Nodulation genes amplification model related to gene duplication events in soybean.

    a. Curved lines within the inner circle, colored by green, link paralog pairs on the 20 soybean chromosomes produced by SST, b. LCT and c. ECH. Nodulation subfamily genes are displayed in colors, light salmon (subfamily1), green (subfamily2), grey (subfamily3), yellow (subfamily4), black (subfamily5), blue (subfamily6) and red (subfamily7). Colored curved lines link nodulation gene pairs with Ks < 0.15.