Inheritance of elongated uppermost internode and identification of RAPD marker linked to eui gene in rice

In hybrid rice seed production, one of the major impediments for high seed yield is incomplete panicle exsertion in the wild abortive cytoplasmic male sterility (CMS) lines. Gibberellic acid (GA3) spray to improve panicle exsertion increases seed production cost by at least 10%. Elongated uppermost internode (EUI) trait has been widely used in China as an alternative to GA3. The present study employed segregating populations from crosses between non-EUI (IR58025A, IR58025B) and EUI (IR91-1591-3) parents to elucidate the inheritance of EUI trait and to tag the trait with DNA markers. In F2–3 and test crosses, EUI exhibited a monogenic recessive inheritance. Bulk segregant analysis using RAPD markers identified an association of OPAG011000 with EUI, which was further confirmed by co-segregation and linkage analyses. The marker was linked with EUI at an average map distance of 3.6 cM, promising to be useful in MAS for developing CMS lines with EUI trait.