AM phenotype of della1/della2 roots colonized by G. versiforme. (A and B) Laser-scanning confocal microscope images of G. versiforme in della1/della2 (A) and wild-type (B) roots. Arrowheads mark arbuscules. (Scale bars: 250 µm.) (C) Arbuscule density in della1/della2 and wild-type roots at 13, 17, and 21 d post planting (d.p.p.). Data are averages ± SEM (n ≥ 24, where N denotes the number of infected root sections). (D) Expression of G. versiforme α-tubulin (GvTUB), MtPT4, and MtLEC5 in roots 21 d post inoculation (d.p.i.) assayed by quantitative RT-PCR. Data are averages ± SEM (n ≥ 5, where N denotes the number of independent root samples). (E) Infected root length in della1/della2 roots does not differ dramatically from that in wild-type roots, although significant changes are seen at 17 d.p.p. Data are averages ± SEM (n ≥ 24, where N denotes the number of infected root sections). (F) Level of colonization of della1/della2 and wild-type roots. Data are averages ± SEM (n = 3, where N denotes the number of independent root samples). RLC, root length colonized. **P ≤ 0.01; ***P ≤ 0.001.