IL-34 (NIL) developed by introgressing chromosomal segment substitution from an accession of Oryza minuta (2n=48, BBCC, Acc. No. 101141) into the O. sativa subsp. japonica cv. Hwaseongbyeo, showed significantly higher number of spikelets per panicle (SSP) than the recurrent parent Hwaseongbyeo. QTL analysis in F2 generation derived from the cross between IL-34 and Hwaseongbyeo revealed that ssp7, a QTL was located in the pericentromeric region of chromosome 7. The frequency distribution of spikelets per panicle followed 3:1 ratio for single locus segregation. The additive effect of the O. minuta allele at the QTL was 23 spikelets per panicle, and 43.6% of the phenotypic variance could be explained by the segregation of marker RM21596. To clarify whether ssp7 could be dissected genetically, we carried out fine-scale mapping with 3,700 F2 plants derived from the cross between IL-34 and Hwaseongbyeo using markers flanking spp7. 186 F2 plants having informative recombination breakpoints within the region flanked by two SSR markers RM500 and RM21615 were identified and used for fine mapping of ssp7. ssp7 was mapped between the SSR markers RM21596 and RM418 which was approximately 441kb in length based on the physical map of the region. Of great interests, the QTL region also had effects on primary branch number (PB), grains per panicle (SP) and grain yield (YD). These results are very useful for transferring or pyramiding ssp7 by molecular marker assistant selection in rice breeding programs.

Most soybean cultivars have ovate leaflets, although a few cultivars have narrow or lanceolate leaflets. Narrow leaflet cultivars tend to have more seeds produced per pod than ovate leaflet cultivars, suggesting that the narrow leaflet trait is tightly linked to or cosegregating with the trait controlling number of seeds produced per pod (nspp). The objective of this study was to construct a high resolution map of a chromosomal region controlling narrow leaflet trait and nspp in soybean. A BC3F2 population from a cross between 'Sowonkong' and 'V94-5152' was used. Sowonkong have narrow leaflet and 4-seeded pod and V94-5152 have ovate leaflet and do not have 4-seeded pod. The plants of F2 populations showed a segregation ratio of 3:1 of ovate leaflet to narrow leaflet and then leaflet genotypes were obtained from F2:3 population of each F2 individual. The narrow leaflet-containing plants showed Sowonkong-like pod trait and the ovate leaflet-containing plants V94-5152-like pod trait. The results suggested that, in our mapping population, a single gene controls inheritance of the narrow leaflet character and the narrow leaflet trait is tightly linked to or co-segregating with the trait controlling nspp. Subsequently, we mapped the narrow leaflet locus near Sat_105, Satt270 and SM315 on soybean linkage group I that corresponds with the previously known ln locus. Work is ongoing to construct a fine molecular genetic linkage map on this MLG I region and to find a linkage relationship between ln and nspp. Our results should facilitate further elucidation for the relationship between ln/nspp and yield.