Characterization of QTLs for diameter in panicle neck and substitution mapping of and in rice ( L.).

The vascular bundle system in the panicle neck of rice ( L.) connects the culm to the panicle and transports assimilates. The number of vascular bundles in the panicle neck (VBN) is correlated with the diameter of the panicle neck (DPN), but there are few reported QTLs for DPN. We conducted quantitative trait locus (QTL) analysis using recombinant inbred lines (RILs) derived from a cross between 'Asominori' and 'IR24' and detected three QTLs-, , and -on chromosomes 5, 6, and 11. The , , and were in the same position as the QTLs for VBN reported in previous studies. Within the RILs, there was a significant positive correlation between DPN and VBN. In segregating populations, each QTL had a distinct effect on both values. Analysis of chromosome segment substitution lines showed that and affected DPN and affected VBN. Through substitution mapping, we narrowed down the region of and to 960 kbp between KNJ8 Indel385 and RM18926, and the region of to 750 kbp between C5 Indel5756 and KNJ8 Indel493. Due to the weak effect of in the 'IR24' genetic background, the location of could not be determined.