitution lines revealed that reversions to fertile phenotype resulted from mutational events at the nuclear level. The genetic experiments indicated that the partial fertility observed in the F1 hybrid was controlled by a dominant gene, Ifr1, which was carried by T65B. The results obtained suggested that Ifr1 itself was associated with instability of fertility restoration in the presence of cms-bo cytoplasm since partially fertile plants carrying Ifr1 always showed a tendency for gradual increase in fertility in the later generations. The results are also discussed in relation to a rapid genetic change through intensified gametic selection combined with instability.
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