Fig. 2.

Mesorhizobium strains isolated from nodules tend to be less cooperative if they contain fewer symbiosis genes. Strains with fewer symbiosis genes confer less shoot mass (a) and nitrogen (b) to Acmispon wrangelianus. Strains with smaller draft genomes also contain fewer symbiosis genes (c). Genomes that contain a majority of our high-confidence symbiosis genes (circles) are on average 583 Kbp larger than those with few (squares), which is the approximate size of the Mesorhizobium symbiosis island. Two strains have an intermediate number of symbiosis genes (triangles). Dashed lines indicate the level of a plant trait expressed by uninoculated control plants