Identification and characterization of stable QTLs for vascular bundle number at the panicle neck in rice ( L.).

A large vascular bundle number (VBN) in the panicle neck in rice ( L.) is related to the ability to transport assimilates from stem and leaf to reproductive organs during seed maturation. Several quantitative trait loci (QTLs) for VBN have been identified by using segregating populations derived from a cross between and rice cultivars. However, the detailed location, effect, and interaction of QTLs for VBN were not understood well. Here, to elucidate the genetic basis of VBN, we identified three stable QTLs for VBN-, and -by using 71 recombinant inbred lines derived from a cross between 'IR24' and 'Asominori'. We confirmed their positions and characterized their effects by using chromosome segment substitution lines (CSSLs) with an 'IR24' genetic background. had the most substantial effect on VBN, followed by and . We developed pyramided lines carrying two QTLs for VBN to estimate their interaction. The combination of and accumulated VBN negatively in the pyramided lines owing to the independent actions of each QTL. The QTLs detected for VBN will enhance our understanding of genetic mechanisms of VBN and can be used in rice breeding.