Analysis of QTLs for the micromorphology on the seed coat surface of soybean using recombinant inbred lines

The seed coat of soybean (Glycine max (L.) Merrill) must protect the seed but allow water intake. Overprotection, causing impermeability, is assumed to be due to the presence of an impermeable layer in the seed coat, although validation of this assumption has relied on imbibition testing, which tends to be influenced by microfractures in the seed coat. Recent micromorphological analyses using laser-assisted topography microscopy revealed links to the surface roughness (SR) of the seed coat. To verify genetic links between hardseededness and SR, we analysed quantitative trait loci (QTLs) governing SR formation using 148 recombinant inbred lines (RILs) with a genetic linkage map covering 2663.6 cM of all 20 linkage groups of soybean, with 355 DNA markers and 5 phenotype markers. Five QTLs were detected, including previously identified hardseededness QTLs for ratio of seeds absorbing water, namely RAS1 and RAS2, which accounted for 20% of the phenotypic variance, and one near a locus inhibiting seed coat colour (I). These results indicate that the impermeability of soybean seed is genetically related to the reduction of SR.