Effects of auxin-related gene function on Suillus bovinus-induced Arabidopsis thaliana root development. a Number of root branches in A. thaliana col1 wildtype and in the T-DNA insertion mutant lines yuc1, aux1, pin1, pin3, arf19, and tir1 grown in the presence of S. bovinus (Sb) volatile organic compounds (VOCs) and in the absence of S. bovinus VOCs (NM) (n = 15). Error bars indicate ± the SE. *, P < 0.05; **, P < 0.01; ns, no significant difference between treatments. b Photographs showing the influence of S. bovinus VOCs on root architecture. Scale bar: 2 cm.