## 3 Results
### Polymorphism of SSR Loci by Time Period of Release Years and Population Structure
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Release Period**} \\ \cline{2-9}
**Marker** & \multicolumn{2}{c}{**Before 1980**} & \multicolumn{2}{c}{**1980s**} & \multicolumn{2}{c}{**1990s**} & \multicolumn{2}{c}{**2000 or later**} \\ \cline{2-9}  & \(\mathbf{N_{A}}\).\({}^{\ddagger}\) & **PIC** \(\ddagger\) & \(\mathbf{N_{A}}\). & **PIC** & \(\mathbf{N_{A}}\). & **PIC** & \(\mathbf{N_{A}}\). & **PIC** \\ \hline Sat\_374 & 9 & 0.8143 & 9 & 0.8198 & 17 & 0.9006 & 20 & 0.8999 \\ AW132402 & 8 & 0.7941 & 7 & 0.7928 & 10 & 0.8383 & 13 & 0.8604 \\ Sat\_197 & 10 & 0.8431 & 7 & 0.7713 & 13 & 0.8890 & 15 & 0.9121 \\ Sat\_342 & 10 & 0.8431 & 10 & 0.8288 & 15 & 0.8724 & 19 & 0.9028 \\ Sat\_164 & 4 & 0.6658 & 6 & 0.7817 & 7 & 0.7810 & 7 & 0.7188 \\ Sat\_076 & 13 & 0.9001 & 13 & 0.8846 & 19 & 0.9165 & 24 & 0.9285 \\ Sat\_179 & 5 & 0.6987 & 6 & 0.5299 & 5 & 0.5851 & 6 & 0.7093 \\ Sat\_216 & 8 & 0.6886 & 6 & 0.5769 & 10 & 0.8074 & 11 & 0.7779 \\ Sat\_022 & 12 & 0.8795 & 9 & 0.8032 & 15 & 0.8927 & 18 & 0.9116 \\ Sat\_185 & 12 & 0.8929 & 9 & 0.8427 & 11 & 0.8395 & 15 & 0.8727 \\ Sat\_417 & 8 & 0.8197 & 11 & 0.8752 & 17 & 0.9127 & 20 & 0.9252 \\ Sat\_210 & 10 & 0.8645 & 9 & 0.8427 & 12 & 0.7753 & 16 & 0.8778 \\ Sat\_434 & 9 & 0.8024 & 9 & 0.8343 & 13 & 0.8682 & 17 & 0.8904 \\ Sat\_105 & 9 & 0.8422 & 8 & 0.8339 & 12 & 0.8724 & 17 & 0.9074 \\ Sat\_151 & 7 & 0.7900 & 7 & 0.7157 & 10 & 0.7695 & 16 & 0.8350 \\ Sat\_043 & 10 & 0.8640 & 11 & 0.8830 & 15 & 0.9003 & 17 & 0.8982 \\ Sat\_245 & 12 & 0.8724 & 6 & 0.7907 & 14 & 0.8989 & 18 & 0.9052 \\ Sat\_391 & 11 & 0.8649 & 9 & 0.8266 & 12 & 0.8470 & 15 & 0.8889 \\ Sat\_339 & 8 & 0.7704 & 5 & 0.7557 & 11 & 0.8034 & 12 & 0.8001 \\ Sat\_190 & 10 & 0.8645 & 10 & 0.8372 & 13 & 0.8612 & 19 & 0.8399 \\ Total & 185 & & 167 & & 251 & & 315 & \\ \hline Mean & 9.25 & 0.8188 & 8.35 & 0.7913 & 12.55 & 0.8416 & 15.75 & 0.8631 \\ \hline \hline \end{tabular} \({}^{\ddagger}\) number of alleles; \({}^{\ddagger}\) polymorphic information content.  
\end{table} 
Table 6: Information of 20 markers used for SSR analysis by release period. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Release Period** & **Before 1980** & **1980s** & **1990s** & **2000 or Later** \\ \hline Before 1980 & - & & & \\
1980s & 0.3382 & - & & \\
1990s & 0.4906 & 0.4444 & - & \\
2000 or later & 0.5587 & 0.5731 & 0.1909 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Genetic distance between all pairings of group by release period based on SSR analysis. The population structure of the 172 Korean soybean varieties was inferred using the Structure V2.3.3 software, based on 20 SSR markers. For each K value (\(K\) = 1-10), we determined the optimal value of K by calculating \(\Delta K\). As we used Korean soybean varieties in this study, we surveyed the highest \(\Delta K\) value over \"K = 3\". The three sub-populations, referred to as Pop. 1-3, were observed with the highest \(\Delta K\) value (Figure 2) and 17 varieties were admixture type, with a membership probability \(<\) 90% (Figure 3). Most soybean varieties were distinguished according to release period. The result of population structure analysis is shown in Table 8.