NBS-class genes amplification model related to gene duplication events in soybean.
a. The curved lines within inner circle, colored by green, linked paralog pairs on soybean 20 chromosomes produced by SST, b. LCT and c. ECH. NBS-class subfamily genes with darkblue (NBS-CC) and darkorange (NBS-TIR). Colored curved lines linked nodulation gene pairs with Ks < 0.15.